This article was downloaded by: [Nipissing University]On: 17 October 2014, At: 02:40Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,UK
Journal of Plant NutritionPublication details, including instructions forauthors and subscription information:http://www.tandfonline.com/loi/lpla20
Citrus Decline: Soil Fertilityand Plant NutritionA. K. Srivastava a & Shyam Singh aa National Research Centre for Citrus , Nagpur,Maharashtra, IndiaPublished online: 29 Jan 2009.
To cite this article: A. K. Srivastava & Shyam Singh (2009) Citrus Decline: SoilFertility and Plant Nutrition, Journal of Plant Nutrition, 32:2, 197-245, DOI:10.1080/01904160802592706
To link to this article: http://dx.doi.org/10.1080/01904160802592706
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all theinformation (the “Content”) contained in the publications on our platform.However, Taylor & Francis, our agents, and our licensors make norepresentations or warranties whatsoever as to the accuracy, completeness,or suitability for any purpose of the Content. Any opinions and viewsexpressed in this publication are the opinions and views of the authors, andare not the views of or endorsed by Taylor & Francis. The accuracy of theContent should not be relied upon and should be independently verified withprimary sources of information. Taylor and Francis shall not be liable for anylosses, actions, claims, proceedings, demands, costs, expenses, damages,and other liabilities whatsoever or howsoever caused arising directly orindirectly in connection with, in relation to or arising out of the use of theContent.
This article may be used for research, teaching, and private study purposes.Any substantial or systematic reproduction, redistribution, reselling, loan,
sub-licensing, systematic supply, or distribution in any form to anyone isexpressly forbidden. Terms & Conditions of access and use can be found athttp://www.tandfonline.com/page/terms-and-conditions
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Journal of Plant Nutrition, 32: 197–245, 2009
Copyright © Taylor & Francis Group, LLC
ISSN: 0190-4167 print / 1532-4087 online
DOI: 10.1080/01904160802592706
Citrus Decline: Soil Fertility and Plant Nutrition
A. K. Srivastava and Shyam Singh
National Research Centre for Citrus, Nagpur, Maharashtra, India
ABSTRACT
Soil physical properties related constraints (clay gradient in soil profile,drainage/irrigation/waterlogging) and soil fertility constraints induced by soil pH, salin-ity (specific ion-and cumulative osmotic pressure effect), calcareousness (pedogenic ornon-pedogenic CaCO3), besides increasing menace of nutrient mining, are the impor-tant pedological factors contributing to citrus decline. But, the orchards established onlater two soil orders confronted with subsurface constraints in form of argillic (clay richhorizon with acidic or alkaline pH and varying intensity/forms of calcareousness) andspodic horizonation (organic hardpan with very acidic pH), in addition to multiple soilfertility constraints. Soil condition-based rootstock alternatives, site specific nutrientmanagement coupled with variable rate application, and integrated soil managementsystems representing different modules of INM, are the viable means of combating anuntimely decline in citrus orchards’ productivity.
Keywords: plant nutrition, nutrient models, horticulture crops
INTRODUCTION
Citrus is considered to be one of the most remunerative fruit crops that have alasting niche in international trade and world finance. World citrus productionis dominated by the northern hemisphere, followed by the southern hemisphere,and Mediterranean region contributing 45%, 35%, and 20%, respectively (FAO,2005). There are three basic requirements for successful cultivation of citrus,namely, climate relatively free from frost hazards, good quality of irrigationwater, and reasonably deep and uniform fertile soil with good internal drainage(Nemec, 1986). Citrus decline as popularly known in citrus belts of Indian
Received 13 August 2007; accepted 21 January 2008.Address correspondence to A. K. Srivastava, National Research Centre for Citrus,
Amravati Road, Nagpur 440 010, Maharashtra, India. E-mail: aksrivas [email protected]
197
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
198 A. K. Srivastava and S. Singh
subcontinent has been the subject of considerable research world over. Cit-rus decline is also known by various other names such as blight in Florida,declinio in Brazil, declinamiento in Argentina, and marchitamiento repentinoin Uruguay, depending upon causal factor. It is referred to as frenching, de-cay, chlorosis, neglectosis, and amachamients in Mexico. The causal factors ofcitrus decline vary in magnitude with the nature of factors (Figure 1).
Analysis on contribution of climate, soil, and management factors on yieldof Satsuma mandarin demonstrated that yield is more affected by physiographicenvironment than either climate or even fertilizer application (Egashira et al.,1990). A definite correlation exists between elevation and particle size com-position of soils. The average concentration of clay fraction increased from 31to 38% as the elevation increased from 850 to 1500 m above mean sea level(Kong-Tau, 1986). Likewise, many of the soil fertility parameters are reportedto be influenced by variation in altitude (Singh and Dutta, 1983; Avasthe andAvasthe, 1995). These observations assume a greater significance consideringthe fact that citrus culture for commercial purposes is being practiced up to analtitude as high as 2400 m above mean sea level (Ding et al., 1990). But, someof the ornamental species of citrus are grown up to 2800 m in the areas closeto equator (Camacho and Saul, 1981).
The citrus soils differ from other cultivated soils in many respects. Thecultivated soils remain fallow for 3–6 months every year, which results indepletion of soil organic matter as very little carbon (C) is added during thefallow phase, while biological oxidation of existing C continues at the samerate as in citrus soils (Sharma and Singh, 2001). Hence, the state of nutrition,size, and yield of citrus are closely related to the amount of soil explored by theroot system (Avilan et al., 1987). Many investigations enumerated the declineof citrus trees to unfavorable surface and subsurface soil conditions (Wutscher,1989; Srivastava and Singh, 2004a).
Taxonomically, highest quantum of citrus production from citrus is har-nessed from the soils represented by soil orders Entisols, Alfisols, Ultisols, and
Citrus Decline
Abiotic Factors Biotic Factors
Soil-relatedconstraints
Irrigation Cultural Physiolgical Entomological Pathological* Waterlogging* Water stress
* Pruning/shading* Excessive bearing* Rootstock-scion incompatibility* Union creasing
* Hormonal imbalance* Alteration in‘on’and ‘off’year cycle
* Blackfly* Psylla* Bark eating caterpillar* Leaf miner* Aphids* Mealy bug* Mites
* Fungal diseases* Bacterial diseases* Viral
* Salinity* Calcareousness diseases* Nutrient toxicity/ deficiency* Clay gradient* Compaction/ hardpan in subsurface
Figure 1. Classification of causal factors to citrus decline.
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Citrus Decline: Soil Fertility and Plant Nutrition 199
Oxisols (Srivastava and Singh, 2003). Comparative studies made on the soilconditions in a young sweet orange orchard with patches of poor growth and inadjacent areas with normal growth revealed that soil conditions in the affectedareas had the presence of higher total soluble salts, higher concentration ofsoluble and exchangeable sodium (Na), and lower soluble calcium (Ca) andmagnesium (Mg) (Milad et al., 1975; Malewar et al., 1983).
DIAGNOSIS OF CITRUS DECLINE
Morphological Symptoms
The problem of citrus decline is often confused with die-back and most of thetime, citrus decline is considered similar to citrus die-back, considering thefact that no sharp distinction exists between them even today. However, for allpractical or operational purposes, the term die-back denotes a lethal conditionleading to rapid death of the plant from top to downward due to one or morepathogenic causal factors, whereas the decline refers to a gradual reduction inorchard’s productivity which may occur due to nonpathogenic factor (Ghosh,1985).
The visual symptoms are variable, often nonspecific, and unreliable todetermine the cause- and -effect relationship. Among the factors responsiblefor citrus decline, malnutrition is frequently ascribed to chlorotic condition oftrees. This condition usually develops after initial few years of excellent ‘on’years. Various symptoms comprise of: light green interveinal areas with themidrib, causing yellowish condition of leaf at advanced stages. In this way,growth of the plant is partially retarded, and the plant bears short twigs withnarrow leaves. The shoots have a tendency to die-back and even cause the wholeof the tree to dry completely in the subsequent years. Kiely (1957) describedthe features of morphological symptoms of citrus decline in Sri Lanka as asymptom of a special chlorosis in form of appearance of silvery grey spotson upper surface of leaf in the areas having sandy soils, which resembledvery much the symptoms of marble chlorosis induced by manganese (Mn)-deficiency. These symptoms also resemble to those of zinc (Zn)—and iron(Fe)—deficiencies in Kinnow mandarin orchards of northwest India (Randhawaet al., 1967). Of late, multi-micronutrient deficiency in Marathwada region ofMaharashtra, India was established to be the causal factor for sweet orangedecline (Srivastava and Singh, 2004a).
The declinio in Brazil showed the similar symptoms and characteristics asblight in Florida (Syvertsen et al., 1980). The leaves of affected trees indicateZn-deficiency like symptoms, wilt in the canopy, followed by leaf fall, twigdie-back, abnormal flowering, and general canopy decline Visual symptoms arealso adapted for a rational canopy rating: zinc deficiency symptoms in leaves,wilting of part or all canopy, leaf drop, twig die-back, abnormal lowering,
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
200 A. K. Srivastava and S. Singh
general canopy decline, internal growth of new shoots, or reduced size of fruit(Rossetti et al., 1990). Canopy rating by these visual symptoms is recommendedon the scale of 0.0–3.0 (0.0 healthy, 0.0–1.0 initial declinio stage, 1.0–2.0intermediate stage, and > 3.0 advanced stage).
Diagnostic Criteria
Important criteria to distinguish decline-affected trees from healthy trees are:reduced water uptake in the trunk by water injection, presence of amorphousplugs in xylem vessels, rate of canopy decline by visual tree vigor, high zincaccumulation in the trunk wood and phloem, and low or no water flow throughsecondary roots of affected trees (Lee et al., 1984; Brlansky et al., 1986; Rossettiet al., 1990). These criteria are the same as those applied to distinguish blightedtrees in Florida. Soil fertility does not appear to be a direct causal factorin blight incidence, though a considerable redistribution of nutrient elementstakes place within the trees as a secondary transformation. This diagnostic test,along with trunk water uptake, is widely used to identify citrus blight in thecountries like South Africa, Uruguay, and Argentina (Wutscher et al., 1982a;1982b). Young et al. (1980) showed that trunk wood Zn accumulation occurredin outer wood, whereas reduced water movement took place in inner wood.Wutscher and Hardesty (1981) proposed cation-anion ratio and water solublenutrients in soil as promising approaches to explain the citrus blight syndrome.According to many studies, an elevation in wood Zn concentration took placeprior to visual symptoms in 58% of the trees developing blight, and in restof the 42% of these trees accumulation occurred 3 years before the develop-ment of such visual symptoms (Wutscher et al., 1977; Wutscher and Hardesty,1981).
SOIL PHYSICAL PROPERTIES RELATED CONSTRAINTS
Most of the soil-plant-water relations are governed by physical properties ofsurface and sub-surface soil. Influence of soil physical properties on tree growthof mid-season cultivars (20-year-old sour lemon and 25-year-old Valencia onsweet lemon rootstock indicated a much better tree growth under grass on thesoil type having clay content 10% at 30–70 cm than on the soil type under cleancultivation (Nel, 1980).
Particle Size
Particle size distribution in governs soil-water-plant relation. Review of texturalvariation in Ap horizon of citrus growing soils across the commercial citrus belts
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Citrus Decline: Soil Fertility and Plant Nutrition 201
showed that the soils predominantly high in sand with comparatively heaviersubsurface are best suited for top citrus production. These soils preferably be-long to soil orders viz., Entisols, Inceptisols, Alfisols, and Spodosols (Florida,USA) with a small proportion of Ultisols (India, Brazil, SriLanka, China, andJapan), Aridisols (Argid in California and Arizona of the USA, Mexico, SouthAustralia, and South-west Africa), and Vertisols (central India, Greece, Mexico,and Venezuela) having large variation in pH and CaCO3 (Table 1). Compar-ison of physical characteristic of soils belonging to Floridana (Entisols) andHolopaw (Alfisols) families under healthy versus blight affected Hamlin treesshowed a comparatively higher proportion of fine textured particles in the rootzone of latter soil type associated with lower hydraulic conductivity and avail-able water (Shih et al., 1986). Decline of sweet orange trees (marchitamientorepentino) on trifoliate orange (Poncirus trifoliata) occurred only in patchesof heavy clay soil in the area of Concordia, Enter Rios province of Argentina(Swartz et al., 1980), since the amount of clay in soil correlated negatively withfeeder roots in all the soil layers (Koudounas, 1994).
In central India, in the absence of low temperature (cumulative 8–10 hoursof 5–10◦C for 12–14 days during December-January for spring flush) sufficientto induce flowering, soil water deficit stress is usually adopted by withholdingirrigation (duration of which varies as per soil depth and texture) which resultsinto concerted flowering following the resumption of irrigation. The successto induction of flowering is, therefore, largely dependent upon the physico-chemical properties of both surface as well as sub-surface soil (Table 2), whichin turn influenced the orchard efficiency (Srivastava and Singh, 2004b).
Clay content > 600.0 g kg−1 at soil depth below 30 cm was observedundesirable from the point of view of regular flowering, fruit set, and fruityield in Nagpur mandarin (Dass et al., 1998). The clay content during peaksoil moisture deficit stress was observed in the range of 350–450 g kg−1 at0–30 cm soil depth, sufficient for the surface soil to deplete its moisture duringthe peak stress period (215 mm m−1 soil moisture recorded on an average). Inthe next layer immediately below it and up to 150 cm depth, due to high claycontent (600.0–820.0 g kg−1), virtually no depletion of moisture took place(378.0 mm m−1 soil moisture on an average). Such a differential distributionof clay induced the spontaneous flow of moisture from wetter soil zone (lowersoil depths below 30 cm) to a comparatively drier zone (upper soil depth of30 cm) across the sharp moisture gradient within the soil profile that helpedtrees continue its un-interrupted vegetative growth, instead of trees undergoinga physiological rest, a pre-condition for induction of flowering to take place.This set-up of soil-water-plant relationship failed to induce any floral stimulusin the trees, unless growth retardant like paclobutrazol (9–15 g tree−1 soilapplication at the time of imposition of stress) is used to stop vegetative growthduring the stress period, forcing the trees undergo a physiological stress (Singhet al., 1999). Resultantly, the lower intensity of flowering in soils having highsubsurface clay, in turn adversely influenced the fruit yield. Hernandez et al.
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Tabl
e1
Phys
ico-
chem
ical
soil
prop
ertie
sof
Ap
hori
zon
ofci
trus
soils
ofco
mm
erci
alci
trus
belts
Part
icle
size
(%)
pHE
CC
aCO
3
Sr.N
o.C
itrus
belts
Sand
Silt
Cla
y(H
2O
)(d
Sm
−1)
(%)
Maj
orta
xono
mic
clas
s
1.A
ntal
ya,T
urke
y24
4432
7.5
—11
.6C
ambo
rthi
d,X
eror
then
t,X
eroc
hrep
t,R
hoda
xera
lf,C
alci
xero
ll2.
Ass
iut,
Egy
pt61
1029
7.6
1.2
3.2
Torr
ent,
Torr
ifluv
ent,
Torr
ipsa
mm
ent
3.C
ape,
Sout
hA
fric
a91
36
7.6
0.16
2.0
Cam
bort
hid,
Cam
borc
hrep
t,X
eroc
hrep
t.4.
Cen
tral
Indi
a39
1744
7.6
0.12
7.6
Ust
orth
ent,
Ust
ochr
ept,
Hap
lo/P
ellu
ster
t5.
Col
ima,
Mex
ico
8311
68.
30.
752.
5C
ambo
rthi
d,G
ypsi
orth
id,S
alor
thid
6.C
orsi
ca,F
ranc
e67
2211
5.0
—0
Pale
udul
t,Pa
leus
talf
7.C
rete
,Gre
ece
1716
678.
0—
0C
hrom
oxer
ert,
Pellu
xere
rt,
8.Fl
orid
a,U
SA93
43
5.6
——
Eut
roch
rept
,Udo
rthe
nt,
Qua
rtzi
psam
men
t,O
rcha
qual
f,H
apla
quod
,Psa
mm
aque
nt9.
Gila
t,Is
rael
7013
178.
01.
415
.4Q
uart
zips
amm
ent,X
eror
then
tTor
rior
then
t,N
atra
rgid
,Tor
rips
amm
ent
10.
Ibad
an,N
iger
ia67
1221
6.5
——
Pale
usta
lf,P
ropu
dalf
,Tro
pops
amm
ent,
Pale
udul
t,Pa
leus
tult,
Ust
ipsa
mm
ent,
Tro
port
hent
11.
Jian
gxi,
Chi
na64
2214
6.2
——
Um
brih
umul
t,Um
bric
/Eut
roch
rept
,U
diflu
vent
,Hap
luda
lf
202
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
12.
Ker
iKer
i,N
ewZ
eala
nd45
2827
5.6
——
Um
braq
ualf
,Ust
ochr
ept,
Eut
roch
rept
,H
aplu
stal
f,H
aplu
dalf
13.
Kor
at,T
haila
nd84
124
6.4
——
Ust
ifluv
ents
,Tro
paqu
ept,
Pale
aqul
t,Pa
leus
tult
14.
Maz
oe,Z
imba
bwe
6910
217.
5—
11.2
Pellu
ster
t,H
aplu
ster
t15
.M
urci
a,Sp
ain
7117
128.
60.
58.
6X
eroc
hrep
t,X
eror
then
t,X
erop
sam
men
ts,X
eral
fs16
.N
orth
wes
tFro
ntie
r,Pa
kist
an54
2818
8.0
0.8
9.2
Cam
bort
hid,
Ust
orth
ent,
Ust
ifluv
ent
17.
Riv
erla
nd,A
ustr
alia
7217
118.
41.
