Vol.1, No.1, 10-16 (2010)s
Copyright © 2010 SciRes. Openly accessible at http://www.scirp.org/journal/as/
Agricultural Science
Rice yield, nitrogen utilization and ammonia
volatilization as influenced by modified rice cultivation
at varying nitrogen rates
Limei Zhao1,2, Lianghuan Wu1*, Cunjun Dong3, Yongshan Li4
1Ministry of Education Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and
Resource Sciences, Zhejiang University, Hangzhou, China; *Corresponding Author: finm@zju.edu.cn
2College of Ecology and Environmental Science, Inner Mongolia Agricultural University, Huhhot, China
3College of Agriculture & Biotechnology, Zhejiang University, Hangzhou, China
4Cotton Research Institute, Shanxi Academy of Agricultural Sciences, Yuncheng, China
Received 15 March 2010; revised 5 April 2010; accepted 10 April 2010.
Field experiments were conducted in 2006 to
investigate the impacts of modified rice cultiva-
tion systems on: grain yield, N uptake, ammonia
volatilization from rice soil and N use efficiency
(ANUE, agronomic N use efficiency; and PFP,
partial factor productivity of applied N). The tri-
als compared rice production using modified
methods of irrigation, planting, weeding and
nutrient management (the system of rice inten-
sification, SRI) with traditional flooding (TF).
The effect s of differen t N application rates (0, 80,
160, 240 kg ha-1) and of N rates interacting with
cultivation methods were also evaluated. Grain
yields ranged from 5.6 to 6.9 t ha-1 with SRI, and
from 4.0 to 6.1 t ha-1 under TF management. On
average, grain yields under SRI were 24% higher
than that with TF. Ammonia volatilization was
increased significantly under SRI compared
with TF and the average total amount of ammo-
nia volatilization loss during the rice growth
stage under SRI was 22% higher than TF. With
increases in application rate, N uptake by rice
increased, and the ratio of N in the seed to total
N in the plant decreased. Furthermore, results
showed that higher ANUE was achieved at a
relatively low N fertilizer rate (80 kg ha-1 N) with
SRI. Results of these studies suggest that SRI
increased rice yield and N uptake and improved
ammonia volatilization loss from rice soil com-
pared with TF. Moreover, there were significant
interactions between N application rates and
cultivation methods. We conclude that it was
the most important to adjust the amount of N
application under SRI, such as reducing the
amount of N application. Research on effects of
N fertilizer on rice yield and environmental pol-
lution under SRI may be worth further studying.
Keywords: Ammonia Volatilization; N Use
Efficiency; Paddy Soil; Rice Yield; The System of
Rice Intensification
Nitrogen (N) is the most important nutrient in irrigated
rice production [1], and current high yields of irrigated
rice are usually associated with large applications of
fertilizer N [2] . China is currently the world’s largest
consumer of nitrogen fertilizers, accounting for 35% of
the global N fertilizer consumption [3], and about 7% N
was applied to irrigated rice [4]. Nitrogen use efficiency
for rice is lower about 30-35% and with N losses up to >
50% in China [5]. The unique condition of the paddy can
promote N losses through denitrification, ammonia vola-
tilization and leaching, and N losses not only lead to
decrease in N fertilizer efficiency but also to soil, water
and atmospheric pollution. Therefore, the measurement
and assessment of N losses and increased N use effi-
ciency have been of great significance for sustainable
agriculture and environmental protection. Ammonia vo-
latilization is the major process of N losses in irrigated
rice, accounting for 0.41-40% of applied N as urea in
China [6]. Ghosh and Ravi reported that ammonia vola-
tilization losses in flooded soil ranged from negligible
amounts to 60% of applied N [7]. The impact of ammo-
nia volatilization losses on environmental quality has
attracted a great deal of attention [6,8].
