effects of split nitrogen fertilization on post-anthesis photoassimilates, nitrogen use efficiency...
TRANSCRIPT
This article was downloaded by: [University of New Mexico]On: 27 November 2014, At: 00:01Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: MortimerHouse, 37-41 Mortimer Street, London W1T 3JH, UK
Acta Agriculturae Scandinavica, Section B — Soil &Plant SciencePublication details, including instructions for authors and subscription information:http://www.tandfonline.com/loi/sagb20
Effects of split nitrogen fertilization on post-anthesisphotoassimilates, nitrogen use efficiency and grainyield in malting barleyJian Cai a , Dong Jiang a , Fulai Liu b , Tingbo Dai a & Weixing Cao aa Key Laboratory of Crop Physiology and Ecology in Southern China, MOA/Hi-TechKey Laboratory of Information Agriculture, Jiangsu Province , Nanjing AgriculturalUniversity , Nanjing, Chinab Department of Agriculture and Ecology , University of Copenhagen, Faculty of LifeSciences , Højbakkegaard Allé 13, Taastrup, DenmarkPublished online: 15 Mar 2011.
To cite this article: Jian Cai , Dong Jiang , Fulai Liu , Tingbo Dai & Weixing Cao (2011) Effects of split nitrogenfertilization on post-anthesis photoassimilates, nitrogen use efficiency and grain yield in malting barley, Acta AgriculturaeScandinavica, Section B — Soil & Plant Science, 61:5, 410-420
To link to this article: http://dx.doi.org/10.1080/09064710.2010.497158
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) containedin 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 ofthe Content. Any opinions and views expressed in this publication are the opinions and views of the authors,and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be reliedupon and should be independently verified with primary sources of information. Taylor and Francis shallnot be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and otherliabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to orarising out of the use of the Content.
This article may be used for research, teaching, and private study purposes. Any substantial or systematicreproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in anyform to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions
ORIGINAL ARTICLE
Effects of split nitrogen fertilization on post-anthesis photoassimilates,nitrogen use efficiency and grain yield in malting barley
JIAN CAI1, DONG JIANG1, FULAI LIU2, TINGBO DAI1 & WEIXING CAO1
1Key Laboratory of Crop Physiology and Ecology in Southern China, MOA/Hi-Tech Key Laboratory of Information
Agriculture, Jiangsu Province, Nanjing Agricultural University, Nanjing, China, 2University of Copenhagen, Faculty of Life
Sciences, Department of Agriculture and Ecology, Højbakkegaard Alle 13, Taastrup, Denmark
AbstractSplit nitrogen applications are widely adopted to improve grain yield and enhance nitrogen use effective in crops. In a two-year field experiment at two eco-sites, five fractions of topdressed nitrogen of 0%, 20%, 30%, 40% and 50% wereimplemented. Responses of radiation interception and leaf photosynthesis after anthesis, dry matter accumulation andassimilates remobilization, nitrogen use efficiency and grain yield to fraction of topdressed nitrogen treatments wereinvestigated in malting barley. Net photosynthetic rate of the penultimate leaf, leaf area index and light extinction coefficientincreased with increasing fraction topdressed nitrogen from 0% to 30%, and then decreased from 30% to 50%. The putativegross maximum canopy photosynthesis was the highest for fraction of topdressed nitrogen of 30%, which was concomitantwith the highest amount of post-anthesis accumulated assimilates. The remobilization of pre-anthesis stored assimilatesfrom vegetative organs into grains was hardly significantly affected by fractions of topdressed nitrogen. Grain yield was thehighest for fraction of topdressed nitrogen of 30%, which coincided with the highest plant nitrogen uptake and physiologicaland agronomic nitrogen use efficiencies. The enhanced nitrogen use efficiency was corresponding to the improvedphotosynthetic nitrogen-use efficiency in the leaves at fraction of topdressed nitrogen of 30%. In conclusion, appropriatefraction of topdressed nitrogen application on malting barley improved assimilation rate and nitrogen use efficiency resultingin higher grain yields and proper grain protein content in malting barley.
Keywords: Grain yield, malting barley, photosynthesis, photosynthetic nitrogen use efficiency, split nitrogen fertilization.
Introduction
Approximately 70�90% of the final grain yield in
wheat and barley is derived from photoassimilates
synthesized during the period from anthesis to
maturity under non-stress conditions (Austin et al.
1977, Bidinger et al. 1977). It is well known that the
availability of photoassimilates relies largely on the
amount and utilization efficiency of the intercepted
photosynthetic active radiation (PAR) by the canopy
(Monteith 1977, Sinclair & Muchow 1999). The
amount of the intercepted PAR depends on the leaf
area index (LAI) and the extinction coefficient (K)
(Casanova et al. 1998). Therefore, reduction in LAI
will result in a decrease of the amount of PAR
intercepted by the crop (Olesen et al. 2000, Kiniry
et al. 2004). Nitrogen (N) deficiency is reported to
reduce LAI (Caviglia and Sadras 2001), while better
N fertilization application practices such as appro-
priate N rates (Jiang et al. 2008), split N application
(Lone and Khan 2007) and appropriate application
timing (Jiang et al. 2005) are found to improve leaf
photosynthesis under non-stress conditions leading
to an increase of crop yields (Baethgen et al. 1995,
Reddy et al. 2003, Angas et al. 2006).
It has been shown that leaf photosynthesis is
closely correlated with leaf N status (Bindraban
1999, Dreccer et al. 2000, Javier et al. 2003,
Tambussi et al. 2005), as about 60�80% of the leaf
N is invested in the photosynthetic apparatus in C3
crops (Makino and Osmond 1991). Photosynthetic
N use efficiency (i.e. PN/N-photosynthetic rate per
unit N concentration in leaf) has been used to
describe the efficiency of a crop to use N for biomass
Correspondence: Dong Jiang, Key Laboratory of Crop Physiology and Ecology in Southern China, MOA/Hi-Tech Key Laboratory of Information Agriculture,
Jiangsu Province, Nanjing Agricultural University, Nanjing 210095, China. Tel/Fax: 0086 25 84396575. E-mail: [email protected]
Acta Agriculturae Scandinavica Section B � Soil and Plant Science, 2011; 61: 410�420
(Received 24 February 2010; revised 24 May 2010; accepted 25 May 2010)
ISSN 0906-4710 print/ISSN 1651-1913 online # 2011 Taylor & Francis
DOI: 10.1080/09064710.2010.497158
Dow
nloa
ded
by [
Uni
vers
ity o
f N
ew M
exic
o] a
t 00:
01 2
7 N
ovem
ber
2014
production (Kumar et al. 2004). Thus effect of N
fertilization on leaf photosynthesis is related to its
regulatory effect on leaf N status in leaf. Studies have
demonstrated that excessive N rates or heavy top-
dressed N fertilization during the growing season
could result in high N content in leaves, which may
decrease the PN/N (Jiang et al. 2005); whilst
increasing basal N fertilization causes a low crop N
uptake rate and thus a reduced fertilizer N use
efficiency (Lopez-Bellido et al. 2005).
