study of soil fertility and plant nutrition of proteas cultivated under subtropical conditions
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This article was downloaded by: [Temple University Libraries]On: 23 November 2014, At: 18:59Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,UK
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Study of Soil Fertility and PlantNutrition of Proteas Cultivatedunder Subtropical ConditionsMercedes Hernández a , Marino Fernández‐Falcón a
& Carlos E. Alvarez aa Departamento de Agrobiología y Medio Ambiente ,Instituto de Productos Naturales y Agrobiología –CSIC , La Laguna, Tenerife, SpainPublished online: 26 Aug 2008.
To cite this article: Mercedes Hernández , Marino Fernández‐Falcón & Carlos E.Alvarez (2008) Study of Soil Fertility and Plant Nutrition of Proteas Cultivated underSubtropical Conditions, Communications in Soil Science and Plant Analysis, 39:13-14,2146-2168, DOI: 10.1080/00103620802135427
To link to this article: http://dx.doi.org/10.1080/00103620802135427
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Study of Soil Fertility and Plant Nutrition of ProteasCultivated under Subtropical Conditions
Mercedes Hernandez, Marino Fernandez-Falcon, and Carlos E. Alvarez
Departamento de Agrobiologıa y Medio Ambiente, Instituto de Productos
Naturales y Agrobiologıa – CSIC, La Laguna, Tenerife, Spain
Abstract: A study of soil physicochemical characteristics and mineral nutrition of
four cultivars of Leucospermum cordifolium (‘Scarlett Ribbon,’ ‘High Gold,’
‘Veldifre,’ ‘Sunrise’) and Leucospermum patersonii species was carried out along 2
years in commercial protea plantations, distributed throughout a subtropical
region (La Palma Island, Canarian Archipelago). Soils presented a slightly acid
pH range, whereas organic matter showed suitable values. Generally, available
soil phosphorus (P) contents were less than 25 mg kg21, with high available
potassium (K) and calcium (Ca) levels, though the ratio of Ca of the sum of
available cations was usually appropriate. Despite the high electrical conductivity
(EC) levels (4.31–8.87 dS m21) determined in some soils, no salinity symptoms
were ever detected. Distribution and behavior of foliar nutrients nitrogen (N), P,
K, Ca, magnesium (Mg), and sodium (Na) along time showed that nutritional
needs varied in some cases among cultivars and species. L. patersonii presented
the least N concentration, whereas ‘High Gold’ and ‘Veldfire’ had the greatest
levels. Data denoted that P requirements were larger in younger plants, during the
recovery after pruning, and while new buds developed. ‘Sunrise’ cultivar stood
out for its large foliar levels of P, whereas ‘Scarlett Ribbon’ and ‘Veldfire’ had the
least K contents. As a general pattern, K decreased in winter samplings. L.
patersonii species and the cultivar ‘Sunrise’ exhibited the highest Ca values, and
the same was true for Mg only in the species. A special need for Na appeared in
all the cultivars and species studied. L. patersonii and the cultivar ‘Sunrise’
showed the greatest Na levels. A general stabilization of nutrient concentrations
Received 27 February 2007, Accepted 22 October 2007
Address correspondence to Carlos E. Alvarez, Departamento de Agrobiologıa
y Medio Ambiente, Instituto de Productos Naturales y Agrobiologıa – CSIC,
Apartado de correos, s/n, 38200 La Laguna, Tenerife, Spain. E-mail: carlose@
ipna.csic.es
Communications in Soil Science and Plant Analysis, 39: 2146–2168, 2008
Copyright # Taylor & Francis Group, LLC
ISSN 0010-3624 print/1532-2416 online
DOI: 10.1080/00103620802135427
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was observed in the fourth, fifth, and/or sixth samplings, so that November is
recommended for taking samples for current foliar analysis. In this context, foliar
ranges for the studied nutrients are suggested.
Keywords: Nutrient foliar ranges, nutrition, protea, sampling time, soil fertility
INTRODUCTION
Proteas grow normally on leached, acidic soils, which are poor in availableminerals (Thomas 1974; Meynhardt 1976; Silber, Neumann, and Ben-
Jaacov 1998). Soil texture plays an important role in protea development.
Vogts (1979) and Claassens (1981) indicated that clay soils should be
avoided, because they tend to become waterlogged as a result of their low
permeability. Montarone (2001) stressed that the preferred soils for these
crops are sandy with less than 20 g kg21 clay and less than 40 g kg21 silt.
Regarding pH, Thomas (1974) reported that many protea plants
prefer acid soils. On the other hand, Claassens (1981) stated that manyprotea cultivars prosper on a wide pH range, with most species growing
well between 5.5 and 7.0. This author also reported that proteas are
occasionally found on calcareous soils with a considerably higher pH.
Silber, Mitchnick, and Ben-Jaacov (2001) stressed that pH affects root
development and indirectly affects nutrient availability and ion uptake.