In addition, irrigation plays a critical role in the ability
of the rice sector to expand production to meet continu-
ally growing demand [9] since about 75% of rice pro-
duction in the world comes from irrigated lowland rice
fields [10]. China’s 31.7 million ha of rice fields account
for about 20% of the world’s rice area and produce about
L. M. Zhao et al. / Agricultural Sciences 1 (2010) 10-16
Copyright © 2010 SciRes. Openly accessible at http://www.scirp.org/journal/as/
35% of total rice production [11]. However, fresh water
for irrigation is becoming scarce because of increasing
competition from urban and industrial demand [12-14].
Water resource limitations threaten the sustainability of
irrigated rice systems in many countries, and wa-
ter-saving rice cultivation methods are urgently needed
to keep up with future food demands. Water-saving rice
cultivation is important for rice production systems in
the future.
A water-saving rice cultivation method known as the
System of Rice Intensification (SRI) has been introduced
into China from Madagascar where rice productivity is
reportedly increased by simultaneously modifying sev-
eral practices in rice cultivation [15]. With SRI, changes
in standard management practices include: transplanting
very young seedlings at the 2-3 leaf stage; having just
one seedling per hill with wider spacing in a square pat-
tern rather than rows; maintaining non-flooded soil con-
ditions during the vegetative stage and very shallow ir-
rigation after flowering; soil-aerating hand weeding; and
application of large quantities of organic manure [15,16].
SRI alters the environment for growing rice with no
standing water during the vegetative growth period and
only a thin layer of water on the field (1-2 cm) from
panicle initiation until 10-15 days before harvest. These
practices may be influence on nutrient form in soil and
nutrient uptake and utilization by rice. Lower nitrogen
efficiency with conventional plant/soil/nutrient man-
agement and high nitrogen losses from the soil/plant
system, adversely affecting environmental quality, has
attracted a great deal of attention. However, there is little
information about what happens (specifically, N use ef-
ficiency and N losses as ammonia) with SRI practices.
The objective of this study was to evaluate the impact of
different rice cultivation methods and nitrogen fertiliza-
tion rates on rice yield, N uptake, and N-use efficiency
and ammonia loss.
2.1. Site Description
Located in the northern part of Zhejiang Province, east-
ern China, field experiment was conducted on the farm
of Zhejiang University, Huajia Chi Campus in Hangzhou
(30°16N, 120°12E). The elevation is 4.3 m. At the ex-
perimental site, the Hungson paddy soil (clay loamy
typic-hapli-stagnic anthrosol) has a pH of 6.8, organic
matter of 11.2 g kg-1, available N of 104.8 mg kg-1, Ol-
sen-P of 83.6 mg kg-1, and available K of 65.2 mg kg-1.
2.2. Experimental Design, Fertilization and
Cultural Practices
The field experiment utilized a split-plot design with
cultivation methods as main plots (traditional flooding =
TF, or system of rice intensification = SRI), and N rates
as subplots, all with three replications. The subplots
(5.5 m × 4.2 m = 23.1 m2) of the main TF and SRI plots
received, respectively, either 0 kg N ha-1, 80 kg N ha-1,
160 kg N ha-1 or 240 kg N ha-1. 60% of the total N ap-
plication as basal fertilizer (on May 19) was applied (as
urea) one day before transplanting; then 20% of the total
N was applied as tillering fertilizer on June 29 and as
booting fertilizer on July 29, respectively. Other fertiliz-
ers applied were 54 kg P2O5 ha-1 (as calcium phosphate)
and 67.5 kg K2O ha-1 (as potassium chloride), incorpo-
rated one day before transplanting as basal fertilizer.
All plots were surrounded by consolidated bunds lined
with plastic sheets installed to a depth of 0.3 m to pre-
vent seepage between plots. Land preparation for both
TF and SRI was the same, with wet tillage and harrow-
ing. Seedlings of 13 days age for SRI and 20 days age
for TF were transplanted with one seedling per hill.