4—
Psam
men
t,O
chre
pt,C
ambo
rthi
d,Sa
lort
hid
18.
Sao
Paul
o,B
razi
l81
910
5.2
——
Hap
lort
hox,
Dys
troc
hrep
t,E
utro
chre
pt19
.Si
cily
,Ita
ly60
2218
7.8
—8.
5H
aplo
xera
lf,U
stoc
hrep
t,H
aplu
stal
f,O
chra
qual
f,H
aplu
stol
l20
.St
.Vin
cent
,Tri
nida
d85
69
6.9
——
Hap
lust
alf,
Och
raqu
alf,
Dys
troc
hrep
t
1.O
zbek
,196
9;2.
El-
Foul
yet
al.,
1984
;3.
Sing
eret
al.,
1995
;4.
Sriv
asta
vaan
dSi
ngh,
2005
;5.
Oro
zco-
Rom
ero
and
Sepu
lved
a-To
rres
,19
81;6
.Cas
sin
etal
.,19
69;7
.Nyc
has
and
Kos
mas
,198
4;8.
Cal
houn
etal
.,19
74;9
.Sag
eeet
al.,
1992
;10.
Lal
,197
6;11
.Wan
gan
dG
ong,
1998
;12
.Har
tyet
al.,
1996
;13
.McC
all,
1965
;14
Nya
map
fene
,198
4;15
.Cas
tel
and
Buj
,199
2;16
.Haq
etal
.,19
95;
17.R
obin
son,
1977
;18
.Dos
Anj
oset
al.,
1995
;19.
San
Lio
etal
.,19
88;2
0.B
row
nan
dB
ally
,197
0.
203
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
204 A. K. Srivastava and S. Singh
Table 2Distribution of CaCO3 and clay in regular (Rf) and irregular flowering(Irf)orchards
OrchardCaCO3(g kg−1) Clay (g kg−1)
Type 1 2 3 1 2 3
Rf. 4.5 8.6 12.3 44.1 42.3 46.6Irf. 4.2 4.4 6.5 51.2 58.1 68.4Sig. (p = 0.05) 2.8 2.9 3.2 5.8 10.2 9.6
1, 2 and 3 represents depth 0–15, 15–30 and 30–60 cm.Source: Dass et al., 1998.
(1987) comparing the mandarin yield on ferrrallitic red earths (clay 310–420 gkg−1) against ferrsiallitic yellow earths (clay 510–680 g kg−1) soil types undersubtropical climate of Western Georgia, demonstrated a higher fruit yield (21.4tons ha−1) in former than latter soil types (18.3 tons ha−1) due to difference innutrient supply to mandarin trees.
Soil Compaction and Drainage
Soil compaction and drainage complementary to each other, but a strong lim-iting factor to root growth and tree performance, is well established. Poordrainage due to clay rich sub-surface or caco3-induration (hardpan or clay pan)restricting the root development is claimed to be one of edaphic causal fac-tors to lower fruit yield of citrus at number of locations like northwest India(Kanwar and Randhawa, 1960), San Joaquin Valley, USA (Chapman, 1961),Aegean region, Turkey (Kovanci et al., 1978), Yaracuy, Venezuela (Sanchezet al., 1998), Concordia and Enter Rios provinces, Argentina (Swartz et al.,1980), and Nelspruit, South Africa (Abercrombie and du Plessis, 1996). Anessential point concerning hardpan, in contrast to clay pan, is that once hardpanis broken-up, it stays broken-up. Clay pan on the other hand, when broken,softens and runs together with first liberal application of water. Reduction inroot- and tree growth of valencia orange due to hard sub-surface induced poordrainage (Merlo et al., 1990) is reported to be determined by soil penetrationresistance exceeding 500 kpa (Nel and Bennie, 1984) to as high as 2000 kpa(Abercrombie and du Plessis, 1996). Factors contributing variation in fruit yieldfrom other angles revealed that 10 cm water table could be infiltered in 11 daysin low-yielding orchards (48 kg per tree), while on the same soil type, sameamount of water could be infiltered within 5–6 hours in high-yielding orchards(162 kg per tree) according to Nunez-Moreno and Valdez-Gascon (1994).
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Citrus Decline: Soil Fertility and Plant Nutrition 205
Indeed, soils are classified into different potential classes for citrus depend-ing on rooting depth (De la Rosa and Carlisle, 1978). Restricted root depth isone of the major factors limiting yield. Plowing to a soil depth of 80 cm on acompacted soil helped restore a favorable rooting volume for regeneration ofroots (Hoffman and Abercrombie, 1999; Abercrombie and du Plessis, 1995).Besides yield, quality of fruit is also improved substantially following theloosening of compacted soil layer (Okada, 1994). However, such soil manage-ment practices often resulted in pruning of roots, might later affecting the treeperformance. The ability of roots to regenerate following such a treatment isattributed to factors such as soil fertility, rootstock, cultivar, and root thicknessin addition to timing and intensity of treatment (Van Zyl and Van Huyssteen,1987).
Analysis on causes of low fruit yield (25–67 kg 0.67 ha−1) of man-darin cultivar Wenzhoumigan on Beach land in Yueqing county of Zhejiang,China showed that heavy clay texture of soil coupled with non-capillary pores(0.15–0.33%) and highly compacted layer (169 kg cm−1) at 10–40 cm depth arethe contributory factors. The efficacy of soil improvement measures assessedfrom yield increments decreased with treatment involving combined use offerrous sulfate, alum, sulfur, and gypsum or green manuring and phosphorus(P)- fertilization (Lou and Yin, 1986).
SOIL FERTILITY RELATED CONSTRAINTS
The soil-related constraints are highly varied in nature, when compared thecitrus orchards established on plain land to that of hilly land, latter remain-ing loaded with problems in both time and scale. Chief soil constraints are:reduced soil depth due to slicing of fertile layer exposing the laterite/plinthitelayer, exposure to water stress due to curtailed available water capacity, lowsoil air temperature, reduced workability, low cation exchange capacity, de-ficiency of nitrogen (N), phosphorus (P), potassium (K), toxicity of alu-minum (Al) and magnesium (Mn) in addition to non-competitive Fe-toxicityinduced Zn-deficiency (Srivastava and Singh, 2006). Multiple nutrient defi-ciency linked decline in citrus orchard productivity is reported world over(Table 3).
Soil pH
It one of the properties that dictates the nutrient availability. Establishment ofHamlin orange trees in Florida flatwood soils showed no relationship betweensoil pH and tree canopy volume or orange yield in the soil pH range of 4.6–8.0.Below pH 4.6, tree size and yield reduced substantially due to toxic effect ofAl3+ and H+ ions (Obreza, 1973). Analysis of soil samples from old citrus
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Tabl
e3
Glo
bald
istr
ibut
ion
ofnu
trie
ntde
ficie
ncie
sin
citr
usor
char
ds
S.N
o.C
itrus
regi
ons
Nut
rien
tdefi
cien
cies
Ref
eren
ces
1.A
rgen
tina
(Tuc
uman
)N
,Cu,
Fe,M
g,Z
nA
soan
dD
antu
r,19
702.
Aus
tral
ia(N
ewSo
uth
Wal
es,
Riv
erla
nd,S
unra
yasi
a)N
,P,C
u,M
n,Z
n,B
Hal
se,1
963;
Dun
can,
1969
3.B
razi
l(Sa
oPa
ulo,
Para
na)
Ca,
Mg,
P,K
,Zn,
B,
Cae
tano
etal
.,19
84;F
idal
skia
ndA
uler
,199
74.
Chi
le(A
zapa
,Elq
ui,L
imar
i,C
acha
poal
)N
,Zn,
Mn,
P,S
Ver
egar
aet
al.,
1973
5.C
hina
(Fuj
ian,
Sich
uan)
Ca,
P,Fe
,Mn,
Zn,
Mo
Lie
tal.,
1998
;Yin
etal
.,19
986.
Cos
taR
ica
(Atla
ntic
zone
)N
,P,K
,Ca,
Mg,
Mn,
Zn
Bor
nem
isza
etal
.,19
85;A
lvar
doet
al.1
994;
Ara
yaet
al.,
1994
7.E
gypt
(Asw
an,B
ehei
ra,T
ahri
r)N
,P,F
e,M
n,Z
n,E
l-Fo
uly
etal
.,19
84;S
alem
etal
.,19
95;
8.In
dia
(nor
thw
est,
nort
heas
t,so
uth,
cent
ralr
egio
n)N
,P,C
a,M
g,Fe
,Mn,
Zn
Aw
asth
ieta
l.,19
84;D
hatt,
1989
;Sri
vast
vaet
al.,
2001
;Sri
vast
ava
and
Sing
h,20
069.
Iran
(Jir
off
valle
y)Z
n,M
n,C
uR
ao,1
993
10.
Isra
el(N
egev
,Sin
ai,J
orda
nva
lley)
Ca,
Mg,
Fe,Z
nSh
aked
and
Ash
kena
zy,1
984;
Hor
esh
etal
.,19
8611
.It
aly
(Sic
ily,C
alab
ria,
Bar
asili
cata
)N
,K,M
g,C
uPe
nnis
i,19
7512
.Ja
pan
(Shi
zuok
a,E
him
e,K
anag
awa)
N,P
,K,M
g,Z
nTa
kats
ujia
ndIs
hiha
ra,1
980;
Koz
aki,
1981
;Wad
aet
al.,
1981
13.
Ken
ya(R
iftv
alle
y)N
,P,B
,Fe,
Zn,
Cu,
Mn,
Mo
Kim
ani,
1984
206
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
14.
Kor
ea(J
eju
Isla
nd)
N,P
,K,C
a,M
g,S,
Cu,
Zn
Kim
etal
.,19
69;M
oon
etal
.,19
8015
.M
oroc
co(S
ouva
lley)
Fe,M
n,Z
nPe
nkov
etal
.,19
7916
.N
epal
(Dha
nkut
a,L
amju
ng,G
orkh
a),
B,M
g,C
u,C
a,Z
nG
upta
etal
.,19
89;T
ripa
thia
ndH
ardi
ng,2
001
17.
Paki
stan
(Pun
jab)
K,Z
n,B
Haq
Izha
ret
al.,
1995
18.
Sier
raL
one
(Sie
rra)
N,P
,K,C
a,M
g,Z
nH
aque
and
God
frey
,197
619
.Sp
ain
(Val
enci
a,Se
ville
,Mur
cia,
Cat
ania
)N
,P,K
,Ca,
Mg,
Fe,M
n,Z
nM
ajor
ana,
1960
;Hel
linet
al.,
1988
20.
Tha
iland
(Kor
atPl
atea
u)C
a,M
g,P
Zn
McC
all,
1965
21.
Tri
nida
d(C
arib
bean
area
)M
g,Z
n,M
nW
eir,
1969
;197
122
.T
urke
y(I
zmir
,Aeg
ean
regi
on)
Ca,
Mg,
Fe,Z
nE
rciv
an,1
974;
Saat
cian
dM
ur,2
000
23.
USA
(Flo
rida
,Cal
ifor
nia,
Texa
s)N
,P,K
,Fe,
Mg,
Zn,
Mn,
Cu,
B,M
oK
oo,1
982;
Zhu
and
Alv
a,19
93;T
ucke
ret
al.,
1995
;Zha
nget
al.,
1997
24.
Ven
ezue
la(C
arab
obo)
N,P
,Ca,
Mg,
Zn
Pint
oan
dL
eal,
1974
207
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
208 A. K. Srivastava and S. Singh
orchards and from adjacent virgin soil in several districts of South Africaindicated no differential accumulation or depletion of any nutrient, and no pHsoil change was observed in growing citrus for 20 years or more (Bredell andConradie, 1975). The performance of Balady lime, Cleopatra mandarin, andSour Orange seedlings evaluated at various soil pH values showed a reductionin growth by 9.8, 25.4, and 40.1% at soil pH 6.0, 7.0, and 8.0, respectively(Shawky et al., 1980). Canopy of Satsuma mandarin at soil pH 4.0 was observedas half of trees growing at soil pH 5.0, and attributed low soil pH to heavy N-fertilization (Yuda, 1985). However, the effect of copper (Cu) on the growth ofHamlin orange trees was more pronounced at soil pH range of 5.5–6.0 than athigher or lower soil pH regimes (Alva et al., 1995). Double acid extractable-Ca(272–1249 mg kg−1) and soil pH (5.8–6.2) under blighted trees were higherthan Ca (112–532 mg kg−1) and pH (4.8–5.7) under healthy trees representingsix major citrus belts of Florida, USA (Wutscher, 1989).
Soil Salinity
Damage to citrus crop due to excessive accumulation of salts is well recognizedin many parts of the world growing citrus, especially in semi-arid and aridregions where saline water is largely used for irrigation. Citrus trees are quitesensitive to excess salts (Bielorai et al., 1988; Srivastava and L. Ram, 2000), andtolerance to soil salinity is correlated with its ability to restrict the entry of toxicions [sodium (Na), chlorine (Cl), and boron (B)] into roots and onward transportto shoots. Visible symptoms of salinity include: leaf bronzing, defoliation,leaf chlorosis similar to iron induced chlorosis, small leaves, small fruits, anddie-back of young twigs (Cole, 1985). Goell (1969) described salinity boundchlorosis in Eureka lemon leaves into five groups as: 0) dark green and healthyleaves, 1) light green color and slight bronzing, 2) beginning of chlorosis andyellowing of margins and tips, 3) pronounced chlorosis on margins and tipswith blotching, 4) wholly chlorotic leaves with necrotic spots on margins andtips, and 5) advanced chlorosis in form of necrosis on margins and tips coupledwith interveinal necrotic spots. Maas (1992) observed a decrease in Satsumayield at the rate of 13% for each 1.0 dS m−1 increase in EC of saturated soilextract beyond the threshold EC limit of 1.4 dS m−1. However, increasingsalt stress delayed fruit maturation, but had little effect on quality of Valenciaorange (Cerda et al., 1990; Dasberg et al., 1991; Nieves et al., 1991a; 1991b)and a slight increase in TSS and TSS/acid ratio in Shamouti orange (Bieloraiet al., 1988).
The methods of combating salinity consists of: identifying and screeningcitrus rootstocks against their reaction to salinity (Singh et al., 1997), use ofmicro-irrigation systems (Singer et al., 1995), chemical amendments (Zekriand Parsons, 1990), and breeding rootstocks for salinity tolerance. The Cl− andNa+ exclusion behavior is widely used in rating the citrus rootstocks against
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Citrus Decline: Soil Fertility and Plant Nutrition 209
salinity. Grieve and Walker (1983) observed that trifoliate orange possesseda better Na+ exclusion property than limes and mandarins, which are betterCl−excluders. The common rootstocks such as rough lemon, trifoliate, andtroyer citrange are considered salt sensitive rootstocks. While Rangpur lime,Cleopatra mandarin, and Citrus macropylla are salt tolerant rootstocks (Singhet al., 1997). It is often observed that selections made for tolerance at earlygrowth stage proved to be not as tolerant during the later growth stages or atother salinity concentrations (Shannon, 1979) in order to harvest the sustainableproduction.
Acidity
Ironically, soil acidity is the major production constraint but the world’s topcitrus production is obtained from those soils (Srivastava and Singh, 2001a).Soil acidity is defined as a soil system having proton-yielding capacity during itstransition from a given state to a reference state. The soil acidity is partitionedinto pH-dependent acidity and exchange acidity collectively known as totalacidity. The growth of some sensitive citrus species is adversely affected atexchangeable-Al as low as 1–5 mg kg−1 and hazard to more tolerant speciesincreased at > 5–10 mg kg−1 (Robinson, 1989). Based on the response ofcitrus rootstocks to varying levels of Al+, the relative tolerance of rootstockswas rated as: Cleopatra mandarin > Rough lemon > Sour orange > Swinglecitrumelo > Carrizo citrange with respective optimum Al concentration of 163,93, 89, 85, and < 50 µm (Lin and Myhre, 1991).
Calcareousness
Calcareousness is characterized by the presence of calcium carbonate (CaCO3)which has relatively high solubility, reactivity, and alkalinity. Its dissolution insoil produces high solution bicarbonate ion (HCO3
−) concentration bufferingthe soil in the pH range of 7.5–8.5. Lime-induced chlorosis is known to beone of the oldest forms of decline due to immobilization of micronutrientsavailable in soil. The primary factor associated with Fe-chlorosis in soils rich inCaCO3 emerges from the effect of HCO3
−) in reducing Fe-uptake and onwardtranslocation to leaves. However, it is still not clear about the mechanisminvolved in Fe-inactivation in chlorotic leaves.
Carbonates have their own inherent particle size which affect the availabil-ity of nutrients and modify soil texture in highly calcareous soils dependingupon their origin (Yaalon, 1957). Presence of CaCO3 in soil is classified intopedogenic (geogenic) and non-pedogenic (lithogenic) forms, the former beingmore active, hence not desirable from nutrient availability point of view. Theorigin of CaCO3 and their influence further confirm their properties in a cross
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
210 A. K. Srivastava and S. Singh
section of Vertisol types (Srivastava and Singh, 2002; 2003). Although CaCO3
rich nodules are common in smectite-dominant Vertisols (Srivastava and Singh,2001a; 2002), no significant difference was observed with respect to CaCO3
under healthy (28.0–142.0 g kg−1) versus declining trees (22.0–112.0 g kg−1).Presence of non-pedogenic (geogenic) CaCO3 contributed substantially to soilnutrient pool under healthy trees compared to declining trees. Strong associ-ation of CaCO3 nodules with micronutrient-containing minerals (nontronite,suponite, and suconite), later these micro-nutrients released into soil solutiondue to combined influence of argillo-pedoturbation and high rate of manuringcollectively improved the available pool of nutrients in soil to act as a stimulanttowards improved performance of trees. Common occurrence of citrus blighton shallow soils above limestone in Florida (Cohen, 1980), Uruguay, Argentina(Wutscher et al., 1977), Cuba (Wutscher et al., 1983), and Brazil (Rodriguez,1985) supported the possible involvement of nature of soil as a contributoryfactor.