It is also well known that grain yield also relies on
the effectiveness of the re-mobilization of the pre-
anthesis stored photoassimilates in the leaves and
stems into grains during grain filling (Gebbing et al.
1999). Nitrogen fertilization has been reported to
affect this process (Papakosta and Gagianas 1991,
Dordas 2009). Earlier studies have shown that
appropriate N rates increase photoassimilates remo-
bilization efficiency thereby increasing grain yields
(Dordas 2009), whereas excessive N rates reduce
grain yields probably due to a lower efficiency in the
remobilization of photoassimilates from the vegeta-
tive organs to the grains (Yang et al. 2001, Yang and
Zhang 2006). However, until now the effects of split
N fertilization on the remobilization efficiency of
storage photoassimilates during grain filling are less
documented in cereal crops.
In the present study, different split N fertilization
treatments were applied to malting barley in a two-
year field experiment at two eco-sites in China. Our
objectives were to investigate the effects of those
N fertilization treatments on leaf photosynthesis,
photoassimilates remobilization, and grain yields,
and to recommend appropriate FTN application
for high yield, high N use efficiency and proper grain
protein level thereby maintaining malting quality.
Materials and methods
Experimental sites and design
The field experiment was conducted at Nanjing
(32802?N, 118850?E, downstream area of Yangtze
River) and Yancheng (33838?N, 120813?E, coast
barley production area), Jiangsu Province China on
two consecutive growing seasons in 2004�2005
(denoted 2005 henceforth) and 2005�2006 (de-
noted 2006) of barley (cultivar Supi 3). The previous
crop was rice in both years. The experimental soil
type was clay and loam in Nanjing (NJ) and
Yancheng (YC), respectively. The soil nutritional
status of the experimental soil is given in Table I.
At both experimental sites, plants (cultivar Supi 3)
were grown at the density of about 225�104 plants
ha�1 with a row space of 25 cm. Potassium (K2O)
and phosphorus (P2O5) fertilizers were applied
during soil preparation before sowing at a rate of
65 kg P ha�1 and 100 kg K ha�1. Nitrogen (N)
fertilizer was applied at two times: during soil
preparation before sowing (basal N) and at the
beginning of elongation stage (topdressed N) with
a total amount of 225 kg ha�1. The topdressed N
was applied at 0%, 20% (only in NJ site), 30%, 40%
and 50% of the total N which corresponded to the
FTN0, FTN20, FTN30, FTN40 and FTN50, respec-
tively. The form of N fertilizer used was urea. In
addition, a treatment of no N fertilization use was
assigned at both sites for the calculation of agro-
nomic nitrogen use efficiency. The experiment was
arranged as a complete random block design with
three replicates per treatment. The plot size was
9 m2. To avoid edge effects, two metres of border
plants were grown around the experimental plots.
The climates were described as semi-tropical mon-
soon and humid, and the precipitation was more
than the demands for barley growth at both sites in
both years. Thus, no irrigation was needed while
drainage was conducted to avoid waterlogging dur-
ing the experiment. Owing to prevention in advance,
there was no disease and pests in both years. The
sowing date, topdressing date, anthesis date and
maturity date was 20 Oct, 6 Mar, 15 Apr, 22 May in
2005 in YC, 5 Nov, 2 Mar, 12 Apr, 16 May in 2005
in NJ, 25 Oct, 8 Mar, 18 Apr, 23 May in 2006 in YC
and 8 Nov, 5 Mar, 16 Apr, 21 May in 2006 in NJ,
respectively.
Measurements and methods
Uniform flowering plants on the same date were
tagged at anthesis, which ensured good sampling in
the experiment. Moreover, all measurement plants
Table I. Soil nutrient contents in the experimental soil.
Year Site
Organic matter
(g kg�1)
Mineral nitrogen
(mg kg�1)
Olsen phosphorus
(mg kg�1)
Available potassium
(mg kg�1)
2005 Nanjing 26.0 24.6 49.7 153.0
Yancheng 17.1 15.5 37.5 99.5
2006 Nanjing 30.2 22.6 50.4 79.6
Yancheng 19.6 17.7 44.8 92.7
Split nitrogen applications in malting barley 411
Dow
nloa
ded
by [
Uni
vers
ity o
f N
ew M
exic
o] a
t 00:
01 2
7 N
ovem
ber
2014
were sampled from tagged plants at five spots inside
plots. The penultimate leaves were used for PN
measurement, since the flag leaves were difficult for
net photosynthesis (PN) measurement because
the flag leaves were small and with minor importance
to grain yield in barley. Five leaves per replicate
were measured for PN by a LI-COR 6400 portable
photosynthesis system (Licor Inc., USA) between
9:30 am and 11:30 am with chamber CO2 concen-
tration of about 385 mmol L�1, and photosynthetic
active radiation (PAR) of 1000 mmol m�2 s�1.
Leaf area index (LAI) and light extinction
coefficient (K) were measured with an AccuPAR
80 ceptometer (Decagon Devices, Inc., Pullman,
WA, USA) between 10:30 am and 11:30 am. The
ceptometer contains 80 individual quantum sensors
on the probe and can automatically calculate LAI
based on PAR readings at the bottom and the top
of the canopy. K was automatically calculated
using the following Beer�Lambert law by the
ceptometer:
K��LN(I=I0)�LAI�1
where, I and I0 denote PAR at the bottom and the
top of the canopy, respectively.
Assuming that PN of all the leaves are the same as
the penultimate leaf, PN*LAI can be considered as
the maximum canopy photosynthesis (Jiang et al.
2004). Then the gross maximum canopy photo-
synthesis (GCP) can be calculated by the cumulative
PN*LAI over
Cumulative (GCP)
�XPN �LAId(n) � PN �LAId(n�1)
2
�(d(n�1)�d(n))
grain filling.
Here, d(n) and d(n�1) denote the consecutive
measuring Day n and Day n�1.
Plants of 3 m2 in the plots inside in each replicate
were hand-harvested to determine the grain yield.