Transplanting spacing between hills was different: 25 cm
× 30 cm for SRI, and 25 cm × 17 cm for TF; plant popu-
lations, respectively, were 13.3 and 23.5 m-1. A japonica
rice variety was used (Bing 98110) transplanted on 13
May and harvested on 13 October.
TF plots were continuously flooded with 2-10 cm wa-
ter depth except at the end of the tillering stage, when
plots were drained 7 days before harvest. SRI plots were
kept saturated the first week after transplanting; thereaf-
ter they were maintained in a moist condition without
standing water covering the field until 15 days after pa-
nicle initiation when a thin layer (2 cm) of water was
maintained. Each main plot was irrigated separately,
with water supplied every 3-7 days, depending on am-
bient temperature affecting evapotranspiration. Irriga-
tion water was provided from a tap to a depth of 2 cm
each time, as measured by a plastic ruler inserted into
the plot.
2.3. Ammonia Sampling and Chemical
Ammonia volatilization from soil in rice field was de-
termined by venting method, and the instrument used is
shown in Figure 1 [17]. The diameter and height of the
Figure 1. Design of instrument for collecting
ammonia volatilization from the soil surface.
15 cm
L. M. Zhao et al. / Agricultural Sciences 1 (2010) 10-16
Copyright © 2010 SciRes. Openly accessible at http://www.scirp.org/journal/as/
PVC cylinder was 15 cm and 30 cm, respectively. Two
pieces of sponge (2.5 cm thickness) were installed in a
PVC cylinder after being immersed with 15 ml glycerol
phosphoric acid (5%, v/v, phosphoric acid and 4%, v/v,
glycerol). The base of the cylinder was inserted 2 cm
into the soil. The lower sponge was 20 cm distance of
the soil surface and used to absorb ammonia volatilized
from the soil surface in the cylinder, and the upper
sponge was 5.0 cm distance of the lower sponge and was
to absorb ammonia from outside the cylinder and to
prevent its absorption by the lower sponge. After fertil-
izer was applied, the instrument was installed immedi-
ately. Within one week after fertilization, the lower
sponge was replaced with a new one after 24 h, and after
one week, the lower sponge was replaced with a new
one after 48 h. The upper sponge was changed every 3
days. The sponges were extracted with 300 ml of 1 mol/L
KCl for 1 h and analyzed N content by nitrogen auto
analyzer (KDN-102C, China).
2.4. Statistical Analysis
Analysis of variance (ANOVA) was performed on a
split-plot design with cultivation methods as the main
factor and N rates as the sub-factor. When cultivation
methods or N rates effects were significant, pair-wise-
testing with the t-test was done between cultivation
methods or among N rates. The level of confidence was
set at 95%. Statistical procedures were conducted using
the data processing system software [18].
3.1. Effects of SRI and N Fertilizer Rate on
Grain Yield
Grain yield ranged from 5.6 to 6.9 t ha-1 under SRI, and
from 4.0 to 6.1 t ha-1 under TF (Table 1). The maximum
grain yield was at N1 level (80 kg N ha-1) under SRI and
at N2 level (160 kg N ha-1) under TF. SRI significantly
increased grain yield compared to TF in N0 and N1;
however, there was no significant difference at N2 and
N3 levels. Over the whole range of N application rates,
SRI gave on average yields 22% higher than TF using
much less irrigation water.
At maturity, grain yield was determined as the mean
of two 5-m2 samples per sub-plot. Plant samples were
taken from 5 hills in every sub-plot to determine the
amount of aboveground biomass after the samples were
dried at 70C. Total N content was determined using the
standard Kjeldahl method.
Agronomic N use efficiency (ANUE, kg grain kg N
applied-1) was calculated from the difference in grain
yields N between fertilized and unfertilized plots divided
by the N application rate. Partial factor productivity of
applied N (PFP, kg grain kg N applied-1) was calculated
as grain yields divided by the N application rate.
3.2. N Uptake by Rice and Distribution in
Different Organs
SRI plants had greater N uptake than TF plants (Figure
2). N uptake by rice ranged from 308.8 to 596.4 mg
Table 1. Grain yield of rice under SRI and TF with N rates (n = 3).