The use of salt tolerant rootstock holds a greater potential to counter theadverse effect of soil salinity or calcareousness, which is genetically controlled.Earlier studies (Shaked et al., 1988; Gallasch and Dalton, 1989; Sagee et al.,1992) have shown the response of citrus rootstocks to soil calcareousness.However, limited studies are available to suggest the rootstock alternativeswhich can withstand high soil CaCO3. The effect of soil texture on the responseof citrus rootstock seedlings to CaCO3 showed the better performance onclay soil (47% clay, 39% silt, and 14% sand) with 33% CaCO3 than on siltyclay soil (21% clay, 19% silt, and 60% sand) containing only 23% CaCO3
(Sagee et al., 1992). In another study, Sagee (1996) demonstrated that thetolerance of citrus rootstock to CaCO3 is governed by the ability of rootstockto lower the pH of the medium. Screening of six rootstock seedlings againstcalcareousness (Rough lemon, Cleopatra mandarin, Rangpur lime, Carrizo,Troyer citrange, and Trifoliate orange) suggested Cleopatra as most tolerantrootstock (El-Otmani, 1996). In countries where Poncirus trifoliata and roughlemon rootstocks are commercially used, they are exposed to intolerance oncalcareous soils (Castle, 1987). These rootstocks might face twin problem withregard to salinity as well as calcareousness.
Nutrient Constraints
Soil fertility is that component of productivity which primarily deals with nu-trient supplying capacities of soil to the plant. The occurrence of multi-nutrientconstraints contributing to citrus decline like condition is widely reported.Consequently, the impact of nutrient management on improvement in orchardproductivity is widely acclaimed (Ghosh and Singh, 1993; Zhou et al., 1996;Li et al., 1999; Srivastava and Singh, 2003; Srivastava and Singh, 2005).
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Citrus Decline: Soil Fertility and Plant Nutrition 211
It is often observed a kind of secondary transformation of decline-likesymptoms. In such cases, nutrient constraint may not be necessarily involved.Higher K associated lower concentration of Fe, Mn, and Zn is common inthe rhizosphere soil of blighted trees than those of healthy trees (Pavan andWutscher, 1993). Comparison of soil properties under etiolated versus normalcitrus trees showed a significantly higher pH, exchangeable Ca2+, and Mg2+
(7.7, 146.1 mg kg−1, and 110.9 mg kg−1) under etiolated trees than the cor-responding values (5.3, 514.1 mg kg−1, and 82.9 mg kg−1) of the soils undernormal trees (Cheng and Zeng, 1991). Differences in soil fertility in sweet or-ange orchards of Agra region (India) revealed no significant difference betweenhealthy and chlorotic trees. However, the leaf analysis values established Zn-deficiency induced chlorosis due to antagonistic effect of Fe- on Zn-availability(Singh and Tripathi, 1985).
Changes in cation-anion ratio and water soluble nutrients in soil were pro-posed to be promising approaches to explain citrus blight syndrome (Wutscherand Hardesty, 1981). Mean exchangeable-Ca2+ was observed to be higher (33.8mg 100 g−1) under healthy trees (Table 4) compared to declining Nagpur man-darin trees (29.2 mg 100 g−1) established on Entisols, Inceptisols, and Vertisols.The nutrient mining-linked fertility depletion in surface (Srivastava and Singh,2004a) and sub-surface soil (Dass et al., 1998; Reddy et al., 2003) is by andlarge responsible for citrus decline in Deccan plateau of India.
THRESHOLDS OF SOIL PROPERTIES
The central element for optimization of soil properties is the optimum value,best regarded not as a constant, but having a range of values associated withhighest crop yield. The idea has become firmly established that the optimumvalue is rather a variable quantity, but the current models of soil fertility takelittle or no notice of this fact (Medvedev, 1990). Larson and Pierce (1991)suggested that minimum data set consisting of soil attributes namely, nutrientavailability index, total organic carbon, labile organic carbon, particle size,plant available water content, soil structure, soil strength, rooting depth, pH, andelectrical conductivity must be considered for suitability appraisal. For subsoilappraisal, Koga (1972) advocated the basic factors affecting the productivity ofSatsuma mandarin orchards, as non-capillary porosity and bulk density, whichalong with soil depth can be used a criteria to decide whether a soil can beadapted for Satsuma production in addition to methods of soil management.
Shishov and Kapshuk (1984) suggested that reddish brown soils of theTripolitanian coastal plain of USSR are considered suitable for Citriculture, ifthe following criteria are met: soil depth more than or up to 60 cm, CaCO3 lessthan or up to 8–12%, EC less than or up to 5.0 mmhos cm−1, and gypsum lessthan or up to 30%. Ko and Kim (1987) observed that high yielding orchardshad high mineral content, but low in available P. Available N and K levels were
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Tabl
e4
Com
pari
son
ofso
ilph
ysic
o-ch
emic
alpr
oper
ties
unde
rhe
alth
yan
ddi
seas
edsw
eeto
rang
eor
char
dsof
Mar
athw
ada
regi
on,M
ahar
asht
ra,I
ndia
EC
CaC
O3
Exc
hang
eabl
eca
tions
(me
100
g−1)
Tre
est
atus
pH(d
Sm
−1)
(%)
Ca2+
Mg2+
K+
Na+
Hea
lthy
8.0
0.16
7.3
33.8
12.6
1.2
8.0
Dis
ease
d∗7.
90.
187.
329
.213
.61.
36.
4Si
gnifi
canc
eN
SN
SN
S3.
1N
SN
S0.
98So
ilav
aila
ble
nutr
ient
s(m
gkg
−1)
NP
KC
aM
gFe
Mn
Cu
Zn
BM
oH
ealth
y12
6.0
13.2
173.
90.
1911
2.7
10.6
8.2
2.8
22.6
0.41
0.11
Dis
ease
d∗11
0.3
10.5
151.
00.
1210
8.5
7.4
5.9
2.8
16.1
0.28
0.09
Sign
ifica
nce
10.2
2.4
10.2
0.04
NS
1.1
0.9
NS
5.2
0.04
NS
Tota
llea
fnu
trie
nts
(%)
Tota
llea
fnu
trie
nts
(ppm
)N
PK
Ca
Mg
FeM
nC
uZ
nB
Mo
Hea
lthy
2.01
0.13
1.58
2.59
0.32
95.6
63.5
5.9
22.1
29.8
0.34
Dis
ease
d∗1.
830.
091.
732.
210.
3075
.453
.75.
517
.721
.20.
30Si
gnifi
canc
e0.
110.
030.
240.
38N
S10
.19.
8N
S4.
12.
8N
S
∗ Sho
win
gnu
trie
ntde
clin
e.So
urce
:Sri
vast
ava
and
Sing
h,20
04a.
212
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Citrus Decline: Soil Fertility and Plant Nutrition 213
high in those orchards practicing cultivation of mid-season cultivars in Jejucounty of Korea with average values of soils as pH 5.7, organic matter 8.9%,and exchangeable K, Ca, Mg, and N levels of 1.4, 6.7, 2.3, and 0.2 me 100 g−1
soil, respectively. Other studies with reference to highest fruit yield of Satsumamandarin (10–12 tons ha−1) suggested the values in soil as: 31–49 mg 100 g−1
exchangeable K, 52–54 mg 100 g−1 Mg, and 197–223 mg 100 g−1 Ca withCa: Mg 2.5–3.0, Mg:K2O 3.0–4.0, and Ca:K2O 8.0–10.0 in Western Georgia(Beridze, 1987).
Evaluation of various citrus growing soil series for citrus production incentral Taiwan revealed the suitability of 27 soil series and 5 great groups.Orchards established on dark grey colluvial soils registered the highest fruityield of 28.1 tons ha−1 and lowest yield of 16.1 tons ha−1 on yellow soils.In terms of soil series, the highest fruit yield of 39.6 tons ha−1 and 16.1 tonsha−1 was observed on grey yellow colluvial and yellow earth colluvial soils,respectively (Lay and Wang, 1997). Soils maintaining exchangeable-Ca and-Mg collectively above 50–65% of CEC showed no response of Ca- and Mg-application in Valencia orange and rough lemon (Aso and Dantur, 1971). Thisis in contrast to other study (Quaggio et al., 1992) which showed that maximumyield of Valencia orange on Rangpur lime rootstock was obtained at the soilexchangeable Mg level constituting more than 10% of total cation exchangecapacity.
Aso and Bustos (1981) based on different citrus regions of Argentinareported the appearance of hidden signs of Mg-deficiency on soils havingexchangeable Mg2+ less than 0.8 me 100 g−1. Hidden hunger signs are alsoproduced due to high K (K/Mg >4.0) or Ca (Ca/Mg > 7) content. Nunez-Moren and Valdez-Gascon (1994) observed average values of different soilproperties as: 1.1 dS m−1 ECe, 6 me L−1 water soluble Na, 4 me L−1 Ca, 1.2me L−1 Mg, and exchangeable sodium percentage 4.6 me L−1 for the orchardshaving high productivity of 162 kg per tree. These values were different atlower productivity level of 48 kg per tree as: 3.8 dS m−1 ECe, 12 me L−1 watersoluble Na, 16 me L−1 Ca, 3.8 me L−1 Mg, and 7.3 me L−1 exchangeablesodium percentage.
Poor growth of Nagpur mandarin in central India (Nilangekar and Patil,1982) and Kinnow mandarin in northwest India (Brar et al., 1986) was attributedto presence of high clay, silt, CaCO3 in subsoil. Deep tillage has met with mixedsuccess as a method of ameliorating subsoil, a physical limitation to root growth.In many cases, benefits are transient and variable (Eck and Unger, 1985). Thisin large parts stems from not understanding the basic factors influencing theeffectiveness of the modification and the subsequent maintenance of structuralstability. Attempting to ameliorate a physical problem without correcting anunderlying chemical cause is a common mistake. An example is the failureof deep ripping of subsoil without ameliorating sodicity (Rengaswamy et al.,1992). Some of the citrus growing soil types (Orthents and Psamments) inValencia, Spain are so nicely managed that the fruit yield of > 35 tons ha−1
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
214 A. K. Srivastava and S. Singh
on an average is common even with limitation of sub-soil CaCO3 high as37.8–39.9% and soil pH 7.9–8.1 (Hernando, 1969).
RESPONSE OF AMENDMENTS
The depth of soil to be modified is a function of both economic and rootfactors, and possibly depth to a drainable layer. The amendments in formof lime/dolomite in acid soil conditions and gypsum/phosphogypsum insodic/saline soil conditions have proved effective beyond doubt, to raise thesoil productivity potential. Number of studies (Davitadze, 1991; Nemec andLee, 1992; Liu, 1993; Panzenhager et al., 1999) in the past reported the fa-vorable response of citrus to lime and deep tillage or dolomite combined withorganic matter and NPK (Chen et al., 1997). Quaggio et al. (1998) reported bestresponse of phosphogypsum (4 tons ha−1) + dolomite (3 tons ha−1) incorpo-rated into surface 20 cm soil of Oxisol soil type with reference to improvementin the base saturation and reduction in soil pH under Valencia sweet orange.The moderate lime application (2.5 kg per tree) in a red soil growing 11–17-year-old trees of Satsuma mandarin, increased the fruit yield by 13.2–29.2%over untreated trees, besides improvement in fruit quality (Liu, 1993). Anotherstudy by Meng et al. (1991) showed an increase in yield of Satsuma mandarinby 37.2% as a result of lime application at the rate of 2.5 tons ha−1 in redsoil containing 1.02–1.13% organic matter, 0.038–0.045% N, 0.030–0.034%phosphorus pentoxide (P2O5), and 0.88–1.02% dipotassium oxide (K2O).
Surface application of 400 kg ha−1 quick lime or 520 kg ha−1 magnesiumcarbonate (MgCO3) soil pH increased at 0–25 cm soil depth, in an orchardwith highly acidic but regular application for 4 years is needed to notice sub-soil changes with regard to increased nutrient availability (Obreza, 1990) withapplication of CaCO3 and CaSO4 (200–800 mg Ca kg−1 soil) and reducedthe Cu-phytotoxicity (Alva et al., 1995) in sandy siliceous hyperthermic AericHaplaquods. Addition of Ca on the other hand to saline irrigation water helpedsour orange seedlings to tolerate sodium chloride (NaCl) toxicity by reducingaccumulation of Na+ and Cl− in the leaves (Zekri and Parsons, 1990). Shi-mogori et al. (1980) observed that application of 400 kg dolomite ha−1 per yearled to an extra fruit yield of about 300 kg 10 acres−1 per year in the 6 years ofexperiment.
DECLINE MANAGEMENT AND FERTILIZER TREATMENT
Effect of nutrients on plant growth and development has been studied for over350 years since the experiments of van Helmont in 1648 (Epstein, 1972). Ex-citing progress has been made in the past to develop and improve diagnostictechniques of identifying nutritional constraints and accordingly, the fertilizer
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Citrus Decline: Soil Fertility and Plant Nutrition 215
management strategies have changed from time to time. Multiplicity of meth-ods and techniques currently available for determining nutrient requirementemphasizes the importance attributed to an awareness of fertilizer require-ments.
The widely used approaches to fertilizer recommendations are: the defi-ciency correction philosophy (originates from nutrient constraint-based cropresponse through nutrient additions to the point of maximum economic yield),maintenance concept (aims to maintain soil fertility level slightly above thepoint of maximum economic yield), and nutrient removal or balanced philoso-phy (emphasizes the return to the soil what is removed by the crop to maintainproductivity, but often over-recommends nutrient need, since it does not takeinto account for the soil’s ability to supply available nutrients to the plants overtime). An optimum supply of nutrients is, therefore, aimed to meet two primeconditions: i) all nutrients should be available in quantities which exclude thepossibility of absolute deficiency or excess, and ii) the proportion of all thenutrients should be such as to exclude any deficiency as no nutrient worksindependent to each other.
The fertilizer requirement of citrus depends whether the purpose is to growthe crop (pre-bearing stage) or feed the crop (bearing stage). Based on theseobjectives, two types of fertilization viz., corrective and preventive are usuallyadopted. According to Gallasch (1992), an optimum fertilizer program is onein which the cost of each unit of fertilizer applied is at least covered by an extrareturn through fruit yield obtained in both, the short and long term life of acitrus orchard.
A successful nutrient management program in citrus can be separatedinto four major components (Obreza, 2003). These are: monitoring, programdevelopment, application, and evaluation. Monitoring can be qualitative (vi-sual observations of orchard performance in terms of growth and yield) orquantitative (laboratory-based analysis of soil or leaf samples). In the programdevelopment, the factors like type of fertilizer sources, the rate, timing, andfrequency are considered. The application phase concentrates on methods offertilizer application e.g. basin application, foliar spray or fertigation, etc. Fol-lowing fertilizer application, the evaluation step determines the crop responsethrough improvement in tree growth, fruit yield, and quality. Nutrient manage-ment can become a complex task, if all the factors affecting the efficiency offertilizer use are considered. Therefore, relative sensitivity of citrus to variousnutritional factors is of utmost importance. The sensitivity of citrus trees toshortage or excess of individual nutrients differs greatly. For example, Mn-deficiency does not affect the production as much as N-deficiency or excessof B affects fruit quality more than an excess of Mg. Likewise, related tosoil fertility changes, a decreasing level of exchangeable K may be less of aproblem than a large decrease in organic carbon because K may be replacedby weathering mineral or inorganic fertilization, whereas improving organiccarbon to the original level is cumbersome. Diagnosis and recommendation
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
216 A. K. Srivastava and S. Singh
integration system (DRIS)-based leaf or soil analysis in relation to growth oryield performance can provide the information on the relative importance ofdifferent nutrients.
Nutrient management program for citrus trees is often based on nutrientremoval of fruits (Quaggio et al., 1996). The knowledge of the nutrient distri-bution in trees is important to establish sound nutrient management programsfor citrus production. Earlier studies (Smith, 1966; Chapman, 1968) discussedthe mineral composition of citrus trees published between the 1930s and the1960s. These authors reported results of several chemical analyses of importantcomponents of citrus tree biomass, which allowed a broad understanding ofamounts of proportion and distribution of nutrients in the various compartmentsof the plant. The distribution of the total tree dry weight (%) was observed as:fruit 30.3, leaf 9.7, twig 26.1, trunk 6.3, and root 27.8. Calcium made up thegreatest amount of nutrient in the citrus tree (273.8 g per tree), followed by N(234.7 g per tree), and K (181.5 g per tree). Other macronutrients collectivelycomprised about 11% of the total nutrient content of trees. The contents ofvarious nutrients in fruits (kg ton−1) were: N 1.20, K 1.54, P 0.18, Ca 0.57, Mg0.12, sulfur (S) 0.09, B 1.63 × 10−3, Cu 0.39 × 10−3, Fe 2.1 × 10−3, Mn 0.39× 10−3, and Zn 0.40 × 10−3. Total contents of N, K, and P in the orchard cor-responded to 66.5, 52.0, and 8.3 kg ha−1, respectively, which were equivalentto the amounts applied annually by fertilization (Mattos et al., 2003). Thereis an agreement that Ca, N, and K are the dominant constituents of citrus treebiomass. While, P, Mg, and S represent a smaller proportion (∼10%) followedby micronutrients (<1%). However, the proportion of individual nutrients mayvary among different cultivars and tree age depending upon horticultural prac-tices. Such a large pool of nutrients present in the structural frame work of treesrepresent a large storage which is carried from year to year, and provides nu-trients for fruit production during deficiency of applied nutrients (Legaz et al.,1995).