As far as organic matter is concerned, Witkowski (1989) reported
levels around 8.7 mg kg21, both in the field and in greenhouses, lowerthan the normal levels of horticultural crops (Maier and Robinson 1996).
The requirements of phosphorus (P) differs depending on species and
genera of family Proteaceae (Thomas 1980; Handreck 1991; Montarone
and Ziegler 1996), as well as their sensitivity to high P concentration in
the soil (Buining and Cresswell 1993). Phosphorus concentration in the
rhizosphere affects development of the root system (Silber, Neumann, and
Ben-Jaacov 1998), involving the formation of proteoid roots that, inaccordance with Jeffrey (1967), is the response of the plant to the low level
of P. Contrarily, Lamont (1972) reported that an increase in P nutrition is
accompanied by an increase in the production of proteoid roots. Toxicity
symptoms, such as growth reduction and leaf necrosis in the presence of
high P concentration, have been described in numerous plants of the
Proteaceae (Goodwin 1983; Prasad and Dennis 1986). Nichols (1983)
classified Leucospermum cordifolium as highly susceptible to P, indicating
toxicity values based on concentrations of available P greater than 15 mgkg21, although Parvin (1986) gave values of up to 25 mg kg21. In Israel,
protea cultivation has been restricted to soils with less than 15 mg kg21 of P
(Silber, Neumann, and Ben-Jaacov 1998). Jamienson (1985) recommended
a maximum level of P of 30 mg kg21 for proteas, with the exception of
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Leucadendron ‘Safari Sunset,’ which can withstand concentrations up to
45 mg kg21. However, Maier et al. (1995) found that large concentrations
of P (up to 64 mg kg21) could not be related to low production.
Usually proteas are tolerant to low N levels in soils (Van Standen
1967), and some species prefer ammonia (NH3)–nitrogen (N) (Claassens
1986). As far as available cations are concerned, Jamienson (1985)
recommended soil calcium (Ca) values less than 6.2 cmol kg21 and
potassium (K) levels less than 1.0 cmol kg21, whereas concentrations of
magnesium (Mg) should be less than 1.2 cmol kg21. Parvin (1986)
reported K values between 1.4 and 2.5 cmol kg21 for Banksia, 1.2 cmol/
kg for Leucospermum, and between 0.9 and 2.7 cmol kg21 for Protea. In
this regard, Cecil et al. (1995) and Maier et al. (1995) confirmed small K
requirements for optimum growth of protea plants.
As far as salts are concerned, Vogts (1982) considered proteas to be
glycophytic (salt-sensitive) because protea plants absorb salts to a
harmful degree. In contrast, Walters, Jooste, and Raitt (1991) stated
that several species thrive in soils with similar sodium (Na) contents to
those observed in halophytic (salt-tolerant) plants. Claassens (1981)
suggested that many species of proteas can tolerate relatively high salt
concentrations, providing that the levels of nutrients such as nitrates and
phosphates are not overly great. Rodrıguez Perez, Fernandez Falcon, and
Socorro Monzon (2000) reported that Protea obtusifolia is moderately
tolerant to salts, indicating that the thresholds for electrical conductivity
of irrigation water and saturated soil extract for dry-matter production
were 2.7 and 6.0 dS m21, respectively, and that Leucospermum
cordifolium can be considered to be moderately sensitive to salinity,
establishing thresholds in this regard at 1.5 and 1.9 dS m21 (Rodrıguez
Perez, Fernandez Falcon, and Socorro Monzon 2001).
Large differences in nutrient content between genera as well as
between cultivars and species within genera have been reported (Classens
1986; Montarone 2001). Montarone et al. (2003) studied the nutritional
requirements of the genera Protea and Leucospermum and found that the
genus Leucospermum absorbs twice as many minerals as the genus
Protea. ‘High Gold’ and ‘Succession’ cultivars demanded much K, with a
K/N ratio of 1.6, whereas in Protea this ratio was near to 1. The genus
Leucospermum, and specifically L. candicans, withstands greater P levels
than genera Banksia, Leucadendron, Protea, and Telopea (Thomas 1980).
On the other hand, several authors have reported P toxicities (Nichols
1983; Prasad and Dennis 1986). Prasad and Dennis (1986) and
Montarone (2001) have emphasized the limited information that exists
on nutrition requirements of these plants.
The development of this culture in a subtropical region (La Palma
Island, Canarian Archipelago) is mainly based on the genus
Leucospermum. Among them, L. cordifolium (‘Scarlett Ribbon,’ ‘High
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Gold,’ ‘Veldifre,’ ‘Sunrise’) and the species L. patersonii are some of the
most promising. The objective of this article is to study macronutrient
distribution in soils and leaves of those cultivars and species along time,
grown in commercial plantations, as well as to suggest foliar ranges and
sampling time for the studied nutrients.
MATERIALS AND METHODS
The study of the cultivars ‘Scarlett Ribbon,’ ‘High Gold,’ ‘Veldfire,’ and
‘Sunrise’ of Leucospermum cordifolium, and of the species L. patersonii,
was carried out in commercial plantations located in eight municipalities
of La Palma (Canary Islands), distributed around the island. Soils were
Inceptisols Andepts and an Ultisol Udult.