Grain yield (t ha-1)
N (kg ha-1) TF SRI Difference
0 (N0) 4.0 b 5.6 b 1.6
80 (N1) 4.9 a 6.9 b 2.0
160 (N2) 6.1 a 6.7 a 0.6
240 (N3) 5.7 b 6.1 a 0.4
Analysis of variance
N level
Cultivation × N rates **
Notes: Values followed by the same letter in a column are not significantly different at the 5% level by LSD; ns = not significant; * = P <
0.05; ** = P < 0.01 between SRI and TF.
N0 N1 N2 N3N0 N1 N2 N3
N uptake (mg plant
Leaf Stem and sheathsPanic le
N0 N1 N2 N3N0 N1 N2 N3
N distribution in different organ
(a) (b)
Notes: The same letter within different N rate under SRI and TF are not significantly different by LSD at the 0.05 level.
Figure 2. N uptake and distribution in stem and sheaths, leaf and panicle at maturing stage.
L. M. Zhao et al. / Agricultural Sciences 1 (2010) 10-16
Copyright © 2010 SciRes. Openly accessible at http://www.scirp.org/journal/as/
plant-1 under TF and ranged from 673.1 to 957.4 mg
plant-1 under SRI management. SRI significantly in-
creased total N uptake by individual plants, and N up-
take by leaves, stem-sheaths and panicle irrespective of
the N application rate compared to TF. Total N per plant,
N uptake by leaves and stem-sheaths increased with in-
creased N application rate; however, maximum amount
of N uptake in panicle was in N2 level and then de-
creased under both SRI and TF when N applications
were higher (Figure 2(a)). The ratio of N in leaves and
stem-sheaths to total N uptake increased with increased
N rate, while the ratio of N in panicle to total N uptake
decreased (Figure 2(b)).
3.3. Effects of SRI and N Fertilizer Rate on
Nitrogen Use Efficiency
The interactive effects of cultivation methods and N rate
on ANUE and PFP were significantly different. Values
of agronomic N use efficiency (ANUE) ranged from 7.1
to 12.6 kg grain kg-1 N applied under TF, and from 2.1 to
15.7 kg grain kg-1 N applied under SRI (Table 2). Values
for partial factor productivity of applied N (PFP) ranged
from 23.9 to 61.3 kg grain kg-1 N applied under TF, and
25.5 to 86.0 kg grain kg-1 N applied under SRI. Com-
pared with TF, ANUE with SRI methods was higher in
N1 and lower in N2 and N3. However, PFP under SRI
was higher than TF in each N treatment. N application
and cultivation methods significantly influenced ANUE
and PFP.
3.4. Effects of SRI and N Fertilizer Rate on
Ammonia Volatilization
Changes in ammonia volatilization rate at basal, tillering
and booting stages under both SRI and TF treatments
were similar (Figure 3), and the highest rate appeared 4
days after basal and tillering fertilization and 3 days after
booting fertilization, respectively. The total amount of
ammonia volatilization loss ranged from 2.14 to 13.13
kg ha-1 under TF and from 3.14 to 16.23 kg ha-1 under
SRI, respectively. This accounted for 3.2-5.3% and
3.9-5.8% of the total N applied (Ta b l e 3). Total ammo-
nia volatilization loss increased by 23.6~46.7% with SRI
compared to TF. N fertilizer input significantly led to
higher ammonia volatilization rate and loss than the
N-zero controls for both TF and SRI.
4.1. Grain Yield
Compared to TF, SRI significantly increased grain yield.
This may be attributed to the increase of the number of
Table 2. Agronomic N use efficiency (ANUE, kg grain kg N applied-1) and partial factor productivity of applied N (PFP,
kg grain kg N applied-1) under SRI and TF with N rate (n = 3).