Expert Systems for Fertilization Program
The fertilizer program for the bearing orchard basically consists of replacingwhat is removed by the crop, and supplying what is needed to replace leaveslost due to old age, insects, diseases, or pruning. Little is required beyond thesebasic needs, since extra fertilizer is likely to produce only extra growth whichis subsequently required to be pruned off and increase the likelihood of groundwater pollution. This prompted to reassess the fertilizer practices and evolvecomputer based decision support systems that can be readily integrated intoproduction system. In an attempt to tailor best management practices (BMPs)to specific production conditions, researches have also focused on modelingbiological processes to assess citrus nutrient requirement and to incorporateinformation into computer-based decision support systems (Bustan et al., 1999).
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Citrus Decline: Soil Fertility and Plant Nutrition 217
Various models like quadratic plateau model (Obreza et al., 1993; Srivastavaand Singh, 2001b; 2002; 2003), DRIS-based norms as discussed earlier, DRISderived FTOVAL (Sautoy, 1992; Woods and De Villiers, 1992), simulationmodels (Jones, 1998), fertilization program model (Gallasch, 1992), and twostochastic dynamic optimization models (Feinerman and Voet, 1995) suggesteddifferent methods of arriving at sound citrus fertilization program under diversegrowing conditions. These decision support systems can provide informationon site specific irrigation scheduling, nutrient requirement, seasonal variationin nutrient uptake, and nutrient budgeting through annual orchard specificnutrient recommendations; eventually to reduce production cost and negativeenvironmental impacts.
Expert system for citrus fertilization (SEFEAG) proposed by Resina et al.(1992) is an advanced prototype aimed to study the citrus nutritional problemsand maximizing the effect of fertilizers. The system identifies the causes ofnutrient excess or deficiency on the basis of information collected in the field(visual analysis) and using data on orchard history, values of leaf and soilanalysis obtained from interfaced data bank or from interactive interviews. In asubsequent publication, Basile et al. (1992) described the data base required forcitrus fertilization which can be used in SEFEAG consists of cultivar features,production characteristics, cultural techniques, technological standards, andresults of leaf/soil/water analysis. With this data bank using SEFEAG, it ispossible to improve fertilizer management for individual farm to establishyield and quality standards for each cultivar in different areas to compare andevaluate the relationship between cultural techniques and orchard performancein various locations. Chiriatti and Plant (1996) proposed a prototype, casebased reasoning (CBR) system for fertilizer application management, adoptingthe case based planning technique and a planning system in cooking domain.Although not yet in a form suitable for field implementation, the prototypeprovides an insight into how CBR system can be used to provide decisionsupport in nutrient management program.
Optimum Foliar Applied Nutrients
The foliar fertilization is better than conventional soil fertilization under theconditions: i) soils having an acute shortage of nutrient supply, ii) nutrientsimmobilized on account of unfavorable soil conditions, iii) under soil nutrientimbalances i.e. having an unfavorable influence on root absorption for anoptimal growth, and iv) restricted nutrient uptake through the plant roots.Studies in the past applying foliar sprays of urea (28–31 kg N ha−1) in Valenciaorange (Albrigo, 2000), multiple application at 1% urea in Codoux clementinemandarin (El-Otmani et al., 2002), 10% potassium chloride (KCl) in Eurekalemon (Qin et al., 1996), 5% potassium nitrate (KNO3) with 18–20 ppm 2,4-Din Shamouti orange (Erner et al., 1993), and 5% KNO3 in Valencia orange
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
218 A. K. Srivastava and S. Singh
(Koo et al., 1984) demonstrate that only two nutrients, N and K amongstmacronutrients are effective through foliar application.
Foliar sprays of micronutrients are more popular and, therefore, fre-quently used. A large variation exists with regard to foliar recommendationof micronutrients-based chelates viz., Fe-ethylenediamine-di-o-hydroxyphenylacetic acid (EDDH) (0.1%) for Valencia orange (Zude et al., 1999), Fe-polyflavonoid (1%) for Verna lemon (Fernandez-Lopez et al., 1993), Fe (50ppm)—manganese sulfate (MnSO4) (5 ppm)—Zn (75 ppm) for WashingtonNavel (Hassan, 1995), MnSO4—zinc sulfate (ZnSO4) (0.15% each) for Thomp-son Navel (Razeto et al., 1988), ferrous sulfate (FeSO4)—copper sulfate(CuSO4) (0.25% each)—ZnSO4 (0.5%) for Coorg mandarin (Desai et al.,1991), ZnSO4 (0.60 g l−1)—MnSO4 (1.2 g l−1) for Valencia orange (Garcia-Alverez et al., 1986), Zn-EDTA (0.4%)—Cu-EDTA (0.2%) for Kinnow man-darin (Sharma et al., 1999), and borax—magnesium sulfate (MgSO4) (0.2%each)—ZnSO4 (0.1%) for Jiaogan mandarin (Wang, 1999).
Optimum Soil Applied Nutrients
Response of fertilizer applied through soil on growth, yield, and quality ofdifferent citrus cultivars is well recognized under different agroclimatic citrusregions (Ghosh et al., 1989; Tachibana and Yahata 1996). Contrary to foliarfertilization, soil application of macronutrients is more efficacious. The opti-mum requirement of macronutrients for different commercial citrus cultivarssuggest: 475 g N, 320 g P2O5, 355 g K2O per tree for Satsuma mandarin inTurkey (Koseoglu et al., 1995), 240 g N, 40 g P2O5, 100 g K2O ha−1 for DancyTangerine in Spain (Pedrera et al., 1988), 1.4 kg N, 1.08 kg P, 1.1 kg K per treefor acid lime (Chundawat et al., 1991), 400–1200 kg N, 200 kg P2O5 ha−1 forKinnow mandarin in India (Sharma et al., 1993), 120 kg N, 150 kg P, 75 kg S,6 kg Cu, 0.8 kg molybdenum (Mo), 5.0 kg Zn ha−1 for Neck Orange in Korea(Lim et al., 1993), 1.02 kg N, 0.58 kg P2O5, 0.55 kg K2O per tree for Satsumamandarin in Georgia (Liu et al., 1994), 200 kg N, 140 kg P, 210 kg K ha−1 forPera sweet orange in Brazil (Cantarella et al., 1992), 0.5 kg N, 0.5 kg P2O5, 1.0kg K2O ha−1 for Grapefruit in Greece (Androulakis et al., 1992), and 1.5 kgurea, 0.25 kg superphosphate, 1.25 kg potassium chloride, 1.1 kg magnesiumsulfate, 0.10 kg zinc sulfate per tree for Jincheng orange in China (Yin et al.,1998).
The researchers even today are not unanimous on the efficacy of soil versusfoliar fertilization with reference to micronutrients. Elevating Zn concentrationonly in the tops of Zn-deficient plants with foliar sprays partially restored thenormal root growth, but clearly was not as effective as the roots absorbingZn directly from in soil (Swietlik and Zhang, 1994). The micronutrient-basedZn chelater complexes are poorly or not at all absorbed by plant roots, asdemonstrated through water culture studies (Chaney, 1988). Soil application
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Citrus Decline: Soil Fertility and Plant Nutrition 219
of micronutrient, e.g., Zn from ZnSO4 is fixed in the surface soil, while thechelated-Zn remain soluble and get distributed evenly throughout the soil,as evident from 46-times higher uptake of Zn from Zn-EDTA than ZnSO4
on sandy soils (Parker et al., 1995). The studies carried out world over have,therefore, shown some diversity in optimum doses of micronutrients establishedthrough long term field experiments. These include: Fe-citrate (2.6- 6 mgkg−1)-MnSO4 (1.3–3 mg kg−1) for Satsuma mandarin (Liu and Nan, 1996),(292 g Fe-292 g Mn-315 g Zn-EDTA ha−1) for Valencia orange (He et al.,1998.), MnSO4 (483 kg per tree)-ZnSO4 (304 g per tree) for Valencia orange(Garcia-Alvarez et al., 1986), and Zn-EDTA (30 g per tree) for WashingtonNavel orange (Swietlik, 1996). The combination of two methods is also oftenused consisting: e.g. ZnSO4
– K2SO4 (0.5%-foliar spray)-K2O as potassiumsulfate (K2SO4) (210 g per tree, -soil application) for Kinnow mandarin (Singhet al., 1989) and ZnSO4-iron sulfate (FeSO4)-MnSO4 (50 g per tree each,-soilapplication)+ (0.50%-foliar application) for Sathgudi sweet orange (Devi et al.,1996).
Site Specific Nutrient Management
Large variations in tree canopy and subsequently, the tree-to-tree yield dif-ference, are common in many of the large size citrus orchards. Knowing therequired nutrients for all stages of growth, and understanding the soil’s abilityto supply those needed nutrients are critical to profitable crop production. Therecommendations on fertilizer application may not, however, produce the samemagnitude of yield response when practiced in an orchard of large area, becauseof its inability to accommodate variation in soil fertility status. Slight changesin the nature of soil, local climate, and agronomic practices etc. may seriouslyaffect the nutrient utilization capacity of the plant.
The conventional long term fertilizer trials (Tiwari, 2002) revealed that: i)omission of limiting macro- or micronutrient leads to its progressive deficiencydue to heavy removals; ii) sites initially well supplied with P, K, or S becomedeficient when continuously cropped using N alone; and iii) fertilizer ratesconsidered optimum still resulted in nutrient depletion at higher productivitylevels, if continued, become sub-optimum rates. There is a strong necessity tokeep overall nutrient balance in relation to total crop load. Application of asingle rate of nutrients may result in over-application of nutrients at some sitesand under-application at other sites, often lead to reduced FUE. Under suchcircumstances, site specific nutrient management is adopted in big orchardsrequiring variable precision application as per soil variability so as to improvethe orchard efficiency (average yield of specified trees in relation to averageorchard yield) in ultimate terms.
With new advances in technology, grid sampling for precision citricultureis increasing. The first step in the process is to divide large fields into small
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
220 A. K. Srivastava and S. Singh
zones using a grid. Next, a representative location within the grid is identifiedfor precision soil sampling. Grid sampling is integrated into global positioningsystem (GPS) based soil sampling and nutrient-mapping that in turn uses ageographic information system (GIS) to identify spatial variation in productiv-ity and accordingly, employ variable rate technology for fertilizer applications(Schumann et al., 2003; Zaman et al., 2005).
Variable Rate Fertilization
It is one of the most effective techniques for rationale use of fertilizers executedby matching the fertilizer rate with tree requirement on a per tree size basis. Sitespecific management of 17-year old ‘Valencia’ grove (2980 trees) in Floridausing automated sensor system equipped with differential global positioningsystem and variable rate delivery of fertilizers (135–170 kg N ha−1 per year)on a tree size basis (0–240 m3 per tree), achieved a 38–40% saving in granularfertilizers cost. While, conventional uniform application rate of 270 kg N ha−1per year showed that trees with excess nitrogen (>3%) had canopies less than100 m3 with lower fruit yield and inferior quality (Zaman et al., 2005). Inanother long term experiment, the large fruit yield difference of 30.2 and 48.9kg per tree initially observed on shallow soil (Typic Ustorthent) and deep soil(Typic Haplustert) in an orchard size of 11 ha, reduced to respective fruit yieldof 62.7 and 68.5 kg per tree with corresponding fertilizer does (g per tree)of 1200 N-600 P-600 K-75 Fe-75 Mn -75 Zn-30 B and 600 N-400 P-300 K-75 Fe-75 Mn –75 Zn-30 B, suggesting the necessity of fertilizer applicationon variable rate application for rationality in fertilizer use (Srivastava et al.,2006).
Analysis of tree size of 3040 trees space of 40-acre grove showed a skeweddistribution with 51.1% trees having 25–100 m3 per tree size classes and amedian size of 82 m3 per tree. At a uniform fertilization rate of 240 kg N ha−1
per year, the leaf N concentration of 12 trees with different canopy sizes thatwere randomly sampled in the grove showed optimal levels (2.4–2.6%) in thelarge trees and excess levels (> 3%) in the medium to small trees (Tucker et al.,1995). From the regression line, trees with excess N had canopies < 100 m3
per tree, and constituted 62% of the grove. Under such conditions, variablerate fertilization can, therefore, save production costs, reduce N leaching, andincrease yields per variable acre (Schumann et al., 2003). A 30% saving ingranular fertilizer cost was estimated for this ‘Valencia’ grove if variable Nrates were implemented on a per tree basis ranging from 129 to 240 kg N ha−1
per year. For comparison purposes, the eastern half of the grove received thefull uniform rate of 240 kg N ha−1 per year. No fertilizer was allocated byspreader to skips or resets of one-to-three year age. Due to a very restricted rootsystem, new resets should be fertilized individually, usually by hand (Tuckeret al., 1995), ensuring that the granules are accurately placed adjacent to the
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Citrus Decline: Soil Fertility and Plant Nutrition 221
tree. Application of variable fertilizer rate technology in this grove saved innitrogen equivalent to the 32 to 43% reduction of N rates achieved through useof fertigation and foliar sprays of urea (Lamb et al., 1999).
Fertigation
Low water—(WUE) and fertilizer-use-efficiency (FUE) are amongst the majorproduction related constraints (Germana, 1992; Srivastava and Singh, 2003).Flood irrigation in tree basin is widely used in citrus orchards, but it has severaldrawbacks in terms of losses through conveyance, percolation, evaporation,and distribution, yet without much adverse impact on growth, yield, and fruitquality (Shirgure et al., 2001a). In light of growing scarcity of water and poorWUE under basin irrigation, micro-irrigation based fertigation has gained wideapplication in citrus orchards.
Fertigation (application of nutrients through irrigation) has produced betterresults in improving the tree growth, fruit yield, quality, the reserve pool of soilnutrients, and consequently the plant nutritional status (Zhang et al., 1996;Shirgure et al., 2001b). Besides the better mobility of nutrients, fertigation hasbeen shown to have several advantages over broadcast application of granularfertilizers (Willis et al., 1991) with respect to growth response (Koo, 1979),nutrient uptake (Koo, 1980), effective placement of nutrients and flexibility inapplication frequency (Ferguson and Davies, 1989), development of uniformroot distribution in wetted zone, an important pre-requisite for better FUE (Alvaand Syvertsen, 1991; Zhang et al., 1996), fruit yield (Koo and McKornack,1965), fruit quality (Bowman, 1996), and fertilizer savings (Srivastava andSingh, 2003).
Other studies showed far superior results with fertilizers applied throughdrip irrigation (fertigation) in Spain (Legaz et al., 1981), central India (Shirgureet al., 2001a; 2001b) and in Arizona (USA) using microsprinklers over basalfertilizer application under flood irrigation (Weinert et al., 2002). Zhang et al.(1996) evaluating the effect of fertigation versus broadcast application of watersoluble granular fertilizer on the root distribution of 26-year-old ‘White Marsh’grapefruit trees on sour orange rootstock, showed 94% of the root density in thetop 0–30 cm depth with soluble granular fertilizers. These observations supportthe earlier observations that shallow depth of wetting and delivery of nutrientsin fertigated production systems, results in most of the roots concentrated insurface soil (Alva and Syvertsen, 1991; Zhang et al., 1998).
Koo (1984a; 1984b) while describing the importance of ground coverage oforchard floor by fertigation reported that the treatment having 37% coverage ofground and 82% of canopy area produced fruit yield higher than the broadcastfertilizer treatment covering 100% of ground surface and 53% canopy area.These observations suggest the importance of canopy coverage for high nutrientuptake efficiency and higher yield. Response of six year-old ‘Hamlin’ orange
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
222 A. K. Srivastava and S. Singh
to fertigation frequency using 324 to 464 g N per tree showed nitrogen uptakeefficiencies ranged from 24 to 41% of N applied, but no effect of fertigationfrequency on the amount of N taken up by the trees, was observed whenfertigation frequency increased from 12 to 80 times a year (Syvertsen andJifon, 2001). Alva and Obreza (1998) earlier found that 18 split fertigationapplications through microsprinklers under the trees increased the fruit yieldwith fertigation than equivalent rates of granular fertilizer treatments due togreater nutrient uptake efficiency.
Alva et al. (2003) studied the comparative response of 32 months-old non-bearing ‘Hamlin’ orange trees on a Candler fine sand (Typic Quartzipsamments)using three methods of fertilization namely, fertigation (FRT), controlled re-lease fertilizers (CRT), and water soluble granular fertilizers (WSG) at tworates, high and low fertilizers rates. Total N content in tress which received thehigher fertilizer rates were 82.3, 70.2, and 41.4 g per tree for the FRT, CRF, andWSG sources, respectively. The corresponding values for the low- fertilizerrate treatments were 38.6, 50.4, and 28.4 g per tree. However, the proportionof total N partitioned to leaves was greater for WSG than for the CRF and FRTsources at both the fertilizer rates. Similar observations were made through theresponse of 25 yr-old ‘Hamlin’ orange in Highland county with varying N rates(112–180 kg ha−1) and fertilizer management practices (WSG, CRF, and FRT).Spring flush leaf N content increased with increasing N rates decreased in theorder of FRT > WSG > CRF (Paramasivam et al., 2000). Other studies byHe et al. (2003) involving CRF (1 application per year), FRT (15 applicationsper year), and WSG (3 applications per year) showed no response of fertilizersources either on fruit yield of grapefruit or leaf nutrient composition on ArenicGlossaqualf soil.