Soil Sampling and Analysis
Soil samples were collected in May and November, 2002 and 2003, at a
depth of 0 to 20 cm with an Eijkelkamp soil sampler. These sample times
coincided with the vegetative growth period beginning after pruning and
the beginning of blossom. Three replications were taken from every farm
sampled, each one consisting of a composite sample of five subsamples.
The samples were air dried and passed through a 2-mm mesh. The pH
was measured in water in a ratio of 2:5, shaken, and allowed to settle for
10 min. Organic matter was determined by the Walkley and Black
method as modified by the Comision de Metodos Analıticos del Instituto
de Edafologıa y Agrobiologıa ‘‘Jose M. Albareda’’ (1973).
Available cations were extracted with an ammonium acetate 1 M
solution at pH 7 and determined by inductively coupled plasma (ICP;
Perkin-Elmer, Waltham, Mass.). Available phosphorus (P) was extracted
by the Olsen et al. (1954) method and determined by the Watanabe and
Olsen (1965) method.
Electrical conductivity (EC) was measured in the saturated soil
extract, and texture was determined by the Bouyoucos method (Lopez
and Lopez 1990).
Plant Samplings and Analysis
Five foliar samplings were carried out along the cultivation cycle (12
months long) during 2 years. The first one was in May 2003, which
coincided with the beginning of the vegetative growth period of the plants (2
months after pruning). The sampled leaves were the last fully developed
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ones (Jones, Wolf, and Mills 1991), which usually matched with the fourth
or fifth leaf counting from the apex. Three replications were taken from
every cultivar and species in each plantation. Each replication consisted of a
composite sample of leaves from 15 plants that were chosen at random.
The samples were washed in distilled water and dried in an oven at 80 uC,
after which they were ground to powder. One gram of the powder was ashed
in an oven at 480 uC and then mineralized by dry ashing with 6 M hydrochloric
acid (Chapman and Pratt 1961). The levels of Ca, Mg, Na, and K cations were
determined by ICP. Phosphorous was determined by colorimetry according to
the vanadate–molybdate method (Chapman and Pratt 1961). Nitrogen was
determined by the Kjeldahl method (Cottenie 1980).
Statistical Analysis
Data were subjected to one-way variance analysis, correlation, linear
regression, time series analysis, and chi-square test by Statgraphics Sgwin
4.0 software (Statgraphics, 1999). Foliar reference levels consisted of a
range determined by adding and subtracting the standard deviation to the
mean of each nutrient concentration.
RESULTS AND DISCUSSION
Soils
Data of the physical analysis of soils are shown in Table 1, and the
chemical properties are reported in Tables 2 to 7.
Texture
Several plantations had compensated soil texture (sandy clay loam), but
some soils showed high clay contents (Table 1) that are not recommended
for proteas (Vogts 1979; Claassens 1981; Montarone 2001). Nevertheless,
good growth and productions were observed in most plantations,
probably due to their organic-matter content, which improved protea
growth conditions.
pH
Most soils presented slightly acid pH range (Tables 2–6), which is in
agreement with pH reported by other authors (Witkowski 1989; Cecil
et al. 1995; Maier et al. 1995). According to Claassen (1981) and
Montarone (2001), proteas adapt easily to this pH range.
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Organic Matter
The values of organic matter (OM) were acceptable (between 20 and
50 g kg21) in the greater part of the soils where ‘Scarlett Ribbon,’
‘High Gold,’ and ‘Sunrise’ were cultivated. Farms with less than 20 g
Table 1. Texture of the soils of the plantations where the studied proteas were
grown
‘Scarlett
Ribbon’ ‘High Gold’ ‘Veldfire’ ‘Patersonii’ ‘Sunrise’
Farm Texture Farm Texture Farm Texture Farm Texture Farm Texture
1 Sandy
clay
loam
2 Sandy
clay
loam
3 Sandy
clay
loam
4 Sandy
clay
loam
9 Clay
9 Clay 4 Sandy
clay
loam
4 Sandy
clay
loam
6 Sandy
clay
11 Clay
12 Clay 8 Clay 5 Sandy
clay
loam
7 Sandy
clay
loam
16 Sandy
clay
loam
13 Clay 9 Clay 15 Clay 10 Sandy
clay
loam
17 Clay
14 Clay 13 Clay 19 Sandy
loam
19 Sandy
clay
loam
18 Clay
15 Clay 15 Clay 21 Clay 20 Sandy
clay
loam
— —
Table 2. Cultivar ‘Scarlett Ribbon’ and chemical characteristics of the soils of
the different plantations
Farm pH OM (g kg21) P (mg kg21)
Available cations (cmol kg21)
K Ca Mg Na
1 6.48a 57.6a 3.5c 2.44 a 12.05 ab 3.31 bc 0.56 a
9 6.30a 33.5c 7.0bc 2.41 ab 10.57 ab 4.04 b 0.19 c
12 6.60a 35.8bc 23.0b 1.18 c 13.26 a 7.54 a 0.48 a
13 5.42b 36.8bc 52.4a 2.38 a 10.40 b 2.67 c 0.32 bc
14 6.22a 31.6c 42.8a 1.53 bc 13.70 a 3.31 bc 0.41 ab
15 5.33b 40.9b 0.9d 1.54bc 5.31 c 3.12 bc 0.43 ab
Note. Data of the columns followed by different letters are statistically
significant at the p 5 0.05 level.