Nitrogen content in plants was analysed using
the Kjeldahl method. N accumulation per leaf area
(g N m�2) of the penultimate leaf at anthesis was
obtained from the product of leaf biomass and
nitrogen content. The photosynthetic nitrogen use
efficiency (PN/N, mmol CO2 g�1 N s�1) was then
calculated according to the ratio of PN to nitrogen
accumulation per leaf area (Kumar et al. 2004).
Physiological nitrogen use efficiency (PE, g g�1) was
defined as grain production per unit N taken up by
plant (Ladha et al. 1998). Agronomic nitrogen use
efficiency (AE, kg grain kg�1 N) was calculated
from the grain yields difference between the nitrogen
fertilized treatments and the non-fertilized treatment
divided by 225 kg ha�1 (total N applied for the
fertilized plots) (Delogu et al. 1998).
Ten plants per plot were harvested at anthesis
and maturity for determination of dry matter (DM)
weight. Assimilates formed before and after ant-
hesis and their contributions to grain yield were
calculated as suggested by Tan et al. (2008). The
apparent remobilization amount of pre-anthesis
stored assimilates from the aboveground vegetative
organs to grain (RAP) was obtained by the difference
in DM of the aboveground vegetative organs be-
tween anthesis and maturity (g plant�1). Contribu-
tion of RAP to grain mass (CoRAP) was calculated
as the percentage of RAP to grain DM. The
apparent amount of post-anthesis transfer of accu-
mulated DM into grain (APA) was the difference
between final grain DM at maturity and RAP (g
plant�1), while its contribution to grain DM
(CoAPA) was the percentage of APA to grain DM
at maturity (%). RAP and APA were expressed as
‘apparent’ because the dry matter loss due to
respiration or translocation was not considered
(van Herwaarden et al. 1998). Harvest index (HI)
was calculated by dividing the grain DM with the
aboveground total DM at maturity.
Statistics
The data were subjected to one-way analysis of
variance (ANOVA) followed by the Duncan’s SSR
(shortest significant ranges) test. The significance
was evaluated by t-test.
Results
Net photosynthetic rate (PN)
Net photosynthetic rate of the penultimate leaf
gradually decreased after anthesis in both years at
both experimental sites (Figure 1). During the early
grain filling stage (0 to 14 days after anthesis, DAA)
in Nanjing (NJ) or 0 to 10 DAA in Yancheng (YC),
PN increased with increasing fraction of topdressed
nitrogen (FTN), and reached the maximum at
FTN30, and then decreased with further increase
in FTN. Thus, a proper fraction of topdressed
nitrogen maintained a high PN during the early grain
filling. However, at 21 DAA in NJ and 20 DAA in
YC, the maximum PN occurred at FTN40, followed
by FTN30. At 28 DAA in NJ and 30 DAA in YC,
PN was improved by increasing FTN. Thus, a high
fraction of topdressed nitrogen maintained a high
leaf PN during late grain-filling stage. Significant
differences in PN at anthesis were found between
treatments (pB0.01), between experimental years
(pB0.01) and between sites (pB0.01). PN was
412 J. Cai et al.
Dow
nloa
ded
by [
Uni
vers
ity o
f N
ew M
exic
o] a
t 00:
01 2
7 N
ovem
ber
2014
higher in year 2005 than 2006, and was higher in YC
than in NJ.
Leaf area index (LAI) and light extinction coefficient (K)
Leaf area index decreased sharply after anth-
esis (Figure 2), whereas K at 14 DAA in NJ and at
10 DAA in YC was higher than at both anthesis and
late grain-filling stages (Figure 3). LAI and K were
significantly affected by FTN treatment (pB0.01)
and both were the highest for FTN30. In addition,
LAI at anthesis in YC was significantly higher than
in NJ (pB0.01) in both years. Significant differ-
ence in LAI was observed between the two years
(pB0.05). In addition, there was also significant
difference in K between the two years (pB0.01) and
between the two sites (pB0.01) at 14 DAA in NJ
and 10 DAA in YC.
FTN50
FTN40
FTN30
FTN20
FTN0
10
20
30
10
20
30
0 7 14 21 28 0 10 20 30
PN
(µm
ol C
O2
m-2
s-1
)
2005 NJ
2005 YC
2006 NJ
2006 YC
Days after anthesis (DAA)
Figure 1. Effect of fraction of topdressed N on changes in PN of the penultimate leaf of malting barley in Nanjing (NJ) and Yancheng (YC)
in 2005 and 2006.
0
3
6
9
0
3
6
9
0 14 28 0 10 20
FTN50FTN40FTN30FTN20FTN0
LA
I
2005 NJ
2005 YC
2006 NJ
2006 YC
Days after anthesis (DAA)
Figure 2. Effect of fraction of topdressed N on changes in LAI of malting barley in Nanjing (NJ) and Yancheng (YC) in 2005 and 2006.
Data are means of three replicates � s.e.
Split nitrogen applications in malting barley 413
Dow
nloa
ded
by [
Uni
vers
ity o
f N
ew M
exic
o] a
t 00:
01 2
7 N
ovem
ber
2014
Dry matter (DM) and assimilates remobilization
The effects of FTN treatments were significant
(pB0.01) on the amount of post-anthesis acc-
umulated assimilates transferred to grains (APA),
contribution of APA to grain mass (CoAPA, %) and
contribution of remobilization amount of pre-
anthesis stored dry matter from vegetative organs
into grains (RAP) to grain mass (CoRAP, %),
while not significant on RAP (Table II). APA and
CoAPA increased from FTN0 to FTN30 and then
decreased from FTN30 to FTN50, whereas CoRAP
showed a reverse changing pattern. Significant
differences in APA, CoAPA and CoRAP were only
observed between FTN30 and FTN50 or FTN0,
while not between FTN30 and FTN40 or FTN20
0 14 28 0 10 20
FTN50FTN40FTN30FTN20FTN0
0.3
0
0.6
0.9
0.3
0
0.6
0.9
2005 NJ
2005 YC
2006 NJ
2006 YC
Days after anthesis (DAA)
Lig
ht e
xtin
ctio
n co
effi
cien
t (K
)
Figure 3. Effect of fraction of topdressed N on changes in light extinction coefficient (K) of malting barley in Nanjing (NJ) and Yancheng
(YC) in 2005 and 2006.
Table II. Effect of fraction of topdressed N on dry matter and assimilates remobilization in malting barley.