Irrigation at 20% depletion of available water content (AWC) combinedwith fertilizer treatment of 500 g N + 140 g P + 70 g K per tree per year pro-duced a significantly higher fruit yield per cubic meter of canopy in addition tohigher nutrient status and fruit quality compared to other treatments involvingirrigation either 10% depletion or 30% depletion of AWC with 600 g N + 200g P + 100 g K per tree per year in 14-yr-old Nagpur mandarin (Citrus retic-ulata Blanco) on an alkaline calcareous Lithic Ustochrept soil type (Shirgureet al., 2003; Srivastava and Singh, 2003). Field experiments on response ofpre-bearing acid lime plants to differential N-fertigation versus circular bandplacement (CBP) method of fertilizer application showed superiority of formerover latter treatments. The higher leaf N, P, and K with 80% fertigation over100% N through CBP further demonstrated that saving of N up to 20% isattainable (Shirgure et al., 2001c). Experiments carried out by Garcia-Petillo(2000) demonstrated 50% higher leaf N content with 64% higher yield oncumulative basis in fertigation treated trees compared to conventional methodof fertilization. These studies provided strong support in favor of fertigationbeing better than conventional basin or flood irrigation with broadcast methodof fertilizer application.
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Citrus Decline: Soil Fertility and Plant Nutrition 223
Cropping system Nutrient requirement Soil fertility
Nutrient recommendation
INM
* Organic manures * Biofertilizers* Crop residues
* N, P, K & S* Fe, Mn, Cu, Zn, Mo & B
Soil pH Low High
Lime Gypsum
Agricultural
Available fertilizers
Integration Environmental
Legislation
Nutrient management plan
Figure 2. Schematic plan for simplified form of INM.
INTEGRATED PLANT NUTRIENT MANAGEMENT
Renewed emphasis is being given on the importance of integrated soil produc-tivity management strategies and technologies for enhanced and sustainableagricultural production systems. Over the last few years, the concepts of in-tegrated nutrient management (INM) and integrated soil management (ISM)have been gaining acceptance, moving away from a more sectoral and input-driven approach. The advocates the careful management of nutrient stocks andflows in a way that leads to profitable and sustained production. Integrated soilmanagement not only emphasizes the management of nutrient flows, but alsohighlights the other important aspects of the soil complex, such as maintainingorganic matter content, soil structure, moisture and biodiversity. Still more at-tention is needed to integrate soil biological management as a crucial aspect ofsoil fertility management.
Fertilizer recommendation using INM approach embodies a strategy for theeconomic use of fertilizers, taking into account a number of modifying factors(Figure 2). Two important modifying factors are soil type (texture and pH) andcrop requirement, upon which, the role of INM-based components viz., organicmanures, biofertilizers, and inorganic chemical fertilizers vary, and collectivelyfulfill the twin requirement as nutrient source and soil amendment as well.
Integrated Soil Management
The use of conservation practices like trench planting on Ultisols (Lu et al.,1997), ridging (Coetzee, 1995), flat bottom trench (Muldabaev and Zaitsev,
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
224 A. K. Srivastava and S. Singh
1989), and half moon terraces (Chanukvadze, 1990), have proved highly effec-tive in enhancing the productive life of citrus orchards on. These conservationpractices warranted zero tillage or permanent sod in citrus orchards that helpedin regulating soil temperature regimes to benefit citrus orchards in the hillyterrain (Cary, 1981).
Cover crops, on the other hand have proved equally effective in improvinginfiltration, microbial biomass, P-uptake, and suppressed weed growth (Huang,1998) in addition to protection against freeze (Santinoni and Silva, 1995).Huang (1998) based on 20 years of experimentation in hill side citrus orchardsestablished on red soil types (Alfisols) observed suitable intercrops as: Indiancowpea (Vigna unguiculata), groundnut (Archies hypogea), soybean (Vignaradiata), vetch (Vicia sativa), and Chinese milk vetch (Astragalus sinicus).Based on eight-years of experimentation, Luo et al. (1992) showed yellowclover (Melliotus officinalis) as a promising green manure crop for citrus thatadded 7.5–12.0 tons ha−1 green biomass supplying 36.7–58.8 kg N, 3.7–6.0 kgP, and 23.2–37.2 kg K ha−1 into the soil.
Cultivation of soil (43–49% sand and 23–30% clay) with Acanthus mollisand Amaranthus retroflexa in spring liberated good amount of tied N, improvingyield of mandarin from 66.0 to 80.7 tons ha−1 (Pisa and Fenech, 1990). Anexcellent performance of Satsuma mandarin in Sichuan basin was observed oneast, west or south facing mountain slopes (30%) with 1 m depth of cultivatedsoil in pH range of 5.5–7.3 and organic carbon content of 2.5–3.0% using80–100 kg organic manure, 0.50–0.80 kg urea and 0.50–1.00 kg complexfertilizer per tree per year (Xong and Zhou 1997).
Integrated Nutrient Use
Many studies viz., 400 g N-150 g P-300 g K-FYM 25 kg per tree in Khasimandarin (Ghosh and Besra, 1997), 800 g N-300 g P-600 g K per tree—neemcake 15 kg per tree in sweet orange (Tiwari et al., 1997), 150 kg N-120 kgP-80 kg K-5 tons FYM ha−1 in Meyer lemon (Beridze, 1990), 600 g N-200 gP-300 g K-25 kg FYM per tree in Nagpur mandarin (Huchche et al., 1998),and 100 kg N-20 tons rice straw ha−1 in Satsuma mandarin (Tachibana and Ya-hata, 1996), have shown experimentally that application of inorganic fertilizersin combination with organic manures has proved superior over conventionalinorganic fertilization.
Improving soil quality is one of the important core problems for sus-taining productivity on long term basis. The quality index of citrus growingmeadow soils (Umbric Fluvisols: pH 7.5–8.2 and base saturation 85–100%)was observed higher (11.2) than the quality index (6.8) on argillaceous redsoils (Haplic Acrisols: pH 6.5–7.6 and base saturation 88–92%) in Jiangxiprovince of China (Wang and Gong, 1998). However, delinking the concept ofsoil quality from productivity, the former with the rationale that it is determined
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Citrus Decline: Soil Fertility and Plant Nutrition 225
by the efficiency in the use and management of resource inputs whereas thelatter is related to a set of intrinsic soil properties capable of addressing thesustainability more effectively. More research is, hence, needed to delineatethe critical limits of soil properties beyond which quality of soil environmentis severely and irretrievably jeopardized.
The organic matter level in the soil is important to help maintain an activepopulation of microorganisms in soil to promote organic matter mineralization.The soil physical condition promotes the absorption of nutrients by plant roots.These effects of soil organic matter are usually considered indicators of thesustainability of soil management system. One of the major advantages to bederived from long term fertility trials is that they enable soil organic matterchanges to be monitored. Norms need to be established for different soils to beused as an index of sustainability of soil management system. The principles ofhow to maintain nutrient and organic matter level, preserve soil structure, andavoid erosion are now well understood. It is an utmost necessity to quantify therate of change for different soils and climates so that the soil changes can bemodeled and lined to the crop performance.
The introduction of site specific practices in citrus orchards, for the si-multaneous analysis for spatial variability in soil properties and tree-to-treeperformance within an orchard using a number of information managementtechnologies such as remote sensing, GIS, GPS, and VRAT may provide betterdecision support tools to develop model orchards and ideotype trees. In thesecond step, the frequent use of these tools as a part of precision citriculturerequires to be popularized to identify sectorial occurrence of citrus decline, andaccordingly develop the averting mechanism. The possibility of exploring cropregulation through soil fertility management to produce fruits throughout theyear holds an equally good promise, to compensate the loss in production onaccount of unsustainability in production.
Improving native soil fertility by exploiting the utility of mycorrhiza needsrevisiting since it has helped in uptake of diffusion of limited nutrients suchas (a) P, Zn, Cu, Mn, and Fe by the host plants (Srivastava and Singh, 2002).However, studies pertaining bioinoculation vis-a-vis soil fertility changes incitrus orchards are very limited.
FUTURE RESEARCH
Analysis of various components of sustainability of specific citrus cultivar ina given citrus belt, demonstrates that climate and soil are the two decisivecomponents of successful citriculture. However, the clues for the sustainabilityof citrus can further be drawn from the success stories accrued through some ofthe infamous commercial citrus belts like, Florida (USA), Bet Dagan (Israel),Jeju plateau (Korea), Nile valley (Egypt), New South Wales (Australia), Koratplateau (Thailand) etc. representing an humanized art of citrus cultivation on
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
226 A. K. Srivastava and S. Singh
soils those having inherently poor nutrient supplying capacity. Developmentof threshold norms for various soil properties including the drainage criteria inrelation to fruit yield offers a better understanding on qualitative relationshipbetween constraints-based soil type and crop response to help to exploit theproductivity potential of soil.
Suitability of different concepts of soil fertility assessments viz., sufficientlevel of available nutrients (based on Mitsherlich equation) and modified fur-ther as critical level concept (Cate and Nelson, 1965), basic cation saturationratio (Bear et al., 1945), fertility capability classification (Boul et al., 1975),quantitative soil fertility evaluation (Janssen et al., 1990), phosphate absorp-tion coefficient (Egashira et al., 1990), and polarity coefficient (Tavdgiridzeand Putkaradre, 1991) need to be explored for an effective production linkedsoil fertility evaluation and subsequently, devising the land use planning as perland capability criteria. The role of substrate dynamics to engineer rhizospheresoil through microbes displaying their ability in growth promotion as well asantagonism against soil borne diseases need to be made more of a regular prac-tice. At the same time, use of open field hydroponics in countries like Australiaand South Africa, has opened new vistas of commercial citriculture withoutgiving due weight to the soil as a medium of growth. Such an option shouldbe continuously tested and scrutinized under different citrus-based productionsystems.
Development of compaction is often regarded as increase in soil bulkdensity, and physico-chemical criteria are often used to measure it. Thesecriteria in many respects are conditional and comparative, and do not providesufficient information needed for a quantitative evaluation of phase interactionand physical consequences. There is a real need for a theory and methods ofevaluating compaction and monitoring physical condition of soils to preciselyrelate with production response of citrus.
REFERENCES
Abercrombie, R. A., and S. F. Du Plessis. 1995. The effect of alleviating soilcompaction on yield and fruit size in an established Navel orange orchard.Journal of South African Society of Horticulture Science 5: 85–89.
Abercrombie, R. A., and S. F. Du Plessis. 1996. Ridge culture with citrus.Journal of South African Society of Horticulture Science 5: 18–26.
Albrigo, L. G. 2000. Effect of foliar application of urea or nutriphite on flow-ering and yields of Valencia orange trees. Proceedings of Florida StateHorticulture Society 112: 1–4.
Alva, A. K., and T. A. Obreza. 1998. Byproduct iron-humate increases treegrowth and fruit production of orange and grapefruit. HortScience 33:71–74.
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Citrus Decline: Soil Fertility and Plant Nutrition 227
Alva, A. M., and J. P. Syvertsen. 1991. Irrigation water with salinity affects soilnutrient distribution root density and leaf nutrient levels of citrus underdrip fertigation. Journal of Plant Nutrition 14: 715–727.
Alva, A. K., J. H. Graham, and C. A. Anderson. 1995. Soil pH and coppereffects on soil young Hamlin orange trees. Soil Science Society of AmericaJournal 39: 481–487.
Alva, A. K., A. Fares, and H. Dou. 2003. Managing citrus trees to optimize drymass and nutrient partitioning. Journal of Plant Nutrition 26: 1541–1559.
Alvardo, A., R. Araya, E. Bornemisza, and R. L. Hernandez. 1994. Nutritionalstudies in eleven citrus cultivars and one local selection in the Atlanticzone of Costa Rica major and minor elements. Agronomia Coastarricense18: 13–19.
Androulakis, I. J., M. H. Loupassaki, F. Beidoum, and I. Tzombanakis 1992.The effect of N, P, K fertilizers on the yield and mineral contents of leavesof grapefruit. In: Proceedings of International Society of Citriculture,Vol. 2, eds. E. Tribulato, A. Gentile and G. Refergiato, pp. 624–627.Acireale, Italy: International Society of Citriculture.
Araya, R., A. Alvardo, R. L. Hernandez, and E. Bornemisza. 1994. Nutritionalstudies in eleven citrus cultivars and one local selection in the Atlantic zoneof Costa Rica. II Micronutrients. Agronomia Costarricense 18(1): 21–27.
Aso, P. J., and V. N. Bustos. 1981. Conditions relating Mg deficiency in citrusorchards of Tucman. Revista Industrial Y Agricola de Tucman 57: 9–13.
Aso, P.J., and N. C. Dantur. 1970. Citrus nutrient deficiencies in Tucuman.Revista Industrial y Agricola de Tucuman 47(2): 10–61.
Aso, P. J., and N. C. Dantur. 1971. The effects of calcium and magnesiumapplication on the yield and quality of Valencia oranges in acid soil. RevistaIndustrial y Agricola de Tucuman 48(2): 31–39.
Avasthe, Y., and R. K. Avasthe. 1995. Relationship between altitude and avail-able nitrogen, phosphorus and potassium in some soils of Sikkim. Journalof Hill Research 8(1): 33–38.
Avilan, R. L., F. Leal, and L. Meneses. 1987. Root system distribution insweet orange (Citrus sinensis) and grapefruit (Citrus paradisi) on sourorange (Citrus aurantium) in calcareous soils of the Lake Valencia basin.Horticulture Abstracts 57(9): 771.
Awasthi, R. P., G. Singh, and R. C. Sharma. 1984. A survey of the mineralnutrients status of mandarin orchards in Nagpur area of Himachal Pradesh.Punjab Horticulture Journal 24: 27–36.
Basile, G., D. Palazzo, C. Resina, F. Interigliolo, A. Giuffrida, and L. Conig-ilione. 1992. Database on citrus fertilization. In: Proceedings of the In-ternational Society of Citriculture, Vol. 2, eds. E. Tribulato, A. Gentileand G. Refergiato, pp. 603–606. Acireale, Italy: International Society ofCitriculture.
Bear, F. E, A. L. Prince, and J. L. Malcom. 1945. Potassium need of New Jerseysoils. New Jersey Agricultural Experiment Station Bulletin 37: 217–222.
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
228 A. K. Srivastava and S. Singh
Beridze, T. T. 1990. The effect of organic fertilizers on lemon tree productivity.Subtropicheskie Kul’tury 3: 83–86.
Beridze, Z. A. 1987. Some factors affecting mandarin growth and yield. Sub-tropicheskie Kul’tury 3: 76–82.
Bielorai, S., S. Dasberg, Y. Erner, and M. Brum. 1988. The effect of salineirrigation water on Shamouti orange production. In: Proceedings of theSixth International Citrus Congress, Vol. 2, eds. R. Goren and K. Mendel,pp. 707–715. Rehovot, Israel: Balaban Publishers, Israel.
Bornemisza, E., R. L. Hernandez, W. Chaverri, and M. F. Veracochea. 1985.Annual variation of foliar levels of seven nutrients in Persian lime and SanFernando and Frost nuclellar Lisbon lemons in Costa Rica. AgronomiaCostarricense 9: 135–141.
Boul, S. W., P. A. Sanchez, R B. Cate, and M.A. Granges. 1975. Soil fer-tility capability classification: a technical soil classification system forfertility management. In: Soil Management in Tropical America, eds.E. Bornemisza and A. Alvarado, pp. 126–145. Raleigh, NC: N.C. StateUniversity.
Bowman, B. J. 1996. Fertigation versus conventional fertilization of flatwoodsgrapefruit. Fertilizer Research 44: 123–128.
Brar, S. P. S., K. Dinesh, S. Balwindar, and G. S. Chohan. 1986. Role ofsoil characteristics on the growth of kinnow mandarin. Indian Journal ofHorticulture 43: 210–215.
Bredell, G. S., and J. H. Conradie. 1975. Replanting of citrus: a survey ofthe chemical composition of old and new soil. Citrus & Subtropical FruitJournal 496: 8–10.
Brlansky, R. H., M. A. Peterson, L. W. Timmer, and J. H. Graham. 1986.Formation of amorphous pluges in citrus trees with blight. Phytopathology76: 707–711.
Brown, C. B., and C. S. Bally. 1970. Land Capability Survey of Trinidadand Tobago, 4. Soils of Central Trinidad. Trinidad: Government PrintingOffice.
Bustan, A., E. E. Goldschmidt, and Y. Erner. 1999. Progress in the developmentof “Citros”—A dynamic model of citrus productivity. Acta Horticulturae499: 69–80.
Caetano, A. A., O. Rodriguez, R. Hiroce, and C. C. Bataglia. 1984. Nutri-tional survey forty sweet orange groves in Babedauro, S.P., Brazil. In:Proceedings of International Society of Citriculture, Vol. 1, eds. H.W.S.Montenegro and C.S. Moreira, pp. 151–154. Sao Paulo, Brazil: Interna-tional Society of Citriculture.
Calhoun, F. G., V. W. Carlisle, R. E. Caldwell, L. W. Zelazny, L. C. Hammond,and H. L. Breland. 1974. Characterization data for selected Florida soils.Research Report. No. 74–1. Gainesville, FL: Soil Science DepartmentIFAS, University of Florida, Gainesville.
Camacho, B., and E. Saul. 1981. Citrus culture in high altitude Americantropics. In: Proceedings of the International Society of Citriculture, eds.
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Citrus Decline: Soil Fertility and Plant Nutrition 229
K. Matsumoto, C. Oogaki, I. Kuzaki, K. Kadoya, F. Mizutani and E. Yuda,Vol. 1, pp. 321–325. Tokyo, Japan: International Society of Citriculture.
Cantarella, H., J. A. Quaggio, O. C. Bataglia, and B. Van Raij. 1992. Responseof citrus to NPK fertilization in a network of field trials in Sao Paulo State,Brazil. In: Proceedings of the International Society of Citriculture, eds.E. Tributato, A. Gentile and G. Refergiato, Vol. 1, pp. 321–325. aCireale,Italy: International Society of Citriculture.