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Table 3. Cultivar ‘High Gold’ and Chemical characteristics of the soils of the
different plantations
Farm pH
OM
(g kg21)
P
(mg kg21)
Available cations (cmol kg21)
K Ca Mg Na
2 6.17 c 72.4 a 4.4 d 1.62 bc 10.75 c 4.42 b 0.64 a
4 6.56 a 51.8 b 21.1 bc 3.07 a 17.11 a 5.57 a 0.71 a
8 6.45 ab 30.0 e 41.9 ab 3.03 a 13.75 b 3.95 b 0.35 b
9 6.27 bc 34.1 de 7.0 cd 2.36 ab 10.73 c 4.15 b 0.39 b
13 5.42 d 36.8 cd 52.4 a 2.38 ab 10.40 c 2.67 c 0. 32 b
15 5.33 d 40.9 c 0.9 d 1.54 c 5.31 d 3.12 c 0.43 b
Note. Data of the columns followed by different letters are statistically
significant at the p 5 0.05 level.
Table 4. Cultivar ‘Veldfire’ and Chemical characteristics of the soils of the
different plantations
Farm pH
OM
(g kg21)
P
(mg kg21)
Available cations (cmol kg21)
K Ca Mg Na
3 6.05 c 91.5 a 3.5 d 1.18 c 10.02 c 1.25 a 0.50 b
4 6.56 b 51.6 b 21.0 b 3.07 a 17.11 b 0.99 ab 0.71 ab
5 6.57 b 98.1 a 12.2 c 1.58 bc 22.18 a 1.11 ab 0.54 b
15 5.51 d 19.3 c 0.9 d 1.44 c 5.55 d 0.84 b 0.48 b
19 6.89 a 17.0 c 11.4 c 2.28 b 11.87 c 1.20 ab 0.52 b
21 6.59 b 33.8 bc 37.1 a 1.92 bc 11.11 c 1.26 a 0.90 a
Note. Data of the columns followed by different letters are statistically
significant at the p 5 0.05 level.
Table 5. Species Leucospermum patersonii and chemical characteristics of the
soils of the different plantations
Farm pH
OM
(g kg21)
P
(mg kg21)
Available cations (cmol kg21)
K Ca Mg Na
4 6.56 b 51.8 b 21.0 b 3.07 a 17.11 c 5.57 b 0.71 ab
6 6.51 b 19.4 d 19.7 b 2.58 ab 17.96 c 8.99 a 0.77 ab
7 6.62 ab 83.4 a 79.9 a 1.30 c 22.17 b 3.11 c 0.33 b
10 6.92 a 28.0 cd 62.9 a 3.03 a 27.93 a 3.79 c 0.62 ab
19 6.46 b 31.1 c 13.5 b 1.64 bc 12.62 d 5.58 b 0.86 ab
20 6.36 b 50.8 b 26.6 b 2.74 a 19.27 bc 5.32 b 1.22 a
Note. Data of the columns followed by different letters are statistically
significant at the p 5 0.05 level.
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kg21 OM should be complemented with this material (Sana, Carles,
and Cohı 1996). In contrast, levels of 70 g kg21 of organic matter have
been quoted by several authors as being too high for some crops,
possibly interfering with micronutrient absorption (Witkowski 1989;
Cecil et al. 1995; Maier and Robinson 1996; Pique, Alvarez, and
Fernandez 1996).
Phosphorus
Soil P levels were low for crops in general, but considering that protea
requirements of this element are small (Prasad and Dennis 1986;
Heinsohn and Pammenter 1986; Maier et al. 1995; Cecil et al. 1995),
such values may prove to be acceptable for this crop, perhaps with the
exceptions of plantations 1, 2, 3, and 15, in which concentrations of P are
significantly less than in the remainning ones.
Potassium
Available K levels were mostly high in the soils of the different cultivars
(concentrations greater than 2 cmol kg21), taking into account that
several authors (Heinsohn and Pammenter 1986; Cecil et al. 1995; Maier
et al. 1995) reported that proteas have small requirements for K, which is
in agreement with the data referred by Jamienson (1985), who
recommended K levels less than 1.02 cmol kg21 for these plants.
Parvin (1986), on the other hand, cited values of 1.24 cmol kg21 for
Leucospermum, and Fernandez Falcon, et al. (2006) indicated concentra-
tions of 0.57 to 1.36 cmol kg21 for the same genus. However, taking into
account the sum of available cations (Sana, Carles, and Cohı 1996), the
proportion of available K is acceptable in some soils, although it remains
high in a considerable number of them.