2005 2006
Site Treatment
RAP
(g plant�1) CoRAP (%)
APA
(g plant�1) CoAPA (%)
RAP
(g plant�1) CoRAP (%)
APA
(g plant�1) CoAPA (%)
Nanjing FTN50 1.07 a 28 a 2.54 c 72 b 1.01 a 28 a 2.66 c 72 b
FTN40 1.09 a 25 b 3.27 ab 75 a 1.02 a 25 b 3.14 a 75 a
FTN30 1.12 a 24 b 3.55 a 76 a 1.03 a 24 b 3.28 a 76 a
FTN20 1.09 a 26 b 3.09 b 74 a 0.98 a 26 b 2.99 b 75 a
FTN0 1.06 a 29 a 2.27 c 71 b 0.98 a 30 a 2.32 d 70 b
Yancheng FTN50 1.20 a 28 ab 2.99 b 72 b 1.13 a 32 a 2.71 b 68 b
FTN40 1.21 a 26 b 3.25 ab 74 ab 1.14 a 28 b 3.08 a 72 a
FTN30 1.22 a 22 c 3.68 a 78 a 1.15 a 27 b 3.26 a 73 a
FTN20 � � � � � � � �FTN0 1.22 a 30 a 2.60 c 70 b 1.12 a 34 a 2.35 c 66 b
F (FTN) NS 56.3** 89.4** 32.3** NS 108.9** 43.8** 97.5**
F (Site) 665.7** 9.6* 111.8** 22.6** 522** 193.2** 8.7* 61**
F (Year) 236.1** 35.7** 18.7** 44.1**
RAP � remobilization amount of pre-anthesis stored dry matter in vegetative organs to grains (g plant�1); CoRAP � contribution of RAP to
grain mass (%); APA � amount of post-anthesis accumulated assimilates transferred to grains (g plant�1); CoAPA � contribution of APA
to grain mass (%). Different small letters in the same column of each cultivar indicate significant differences at p � 0.05. **, * and NS refers
to significant differences at p�0.01, p�0.05 and non-significance, respectively. F (FTN), F (Site) and F (Year) refers to significant
differences among FTN treatments at two sites at one year, between two sites among FTN treatments at one year, and between two years
among treatments at two sites, respectively.
414 J. Cai et al.
Dow
nloa
ded
by [
Uni
vers
ity o
f N
ew M
exic
o] a
t 00:
01 2
7 N
ovem
ber
2014
in most of the cases. In addition, significant differ-
ences were observed between experimental sites
and years in terms of RAP, CoRAP, APA and
CoAPA (pB0.01 or pB0.05).
Grain yield and harvest index (HI)
Grain yield, spike number per ha, kernels per spike,
and 1000 kernel weight (TKW) were significantly
affected by FTN treatment (Table III). Grain yield
increased from FTN0 to FTN30, then decreased
from FTN30 to FTN50 (Table III). Significant
differences in grain yield were observed between
treatments, sites and experimental years. Spike
number per ha and kernels per spike followed the
same tendency with grain yield in response to FTN
treatment. However, TKW decreased from FTN0 to
FTN50, and was significantly higher in YC than
in NJ during both years. TKW was higher in 2006
than in 2005 in NJ, while this was opposite in YC
(pB0.01). HI was the highest at FTN30 in both
sites. HI was much higher than in YC than in NJ,
and was higher in 2005 than in 2006 (pB0.01).
Nitrogen use efficiency
The main effects of FTN treatment, experimental
site and year were significant on photosynthetic
nitrogen use efficiency (PN/N) at anthesis, N taken
up amount at maturity, physiological nitrogen use
efficiency (PE) and agronomic nitrogen use effi-
ciency (AE) (Table IV). PN/N, N taken up amount,
PE and AE increased with increasing fraction of
topdressed N and reached the highest at FTN30. N
taken up amount in 2006 was higher than in 2005
(pB0.01), while PE and AE were higher in 2005
than 2006 (pB0.01). In addition, PN/N, N taken up,
PE and AE were higher in YC than in NJ (pB0.01).
Grain protein content
Grain protein content decreased from FTN50 to
FTN0 during both years and at both sites, and a
significant difference in grain yield was observed
between treatments (Table V). The protein contents
of FTN30, FTN20 and FTN0 treatments could
maintain malting quality in 2005, whereas only the
protein contents of the FTN20 and FTN0 could
maintain malting quality in 2006.
Discussion
Split N fertilization is found to improve grain yield
in wheat (Alcoz et al. 1993, Mahler et al. 1994,
Lopez-Bellido et al. 2005), and a delayed topdressed
N at the mid tillering stage improves grain yield and Table
III.
Eff
ect
of
fract
ion
of
topd
ress
edN
on
gra
inyie
ldan
dyie
ldco
mpon
ents
.
2005
2006
Sit
eT
reatm
ent
Sp
ike
nu
mb
er
per
m�
2
Ker
nel
nu
mb
er
per
�1
1000
ker
nel
wei
gh
t(g
)
Gra
inyie
ld
(kg
ha�
1)
Harv
est
ind
ex
Sp
ike
nu
mb
er
per
m�
2
Ker
nel
nu
mb
er
per
�1
1000
ker
nel
wei
gh
t(g
)
Gra
inyie
ld
(kg
ha�
1)
Harv
est
ind
ex
Nan
jin
gF
TN
50
678
d24.8
b31.1
c5221
c0.3
69
b663
b22.0
ab
36.0
b5082
c0.3
50
b
FT
N40
745
c25.7
b32.4
c5878
b0.3
88
ab
735
a22.7
ab
36.4
b5689
b0.3
60
a
FT
N30
900
a27.1
a34.8
b6494
a0.4
04
a788
a24.2
a37.1
a6167
a0.3
87
a
FT
N20
820
b25.0
b36.3
a5852
b0.3
95
a747
a21.5
b37.6
a4923
c0.3
45
b
FT
N0
620
d23.6
c36.9
a5178
c0.3
71
b580
c20.6
b37.7
a4892
c0.3
33
c
Yan
chen
gF
TN
50
701
c27.3
b40.6
b6310
bc
0.3
86
b666
a23.5
a36.8
b5828
b0.3
72
b
FT
N40
768
b27.5
b40.8
b6495
b0.3
90
a673
a23.9
a37.1
b5933
b0.3
83
a
FT
N30
904
a28.1
a41.5
ab
7063
a0.4
05
a681
a24.5
a37.6
b6298
a0.3
88
a
FT
N20
��
��
��
�F
TN
0628
d27.7
b42.8
a6033
c0.3
83
b572
b23.5
a38.6
a5796
b0.3
75
b
F(F
TN
)232
**
17.8
**
25.3
**
321.5
**
34.1
**
632.5
**
33.6
**
52.7
**
417.4
**
26.4
**
F(S
ite)
7.3
*32
**
118.6
**
227.9
**
9.5
*46.2
**
108.3
**
62.1
**
169.5
**
8.2
*
F(Y
ear)
43.7
**
221.8
**
75.3
**
113.3
**
88.2
**
Dif
fere
nt
small
lett
ers
inth
esa
me
colu
mn
of
each
cult
ivar
ind
icate
sign
ific
an
td
iffe
ren
ces
at
p�
0.0
5.