Cary, P. R. 1981. Soil management factors affecting growth and yield of citrustrees. In: Proceedings of the International Society of Citriculture, eds. K.Matsumoto, C. Oogaki, I. Kozaki, K. Kadoya, F. Mizutani and E. Yuda,Vol. 2, pp. 527–530. Tokyo, Japan: International Society of Citriculture.
Cassin, P. J., L. Blondel, J. M. Bove, C. Bove, E. Jolivet, J. Lacoeuilhe,D. Lefleche, L. Lassois, J. Marchal, P. Martin-Prevel, M. Z. Nicol, andH. Moulinier. 1969. General study of leaf analysis and citrus fruit analysisunder Cersican environmental conditions. In: Proceedings of the Inter-national Citrus Symposium, eds. H.D. Chapman, Vol. 3, pp. 1689–1712.Florida, USA: International Society of Citriculture.
Castel, J. R., and A. Buj. 1992. Growth and evapotranspiration of young, drip-irrigated clementine trees. In: Proceedings of the International Society ofCitriculture, eds. E. Tribulato, A. Gentile and G. Refergiato, Vol. 2, pp.651–656. Acireale, Italy: International Society of Citriculture.
Castle, W. S. 1987. Citrus rootstocks. In: Rootstock for Fruit Crops, eds. R. C.Rom, and R. F. Carlson, pp. 361–399. New York: Wiley.
Cate, R. B. Jr., and L. A. Nelson. 1965. International Soil Testing Series.Technical Bulletin 1. North Carolina Agricultural Experimental Station.Washington, DC: United States Department of Agriculture.
Cerda, A. M., M. A. Nieves, and M. G. Guillen. 1990. Salt tolerance of lemontrees as affected by rootstock. Irrigation Science 11: 245–249.
Chaney, R. L. 1988. Metal speciation and interaction among elements affecttrace element transfer in agricultural and environmental food chains. In:Metal Speciation: Theory, Analysis, and Application, eds. J. R. Kramerand H. E. Allen, pp. 319–360. Chelsea, MI: Lewis Publishers.
Chanukvadze, F. S. 1990. The effectiveness of potassium fertilizers in citrusorchards on Krasnozem soils. Subtropicheskie Kul’tury 1: 99–104.
Chapman, H. D. 1961. The evaluation and management of citrus soil. IndianJournal of Horticulture 18: 251–276.
Chapman, H. D. 1968. Mineral nutrition of citrus. In: The Citrus Industry,Vol. 2, eds. W. Reuther, L. D. Batchelor, and H. J. Webber, pp. 127–189.Berkeley, CA: University of California Division of Agricultural Sciences.
Chen, H., H. Huang, and C. Lu. 1997. Effect of organic fertilizer and dolomiteon the growth and fruit quality of Matou Peiju (Citrus grandis Osbeck,cv. ‘Matou Peiyu’). Special Publication of Taichung District AgriculturalImprovement Station, Tatsuen, Taiwan 38: 69–76.
Cheng, Q. M., and. K. Y. Zeng. 1991. Hongguang, the best strain of NanfengGuangju. China Citrus 20(3): 17–23.
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
230 A. K. Srivastava and S. Singh
Chiriatti, K. C., and R. E. Plant. 1996. NPK : a prototype case based planningsystem for crop fertilization decision support. Ai Applications 10(2):33–42.
Chundawat, B. S., R. A. Khimani, and K. P. Kikani. 1991. Nutritional surveyof elite acid lime orchard in Gujarat. Indian Journal of Horticulture 48:183–186.
Cohen, M. 1980. Non-random distribution of trees with citrus blight. In: Pro-ceedings of 89th Conference International Organisation for Citrus Virolo-gists, eds. E. C. Calavan, S. M. Garnsey, and L. W. Timmer, pp. 206–263.Riverside, CA: University of California, Riverside.
Coetzee, J. G. K. 1995. Ridging soils for new citrus plantation. Citrus Journal5(3): 22–24.
Cole, P. J. 1985. Chloride toxicity in citrus. Irrigation Science 6: 63–71.Dasberg, S., H. Bielorai, A. Haimowitz, and Y. Erner. 1991. The effect of
saline irrigation waters on Shamouti orange trees. Irrigation Science 12:205–211.
Dass, H. C., A. K. Srivastava, L. Ram, and S. Singh. 1998. Flowering behaviorof Nagpur mandarin (Citrus reticulata) as affected by vertical variation inphysico-chemical composition of black soils. Indian Journal of Agricul-tural Science 68: 692–694.
Davitadze, M. M. 1991. Effect of liming on the productivity of young lemon or-chards and fruit biochemical indices. Subtropicheskie Kul’tury (4): 92–95.
De la Rosa, D., and V. W. Carlisle. 1978. Correlation of productive capacityand estimated yields for selected Florida soils. Proceedings of the Soil &Crop Science Society of Florida 37: 134–138.
Desai, U. T., S. M. Choudhary, M. S. Shirsath, and P. N. Kale. 1991. Studies onthe effect of foliar application of micronutrients in Mosambi sweet orange.Maharashtra Journal of Agricultural Universities 5(2): 29–31.
Devi, D. D., P. S. Srinivasan, and K. Balakrishnan. 1996. Carbonic anhydraseactivity as an indicator of zinc status of sathgudi orange. Orissa Journalof Horticulture 24(1/2): 66–68.
Dhatt, A. S. 1989. Nutrient management in citrus with special reference toKinnow. In: Proceedings of a Citrus Show-cum-Seminar on Prospects andProblems of Kinnow Cultivation, eds. K. S. Gill, J. S. Kanwar, and R.Singh, pp. 157–67. Ludhiana, India: Punjab Agricultural University.
Ding, S., X. Zhang, Z. Bao, and M. Liang. 1990. Citrus Ichangensis in Yunnan.In: Proceedings of the International Citrus Symposium, eds. H. Bangyanand Y. Qian, pp. 170–181. Guanzhou, China; International AcademicPublishers.
Dos Anjos, L. H. C., D. P. Franzmeier, and D. G. Schulze. 1995. Formation ofsoils with plinthite on a toposequence in Maranhao state, Brazil. Geoderma64: 257–279.
Duncan, J. 1969. Citrus nutrition survey—M.I.A. Farmer Newsletter 105:17–19.
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Citrus Decline: Soil Fertility and Plant Nutrition 231
Eck, H. V., and P. W. Unger. 1985. Soil profile modification for increasing cropproduction. Advances in Soil Sciences 1: 65–83.
Egashira, K., S. Nakashima, and M. Fujiyama. 1990. Quantification analysisof the contribution of environment, soil and management factors to cropyields—case study of the yield of rice, potato and orange in Nagasakiprefecture. Science Bulletin, Faculty, Agriculture, Kyushu UniviversityFukuoka, Japan 45(1–2): 9–21.
El-Fouly, M. M., A. F. A. Fawzi, A. H. Firgany, and F. K. El-Bazi. 1984.Micronutrient status of crops in selected areas of Egypt. Communicationsin Soil Science & Plant Analysis. 15: 1175–1189.
El-Otmani, M. 1996. Tolerance of seedlings of six citrus rootstocks to high soilcalcium carbonate content. In: Proceedings of the International Societyof Citriculture, Vol. 1, eds. B. Manicom, J. Robinson, S. F. du Plessis, P.Joubert, J. L. Van Zyl and S. du Prez, pp. 290–295. Sun City, South Africa:International Society of Citriculture.
El-Otmani, M., F. Z. Taibi, C. J. Lovatt, and A. Ait-Oubahoce. 2002. Use offoliar urea on Clementine mandarin to manipulate cropping in sustainablecitrus production system. Acta Horticulturae 632: 149–157.
Epstein, E. 1972. Mineral Nutrition of Plants: Principles and Perspectives.New York: John Wiley & Sons.
Ercivan, S. 1974. Incidence of zinc deficiency on satsuma mandarin trees inIzmir. Journal of Turkish Phytopathology 3: 51–56.
Erner, Y., Y. Kaplan, B. Aryzi, and M. Hamou. 1993. Increasing citrus fruitsize using auxints and potassium. Acta Horticulturae 329: 112–119.
FAO. 2005. Citrus Fruit Fresh and Processed. Annual Statistics. Rome: FAO.Feinerman, T., and H. Voet. 1995. Dynamic optimization of nitrogen fertil-
ization of citrus and the value of information from leaf tissue analysis.European Review of Agricultural Economics 22: 103–118.
Ferguson, J. J., and F. S. Davies. 1989. Fertilization of young citrus. FactsheetNo. 79. Gainesville, FL: Florida Cooperative Extension Service, Universityof Florida.
Fernandez-Lopez, J. A., J. M. Lopez-Roca, and L. Almela. 1993. Mineralcomposition of iron chlorotic Citrus limon L. leaves. Journal of PlantNutrition 16: 1395–1407.
Fidalski, J., and P. A. M. Auler. 1997. Nutritional survey of orange plantationsin northwest Parana. Arquivos de Biologia e Tecnologia 40: 443–451.
Gallasch, P. T. 1992. The use of leaf analysis in Southern Australia to developmore efficient fertilizer programs. In: Proceedings of the International So-ciety of Citriculture, Vol. 2, eds. E. Tribulato, A. Gentile and G. Refergiato,pp. 560–563. Acireale, Italy: International Society of Citriculture.
Gallasch, P. T., and D. S. Dalton. 1989. Selecting salt tolerant rootstocks.Australian Journal of Agriculture Research 40: 137–144.
Garcia-Alvarez, N., M. E. Aspiolea, and C. G. Barreto. 1986. Effect of differ-ent zinc and manganese applications on valencia orange yield, economicevaluation. Centro Agricola 13(1): 24–32.
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
232 A. K. Srivastava and S. Singh
Garcia-Petillo, M. 2000. Fertigation versus conventional nitrogen fertilizationof valencia oranges. Agrociencia (Montevideo) 4(1): 23–30.
Germana, C. 1992. Increasing water use efficiency through irrigation manage-ment. In: Proceedings of the International Society of Citriculture, Vol. 2,eds. E. Tribulato, A. Gentile and G. Refergiato, pp. 638–642. Acireale,Italy: International Society of Citriculture.
Ghosh, S. P. 1985. Horticulture in Northeast India. New Delhi: AssociatePublishing Company.
Ghosh, S. P., and K. C. Besra. 1997. Growth, yield and physico-chemicalproperties of sweet orange cv ‘mosambi’ grown in response to organic andinorganic fertilizers under rainfed laterite soils. In: National Symposiumon Citriculture, eds. S. Singh, V. J. Shivankar and A. K. Srivastava, pp.40–44. Nagpur, India: Indian Society of Citiriculture.
Ghosh, S. P., and R. B. Singh. 1993. Citrus in South Asia. Bangkok: FAORegional Office Bangkok, Thailand.
Ghosh, S. P., A. N. Verma, and S. Govind. 1989. Nutritional requirementof bearing khasi mandarin orange (Citrus reticulata Blanco) trees inMeghalaya. Horticulture Journal 2(1): 4–11.
Goell, A. 1969. Salinity effects on citrus trees. In: Proceedings of the Inter-national Citrus Symposium, Vol. 3, ed. H.D. Chapman, pp. 1819–1824.Florida, USA: International Society of Citriculture.
Grieve, A. M., and R. R. Walker. 1983. Uptake and distribution of chloride,sodium and potassium ions in salt treated citrus plants. Australian Journalof Agriculture Research 34: 133–143.
Gupta, R. P., S. P. Pandey, and B. P. Tripathi. 1989. Soil properties and availabil-ity of nutrient element in mandarin growing areas of Dhankuta districts.PAC Technical Paper 113. Dhankuta, Nepal: Pokhbar Agricultural Centre.
Halse, N. J. 1963. Control of copper, zinc, and manganese deficiencies in fruittrees. Journal of Agriculture of Western Australia 4: 241–244.
Haque, A., and S. A. Godfrey. 1976. Nutritional survey of citrus orchardsin Sierra Leone. Communications in Soil Science & Plant Analysis 7:843–860.
Haq Izhar, U. I., A. Ghani, and Habibur-Ur-Rehman 1995. Nutritional statusof citrus orchards in NWFP and the effect of fertilizer application on fruitproduction. Technical Bulletin. 1/95. Tarnab, Pakistan: Directorate of Soiland Plant Nutrition, Agricultural Research Institute.
Harty, A., P. Sutton, and T. Machin. 1996. Clementine orange evaluation inNew Zealand. In: Proceedings of the International Society of Citriculture,Vol. 1, eds. B. Manicom, J. Robinson, S. F. du Plessis, P. Joubert, J. L.Van Zyl and S. du Prez, pp. 177–180. Sun City, South Africa: InternationalSociety of Citriculture.
Hassan, A. K. 1995. Effect of foliar sprays with some micronutrients on Wash-ington Navel orange trees. I. Tree growth and leaf mineral content. Annalsof Agricultural Sciences Moshtohor 33: 1497–1506.
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Citrus Decline: Soil Fertility and Plant Nutrition 233
He, S., L. Deng, T. Z. You, W. T. Long, and G. X. Huang. 1998. Preliminaryreport on using EDDHA-Fe for correcting the leaf yellowing disease ofcitrus grown on purple soil. South China Citrus 27(3): 18–19.
He, Z. L., D. V. Calvert, A. K. Alva, D. J. Banks, and Y. C. Li. 2003. Thresholdsof leaf nitrogen for optimum fruit production and quality of grapefruit. SoilScience Society of America Journal. 67: 583–588.
Hellin, E., R. Urena, F. Sevilla, J. L. Gimenez, and C. F. Alcaraz. 1988.Effects of several Fe-chelates on the iron leaf content of Verna lemontrees. In: Proceeding of 6th International Citrus Congress, Vol. 1, eds. R.Goren and K. Mendel, pp. 555–560. Rehevot, Isreal: Balaban Publishers,Rehevot.
Hernandez, M., I. Harnandez, A. Mesa, and I. Orteza. 1987. Effect of effectivesoil depth and stoniness on citrus yields in red ferrallitic soil. Agrotecniade Cuba 19: 75–79.
Hernando, V. 1969. Soil and leaf analysis of orange tree orchards on severaltypes of soils in Valencia province. In: Proceedings of the InternationalCitrus Symposium, Vol. 3, ed. H. D. Chapman, pp. 1673–1688. Florida,USA: International Society of Citriculture.
Hoffman, J. E., and R. A. Abercrombie. 1999. The effect of alleviating soilcompaction on yield and fruit size in an established navel orange orchard.Neltropika Bulletin 303: 59–63, 67.
Horesh, I., Y. Levy, and E. E. Goldschmidt. 1986. Prevention of lime inducedchlorosis in citrus trees by peat and iron treatments to small soil volumes.HortScience 21: 1363–1364.
Huang, R. Y. 1998. The green manure cultural techniques in hillside citrusorchards. South China Citrus 27(4): 22–23.
Huchche, A. D., M. S. Ladaniya, L. Ram, R. R. Kohli, and A. K. Srivastava.1998. Effect of nitrogenous fertilizers and farmyard manure on yieldand shelf-life of Nagpur mandarin. Indian Journal of Horticulture 55(2):108–112.
Janssen, B. H., F. C. T. Guiking, D. Vander Eijk, E. M. A. Smaling, J. Wolf, andH. Van Reuler. 1990. A system of quantitative evaluation of the fertility oftropical soils (QUEFTS). Geoderma 46: 299–318.
Jones, J. B. 1998. Plant Nutrition Manual. Boca Raton, FL: CRC Press.Kanwar, J. S., and J. S. Randhawa. 1960. Probable causes of chlorosis of citrus
in Punjab. Advances in Horticulture (P.A.U.) 4: 61–67.Kiely, T. 1957. Report on Decline Problem of Citrus in Lower Uva Valley and
Other Areas in Ceylon Colombo. Sri Lanka: Government of Ceylon, SriLanka.
Kim, J. C., S. M. Chung, and S. J. Kong. 1969. Studies on the nutritional statusof Korean citrus trees (Citrus unshiu Marc.) by means of leaf analysis.Research Report: Division of Agriculture Korea 12(2): 45–51.
Kimani, W. 1984. The influence of mineral nutrition on the severity of citrusgreening disease in Kenya. In: Proceedings of International Society of
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
234 A. K. Srivastava and S. Singh
Citriculture, Vol. 1, eds. H. W. S. Montenegro and C. S. Moreira, pp.172–173. Sao Paulo, Brazil: International Society of Citriculture.
Ko, K. D., and S. K. Kim. 1987. Chemical properties of soil and leaf mineralcontents in Cheju citrus orchards. Journal of Korean Society of HorticultureScience 28(1): 45–52.
Koga, H. 1972. Studies on the physical properties of the subsoil of satsumaorchards. Bulletin Shikou Agricultural Experimental Station, Kagawaken,Ishikoku, Japan 25: 119–232.
Kong-Tau, T. 1986. Physical properties of some main soil groups of Vietnam.Soviet Soil Science 18(4): 111–117.
Koo, R. C. J. 1979. The influence of N, K and irrigation on tree size andFred production of ‘Valencia Late’ orange. Proceedings of Florida StateHorticulture Society 92: 10–13.
Koo, R. C. J. 1980. Results of citrus fertigation studies. Proceedings of FloridaState Horticulture Society 92: 33–36.
Koo, R. C. J. 1982. Use of leaf, fruit and soil analysis in estimating potassiumstatus of orange trees. Proceedings of Florida State Horticulture Society75: 67–72.
Koo, R. C. J. 1984a. The importance of ground coverage by fertigation to citruson sandy soils. Journal of Fertilizer Issues 1(2): 75–78.