Table 6. Cultivar ‘Sunrise’ and Chemical characteristics of the soils of the
different plantations
Farm pH
OM
(g kg21)
P
(mg kg21)
Available cations (cmol kg21)
K Ca Mg Na
9 6.05 ab 31.0 bc 5.7 c 3.13 a 10.94 bc 4.86 b 0.40 b
11 6.39 a 38.4 b 73.8 a 1.58 cd 14.08 ab 5.79 a 0.45 b
16 6.30 ab 65.2 a 4.8 c 0.91 d 15.73 a 1.97 d 0.33 b
17 5.91 b 23.9 c 20.5 b 2.12 bc 9.10 c 3.25 c 0.45 b
18 6.14 ab 34.0 b 14.4 bc 2.48 ab 11.72 bc 3.52 c 0.64 a
Note. Data of the columns followed by different letters are statistically
significant at the p 5 0.05 level.
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Calcium
Most concentrations of available Ca in the soils were high (10.02 cmol
kg21 to 19.27 cmol kg21), with the exception of farm 15 of cultivars
‘Scarlett Ribbon’ and ‘Veldfire,’ where their values did not reach the 6.24
cmol kg21 recommended by Jamienson (1985). It should be stressed that
the soils in which L. patersonii was cultivated showed the greatest
contents, reaching a value of 27.93 cmol kg21 (farm 10). When the sum of
cations was considered (Lopez and Lopez 1990), the values of Ca were
quite acceptable in the greater part of the farms studied, irrespectively of
the variety being cultivated.
Table 7. Electrical conductivity of the soils of the cultivars along the different
samplings
Farm Sampling
EC (dS/m)
‘Scarlett
Ribbon’
‘High
Gold’ ‘Veldfire’
L.
patersonii ‘Sunrise’
A 1 1.37 bc 1.32 1.19 b 2.38 b 1.49
2 1.71 b 1.50 2.29 a 8.87 a 1.45
3 0.97 c 1.22 1.47 b 1.38 b 1.33
4 2.46 a 1.73 1.59 b 6.75 a 1.71
B 1 1.84 a 2.37 b 2.31 b 1.01 ab 0.95
2 1.97 a 8.87 a 8.77 a 1.24 a 1.26
3 1.09 b 1.38 b 1.48 b 0.86 b 1.25
4 1.63 a 6.75 a 6.80 a 1.21 b 1.16
C 1 0.86 1.12 1.78 — 1.16 c
2 1.19 1.22 2.02 3.35 a 5.98 a
3 0.82 1.68 1.97 2.10 b 3.84 b
4 0.81 2.84 2.74 2.65 b 3.87 b
D 1 1.47 ab 1.84 a 0.90 a — 0.76
2 1.89 a 1.97 a 0.88 a 6.36 a 0.70
3 1.20 b 1.09 b 0.61 b 6.80 a 0.84
4 1.12 b 1.63 a 0.61 b 1.27 b 0.79
E 1 0.87 1.47 ab 0.85 b 2.33 1.22
2 0.85 1.89 a 2.11 ab 3.09 1.34
3 0.76 1.20 b 1.69 ab 3.90 1.36
4 1.04 1.12 b 4.31 a 5.67 1.22
F 1 0.89 a 0.89 a 0.98 b 2.81 ab
2 1.11 a 1.11 a 1.87 a 1.47 b
3 0.92 a 0.61 b 1.20 b 3.37 a
4 0.59 b 0.61 b 0.95 b 1.81 ab
Note. Farms A, B, C, D, E, and F correspond respectively to the first, second, third,
fourth, fifth, and sixth farms chosen to be sampled for each cultivar and the species.
Data of the columns followed by different letters are statistically significant at
the p 5 0.05 level.
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Magnesium
The values of available Mg (normally between 1.97 cmol kg21 and 5.79
cmol kg21) greatly exceeded the recommendation by Jamienson (1985)
for these plants (1.23 cmol kg21), with the exception of four soils where
‘Veldfire’ was cultivated, with mean values that were less than this limit.
However, when the proportion of Mg in the sum of the cations was taken
into account, this proportion proved to be acceptable (Sana, Carles, and
Cohı 1996) in the majority of the soils of the ‘Veldfire’ cultivar and can be
applied to the remaining crops and species.
Sodium
The detected concentrations of Na were low in general (under 1 cmol kg21),
both when the proportion of cations was taken into account and when
absolute values were considered (Rodrıguez Perez, Fernandez Falcon, and
Socorro Monzon 2001), and they did not negatively affect protea plant
development. However, it must be taken into account that available Na levels
were normal when compared to soils from other crops, because no references
to the content of this element in protea soils have been found in the literature.