**,
*an
dN
Sm
ean
ssi
gn
ific
an
td
iffe
ren
ces
at
p�
0.0
1,
p�
0.0
5,
an
dn
on
-sig
nif
ican
ce,
resp
ecti
vely
.F
(FT
N),
F(S
ite)
an
dF
(Yea
r)re
fers
tosi
gn
ific
an
td
iffe
ren
ces
am
on
gF
TN
trea
tmen
tsat
two
site
sat
on
eyea
r,b
etw
een
two
site
sam
on
gF
TN
trea
tmen
tsat
on
eyea
r,an
dbet
wee
ntw
o
years
am
on
gtr
eatm
ents
at
two
site
s,re
spec
tive
ly.
Split nitrogen applications in malting barley 415
Dow
nloa
ded
by [
Uni
vers
ity o
f N
ew M
exic
o] a
t 00:
01 2
7 N
ovem
ber
2014
yield components in malting barley (Baethgen et
al. 1995). In the present study, compared with the
non-split N fertilization treatment (i.e. FTN0),
grain yield increased with increasing fraction
topdressed nitrogen and was the highest at
FTN30 in both years and at both sites. However,
grain yield decreased when FTN increased from
FTN30 to FTN50, and the yield at FTN50 was
similar to that with FTN0. This indicates that
excessive application of topdressed N decreased
grain yield. Grain yield in YC was higher than that
in NJ, and was higher in 2005 than in 2006. The
higher grain yield was associated with the higher
spike number per ha and kernels per spike; which
supported the finding of Masoni et al. (2007).
The higher yield was also related to higher harvest
index (HI) in this study. Moreover, being malting
barley the grain protein content was very impor-
tant. Our results showed that the appropriate
topdressed N fertilization treatments were FTN20
to FTN30 in terms of achieving higher grain yield
and proper grain protein content.
The assimilates for grain filling in barley derive
from the current assimilates after anthesis and
the remobilized assimilates stored in vegetative
organs before anthesis (Austin et al. 1980). The
current photosynthetic assimilates synthesized
after anthesis contribute most of the final grain
yield in cereal crops (Austin et al. 1977, Bidinger
et al. 1977, Przulj and Momcilovic 2001). In our
case, the post-anthesis synthesized assimilates
accounted for 66�78% (CoAPA), while assim-
ilates stored in vegetative organs before anthesis
remobilized to grains (RAP) accounted for only
22�34% (CoRAP) of the final grain yield. It
should be noted that the high CoRAP was related
with low grain yields at the two high FTN of 50%
and 40%, and at the two low FTN of 20% and
0%, while high CoAPA was related to high grain
yield at a proper FTN of 30% in the present
study. Thus, to improve the amount of post-
anthesis assimilates and its contribution to grain
mass is very important for high grain yield of
barley, and an appropriate FTN treatment, i.e.
FTN30 may benefit the post-anthesis assimilates
production and its contribution to grain yield. In
addition, RAP was not significantly affected by
FTN treatment, but it was significantly affected
by the growing season and experimental sites as it
was higher in 2006 than in 2005 growing season
and it was higher in YC than in NJ. However, the
contribution of RAP to grain mass was lower at
FTN30 than at FTN0 or FTN50 treatment. Thus
the highest grain yield at FTN30 was due mainly
to an increase in the amount of post-anthesisTable
IV.
Eff
ect
of
fract
ion
of
topd
ress
edN
on
PN
/N,
nit
rogen
taken
up
an
dphysi
olo
gic
al
use
effi
cien
cy(P
E)
an
dagro
nom
icef
fici
ency
(AE
)in
malt
ing
barl
ey.
2005
2006
Sit
eT
reatm
ent
Nta
ken
up
(kg
ha�
1)
PE
(gg�
1)
AE
(kg
gra
inkg�
1N
)
PN
/N
(mol
CO
2g�
1N
s�1)
Nta
ken
up
(kg
ha�
1)
PE
(gg�
1)
AE
(kg
gra
inkg�
1N
)
PN
/N
(mol
CO
2g�
1N
s�1)
Nan
jin
gF
TN
50
181.8
a34.2
bc
8.3
c11.3
c184.4
b28.7
c6.8
b11.0
b
FT
N40
193.0
a37.4
b11.2
b12.8
ab
207.7
a30.5
b9.6
a12.3
ab
FT
N30
197.1
a40.6
a13.9
a13.8
a201.4
a32.9
a9.9
a13.3
a
FT
N20
158.6
b32.8
c11.1
b13.4
a159.6
c30.9
b6.4
b12.6
ab
FT
N0
119.3
c30.8
c8.1
c12.1
b132.0
d28.2
c6.0
b11.2
b
Yan
chen
gF
TN
50
190.9
a32.2
b12.7
b13.5
c192.7
b30.7
b8.1
b13.3
c
FT
N40
196.7
a37.0
a13.6
b15.4
b209.9
a33.0
a8.5
b14.7
b
FT
N30
211.1
a39.4
a16.0
a17.8
a214.4
a33.4
a10.2
a16.3
a
FT
N20
��
��
��
��
FT
N0
123.6
b32.9
b11.5
c16.4
ab
145.5
c30.1
b7.9
b14.9
b
F(F
TN
)356
**
78.6
**
98
**
132
**
276
**
57
**
49
**
46
**
F(S
ite)
32
**
66.3
*32
**
23
**
12
*43
**
25
**
55
**
F(Y
ear)
23
**
67
**
221
**
8*
PN
/N�
photo
syn
thet
icN
use
effi
cien
cyin
pen
ult
imate
leav
esat
an
thes
is(m
mol
CO
2g�
1N
s�1),
PE�
physi
olo
gic
al
nit
rogen
use
effi
cien
cy(g
g�
1),
AE�
nit
rogen
agro
nom
icef
fici
ency
(kg
gra
in
kg�
1N
).D
iffe
ren
tsm
all
lett
ers
inth
esa
me
colu
mn
ind
icate
sign
ific
an
td
iffe
ren
ces
at
p�
0.0
5.