Koo, R. C. J. 1984b. Fertigation for citrus on sandy soil: ground coverage.Citrus & Vegetable Magazine 48(1): 10–11.
Koo, R. C. J., and A. M. McCornack. 1965. Effects of irrigation and fertilizationon production and quality of ‘Danci’ tangerine. Proceedings of FloridaState Horticulture Society 10: 10–15.
Koo, R. C. J., C. A. Anderson, I. Stewart, D. P. H. Tucker, P. V. Calvert, and H. K.Wutscher. 1984. Recommended fertilizers and nutritional sprays of citrus.Florida Agricultural Experimental Station Bulletin 536D:30. Gainesville,FL: University of Florida.
Koseoglu, A. T., N. Eryuce, and H. C. ColaKoglu. 1995. The effects of N, P,K fertilizers on fruit yield and quality of satsuma mandarin (Citrus unshiuMarc.). Acta Horticulturae. 379: 89–96.
Koudounas, C. 1994. Soil–citrus relationship studies in Cyprus. Acta Horticul-turae. 365: 147–150.
Kovanci, I., H. Hakerlerler, and W. Hofner. 1978. Causes of chlorosis of man-darin. Plant & Soil 50(1): 193–205.
Kozaki, I. 1981. Introduction to citriculture in Japan. In: Proceedings of theInternational Society of Citriculture, Vol. 1, eds. K. Matsumoto, C. Oogaki,I. Kozaki, K. Kadoya, F. Mizutani and E. Yuda, pp. 27–33. Tokyo, Japan:International Society of Citriculture.
Lal, R. 1976. Soil erosion on Alfisols in western Nigeria, I. Effect of slope,crop rotation and residue management. Geoderma 16: 363–375.
Lamb, S. T., W. D. Graham, C. B. Harrison, and A. K. Alva. 1999. Impactof alternative citrus management practices and groundwater nitrate in the
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Citrus Decline: Soil Fertility and Plant Nutrition 235
Central Florida ridge. Field investigation. Transactions of American Soci-ety of Agricultural Engineering 42: 1653–1668.
Larson, W. E., and F. J. Pierce. 1991. Conservation and enhancement of soilquality. In: Proceedings of International Workshop on Evaluation of Sus-tainable Land and Management in the Developing World 2: 175–203.
Lay, W. L., and C. T. Wang. 1997. The investigation of the nutrient diagnosisand its status of application in citrus production in central Taiwan. Bulletinof Taichung District Agricultural Improvement Station, China 54: 33–45.
Lee, R. F., L. J. Marais, L. W. Timmer, and J. H. Graham. 1984. Syringeinjection of water into the trunk. A rapid diagnostic test for citrus blight.Plant Disease 68: 511–513.
Legaz, F., M. D. Serna, and E. Primo-Millo. 1995. Mobilization of the reservedN in citrus. Plant & Soil 173: 205–210.
Legaz, F., R. Ibanez, P. G. DeBarreda, and E. Millo-Primo. 1981. Influenceof irrigation and fertilization on productivity of ‘Navelate’ sweet orange.Proc. Int. Soc. Citriculture. 2: 591–595.
Li, J., Q. Shi, and W. X. Zeng. 1998. Study on rational fertilizer applicationin citrus orchards in Fujian province by nutritional diagnosis. Journal ofFruit Science 15(2): 145–149.
Li, J. L., X. X. Li, J. C. Peng, and G. Q. Zhuang. 1999. Effect of five mineralelements on nutritional status of Navel orange tree. Journal of HunanAgriculture University 25(11): 36–39.
Lim, M., C. Mualsri, S. Suthipradit, W. Panthanahiran, and S. Lin. 1993.Nutrient element soil cultivation of neck orange. Keastsart Journal ofNatural Science 27: 412–420.
Lin, Z., and D. I. Myhre. 1991. Differential response of citrus rootstocks toaluminum levels in nutrient solutions. 1. Plant growth. Journal of PlantNutrition 14: 1223–1238.
Liu, Y. W. 1993. Study on the effect of satsumas of successive application oflime to a red soil orchard. China Citrus 22(1): 14–16.
Liu, C. M., and Q. Nan. 1996. Effect of Fe and Mn on photosynthesis physiologyof satsumas (Citrsu unshiu Marc.) and diagnosis of its nutritional status.Journal of Southwest Agriculture University 18(1): 29–33.
Liu, Y. W., M. S. Lin, and H. L. Qiu. 1994. Study of fertilizer satsumas. ChinaCitrus 23(2): 7–10.
Lou, M. Q., and P. Z. Yin. 1986. Analyses of causes for low yield of citrusorchards on beach land and effects of soil improvement on the yield.Journal of Zhejiang Agricultural Science 6: 270–275.
Lu, J., M. J. Wilson, and J. Yu. 1997. Effect of trench planting and soil chiselingon soil properties and citrus production in hilly Ultisols of China. SoilTillage 43(314): 309–318.
Luo, L. F., J. S. Zang, J.S. Me, and M. L. Wei. 1992. Yellow sweet clover-agood green manure crop for the citrus orchards. China Citrus 21(3): 37–42.
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
236 A. K. Srivastava and S. Singh
Maas, E. V. 1992. Salinity and citriculture. In: Proceedings of the InternationalSociety of Citriculture, eds. E. Tribulato, A. Gentile and G. Refergiato, Vol.3, pp. 1290–1301. Acireale, Italy: International Society of Citriculture.
Majorana, G. 1960. Symptoms of copper deficiency experimentally confirmedon sweet orange and mandarin trees in Catania province. Teen Agriculture12: 645–661.
Malewar, G. U., S. B. Varade, and N. S. Jadhav. 1983. Evaluation of nutritionalstatus of citrus orchards of Marathwada region (Maharashtra state) byleaf and soil analysis. In: Proceedings, International Citrus Symposium,pp. 14–21. Bangalore, India: Indian Institute of Horticultural Research.
Mattos, D. Jr., J. A. Quaggio, H. Cantarella, and A. K. Alva. 2003. Nutrientcontent of biomass components of Hamlin orange trees. Scientia Agricola60: 155–160.
McCall, W. W. 1965. Zinc deficiency of citrus in Thailand. Kasterast Journal5: 1–9.
Medvedev, V. V. 1990. Variability of the optimal soil density and its causes.Soviet Soil Science 22(7): 65–75.
Meng, C. F., M. F. Zhou, and J. S. Zhou. 1991. Effects of applying phosphorus,potassium fertilizers and lime in red soil orchards on yield and fruit qualityof Satsuma mandarin. China Citrus 20(4): 3–6.
Merlo, M. A. de los, M. S. Gonzales, N. L. Macial, S. De, and N. L. R. Pire. 1990.Study of the physical environment of a citrus orchard in the highlands ofYaracuy state Venezuela. Agronomia Tropical (Maracay) 40(1–3): 67–78.
Milad, S., H. K. Bakhati, M. El-Hakim, and F. B. Moutafa. 1975. The effect ofdifferent soil conditions upon citrus growth. Agriculture Research Review53(3): 31–40.
Moon, D. Y., H. M. Kwon, W. J. Lee, and S. B. Hong. 1980. Studies on thenutritional diagnosis of Jeju orchards by leaf analysis. Research Report,Office Rural Develop, Horticulture and Sericulture, Suwon, Korea.
Muldabaev, S. S., and Yu. I. Zaitsev. 1989. Mandarins in trenches. Subtropich-eskie Kul’tury 1: 80–82.
Nel, D. J. 1980. Infiltration problem in citrus orchard. Information Bulletin.Citrus and Subtropical Fruit Research Station 94: 10–12.
Nel, D. J., and A. T. P. Bennie. 1984. Soil factors affecting root growth and treedevelopment in a citrus orchard. South African Journal 1: 39–47.
Nemec, S. 1986. Soil environment and some biotic factors affecting citrusroot health. In: Proceedings 4th National Citrus Seminar Citrus Researchand Education Centre, pp. 24–33. Lake Alfred, FL: Citrus Research andEducation Center.
Nemec, S., and O. Lee. 1992. Effect of preplant deep tillage of soil amendmentson soil mineral analysis, citrus growth, production and tree health. SoilTillage Research 23: 317–331.
Nieves, M., A. Garcia, and A. Cerda. 1991a. Salt tolerance of two lemon scionsmeasured by leaf chloride and sodium accumulation. Journal of PlantNutrition 14: 623–636.
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Citrus Decline: Soil Fertility and Plant Nutrition 237
Nieves, M., A. Garcia, and A. Cerda. 1991b. Effect of salinity and rootstockon lemon fruit quality. Journal of Horticulture Science 66: 127–130.
Nilangekar, R. G., and V. K. Patil. 1982. Soil factors as related to citrus decline.Journal of Indian Society of Soil Science 30: 213–215.
Nunez-Moreno, J. H., and B. Valdez-Gascon,1994. Effect of soil conditionson orange tree. Communications in Soil Science & Plant Analysis 25:1747–1753.
Nyamapfene, K. 1984. Transmission electron microscopy and electron diffrac-tion studies on the clay fraction of three Zimbabwean Vertisols de-rived from basalt. Zimbabwe Journal of Agriculture Research 22: 111–117.
Nychas, A. E., and C. S. Kosmas. 1984. Phosphate adsorption by dark alkalineVertisols in Greece. Geoderma 32: 319–324.
Obreza, T. A. 1973. Program fertilization for establishment of orange trees.Agriculture Production 6: 546–552.
Obreza, T. A. 1990. Evaluation of citrus groveer fertility status using soil andleaf tissue testing. Proceedings of the Soil & Crop Science Society ofFlorida 49: 66–69.
Obreza, T. A. 2003. Prioritizing citrus nutrient management decisions. Univer-sity of Florida Cooperative Extension Service Bulletin. 199: 6.
Obreza, T. A., A. K. Alva, E. A. Hanlon, and R. E. Rouse. 1993. Citrus groveleaf tissue and soil testing: Sampling, analysis and interpretation. CitrusIndustry 4: 68–71.
Okada, N. 1994. Management of soil and nutrition in root zone control of veg-etables and fruit trees. 5. Root zone restriction culture of satsuma mandarinfor high quality fruit production. Japanese Journal of Soil Science & PlantNutrition 65: 206–214.
Orozco-Romero, J., and J. L. Sepulveda-Torres. 1981. Influences of nitrogen-phosphorus, potassium and timing of application on field of Mexican lime[Citrus aurantifolia (Christm) Swingle]. In: Proceedings of the Interna-tional Society of Citriculture, Vol. 2, eds. K. Matsumoto, C. Oogaki, I.Kozaki, K. Kadoya, F. Mizutani and E. Yuda, pp. 542–543. Tokyo, Japan:International Society of Citriculture.
Ozbek, N. 1969. The diagnosis of trace element deficiencies in orange orchardsin citrus areas according to visual symptoms, leaf and soil analysis. In: Pro-ceedings of the International Citrus Symposium, Vol. 3, ed. H. D. Chapman,pp. 1513–1514. Florida, USA: International Society of Citriculture.
Panzenhager, N. V., O. C. Koller, I. A. Sartori, and N. V. Porte-Linha. 1999.Montenegrina tangerine responses to liming to organic and mineral fertil-izers. Pesquisa Agropecuaria Brasileria 34: 527–533.
Paramasivam, S., A. K. Alva, T. A. Wheaton, J. P. Syvertsen, and D. P. H.Tucker. 2000. Critical leaf nutrient status for optimal fruit production underdiffering fertilizer management practices. In: Proceedings of the Inter-national Society of Citriculture, Vol. 1, pp. 437–439. Agadir, Morocco:International Society of Citriculture.
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
238 A. K. Srivastava and S. Singh
Parker, D. R., W. A. Norvell, and R. L. Chaney. 1995. GEOCHEM-PC: Achemical speciation program for IBM and compatible personal computers.In: Chemical Equilibrium and Reaction Models, eds. R. H. Loeppert, A.P. Schwab, and S. Goldberg, pp. 253–269. Madison, WI: SSSA, ASA.
Pavan, M. A., and H. K. Wutscher. 1993. Accumulation of nutrients at thesurface of roots of blight affected orange trees. Communications in SoilScience & Plant Analysis 24: 979–987.
Pedrera, B., I. Lambert, D. Oviedo, and A. Alfonso. 1988. Study of three ratesof application with bhaal P and K on Dancy mandarin in red ferrallitic soilII. Effects on growth, fruit quality and annual yield performance. Cienciay Tecnica en la Agricultura, Citricos y Otros Frutales 11(2): 17–28.
Penkov, M., A. Al-Alami, and D. Krhistova. 1979. Causes of chlorosis ofclementines grown in the Sous river valley in Morocco. Pochoznonic i.Agrokhimiya 14: 81–90.
Pennisi, L. 1975. Studies on the nutrient status of citrus in experimental fieldsin Sicily, Calabria and Brasilicata. Annali dell’ Instituto Sperimentale perAgrumicoltura 6: 323–337.
Pinto, M. R., and P. F. Leal. 1974. The nutritional status of some orange orchardsin the Valles Altos of Carabobo, Venezuela. Revista de la Facultad deAgronomia, Venezuela 8: 71–80.
Pisa, A. Di., and L. Fenech. 1990. Effects of different rates of nitrogen fertilizeron the yield and nutritional status of mandarins. Tecnica Agricola 42(1):113–126.
Qin, S., Y. Kelin, J. Tang, and S. He. 1996. Role of potassium preventing leafdrop and improving fruit yield and quality of lemon (Citrus limon Burm.).Journal of Southwest Agricultural University 18(1): 20–23.
Quaggio, J. A., H. Cantarella, and D. Mattos, Jr. 1996. Soil testing and leafanalysis in Brazil—recent developments. In: Proceedings of the Interna-tional Society of Citriculture, Vol. 2, eds. B. Manicom, J. Robinson, S. F.du Plessis, P. Joubert, J. L. Van Zyl and S. du Prez, pp. 1269–1275. SunCity, South Africa: International Society of Citriculture.
Quaggio, J. A., J. Teofilo Sobrinho, and A. R. Dechen 1992. Magnesiuminfluence on fruit yield and quality of Valencia sweet orange on Rangpurlime. In: Proceedings of the International Society of Citriculture, Vol. 2,eds. E. Tribulato, A. Gentile and G. Refergiato, pp. 633–637. Acireale,Italy: International Society of Citriculture.
Quaggio, J. A., S. M. Rosa, D. De. Mattos, Jr., and B. Van Ray. 1998. Responseof Valencia orange to lime and gypsum application. Laranja 19: 383–398.
Randhawa, N. S., D. R. Bhumbla, and D. R. Dhingra. 1967. Role of soil andplant composition in diagnosis of citrus decline in Punjab. Journal ofResearch (P.A.U.) Ludhiana 4: 16–24.
Rao, A. C. S. 1993. Diagnosis of nutrient deficiencies of citrus orange orchardsin Jiroff valley of Iran. Agrochimica 37: 41–54.
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Citrus Decline: Soil Fertility and Plant Nutrition 239
Razeto M. B., M. J. Lengueire, Z. S. Rojas, and M. G. Reginato. 1988. Cor-rection of manganese and zinc deficiencies in orange. Agricultura Tecnica48: 347–352.
Reddy Subbi, G., L. G. K. Naidu, and K. Anjaneyulu. 2003. Influence of soilnutrient mining on growth, yield and nutritional disorders in sweet orange(Citrus sinensis Osbeck) orchards. Journal of Citriculture 2(1): 8–11.
Rengaswamy, P., K. A. Olson, and J. M. Kirby. 1992. Sub soil constraints to rootgrowth and high soil water and nutrient use by plants. In: Proceedings ofNational Workshop. Tanunda, Australia: Department of Primary Industries,South Australia.
Resina, C., K. Chiriatti, D. Palazzo, F. Intrigliolo, and L. Conigtione. 1992.SEFEAG: An expert system for citrus fertilization. In: Proceedings of theInternational Society of Citriculture, Vol. 2, eds. E. Tribulato, A. Gentileand G. Refergiato, pp. 580–583. Acireale, Italy: International Society ofCitriculture.
Robinson, B. 1989. Development of soil acidity in Riverland and Sunraysiaorchards. Australian Citrus News 65(6): 18–19.
Robinson, J. B. 1977. Increased growth of young Valencia orange trees in soilamendment gypsum in south Australia. In: Proceedings of the Interna-tional Society of Citriculture, Vol. 1, ed. W. Grierson, pp. 31–33. Sydney,Australia: International Society of Citriculture.
Rodriguez, O. 1985. Soil and its importance in orchard productivity. In: Proc. IstSymposium on Citrus Productivity, pp. 3–11. Jabeticabal, Brazil: UNESP.
Rossetti, V., M. J. G. Berretta, and M. Julia. 1990. Decline of cit-rus trees in Brazil—A review. In: Proceedings of the Interna-tional Citrus Symposium, eds. H. Bangyan and Y. Qian, pp. 687–692. Guangzhou China: International Academic Publishers.
Saatci, N., and B. Y. Mur. 2000. Relationships between concentration of iron,macro and micronutrients in satsuma mandarin leaves (Citrus unshiu.Macf.). Journal of Plant Nutrition 23: 1745–1750.
Sagee, O., D. Hasdai, M. Hamou, and A. Shaked. 1992. Screen house eval-uation of new citrus rootstock for tolerance to adverse soil conditions.In: Proceedings of the International Society of Citriculture, Vol. 1, eds.E. Tribulato, A. Gentile and G. Refergiato, pp. 299–303. Acireale, Italy:International Society of Citriculture.
Salem, S. E., T. A. Ibrahim, L. F. Gudy, and M. Myhod. 1995. Response ofBalady mandarin trees to foliar application of iron, zinc, manganese andurea under sandy soil. Bulletin of Faculty of Horticulture, University ofCairo 46(2): 277–288.