Electrical Conductivity
A large percentage of the soils of the different cultivars (Table 7) showed
salinity indexes within acceptable ranges (less than 2 dS/m), taking into
account that Rodrıguez Perez, Fernandez Falcon, and Socorro Monzon
(2001) concluded that Leucospermum cordifolium is considered to be
moderately sensitive to salinity, with a threshold for electrical con-
ductivity of 1.9 dS m21. On the other hand, and referring to proteas in
general, several authors (Vogts 1979, 1982; Claassens 1981; Maier et al.
1995) reported suitable values of electrical conductivity (EC) as being
between 1.0 and 2.0 dS m21. Although very high values of EC appear
occasionally in the ‘High Gold,’ ‘Veldfire,’ and ‘Sunrise’ cultivars, they
were observed in 63.6% of the soils of L. patersonii species, attaining
values up to 8.87 dS m21. These high values are considered to be harmful
to the majority of crops, and to proteas in particular, which, according to
Vogts (1979), are sensitive to salts. Nevertheless, no salinity symptoms
were detected in any of the cultivars.
Plant Nutrition
Tables 8 to 11 and Figures 1 to 6 show foliar nutrient composition and
variation along time of the studied protea plants.
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Nitrogen
The ranges of our data (between 9.1 and 13.4 g kg21) were in accordance
with the value (11 g kg21) pointed out by Parvin (1986) for L. cordifolium.
In genus Protea, Haigh, Parks, and Cresswell (1997) determined ranges
from 3.5 to 28.3 g kg21, meanwhile Nichols (1988) had reported levels
from 8 to 15 g kg21, and Maier et al. (1995) detected values from 7.7 to
Table 8. Mean foliar levels of N, P, and K (g kg21) in the different cultivars and
species in both years of sampling
Cultivars and
species Years
Mean
N P K
‘Scalett
Ribbon’
1 11.8 1.3 a 4.1
2 12.2 0.9 b 4.3
‘High Gold’ 1 9.1 b 1.3 a 6.1
2 13.4 a 0.8 b 5.6
‘Veldifre’ 1 12.4 1.4 a 5.1
2 12.5 0.8 b 5.5
L. patersonii 1 13.4 1.6 a 6.1
2 12.0 0.9 b 6.3
‘Sunrise’ 1 12.6 1.6 a 7.6
2 11.2 1.2 b 6.6
Note. Data of each cultivar and species in the different years followed by
different letters denote a statistical significant difference at the p 5 0.001 level.
Table 9. Mean foliar levels of Ca, Mg, and Na (g kg21) in the different cultivars
and species in both years of sampling
Cultivars and
species Years
Mean
Ca Mg Na
‘Scalett
Ribbon’
1 6.3 b 2.0 b 5.9 b
2 15.4 a 9.2 a 14.0 a
‘High Gold’ 1 10.0 b 3.3 b 8.7 b
2 13.1 a 5.7 a 11.5 a
‘Veldifre’ 1 10.2 b 2.5 b 5.3 b
2 21.1 a 10.7 a 14.9 a
L. patersonii 1 11.4 b 5.7 b 5.3 b
2 24.7 a 21.4 a 14.9 a
‘Sunrise’ 1 10.8 b 3.8 b 8.5 b
2 27.3 a 16.4 a 20.8 a
Note. Data of each cultivar and species in the different years followed by
different letters denote a statistical significant difference at the p 5 0.001 level.
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8.6 g kg21. In Leucadendron, Ran et al. (2001) obtained concentrations
between 15 and 20 g kg21, and Cecil et al. (1995) reported concentrations
of 3.9 to 6.8 g kg21.
The larger values of the first sampling (with the exception of cultivars
‘Scarlett Ribbon’ and ‘Veldfire’ in the first year), shown in Figure 1, could
be due to a greater N requirement of the plants to recover from the
current winter pruning. Nitrogen fluctuated in the other samplings, which
agreed with Parvin’s (1986) observations.
Most N percentages remained stable between the fourth and fifth
samplings (months of November and January) in both years, with the
exception of cultivar ‘High Gold,’ and Sunrise in the second one. This
fact suggests that these months could be chosen for sampling leaves to
determine the standard N levels.
Phosphorus
Mean concentrations obtained in this study (0.8 to 1.6 g kg21) were
similar to those reported by Parvin (1986) for Leucospermum cordifolium.
Values observed in other protea plants (Nichols 1988; Cresswell 1991;
Maier et al. 1995; Haigh, Parks, and Cresswell 1997) ranged between 0.5
Table 10. Means comparison of foliar macronutrient (g kg21) among the
different cultivars and species, fourth sampling (November) of the second year
Nutrient ‘Scarlett R.’ ‘High Gold’ ‘Veldfire’ ‘Patersonii’ ‘Sunrise’
N 12.3 ab 13.2 a 13.0 a 11.4 b 12.5 ab
P 0.9 b 0.8 b 1.0 b 1.0 b 1.5 a
K 3.9 c 7.5 a 5.8 b 6.5 ab 6.8 ab
Ca 18.6 c 10.5 d 30.5 b 34.7 a 36.6 a
Mg 11.3 d 4.1 e 14.2 c 30.3 a 23.4 b
Na 12.9 b 13.0 b 13.7 b 23.0 a 20.4 a
Note. Data of the same file followed by different letters are statistically
significant at the p 5 0.05 level.
