Effects of Supplemental Irrigation Based on Testing Soil Moisture on Dry Matter Accumulation and Distribution and Water Use Efficiency in Winter Wheat

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1 ACTA AGRONOMICA SINICA Volume 36, Issue 3, March 2010 Online English edition of the Chinese language journal Cite this article as: Acta Agron Sin, 2010, 36(3): RESEARCH PAPER Effects of Supplemental Irrigation Based on Testing Soil Moisture on Dry Matter Accumulation and Distribution and Water Use Efficiency in Winter Wheat HAN Zhan-Jiang 1,2, YU Zhen-Wen 1, *, WANG Dong 1, and ZHANG Yong-Li 1 1 Key Laboratory of Crop Ecophysiology and Cultivation, Ministry of Agriculture, Shandong Agricultural University, Tai an , China 2 Henan Institute of Science and Technology, Xinxiang , China Abstract: Water shortage is a serious problem threatening sustainable development of agriculture in the North China Plain, where winter wheat (Triticum aestivum L.) is the largest water-consuming crop. The objective of this study was to optimize irrigation scheme for high yield and high water use efficiency (WUE) in wheat, on the basis of Jimai 22, a representative cultivar in production. In the field experiments conducted in and growing seasons, unfixed amount of water was supplied at sowing, jointing, and anthesis stages to adjust the soil moisture into a controlled ladder. For example, the relative soil moisture contents in the W0 treatment were 80% at sowing, 65% at jointing, and 65% at anthesis; in the W1 treatment, they were 80%, 70%, and 70%, respectively; analogically, they were 80%, 80%, and 80% in the W2 treatment and 90%, 80%, and 80% in the W3 treatment. These results showed that the amount of dry matter accumulation at maturity was the lowest in the W0 treatment and the highest in the W1 treatment. The grain dry matter ratio was significantly higher in W1 than in W2 and W3. After anthesis, the dry matters in vegetative organs began to drain into grains, and the translocation amount and ratio were both ranked as W0 > W3 > W2 > W1, and the contribution of dry matter accumulation to grains was ranked as W1 > W2 > W3 > W0. Under the W1 condition, the filling rate and net photosynthetic rate maintained a relatively high level at the end of filling stage, which was favorable for increasing accumulation and distribution ratio of dry matter and grain weight at maturity. The WUE was higher in W0 than in other treatments. However, the grain yield was the lowest in treatment W0. In both growing seasons, the grain yield, irrigation water use efficiency (WUE I ), precipitation use efficiency (WUE P ), and irrigation benefit (IB) in W1, W2, and W3 were decreased significantly because more water was supplied. Under the experimental condition, the W1 regime was considered as the optimum. In this regime, the relative soil moisture contents in the cm soil layer were controlled to 80% at sowing, 70% at jointing, and 70% at anthesis stages. When 43.8 and 13.8 mm of water was supplied in the and growing seasons, the final grain yields of W1 treatment were kg ha 1 and kg ha 1, respectively, and the WUE I and WUE P were the highest among the 4 treatments. Keywords: winter wheat; soil moisture content; water-saving irrigation; dry matter accumulation and distribution; water use efficiency Water shortage has become a global problem to be solved urgently. China is one of 13 countries with serious water shortage, in which the capita possession of water resource is only a quarter of the world s average [1]. The North China Plain (NCP) is a major agricultural area in China, especially for wheat (Triticum aestivum L.) and corn (Zea mays L.) production. However, crop yield in this area is often restricted by water shortage and uneven distribution of precipitation. Wheat yield is mainly from the dry matter accumulation after anthesis and the dry matter redistribution in vegetative organs before anthesis, and soil moisture has significant effects on dry matter accumulation and distribution [2, 3]. High or low soil moisture after anthesis may cause a decrease of photosynthetic rate in flag leaf [4], resulting in reduction of dry matter accumulation amount, change of distribution ratio of dry matter among various organs, and a final loss of grain yield [5]. In a certain range, the wheat biomass is promoted with irrigation quantity increasing, and the dry matter Received: 5 September 2009; Accepted: 8 December * Corresponding author. yuzw@sdau.edu.cn Copyright 2010, Crop Science Society of China and Institute of Crop Sciences, Chinese Academy of Agricultural Sciences. Published by Elsevier BV. All rights reserved. Chinese edition available online at DOI: /S (09)