**,
*an
dN
Sm
ean
ssi
gn
ific
an
td
iffe
ren
ces
at
p�
0.0
1,p�
0.0
5,an
dn
on
-sig
nif
ican
ce,re
spec
tive
ly.F
(FT
N),
F(S
ite)
an
dF
(Yea
r)re
fers
tosi
gn
ific
an
td
iffe
ren
ces
am
on
gF
TN
trea
tmen
tsat
two
site
sat
on
eyea
r,b
etw
een
two
site
sam
on
gF
TN
trea
tmen
tsat
on
eyea
r,an
db
etw
een
two
years
am
on
g
trea
tmen
tsat
two
site
s,re
spec
tive
ly.
416 J. Cai et al.
Dow
nloa
ded
by [
Uni
vers
ity o
f N
ew M
exic
o] a
t 00:
01 2
7 N
ovem
ber
2014
accumulated assimilates (APA) in plants and its
contribution to grain mass (CoAPA).
Post-anthesis assimilates synthesis depends on the
intercepted radiation and its use efficiency,
i.e. leaf photosynthesis (Sinclair and Muchow
1999). Leaf area index (LAI) and light extinction
coefficient (K) well determine the intercepted radia-
tion efficiency (Ariosa et al. 2006). N fertilization s
found to improve both intercepted radiation (Salva-
giotti and Miralles 2008) and LAI (Zhong
et al. 2002). In this study both LAI and intercepted
radiation (K) were affected by FTN, and were the
highest at FTN30, together with the highest amount
of post-anthesis accumulated assimilates (APA). This
may be attributed to the size of barley population.
Barley that receives much N at stem elongation could
improve growth status and area of single leaf in fill
ing stage, but the plants that received less N in growth
prophase resulted in small plant population in filling
stage. The plant population for much early N
application was largest at the beginning of elongation
stage, but the population became smaller without
topdressed N, and the single leaf area was lower. So
the single barley leaf area was not highest for FTN30,
but the canopy was largest in filling stage which was
also consistent with the highest spike number. This
result may partially explain the highest grain yield
at FTN30.
PN of the penultimate leaf was also the highest
at FTN of 30% in this study. The canopy
photosynthesis could be more related to grain yield
than the single leaf photosynthesis (Albrizio and
Steduto 2003). We did not measure the canopy
photosynthesis here. However, considering that PN
of the penultimate leaf was the highest after anthesis
(not considering the very small flag leaf), the
cumulative PN*LAI over grain filling could be an
good indicator of the gross maximum canopy
photosynthesis (GCP) after anthesis. It is very
interesting that, both grain yield and APA were
found closely correlated to GCP at both sites and
in both years (Figure 4). In addition, GCP was the
highest for FTN30 treatment (data not shown),
indicating that the improved canopy photosynthesis
Table V. Effect of fraction of topdressed N on contents of grain protein.
2005 2006
Item Site FTN50 FTN40 FTN30 FTN20 FTN0 FTN50 FTN40 FTN30 FTN20 FTN0
Grain protein Nanjing 14.72 a 14.17 a 12.08 b 11.46 b 10.61 c 13.32 a 13.01 ab 12.82 b 11.94 c 11.34 d
content (%) Yancheng 12.83 a 12.18 ab 11.61 b 10.29 c 13.20 a 12.85 b 12.50 b 11.22 c
Different small letters in the same column of each cultivar indicate significant differences at p �0.05.
4000
5000
6000
7000
20052006
4000
5000
6000
7000
20052006
1
2
3
4
5
20052006
800 1600 2400 3200 800 1600 2400 32001
2
3
4
20052006
Gra
in y
ield
(kg
ha-1
)
APA
(g
plan
t-1)
GCP
r = 0.667**
r = 0.638**r = 0.912**
r = 0.723**
r = 0.705**
r = 0.827**
r = 0.863**
r = 0.885**
NJ NJ
YC YC
Figure 4. Correlations of GCP to grain yield and APA in Nanjing (NJ) and Yancheng (YC) in 2005 and 2006. GCP � gross maximum
canopy photoassimilates after anthesis, APA � amount of post-anthesis accumulated assimilates transferred to grains (g plant�1).
Split nitrogen applications in malting barley 417
Dow
nloa
ded
by [
Uni
vers
ity o
f N
ew M
exic
o] a
t 00:
01 2
7 N
ovem
ber
2014
was due to an enhanced leaf photosynthesis and
an optimum LAI. This result was consistent with
earlier findings by Kouki (2003). In addition, GCP
was higher in YC than in NJ, and higher in 2005
than in 2006. This coincided with the fact that APA
and grain yield were the highest for FTN30 treatment
and in 2005 at YC.
It should be noted that FTN treatment also
affected N taken up in barley plants and thus N
use efficiency. Here, PE is defined as grain yield per
unit N taken up by plants (Ladha et al. 1998), AE
represents grain yield gain in response to N fertilizer
applied (Novoa and Loomis 1981, Craswell and
Godwin 1984), while PN/N is the ratio of leaf PN to
leaf N concentration, which can well indicate CO2
fixation capacity under a given N nutritional status
in leaf (Kumar et al. 2004). The highest crop N
taken up was observed for FTN30 or FTN40 treat-
ment, and PE, AE and PN/N were also the highest
for FTN30 treatment. Thus, an appropriate FTN
fertilization, viz. FTN30 not only improved grain
yield but also the N use efficiencies. In good
agreement with our findings, earlier studies have
demonstrated that N fertilizer recovery and use
efficiency in wheat increase when fertilizer is applied
as top dressing prior to stem elongation (Lopez-
Bellido et al. 2005) and PE in rice decreases under
heavier ear N fertilization (Jiang et al. 2005), which
were simliar to our results in malting barley.
Furthermore, it was noteworthy that that PN/N
of the penultimate leaf positively correlated to both
PE and AE (Figure 5), indicating that a great
N use efficiency for CO2 assimilation at the leaf
level contributes significantly to the N use efficiency
for grain production for the crop. A functional
dependence of N taken up on photosynthetic activity
and photoassimilates availability has been inferred in
many experimental studies (Clement et al. 1978,
Rufty et al. 1989). The levels of carbohydrate supply
during darkness are likely to be largely responsible
for the rates of NO3� taken up (Ourry et al. 1996).
There is also a demand for carbon skeletons to
assimilate the NH4� produced from NO3
� to amino
acids (Greg et al. 1992). In our research, the increase
in PN/N at appropriate FTN treatment contributed
significantly to the improvement of photoassimilates
accumulation in barley plants, which, in turn,
provided a strong dependence for NO3� taken up
and assimilation. Therefore, optimized FTN appli-
cation advanced the effective use of N for photo-
synthesis in leaves, which was crucial in PE and AE
improvement in malting barley.