Table 11. Foliar macronutrient ranges (g kg21) among the different cultivars
and species, fourth sampling (November) of the second year
Nutrient ‘Scarlett R.’ ‘High Gold’ ‘Veldfire’ ‘Patersonii’ ‘Sunrise’
N 10.1–14.5 11.0–15.4 11.1–14.9 10.1–12.7 9.2–15.8
P 0.6–1.2 0.5–1.1 0.7–1.3 0.6–1.4 0.7–2.3
K 3.2–4.5 5.3–9.7 4.5–7.1 4.0–9.0 5.2–8.4
Ca 15.8–21.4 8.6–12.4 22.1–38.9 28.9–40.5 31.3–41.9
Mg 9.9–12.7 3.3–4.9 11.6–16.8 26.2–34.4 19.9–26.9
Na 11.2–14.6 7.4–15.5 11.1–16.3 18.4–27.6 18.3–22.5
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and 3.2 g kg21 for proteas in general, whereas Ran et al. (2001) in
Leucadendron quoted values from 0.6 to 1.2 g kg21. Besides, opposed to
the generalized opinion and confirmed by our results, it is outstanding
that Silber et al. (1998, 2001) reported that these plants are not
susceptible to high P levels, because they obtained high concentrations
in leaves (up to 3.4 g kg21) without the plants showing any toxicity
symptoms.
Phosphorus foliar levels were significantly greater in the first year.
Because at the beginning of this study the sampled plants had an age less
Figure 1. Nitrogen evolution along time during sampling cycle of the two years
of assay. Data within the same line with different letters are significantly different
at p 5 0.05.
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than 2 years, these data seem to point to a greater need of P in younger
plants. This hypothesis suggests that the levels of P for obtaining the
standard foliar levels are those of the second year of the assay, because in
this year most plants had reached their maturity.
The high values of P observed in the first sampling (spring) of most
cultivars in both years (Figure 2) could be due to higher P nutritional
requirements along the stage after general pruning and new bud
development (February to March). Maier et al. (1995) and Cecil et al.
(1995) observed also higher concentrations of P in spring than the
remainder of the year.
Figure 2. Phosphorous evolution along time during sampling cycle of the two
years of assay. Data within the same line with different letters are significantly
different at p 5 0.05.
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On the other hand, P values of both years stabilized in the summer–
autumn samplings (July, September, and November), in accordance with
Maier et al., (1995) findings in Australia working with genus Protea. It isinteresting to point out that in cultivars ‘Scarlett Ribbon,’ ‘High Gold,’
and ‘Veldfire’ and the species L. patersonii, the plants that grew in farms
with soils of low P levels did not present significant differences in the
foliar concentrations of this element when they were compared to plants
Figure 3. Potassium evolution along time during sampling cycle of the two
years of assay. Data within the same line with different letters are significantly
different at p 5 0.05.
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growing in farms with high levels of P in their soils. This suggests that a
low P presence in the soil is enough to supply the P requirement of these
plants, a fact that has been observed by other researchers in different
protea cultivars (Nichols 1988; Cresswell 1991). Nevertheless, cultivar
‘Sunrise’ had the greatest foliar contents of P when grown in soils richerin this element, which suggests that its requirements are greater than
those of the other cultivars and species studied. On the other hand, the
absence of P toxicities in the plants developed in soils with the highest P
levels suggest that these plants can resist high soil P concentrations
Figure 4. Calcium evolution along time during sampling cycle of the two years
of assay. Data within the same line with different letters are significantly different
at p 5 0.05.
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(means up to 183 mg kg21) without damage (Fernandez Falcon et al.,
2006). These observations are in contradiction with the statements of
other authors (Jamienson 1985; Heinsohn and Pammenter 1986; Maier et
al. 1995; Cecil et al. 1995).
Potassium
The mean of foliar K pointed out by Parvin (1986) for Leucospermum
cordifolium (4.4 g kg21) was less than the ones (4.1 to 6.6 g kg21) detected
in this assay. In the genus Protea, variations within the range of 1.8 to
4.1 g kg21 have reported by different authors (Price 1986; Nichols 1988;
Haigh, Parks, and Cresswell 1997; Maier et al. 1995). Cecil et al. (1995)
pointed out much smaller values (0.8 to 2.2 g kg21) in Leucadendron, andthe opposite was obtained (5 to 8 g kg21) by Ran et al. (2001). Potassium
concentration decreased in all the cultivars and species in the last
samplings of the 2 years (Figure 3), a trend that Cecil et al. (1995) and
Maier et al. (1995) observed in Leucadendron and Protea, respectively. In
general, K levels stabilized in the third and fourth samplings (September
and November) in both years.