2 accumulation amount and distribution in grains after anthesis are also increased significantly. However, excessive irrigation inhibits dry matter translocating into grains and the final yield is reduced [6]. Moderately limited irrigation is an encouraged practice in wheat production because it is not only favorable for dry matter accumulation and grain filling [7 10], but also able to reduce water consumption and increase water use efficiency (WUE) [11]. Irrigation regime for wheat growing in different ecological environments is a hotspot in wheat cultivation research, and many experiments have been conducted with fixed irrigation amount. However, requirement of irrigation water amount is determined by soil moisture content in wheat field and the growth stage of wheat plant. In this study, we monitored the soil moisture content in cm soil layer during wheat growth and controlled the relative moisture content to designed levels at critical growth stages. Based on soil moisture content, the irrigation amounts were estimated and implemented at sowing, jointing, and anthesis stages. Four irrigation regimes were evaluated with the characteristics of dry matter accumulation and redistribution, final grain yield, and indices of WUE. The aim of this study was to guide water management in wheat field in the NCP region for high-yielding and water-saving production. 1 Materials and methods 1.1 Wheat cultivar and field design The field experiments were conducted with the wheat cultivar of Jimai 22 in Shiwang village (35.41 N, E), Yanzhou, Shandong Province, China in the and growing seasons. The top layer of soil (0 20 cm) contained 1.5% of organic matter, 0.10% of total nitrogen (N), 62.6 mg kg 1 of available N, 25.0 mg kg 1 of available phosphate (P), and mg kg 1 of available potassium (K) in the growing season. The precipitations in the growing season were as follows: 51.4 mm from sowing to jointing stage, 88.4 mm from jointing to anthesis stage, and 88.2 mm from anthesis to maturity stage. Soil field capacities before sowing of 0 20, 20 40, 40 60, 60 80, , , and cm soil layers were 24.70%, 25.27%, 24.73%, 25.01%, 24.63%, 23.51%, and 23.18%; soil bulk densities were 1.55, 1.50, 1.51, 1.52, 1.53, 1.58, and 1.56 g cm 3 ; and relative moisture contents were 62.42%, 54.60%, 75.44%, 89.36%, 77.49%, 77.00%, and 82.73%, respectively. The top layer of the soil (0 20 cm) contained 1.42% of organic matter, 0.11% of total N, mg kg 1 of available N, 31.8 mg kg 1 of available P, and mg kg 1 of available K in the growing season. The precipitations during this growing season were as follows: 59.4 mm from sowing to jointing stage, 54.9 mm from jointing to anthesis stage, and 26.3 mm from anthesis to maturity stage. Soil field capacities before sowing of 0 20, 20 40, 40 60, 60 80, , and cm soil layers were 24.53%, 24.49%, 23.38%, 24.94%, 25.52%, 24.03%, and 22.03%; soil bulk densities were 1.56, 1.53, 1.58, 1.59, 1.57, 1.59, and 1.64 g cm 3 ; relative moisture contents were 74.34%, 71.17%, 75.98%, 87.48%, 83.46%, 85.94%, and %, respectively. Same treatments were designed in both growing seasons with controlled relative soil moisture contents at sowing, jointing, and thesis stages (Table 1). The irrigation amount (mm) was calculated with the following formula: m = 10 ρbh (β i β j ) [12], where, H is the depth of designed moist layer soil at that period (cm), ρb is the soil bulk density of designed moist layer soil (g cm 3 ), β i is the designed moisture content, β j is the natural moisture content, i.e., soil moisture content before irrigation. The field was prepared in a randomized block design with 3 