N (kg ha-1)
TF SRI Difference TF SRI Difference
80 (N1) 10.6 a 15.7 a 5.1
** 61.3 a 86.0 a 24.7
160 (N2) 12.6 a 7.0 b -5.6
** 37.9 b 42.1 b 4.2
240 (N3) 7.1 b 2.1 c -5.0
** 23.9 b 25.5 c 1.6
Analysis of variance ANUE PFP
Cultivation * **
N level ** **
Cultivation × N rate ** **
Notes: Values followed by the same letter in a column are not significantly different at the 5% level by LSD; ns = not significant; *
= P < 0.05; ** = P < 0.01.
Table 3. Ammonia volatilization losses after N fertilizer application at basal, tillering and booting stages (kg N ha-1) (n = 3).
ultivation N rates Basal fertilizer Tillering fertilizer Booting fertilizer Total NH3 loss
TF N0 1.02 a 0.80 a 0.32 a 2.14 a
N1 3.77 b 1.58 b 1.08 b 6.44 b (5.37)
N2 4.91 c 3.03 c 1.84 c 9.78 c (4.77)
N3 6.33 d 4.19 d 2.61 d 13.13 d (4.58)
SRI N0 1.38 a 1.03 a 0.72 a 3.14 a
N1 4.22 b 1.98 b 1.67 b 7.88 b (5.93)
N2 6.06 c 3.65 c 2.48 c 12.19 c (5.66)
N3 7.78 d 5.04 d 3.41 d 16.23 d (5.45)
Notes: Values followed by the same letter within one column are not significantly different by LSD at the 0.05 level under the same cul-
tivation system. The number in parentheses indicated the percentage of the amount of applied N.
L. M. Zhao et al. / Agricultural Sciences 1 (2010) 10-16
Copyright © 2010 SciRes. Openly accessible at http://www.scirp.org/journal/as/
1234567912345679 12345679
Bas alTilleringBoo tin g
Days after fertilize
volatilization rate (mg N m
Figure 3. Average ammonia volatilization rates with four N
rates after N fertilizer application at basal (May 19), tillering
(June 29) and booting (July 29) stage under SRI and TF.
tiller and effective panicles and higher chlorophyll [19];
furthermore, the leaf N content (chlorophyll SPAD) is
closely related to photosynthetic rate and biomass pro-
duction [20]. Another explanation was SRI had greater
root activity and delayed root and leaf senescence during
later growth stages according to research [21,22].
The interactive effects on grain yield between cultiva-
tion and N rate was significant. The yield-increasing ef-
fect with SRI was affected by N fertilizer applied, and the
maximum yield difference in grain yield was in N1 (80
kg ha-1) level, and there were no significantly difference
at N2 (160 kg ha-1) and N3 (240 kg ha-1) level. These
results were explained that SRI plots likely had higher N
uptake from the indigenous supply due to the changes in
the environment for growing rice and had a better root
system under SRI. The SRI changes the environment of
rice growth from anaerobic to aerobic soil conditions,
with no standing water during the vegetative growth pe-
riod and only a thin layer of water on the field (1-2 cm)
from panicle initiation until 10-15 days before harvest.
These practices may affect the structure and functioning
of soil biota, nutrient status and cycling, and root system.
Bonkowski [23] indicated that under more aerobic soil
conditions, there will be larger populations of soil mi-
crobes that contribute to biological processes for supply-
ing N needs of plants. Hence, yield increase with SRI
should not rely on increased nitrogen application, the
moderate water requirements and nitrogen management
under SRI should be paid more attention.