Calcium
Foliar levels (6.3 to 27.3 g kg21) were greater than those (6.7 g kg21)
reported by Parvin (1986) in Leucospermum cordifolium and the ones (3.5
to 13 g kg21) observed by Price (1986), Maier et al. (1995), and Haigh,
Figure 5. Magnesium evolution along time during sampling cycle of the two
years of assay. Data within the same line with different letters are significantly
different at p 5 0.05.
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Parks, and Cresswell (1997) in genus Protea. Cecil et al. (1995) in
Leucadendron pointed out lower values (2.4 to 3.9 g kg21).
In contrast to K, the lower levels of Ca appeared always in the first
and second samplings (May and July) of each year (Figure 4); meanwhile,
it usually increased significantly in the two last sampling of both years,
especially in the last one (winter time). This behavior coincides with thatobserved by Maier et al. (1995) in the Protea genus.
In general, Ca level stabilization differed according to the studied
year, though it was observed more consistently in the second (July) and
fourth (November) samplings.
Figure 6. Sodium evolution along time during sampling cycle of the two years
of assay. Data within the same line with different letters are significantly different
at p 5 0.05.
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Magnesium
Magnesium concentrations (2.0 g kg21 up to 21.4 g kg21) were greater
than the mean (2.4 g kg21) observed by Parvin (1986) in L. cordifolium, as
well as those (1 to 4 g kg21) reported by Nichols (1988) and Haigh, Parks,
and Cresswell (1997) in Protea genus and the range (1.6 to 2.5 g kg21)
detected by Cecil et al. (1995) in Leucadendron. Maier et al. (1995)
reported in genus Protea a gradual increase of this element along time, a
behavior that was also observed in the present study.
Magnesium concentrations also behaved in such a way that
November (fourth sampling) was the most appropriate month to sample
the plants for setting the standard foliar Mg levels (Figure 5).
Sodium
Rodrıguez Perez, Fernandez Falcon, and Socorro Monzon (2000, 2001),
working with genera Leucospermum and Protea, detected an Na range
similar to the one observed in this assay (5.3 to 20.8 g kg21). Although
Nichols (1988) mentioned that concentrations up to 2 g kg21 seem to be
normal, he considered that many proteas can tolerate greater levels.
Haigh et al. (1997) and Maier et al. (1995) in genus Protea, and Cecil et
al. (1995) in Leucadendron, found smaller concentrations than in this
study. Taking into account the low level of Na in the soils of La Palma,
the high concentrations of this nutrient in the different cultivars and
species are surprising. This suggests that these plants have a special
eagerness for Na.
Foliar Na levels of the first sampling (May) of each cultivar and the
species, in both years, showed a trend to be the least (Figure 6). This
could be due to a smaller presence of soil soluble Na in this time because
of the leaching caused by winter rains. The sampling of November
appears with sufficient frequency in the zones of Na level stabilization as
to consider it as suitable for a standard sampling for foliar Na
determination.
Foliar Standard Levels
As it was mentioned previously, a generalized stabilization of nutrient
concentrations is observed in the fourth sampling (November). The
plants of some studied plantations had not yet reached maturity age in
the first year of sampling, so data that belonged to the fourth
(November) sampling of the second year has been considered more
convenient for determining the reference values. These data are shown in
Tables 10 and 11.
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Nitrogen
L. patersonii presented the lowest average concentration, with statistical
differences from cultivars ‘High Gold’ and ‘Veldfire,’ which had the
highest values, that could be due to a greater demand of this element by
these cultivars. On the other hand, the species showed the shortest
standard range.
Phosphorus
When the foliar P levels among cultivars and the species were compared,
‘Sunrise’ differed significantly from the rest, which suggests that this
cultivar has a greater need of this nutrient. The standard range is also
more ample than that of the other protea plants.
Potassium
The contents of K were statistically lower in the cultivar ‘Scarlett
Ribbon,’ followed by ‘Veldfire,’ though the last one is significantly
different only to ‘High Gold.’ The greater limit of the standard variation
range of ‘Scarlett Ribbon’ (0.45 g kg21) is of the same order as the lower
one of the other cultivars and species.
Calcium
The cultivar ‘Sunrise’ and L. patersonii showed significantly higher Ca
levels than the other cultivars, specially ‘High Gold.’ Although average
Ca concentration of ‘Veldfire’ occupies an intermediate position, the
suggested range of variation is the widest of all.
Magnesium
The content of this element in L. patersonii has a behavior similar to that
of Ca, and ‘High Gold’ also presented the lowest levels of Mg. It is
interesting to emphasize that the minimum value of the standard interval
recommended for L. patersonii is higher than the maximum found in
most of the cultivars.
Sodium
The species L. patersonii and the cultivar ‘Sunrise’ had Na levels
significantly higher than the other cultivars. Both exhibit standard
ranges whose minimums are higher than the maximum of the other
cultivars.
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ACKNOWLEDGMENT
We acknowledge Enrique Huertas (technician of the Government
of La Palma Island) and Francisco N. Molina (technician of the
Association of Protea Growers) for their important collaboration. We
acknowledge the Cabildo Insular de La Palma for the funds to carry out
these essays.
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