Acknowledgements
This study was funded by projects of the National
Natural Science Foundation of China (30671216,
30700483, 30971734), the Natural Science Foun-
dation of Jiangsu Province (BK2008329), the
Specialized Research Fund for the Doctoral Pro-
gram of Higher Education (20050307006), the
Program for New Century Excellent Talents in
University (06-0493), and the earmarked fund for
Modern Agro-industry Technology Research
System (nycytx-03).
20
30
40
50
20052006
20
30
40
50
20052006
0
5
10
15
20
20052006
12 14 16 18 12 14 16 180
5
10
15
20
20052006
PE (
g g-1
)
AE
(kg
gra
in k
g-1 N
)
PN/N (µmol CO2 g-1 N s-1)
r = 0.706**
r = 0.665**r = 0.845**
r = 0.711**
r = 0.753**
r = 0.819**r = 0.741**
r = 0.702**
NJ
YC
NJ
YC
Figure 5. Correlations of PN/N to PE and AE in Nanjing (NJ) and Yancheng (YC) in 2005 and 2006. PN/N � photosynthetic N-use
efficiency in penultimate leaves at anthesis (mmol CO2 g�1 N s�1), PE � physiological nitrogen use efficiency (g g�1), AE � agronomic
nitrogen use efficiency (kg grain kg�1 N).
418 J. Cai et al.
Dow
nloa
ded
by [
Uni
vers
ity o
f N
ew M
exic
o] a
t 00:
01 2
7 N
ovem
ber
2014
References
Albrizio, R. & Steduto, P. (2003). Photosynthesis, respiration and
conservative carbon use efficiency of four field grown crops.
Agricultural and Forest Meteorology, 116, 19�36.
Alcoz, M. M., Hons, F. M., & Haby, V. A. (1993). Nitrogen
fertilization timing effect on wheat production, nitrogen
uptake efficiency, and residual soil nitrogen. Agronomy
Journal, 85, 1198�1203.
Angas, P., Lampurlanes, J., & Cantero-Martınez, C. (2006).
Tillage and N fertilization: Effects on N dynamics and barley
yield under semiarid Mediterranean conditions. Soil &
Tillage Research, 87, 59�71.
Ariosa, Y., Carrasco, D., Quesada, A., & Fernandez-Valiente, E.
(2006). Incorporation of different N sources and light
response curves of nitrogenase and photosynthesis by cya-
nobacterial blooms from rice fields. Microbial Ecology, 51,
394�403.
Austin, R. B., Edrich, J. A., Ford, M. A., & Blackwell, R. D.
(1977). The fate of the dry matter, carbohydrates and 14C
lost from the leaves and stems of wheat during grain filling.
Annals of Botany, 41, 1309�1321.
Austin, R. B., Morgan, C. L., Ford, M. A., & Blackwell, R. D.
(1980). Contributions to grain yield from pre-anthesis
assimilation in tall and dwarf barley phenotypes in two
contrasting seasons. Annals of Botany, 45, 309�319.
Baethgen, W. E., Christianson, C. B., & Lamothe, A. G. (1995).
Nitrogen fertilizer effects on growth, grain yield, and yield
components of malting barley. Field Crops Research, 43,
87�99.
Bidinger, F., Musgrave, R. B., & Fisher, R. A. (1977). Contribu-
tion of stored pre-anthesis assimilate to grain yield in wheat
and barley. Nature, 270, 431�433.
Bindraban, P. S. (1999). Impact of canopy nitrogen profile in
wheat on growth. Field Crops Research, 63, 63�77.
Casanova, D., Epema, G. F., & Goudriaan, J. (1998). Monitoring
rice reflectance at field level for estimating biomass and LAI.
Field Crops Research, 55, 83�92.
Caviglia, O. P. & Sadras, V. O. (2001). Effect of nitrogen supply on
crop conductance, water- and radiation-use efficiency of
wheat. Field Crops Research, 69, 259�266.
Clement, C. R., Hopper, M. J., Jones, L. H. P., & Leafe, E. L.
(1978). The uptake of nitrate by Lolium perenne from flowing
nutrient solution II. Effect of light, defoliation, and relation-
ship to CO2 flux. Journal of Experimental Botany, 50, 1173�1183.
Craswell, E. T. & Godwin, D. C. (1984). The efficiency of
nitrogen fertilizers applied to cereals in different climates.
Advances in Plant Nutrition, 1, 1�55.
Delogu, G., Cattivelli, L., Pecchioni, N., De Falcis, D., Maggiore,
T., & Stanca, A. M. (1998). Uptake and agronomic
efficiency of nitrogen in winter barley and winter wheat.
European Journal of Agronomy, 9, 11�20.
Dordas, C. (2009). Dry matter, nitrogen and phosphorus
accumulation, partitioning and remobilization as affected
by N and P fertilization and source-sink relations. European
Journal of Agronomy, 30, 129�139.
Dreccer, M. F., Oijen, M. V., Schapendonk, A. H. C. M., &
Rabbinge, C. S. (2000). Dynamics of vertical leaf nitrogen
distribution in a vegetative wheat canopy. Impact on canopy
photosynthesis. Annals of Botany, 86, 821�831.
Greg, C. V., Heather, C. H., Katherine, D. M. V., & David, H. T.
(1992). Activation of respiration to support dark NO3� and
NH4� assimilation in the green alga Selenastrum minutum.
Plant Physiology, 99, 495�500.
Gebbing, T., Schnyder, H., & Kuhbauch, W. (1999). The
utilization of pre-anthesis reserves in grain filling in wheat.
Assessment by steady-state 13C/12C labelling. Plant Cell and
Environment, 22, 851�858.
Javier, G., Jaume, F., Maurici, M. U. S., Josep, C., Elkadri, L., &
Hipolito, M. (2003). Relationship between maximum leaf
photosynthesis, nitrogen content and specific leaf area in
balearic endemic and non-endemic Mediterranean species.
Annals of Botany, 92, 215�222.
Jiang, D., Dai, T., Jing, Q., Cao, W., Zhao, H., Zhou, Q., & Fan,
X. (2004). Effects of long-term fertilization on leaf photo-
synthetic characteristics and grain yield in winter wheat.
Photosynthetica, 42, 439�446.
Jiang, D., Fan, X., Dai, T., & Cao, W. (2008). Nitrogen fertiliser
rate and post-anthesis waterlogging effects on carbohydrate
and nitrogen dynamics in wheat. Plant and Soil, 304, 301�314.