4.2. N Uptake and Utilization
SRI increased the ratio of panicle N among four N fer-
tilizer levels compared with TF. ANUE and PFP both
decreased with increased N application rates, while the
ANUE in N2 (80 kg ha-1) level was at a maximum under
SRI. These results showed that SRI methods benefited
nitrogen uptake by rice and could promote the transfer of
nitrogen in leaves and stem-sheaths to the panicle, while
high-levels of nitrogen may have resulted just in luxury
uptake of N by rice. These results were supported by
other research [24,25]. Abha and Salokhe [26] indicated
that younger seedlings performed better than older seed-
lings when transplanted into either flooded or non-
flooded soils with greater uptake of nitrogen and man-
ganese than older seedlings. Higher available N in soil
resulting higher N uptake from soil under SRI manage-
ment compared to TF due to increased root biomass and
activity with SRI [21,25], while higher soil microbial
activity contributed to soil processes for supplying
plants’ nitrogen needs [23]. This was supported by Ru-
pela et al. [27] who reported that microbial biomass N,
microbial biomass carbon, dehydrogenase, root mass,
root density and root volume were higher under SRI than
in flooded rice.
4.3. Ammonia Vocalization Loss
N fertilizer significantly increased ammonia volatiliza-
tion loss of both SRI and TF, and ammonia volatilization
loss increased generally with higher N fertilizer rate. The
greatest loss of ammonia volatilization for both SRI and
TF was at the basal stage, next was at tillering stage, and
the smallest loss was at booting stage. This may suggest
that largest ammonia volatilization was affected by high
N fertilizer input and the different ratios of N fertilizer
applied at basal, tiller and booting stage. Higher ammo-
nia volatilization loss at basal stage was due to the root
systems having little sink capacity for N so early in the
crop cycle [28], especially with transplanting young
seedlings (about 15 days old) in our study. Though same
amount of N fertilizer was applied at tillering and boot-
ing stage, there is less loss at booting stage than tillering
stage, suggesting that at booting stage, well-developed
canopies reduced the ammonia volatilization loss due to
lower ammonia gas concentrations and restricted air
movement. Therefore, such results indicated that opti-
mum ratio of N fertilizer at different stages was impor-
tant to reduce ammonia volatilization losses.
Ammonium volatilization is consistently higher under
SRI than TF, suggesting a potentially more intensive N
loss under SRI, though with no significant difference
between both. This may suggest that non-flooded rice
led to higher concentration of NH4
+ in the soil and soil
solution than with flooding, which may have benefited
the long-term nitrogen availability for rice growth under
SRI. There was a significant correlation between NH4
in the soil, soil solution and ammonia volatilization loss
[29]. Cui et al. [30] have reported that ammonia volatili-
zation loss under water-saving irrigation was higher by
22.9% than with continuous flooding. Moreover, trans-
planting young seedlings with wider spacing under SRI
could be another reason to create higher ammonia vola-
tilization loss.
Our results showed that the highest grain yield of rice,
L. M. Zhao et al. / Agricultural Sciences 1 (2010) 10-16
Copyright © 2010 SciRes. Openly accessible at http://www.scirp.org/journal/as/
ANUE and PFP were achieved at a relatively low rate of
N fertilization (80 kg ha-1 N) under the system of rice
intensification (SRI). SRI significantly increased N up-
take during rice growth and promoted N translocation to
the panicle. Though SRI caused higher ammonium vola-
tilization loss than TF, the percentage of loss at 80 kg
ha-1 N is at the similar magnitude to that at higher N fer-
tilizer input rates (160~240 kg ha-1), which were charac-
terized by the decreasing grain yield and N use effi-
ciency (Tables 1-3). To increase N use efficiency and to
decrease N losses, as well as to maintain or improve soil
fertility for sustainable crop production, research efforts
are needed to focus on the effects of SRI on soil fertility
and nitrogen management. Due to the increasing fertil-
izer costs, irrigation water shortages, and growing pollu-
tion/environmental problems in the future decades, the
current study can help further investigate the different
cultivation system and fertilization strategy for the sake
of sustainable rice production and soil management at a
single-season experiment and long-term purpose.
This research was supported by the Key Project of Agricultural Con-
struction Adjustment of Ministry of Agriculture of China (No. 2003-
01-02A), Key Project of Ministry of Science and Technology of China
(2008ZX07101-006) and Key Projects in the National Science & Tech-
nology Pillar Program (No. 2008BADA4B03).