replicates. The plot (16 m 2 ) was 4 m in length and 4 m in width, and separated from each other by a 1.0 m zone. The preceding crop was corn. Stalk residues of corn were crushed and inversely buried into field before wheat sowing. In the growing season, kg ha 2 N, kg ha 1 P 2 O 5, and kg ha 1 K 2 O were applied before sowing, and another kg ha 1 N was applied at jointing stage. In the growing season, kg ha 1 N, kg ha 1 P 2 O 5, and kg ha 1 K 2 O were added before sowing, and kg ha 1 N was added at jointing stage. The fertilizers were urea (contained 46.4% N), diammonium phosphate (contained 46% P 2 O 5 and 18% N), and potassium sulfate (contained 52% K 2 O). The sowing dates were 8 October 2007 and 10 October 2008, and the harvest dates were 11 June and 4 June Seedling density was controlled to 180 plants m 2 at 4-leaf stage. Other field managements were as same as those for high yield production. 1.2 Measurements Soil moisture content Soils between 0 and 200 cm in depth were collected using a drill, and divided into 10 samples with 20 cm per sample. Each soil layer sample was dried in an aluminum box before determination of moisture content. The soil moisture content (%)= (fresh weight of soil sample dry weight of soil sample) / dry weight of soil sample 100%. Table 1 Relative soil moisture contents in various treatments of water supply (%) Treatment Relative soil moisture content designed Sowing Jointing Anthesis W W W W Data are the averages at cm soil layer.

3 1.2.2 Field water consumption amount The calculation was based on soil moisture content. n 10 ( ) [13] ET12 = γ i Hi θi1 θ i2 +M+P+K. i= 1 Where, ET 1 2 is water consumption amount (mm) in certain phase; i is the number of soil layer; n is the total number of soil layer; γ i is the dry bulk density of the ith soil layer (g cm 3 ); H i is the thickness of the ith soil layer (cm); θ i1 and θ i2 are soil moisture contents of the ith soil layer at the start and end of the phase, respectively; M is the irrigation amount in the phase (mm); P is the available precipitation (mm); and K is the supplemental amount from groundwater in the phase (mm). When the groundwater is below 2.5 m from the surface, the K value can be negligible. In this study, it was given to 0 for the groundwater level below 5 m from the surface Dry matter accumulation and distribution Plant samples were collected at anthesis and maturity stages, and separated into leaf, stem + sheath, spike axis + glume, and grain. Each part of samples was dried in an oven at 80 C before weighting. The parameters were calculated as the following definitions [14] : Dry matter translocation amount after anthesis = dry weight at anthesis dry weight at maturity; Dry matter translocation ratio after anthesis (%) = (dry weight at anthesis dry weight at maturity) / dry weight at anthesis 100; Dry matter translocation to grain after anthesis = grain dry weight at maturity dry matter translocation amount after anthesis; Contribution of dry matter translocation to grain after anthesis (%) = dry matter translocation amount after anthesis / dry weight of grain at maturity Photosynthetic characteristics and WUE at single leaf level (WUEL) The photosynthetic characteristics of flag leaf were measured using a CIRAS-2 photosynthesis system (PP System, UK) [15] from 9:00 to 11:00 a.m. (under natural light) at the anthesis day, 10 d after anthesis (DAA), and 20 DAA, respectively. WUE L = P n /T r, where, WUE L (µmol CO 2 mmol 1 H 2 O) is the WUE of a single leaf; P n is the net photosynthetic rate (µmol CO 2 m 2 s 1 ); and T r is the transpiration rate of the leaf (mmol H 2 O m 2 s 1 ), which was measured using photosynthesis system directly Grain-filling rate and grain yield Spikes were tagged at the flowering day and sampled from anthesis to maturity stage at the interval of 7 d. The dry weight of spike was measured with 20 samples per plot after dried at 80 C to constant weight. Grain-filling rate was defined as dry matter accumulation per day. At maturity, plants at 2 m 2 were harvested for each plot. Grain yield was determined based on grain moisture content of 12.5% WUEs and irrigation benefit Total WUE, irrigation WUE (WUE I ), precipitation WUE (WUE P ) and soil WUE (WUE S ) were calculated with the following formulas: WUE =Y/ET [15], WUE I = Y/I, WUE P = Y/P, and WUE S =Y/ S [16 18]. Irrigation benefit was determined as IB = Y/I [19]. Where, Y is the grain yield (kg ha 1 ); P is the available precipitation (mm); S is the soil water consumption amount (mm); Y is the grain yield increment after irrigation (kg ha 1 ); ET is the field water consumption amount during the growing season (mm); and I is the actual irrigation amount (mm). 