Sanchez, A., A. Rosales, and L. Bascones. 1998. Land evaluation for theorange crop. II. Soil suitability for orange production as a function of soilclassification. Agronomid Tropical 38: 85–96.
San Lio, M. D., G. G. Perrotta, S. O. Cacciola, and R. Tuttobene. 1988. Fac-tors affecting soil populations of Phytophthora in citrus orchards. In:
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
240 A. K. Srivastava and S. Singh
Proceedings of the Sixth International Citrus Congress, Vol. 2, eds. R.Goren and K. Mendel, pp. 767–774. Rehevot, Israel: International Societyof Citriculture.
Santinoni, L. A., and N. R. Silva. 1995. Growth, yield and maturation of com-mon mandarin under different soil management practices. HorticulturaArgentina 14(36): 5–11.
Sautoy, N. D. 1992. Field trial evaluation of Valencia fruiting terminals leaf P,K, and Mg norms for a low base status loamy sand. In: Proceedings of theInternational Society of Citriculture, eds. E. Tribulato, A. Gentile and G.Refergiato, Vol. 2, pp. 547–555. Acireale, Italy: International Society ofCitriculture.
Schumann, A. W., A. Fares, A. K. Alva, and S. Paramasivam. 2003. Responseof ‘Hamlin’ orange to fertilizer source, annual rate and irrigated area.Proceedings of Florida State Horticulture Society 116: 256–260.
Shaked, A., and S. Ashkenazy. 1984. Single citrumelo as a new citrus rootstockin Israel. In: Proceedings of International Society of Citriculture, Vol. 1,eds. H. W.S. Montenegro and C.S. Moreira, pp. 48–50. Sao Paulo, Brazil:International Society of Citriculture.
Shaked, A., A. Goell, and M. Hamou. 1988. Screening citrus rootstocks androotstock scion combinations for tolerance to calcareous soils. In: Proceed-ings of the Sixth International Citrus Congress, Vol. 1, eds. R. Goren and K.Mendel, pp. 83–86. Rehevot, Israel: International Society of Citriculture.
Shannon, M. C. 1979. In quest of rapid screening techniques for plant salttolerance. HortScience 14: 587–589.
Sharma, B. K., and N. Singh. 2001. Characteristics and properties of soils undertwo dominant land use systems in western Rajasthan. Journal of IndianSociety of Soil Science 49: 373–377.
Sharma, Y. M., G. S. Rathore, and J. C. Jesani. 1999. Effect of soil and fo-liar application of zinc and copper on yield and fruit quality of seedlesslemon (Citrus limon). Indian Journal of Agricultural Science 69: 236–238.
Sharma, S. C., N. K. Mehrotra, M. R. Gupta, and H. Singh. 1993. Game theoryapproach to nutritional trial on sweet orange (Citrus sinensis Osbeck).Punjab Horticulture Journal 30: 9–12.
Shawky, I., I. Desouky, A. El-Tomi, and M. A. Mohamed. 1980. Effect of pHon the growth and mineral content of some rootstock seedlings. EgyptianJournal of Horticulture 7(1): 19–31.
Shih, S. F., D. L. Myhre, G. W. Schellentrager, V. W. Carlisle, and J. A. Doolittle.1986. Using radar to assess the soil characteristics related to citrus stress.Proceedings of the Soil & Crop Science Society of Florida 45: 54–59.
Shimogori, Y., M. Wada, and H. Hatano. 1980. Soil management on satsumamandarin orchard derived from volcanic ash soil on the growth and fruityield. In: Bulletin 33, pp. 61–72. Miyazaki Japan: Miyazaki AgriculturalExperimental Station.
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Citrus Decline: Soil Fertility and Plant Nutrition 241
Shishov, L. L., and M. P. Kapshuk. 1984. Soil conditions on irrigated citrusplantations in the Libyan arid zone. Problems of Desert Development 1:39–45.
Shirgure, P. S., A. K. Srivastava, and S. Singh. 2001a. Growth, yield and qualityof Nagpur mandarin (Citrus reticulata Blanco) in relation to irrigation andfertigation. Indian Journal of Agriculture Science 71(8): 547–550.
Shirgure, P. S., A. K. Srivastava, and S. Singh. 2001b. Effect of nitrogenfertigation and band placement fertilizer application in soil-leaf nutrientbuild-up and incremental growth of acid lime. Journal of Soil and WaterConservation 45(3–4): 176–181.
Shirgure, P. S., A. K. Srivastava, and S. Singh. 2001c. Effect of drip, microjetsand basin irrigation method on growth, soil and leaf nutrient change inacid lime. Indian Journal of Soil Conservation 29: 229–234.
Shirgure, P. S., A. K. Srivastava, and S. Singh. 2003. Evaluating micro-irrigationsystems in Nagpur mandarin (Citrus reticulata Blanco) under sub-humidtropical climate. Tropical Agriculture 80: 91–96.
Singer, A., K. Willem, and C. Buhmann. 1995. Fibrous clay minerals in the soilsof Namaqualand, South Africa: Characteristics and formation. Geoderama66: 43–70.
Singh, O. P., and B. Dutta. 1983. Characteristics of some hill soils of Mizoram inrelation to altitude. Journal of Indian Society of Soil Science 31: 657–661.
Singh, S., A. K. Srivastava, and A. D. Huchche. 1999. Citrus flowering. In:Technical Bulletin 4, pp. 1–144. Nagpur, India: National Research Centrefor Citrus.
Singh, A. R., V. N. Maurya, N. C. Pande, and R. S. Rajput. 1989. Role of potashand zinc on the biochemical parameters of Kagzi lime (Citrus aurantifoliaSwingle). Haryana Journal Horticultural Science 18: 46–50.
Singh, A., A. K. Srivastava, H. C. Dass, and N. Vijayakumari. 1997. Screeninggermplasm of citrus rootstocks for salinity tolerance. Indian Journal ofHorticulture 55: 283–287.
Smith, P. F. 1966. Citrus nutrition. In: Temperate to Tropical Fruit Nutrition,ed. N. F. Childers, pp. 208–228. New Brunswick, NJ: Rutgers University.
Srivastava, A. K., and L. Ram. 2000. Irrigation water quality of Nagpur man-darin orchards in central India. Indian Journal of Agriculture Sciences 70:679–681.
Srivastava, A. K., and S. Singh. 2001a. Soil properties influencing yield andquality of Nagpur mandarin (Citrus reticulata Blanco). Journal of IndianSociety of Soil Science 49(1): 226–229.
Srivastava, A. K. and S. Singh. 2001b. Soil fertility limit in relation to optimumyield of Nagpur mandarin (Citrus reticulata Blanco). Journal of IndianSociety of Soil Science 49: 758–762.
Srivastava, A. K., and S. Singh. 2002. Soil analysis based diagnostic norms forIndian citrus cultivar. Communications in Soil Science & Plant Analysis33: 1689–1706.
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
242 A. K. Srivastava and S. Singh
Srivastava, A. K., and S. Singh. 2003. Diagnostics of citrus nutrition. In: CitrusNutrition, pp. 237–285. Lucknow, India: International Book DistributionCompany.
Srivastava, A. K., and S. Singh. 2004a. Soil and plant nutritional constraintscontributing to citrus decline in Marathawada region, India. Communica-tions in Soil Science & Plant Analysis 35: 2537–2550.
Srivastava, A. K., and S. Singh. 2004b. Nutrient diagnostic and management incitrus. Technical Bulletin 8. Nagpur, Maharashtra, India: National ResearchCentre for Citrus.
Srivastava, A. K., and S. Singh. 2005. Zinc nutrition, a global concern forsustainable citrus production. Journal of Sustainable Agriculture 25(3):5–42.
Srivastava, A. K., and S. Singh. 2006. Diagnosis of nutrient constraints in citrusorchards of humid tropical India. Journal of Plant Nutrition 29: 1061–1076.
Srivastava, A. K., S. Singh, and K. N. Tiwari. 2006. Site specific nutrientmanagement in Nagpur mandarin (Citrus reticulata Blanco). Better Crops90(2): 22–24.
Srivastava, A. K., S. Singh, A. D. Huchche, and L. Ram. 2001. Yield basedleaf and soil test interpretations for Nagpur mandarin in Central In-dia. Communications in Soil Science & Plant Analysis USA 32: 585–599.
Swartz, R. E., T. Arguelles, P. Monsted, H. Wutscher, and L. Termachuka. 1980.Studies on the cause of fruta bolita or declinamiento diseases of citrusin Argentina. In: Proceedings of the Eight International Organization ofCitrus Virologists, eds. E. C. Calvan, S. M. Garnsey, and L. W. Timmer,pp. 241–250. Riverside, CA: University of California.
Swietlik, D. 1996. Responses of citrus trees in Texas to foliar and soil Znapplications. In: Proceedings of the International Society of Citriculture,eds. B. Manicom, J. Robinson, S. F. du Plessis, P. Joubert, J. L. Van Zyland S. du Prez, Vol. 2, pp. 772–776. Sun City, South Africa: InternationalSociety of Citriculture.
Swietlik, D., and L. Zhang. 1994. Critical Zn2+ activities for sour orangedetermined with chelator buffered nutrient solutions. Journal of AmericanSociety of Horticulture Science 119: 693–701.
Syvertsen, J. P., and J. L. Jifon 2001. Frequent fertigation does not affect treegrowth, fruit yield, nitrogen uptake, and leaching losses. Proceedings ofFlorida State Horticulture Society 114: 88–93.
Syvertsen, J. P., N. G. Bausher, and L. G. Albrigo. 1980. Water relationsand related leaf characteristics of healthy and blight-affected citrus trees.Journal of American Society of Horticulture Science 105: 431–434.
Tachibana, S., and S. Yahata. 1996. Optimizing nitrogen fertilizer applicationfor a high density planting satsuma mandarin. Journal of Japanese Societyof Horticulture Science 65: 471–477.
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Citrus Decline: Soil Fertility and Plant Nutrition 243
Takatsuji, T., and M. Ishihara. 1980. Studies on the potassium nutrition ofsatsuma III. Influence of cold hardiness and leaf composition. BulletinNo. 7, pp. 45–62. Ibaraki, Japan: Fruit Tree Research Station (Yatabe).
Tavdgiridze, G. H., and A. S. Putkaradre. 1991. Effect of nitrogen fertilizertype on polarity coefficient of mandarin trees. Subtropicheskie Kul’tury 4:66–67.
Tiwari, K. N. 2002. Site specific nutrient management for high yield andquality of fruit crops. In: Proc. Workshop: Nutrient Status, Needs andRecommendations for Major Fruit Crops, pp. 105–111. Gurgaon, India:International Plant Nutrition Institute, India Programme.
Tiwari, U. S., S. B. Raijadhav, D. D. Jagtap, and C. V. Pujari. 1997. Effectof organic an inorganic fertilizers on yield and quality of sweet orange(Citrus sinensis Osbeck). Abstract presented at National Symposium onCitriculture, Nagpur, India.
Tripathi, B. P., and A. H. Harding 2001. Nutrient status of mandarin treesin some mandarin growing pockets of Lamzung and Gorkha districts ofNepal. Journal of Indian Society of Soil Science 49: 503–506.
Tucker, D. P. H, A. K. Alva, L. K. Jackson, and T. A. Wheaton. 1995. Nutritionof Florida Citrus Trees. SP 169. Gainesville, FL: University of FloridaCoop. Ext. Service, Gainesville, Florida.
Van Zyl, J. L., and L. Van Huyssteen. 1987. Root pruning. Deciduous FruitGrower 2: 20–25.
Veregara, I., B. E. Schalscha, I. Ruiz, and E. F. Wallihan. 1973. Nutritionalstatus of representative citrus orchards in Chile as evaluated by leaf andsoil analysis. HortScience 8: 325–326.
Vinay, S., and B. R. Tripathi. 1985. Studies on chlorosis in sweet orange inAgra region of Uttar Pradesh. Journal of Indian Society Soil Science 33:333–338.
Wada, M., Y. Shimogoori, and H. Hatano. 1981. Behavior of surface appliedcations in the soil of a satsuma mandarin orchard. In: Proceedings of theInternational Society of Citriculture, eds. K. Matsumoto, C. Oogaki, I.Kozaki, K. Kadoya, F. Mizutani and E. Yuda, Vol. 2, pp. 544–548. Tokyo,Japan: International Society of Citriculture.
Wang, G. C. 1999. Cultural techniques for high quality production of Jiaoganmandarin cultivar in mountainous orchard. South China Citrus 28: 9–10.
Wang, X., and Z. Gong. 1998. Assessment and analysis of soil quality changesafter eleven years of reclamation of sub-tropical China. Geoderma 81:339–355.
Weinert, T. A., T. A. Thompson, S. A. White, and M. A. Maner. 2002. Nitrogenfertigation of young Navel orange: Growth, N status and uptake of fertilizerN. HortScience 37: 334–337.
Weir, C. C. 1969. Investigation on the mineral nutrition of citrus in Caribbeanarea. Technical Bulletin. No. 2, p. 69. West Indies: Citrus Research Unit,University of the West Indies, West Indies.
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
244 A. K. Srivastava and S. Singh
Weir, C. C. 1971. Correction of magnesium deficiency of citrus trees in theCaribbean area. Tropical Agriculture 48: 351–356.
Willis, L. E., F. L. Davies, and D. A. Graetz. 1991. Fertigation and growth ofyoung Hamlin orange trees in Florida. HortScience 26: 106–109.
Woods, D. B., and J. M. DeVilliers. 1992. Diagnosing the nutrient status ofValencia oranges in southern Africa. In: Proceedings of the InternationalSociety of Citriculture, eds. E. Tribulato, A. Gentile and G. Refergiato,Vol. 2, pp. 556–559. Acireale, Italy: International Society of Citriculture.
Wutscher, H. K. 1989. Soil pH and extractable elements under blight affectedand healthy citrus trees on six Florida soils. Journal of American Societyof Horticulture Science 114: 611–614.
Wutscher, H. K., and C. A. Hardesty. 1981. Seasonal levels of water extractablecations and anions in soil under blight affected and healthy citrus trees.Communications in Soil Science & Plant Analysis 14: 719–731.
Wutscher, H. K., N. Del Valle, and A. De Bernard. 1983. Citrus blight andwood pH in Cuba and Florida. HortScience 18: 486–488.
Wutscher, H. K., P. F. Smith, and F. Bistline. 1982a. Zinc accumulation in trunkwood, water extractable ions in the soil and development of symptoms ofcitrus blight. Citrus & Vegetable Magazine 63: 22, 24, 26, 28.
Wutscher, H. K., P. F. Smith, and F. Bistline. 1982b. Zinc accumulation inthe trunk wood and the development of visual symptoms of citrus blight.HortScience 17: 676–677.
Wutscher, H. K., H. G. Campligia, C. Hardesty, and A. A. Salibe. 1977. Similar-ities between Marchitamientto repentio diseases in Uruguay and Argentinaand blight of citrus in Florida. Proceedings of Florida State HorticultureSociety 90: 81–84.
Xong, W., and C. Zhu. 1997. Some key cultural practices for growing Newhalland Skaggs Bonanza Navel orange. South China Fruits 26: 25–31.
Yaalon, D. H. 1957. Problems of soil testing in calcareous soils. Plant & Soil8: 275–277.
Yin, K. L., Y. G. Li, C. Q. Wang, and S. L. Wang. 1998. Specifically prescribedfertilization for citrus trees and the principle component of analysis of foliarFe and Zn and other nutrient elements. Journal of Southwest AgricultureUniversities 20: 1989–1992.
Young, R. H., H. K. Wutscher, and L. G. Albrigo. 1980. Relationship betweenwater translocation and zinc accumulation in citrus trees with and withoutblight. Journal of American Society of Horticultural Science 105: 444–447.
Yuda, E. 1985. Growth retardation of satsuma mandarin (Citrus unshiu Marc.)in acid soils and preventive measures. Japanese Journal of AgricultureResearch 18: 202–208.
Zaman, Q. U., A. W. Schumann, and W. M. Miller. 2005. Variable rate nitro-gen application in Florida citrus based on ultrasonically-sensed tree size.Applied Engineering in Agriculture 21: 331–335.
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
Citrus Decline: Soil Fertility and Plant Nutrition 245
Zekri, M., and L. R. Parsons. 1990. Calcium influences growth and leaf mineralconcentration of citrus under saline conditions. HortScience 25: 784–786.
Zhang, M., A. K. Alva, and Y.C. Li. 1998. Fertilizer rates change root distribu-tion of grapefruit trees on a poorly drained soil. Journal of Plant Nutrition21: 1–11.
Zhang, M., A. K. Alva, Y. C. Li, and C. V. Calvert. 1996. Root distributionof grapefruit trees under dry granular broadcast versus fertigation method.Plant & Soil 183: 79–84.
Zhang, M., A. K. Alva, Y. C. Li, and D.V. Calvert. 1997. Chemical associationof Cu, Zn, Mn and Pb in selected sandy soils. Soil Science 162: 189–192.
Zhou, B., and A. K. Alva. 1993. Distribution of trace metals in some sandysoils under citrus production. Soil Science Society of America Journal 57:350–355.
Zhou, X. W., B. Lu, Z. Y. Li, X. N. Chen, C. F. Cheng, and F. Keyong. 1996.Nutrient characteristics of sweet orange (Citrus sinensis cv. ‘Jinching’)and the technique of fertilization. Journal of Fruit Science 13: 162–166.
Zude, M., A. Alexander, and P. Ludders. 1999. Influenced of Fe-EDDHA andsugar acid derivatives on curing iron chlorosis in citrus. Gesnude Pflanzen51: 125–129.
Dow
nloa
ded
by [
Nip
issi
ng U
nive
rsity
] at
02:
40 1
7 O
ctob
er 2
014