[1] Cassman, K.G., Peng, S., Olk, D.C., Ladha, J.K., Reich-
ardt, W., Dobermann, A. and Singh, U. (1998) Opportu-
nities for increased nitrogen-use efficiency from im-
proved resource management in irrigated rice systems.
Field Crops Research, 56(1-2), 7-39.
[2] Barker, R. and Dawe, D. (2001) The transformation of
the Asian rice economy and directions for future research:
the need for increased productivity. In: Sombilla, M.,
Hossain, M. and Hardy, B., Ed., Developments in the
Asian Rice Economy, International Rice Research Insti-
tute, Los Baños, 1-30.
[3] FAO. (2004) FAO Statistical databases. Food and Agri-
culture Organization (FAO) of the United Nations, Rome.
[4] Peng, S.B., Buresh, R.J., Huang, J.L., Yang, J.C., Zou,
Y.B., Zhong, X.H., Wang, G.H. and Zhang, F.S. (2006)
Strategies for overcoming low agronomic nitrogen use
efficiency in irrigated rice systems in China. Field Crops
Research, 96(1), 37-47.
[5] Qin, S.W., Fan, X.H. and Wang, J.F. (2001) The fertiliza-
tion technique of five main crops. In: Xu, J.A., Ed., Fer-
tilization and Agricultural Service, in Chinese, Chemical
Industry Press, Beijing.
[6] Gao, X.J., Hu, X.F., Wang, S.P., He, B.G. and Xu, S.Y.
(2002) Nitrogen losses from flooded rice field. Pedosphere,
12(2), 151-156.
[7] Ghosh, B.C. and Bhat, R. (1998) Environmental hazards
of nitrogen loading in wetland rice fields. Environmental
Pollution, 102(1), 123-126.
[8] Barthelmie, R.J. and Pryor, S.C. (1998) Implications of
ammonia emissions for the aerosol formation and visibil-
ity impairmenta case study from the Lower Fraser Valley,
Birtish Columbia. Atmospheric Environment, 32, 345-352.
[9] Van Nguyen, N. and Ferrero, A. (2006) Meeting the chal-
lenges of global rice production. Paddy Water Environ-
ment, 4, 1-9.
[10] Maclean, J.L., Dawe, D.C., Hardy, B. and Hettel, G.P.
(2002) Rice almanac. 3rd Edition, International Rice Re-
search Institute, Los Baños, 253.
[11] FAO. (2001) FAO Statistical databases. Food and Agri-
culture Organization (FAO) of the United Nations, Rome.
[12] Bouman, B.A.M. and Tuong, T.P. (2001) Field water
management to save water and increase its productivity
in irrigated rice. Agricultural Water Management, 49(1),
[13] Guerra, L.C., Bhuiyan, S.I., Tuong, T.P. and Barker, R.
(1998) Producing more rice with less water from irri-
gated systems. International Rice Research Institute, Los
Baños, 1-22.
[14] Tuong, T.P. and Bouman, B.A.M. (2003) Rice produc-
tion in water-scarce environments. In: Kijne, J.W., Barker,
R. and Molden, D., Ed., Water Productivity in Agricul-
ture: Limits and Opportunities for Improvement, CABI
Publishing, Wallingford, 53-67.
[15] Stoop, W.A., Uphoff, N. and Kassam, A. (2002) A review
of agricultural research issues raised by the system of
rice intensification (SRI) from Madagascar: Opportuni-
ties for improving farming systems for resource-poor
farmers. Agricultural Systems, 71(3), 249-274.