Jiang, L., Dong, D., Gan, X., & Wei, S. (2005). Photosynthetic
efficiency and nitrogen distribution under different nitrogen
management and relationship with physiological N-use
efficiency in three rice genotypes. Plant and Soil, 271, 321�328.
Kiniry, J. R., Bean, B., Xie, Y., & Chen, P. Y. (2004). Maize
yield potential: critical processes and simulation modeling
in a high-yielding environment. Agricultural Systems, 82, 45�56.
Kouki, H. (2003). A model of dynamics of leaves and nitrogen in a
plant canopy: An integration of canopy photosynthesis, leaf
life span, and nitrogen use efficiency. American Naturalist,
162, 149�164.
Kumar, P., Parry, M., Mitchell, R., Ahmad, A., & Abrol, Y.
(2004). Photosynthesis and nitrogen-use efficiency. In C. H.
Foyer & G. Noctor (eds.) Photosynthetic nitrogen assimilation
and associated carbon and respiratory metabolism, pp. 23�34.
Dordrecht: Kluwer Academic Publishers.
Lopez-Bellido, L., Lopez-Bellido, R.J., & Redondo, R. (2005).
Nitrogen efficiency in wheat under rainfed Mediterranean
conditions as affected by split nitrogen application. Field
Crops Research, 94, 86�97.
Ladha, J. K., Kirk, G. J. D., Bennett, J., Peng, S., Reddy, C. K.,
Reddy, P. M., & Singh, U. (1998). Opportunities for
increased nitrogen-use efficiency from improved lowland
rice germplasm. Field Crops Research, 56, 41�71.
Lone, P. M. & Khan, N. A. (2007). The effects of rate and
timing of N fertilizer on growth, photosynthesis, N accumu-
lation and yield of mustard (Brassica juncea) subjected to
defoliation. Environmental and Experimental Botany, 60, 318�323.
Mahler, R. L., Koehler, F. E., & Lutcher, L. K. (1994). Nitrogen
source, timing of application, and placement effects on
winter wheat production. Agronomy Journal, 86, 637�642.
Makino, A. & Osmond, B. (1991). Solubilization of ribulose-1,5-
bisphosphate carboxylase from the membrane fraction of pea
leaves. Photosynthesis Research, 29, 79�85.
Masoni, A., Ercoli, L., Mariotti, M., & Arduini, I. (2007). Post-
anthesis accumulation and remobilization of dry matter,
nitrogen and phosphorus in durum wheat as affected by soil
type. European Journal of Agronomy, 26, 179�186.
Monteith, J. L. (1977). Climate and the efficiency of crop
production in Britain. Philosophical Transactions of the Royal
Society B: Biological Sciences, 281, 277�294.
Novoa, R. & Loomis, R. S. (1981). Nitrogen and plant produc-
tion. Plant and Soil, 58, 177�204.
Olesen, J. E., Jorgensen, L. N., & Mortensen, J. V. (2000).
Irrigation strategy, nitrogen application and fungicide control
in winter wheat on a sandy soil. II. Radiation interception
and conversion. Journal of Agricultural Science, 134, 13�23.
Ourry, A., Macduff, J. H., Prudhomme, M. P., & Boucaud, J.
(1996). Diurnal variation in the simultaneous uptake and
Split nitrogen applications in malting barley 419
Dow
nloa
ded
by [
Uni
vers
ity o
f N
ew M
exic
o] a
t 00:
01 2
7 N
ovem
ber
2014
‘sink’ allocation of NH4� and NO3
� by Lolium perenne in
flowing solution culture. Journal of Experimental Botany, 47,
1853�1863.
Papakosta, D. K. & Gagianas, A. A. (1991). Nitrogen and dry
matter accumulation, remobilization, and losses for Medi-
terranean wheat during grain filling. Agronomy Journal, 83,
864�870.
Przulj, N. & Momcilovic, V. (2001). Genetic variation for dry
matter and nitrogen accumulation and translocation in two-
rowed spring barley: I. Dry matter translocation. European
Journal of Agronomy, 15, 241�254.
Reddy, B. V. S., Sanjana Reddy, P., Bidinger, F., & Blummel, M.
(2003). Crop management factors influencing yield and
quality of crop residues. Field Crops Research, 84, 57�77.
Rufty, T. W., Mackown, C. T., & Volk, R. J. (1989). Effects of
altered carbohydrate availability on whole-plant assimilation
of 15NO3�. Plant Physiology, 89, 457�463.
Salvagiotti, F. & Miralles, D. J. (2008). Radiation interception,
biomass production and grain yield as affected by the
interaction of nitrogen and sulfur fertilization in wheat.
European Journal of Agronomy, 28, 282�290.
Sinclair, T. R. & Muchow, R. C. (1999). Radiation-use efficiency.
Advances in Agronomy, 65, 215�265.
Tambussi, E. A., Nogues, S., Ferrio, P., Voltas, J., & Araus, J. L.
(2005). Does higher yield potential improve barley
performance in Mediterranean conditions?: A case study.
Field Crops Research, 91, 149�160.
Tan, W., Liu, J., Dai, T., Jing, Q., Cao, W., & Jiang, D. (2008).
Alterations in photosynthesis and antioxidant enzyme activity
in winter wheat subjected to post-anthesis water-logging.
Photosynthetica, 46, 21�27.
van Herwaarden, A. F., Angus, J. F., Richards, R. A., & Farquhar,
G. D. (1998). ‘Haying-off ’, the negative grain yield response
of dryland wheat to nitrogen fertiliser. II. Carbohydrate and
protein dynamics. Australian Journal of Agricultural Research,
49, 1083�1094.
Yang, J. & Zhang, J. (2006). Grain filling of cereals under soil
drying. New Phytologist, 169, 223�236.
Yang, J., Zhang, J., Wang, Z., Zhu, Q., & Liu, L. (2001). Water
deficit-induced senescence and its relationship to the remo-
bilization of pre-stored carbon in wheat during grain filling.
Agronomy Journal, 93, 196�206.
Zhong, X., Peng, S., Sheehy, J. E., Visperas, R. M., & Liu, H.
(2002). Relationship between tillering and leaf area index:
quantifying critical leaf area index for tillering in rice. Journal
of Agricultural Science, 138, 269�279.
420 J. Cai et al.
Dow
nloa
ded
by [
Uni
vers
ity o
f N
ew M
exic
o] a
t 00:
01 2
7 N
ovem
ber
2014