[16] Uphoff, N., Fernandes, E.C.M., Yuan, L.P., Peng, J.M.,
Rafaralahy, S. and Rabenandrasana, J. (2002) Assessment
of the system of rice intensification (SRI). Proceedings of
the International Conference, Sanya, 1-4 April 2002,
Cornell International Institute for Food, Agriculture and
Development (CIIFAD), Ithaca. http://ciifad.cornell.edu./
[17] Wang, C.H., Liu, X.J., Ju, X.T. and Zhang, F.S. (2002)
Field in situ determination of ammonia volatilization
from soil: Venting method. Plant Nutrition and Fertilizer
Science, 8(2), 205-209.
[18] Tang, Q.Y. and Feng, M.G. (2002) Practical application
of statistics analysis and data processing system. Science
Press, Bejing.
[19] Zhao, L.M., Wu, L.H., Li, Y.S., Animesh, S., Zhu, D.F.
and Uphoff, N. (2010) Comparisons of yield, water use
efficiency, and soil microbial biomass as affected by the
system of rice. Communications in Soil Science and
Plant Analysis, 41(1), 1-12.
[20] Peng, S., Garcia, F.V., Laza, R.C., Sanico, A.C., Vis-
peras, R.M. and Cassman, K.G. (1996) Increased N-use
efficiency using a chlorophyll meter on high-yielding ir-
rigated rice. Field Crops Research, 47(2), 243-252.
[21] Xu, F.Y., Ma, J., Wang, H.Z., Liu, H.Y., Huang, Q.L.,
Ma, W.B. and Ming D.F. (2003) The characteristics of
roots and their relation to the formation of grain yield
under the cultivation by system of rice intensification
(SRI). Hybrid Rice, in Chinese, 18(4), 61-65.
[22] Satyanarayana, A. (2005) System of rice intensification:
An innovative method to produce more with less water
and inputs. 4th IWMI-Tata Annual Partners Meeting,
L. M. Zhao et al. / Agricultural Sciences 1 (2010) 10-16
Copyright © 2010 SciRes. Openly accessible at http://www.scirp.org/journal/as/
IRMA, Anand, 24-26 February 2005.
[23] Bonrowski, M. (2004) Protozoa and plant growth: The
microbial loop in soil revisited. New Phytologist, 162(3),
[24] Chen, H.Z., Zhu, D.F., Rao, L.B., Lin, X.Q. and Zhang,
Y.P. (2006) Effects of SRI technique on population qual-
ity after heading stage and yield formation in rice. Jour-
nal of Huazhong Agricultural University, in Chinese,
25(5), 483-487.
[25] Lu, X.M., Huang, Q. and Liu, H.Z. (2006) Research of
some physiological characteristics under the system of
rice intensification. Journal of South China Agricultural
University, in Chinese, 27, 5-7.
[26] Mishra, A. and Salokhe, V.M. (2008) Seedling charactis-
tics and the early growth of transplanted rice under dif-
ferent water regimes. Experimental Agriculture, 44, 1-19.
[27] Rupela, O.P., Wani, S.P., Kranthi, M., Humayun, P.,
Satyanarayana, A., Goud, V., Gujja, B., Punnarao, P.,
Shashibhushan, V., Raju, D.J. and Reddy, P.L. (2006)
Comparing soil properties of farmers’ fields growing rice
by SRI and conventional methods. Proceedings of 1st
National SRI Symposium, Worldwide Fund for Na-
ture-ICRISAT, Hyderabad, 17-18 November 2006.
[28] Schnier, H.F. (1995) Significance of timing and method
of N fertilizer application for N-use efficiency in flooded
tropical rice. Fertilizer Research, 42(1-3), 129-138.
[29] Song, Y.S., Fan, X.H., Lin, D.X., Yang, L.Z. and Zhou,
J.M. (2004) Investigation on ammonia loss from the
flooded rice field in Taihu region and its influencing fac-
tors. Acta Pedologica Sinica, in Chinese, 41(2), 265-269.
[30] Cui, Y.L., Li, Y.H., Lv, G.A. and Sha, Z.Y. (2004) Nitro-
gen movement and transformation with different water
supply for paddy rice. Advances in Water Science, in
Chinese, 15(3), 280-285.