1.3 Data analysis Observed data were managed in Microsoft Excel Statistical analysis was carried out using DPS 7.05 and SPSS 11.5 packages. 2 Results 2.1 Relative soil moisture content in cm soil layer after supplemental irrigation In both growing seasons, the actual relative soil moisture contents close to the designed contents with acceptable errors (hereinafter as regulative errors). For instance, the ranges of regulative errors in the 4 treatments were % at sowing stage, % at jointing stage, and % at anthesis stage (Table 2). This indicated that the designed soil moistures were obtained using the method of supplemental irrigation based on testing of soil moisture. 2.2 Effects of different treatments on photosynthetic characteristics of flag leaf With the increase of relative soil moisture content, photosynthetic rate of flag leaf had significant differences among treatments, i.e., W0 > W1 or W2 > W3 at anthesis (0 DAA); W3 > W2 > W1 > W0 at 10 DAA; and W1 > W2 or W3 > W0 at 20 DAA. Variation of transpiration rate of flag leaf was the same as that of photosynthetic rate among treatments. The highest photosynthetic rate and evapotranspiration were observed in W1 (Fig. 1-A and 1-B), which were favorable for dry matter accumulation and the increase of evapotranspiration at anthesis stage, respectively. WUE L was increased after anthesis, and there were no significant differences among treatments. WUE L was improved with the increase of relative soil moisture content under water-saving cultivation designed in this experiment (Fig. 1-C). 2.3 Effects of different treatments on accumulation and distribution of dry matter Dry matter accumulation amounts at different stages Dry matter accumulation amount had no significant differences among the 4 treatments at wintering and revival stages. At jointing stage, treatment W3 had significantly higher accumulation of dry matter than other treatments (Fig.

4 Treatment HAN Zhan-Jiang et al. / Acta Agronomica Sinica, 2010, 36(3): Table 2 Irrigation amounts and relative soil moisture contents in different treatments Sowing stage Jointing stage Anthesis stage DRMC (%) RMC (%) RE (%) I (mm) DRMC (%) RMC (%) RE (%) I (mm) DRMC (%) RMC (%) RE (%) I (mm) W W W W W W W W Relative soil moisture contents were the averages at cm soil layer. DRMC: Designed relative moisture content; RMC: Relative moisture content; RE: Regulative error; I: Irrigation amount. Fig. 1 Effects of different treatments on photosynthetic rate (A), transpiration rate (B) and leaf water use efficiency (C) in winter wheat ( ) 2). High relative soil moisture content at sowing stage (90% in W3) was favorable for the growth of wheat above ground from revival to jointing stage. However, at anthesis and maturity stages, the largest dry matter accumulation was in W1, followed by W2 and W3, and the least in W0 (Fig. 2) Dry matter distribution in different organs at maturity At maturity, dry matter accumulation was distributed in various organs with the largest amount and ratio in grain and the least in glume. Compared with treatment W0, the 3 irrigation treatments increased dry matter distribution in grain and decreased the ratio of dry matter distribution in stem, sheath, and leaf, especially the W1 treatment (Table 3). This result indicated that moderately low relative soil moisture contents at sowing, jointing, and anthesis stages had positive effects on dry matter distribution in grain and yield increase Dry matter translocation and contribution to grain after anthesis After anthesis, redistribution amount and ratio of dry matters that were stored in vegetative organs before (kg ha 1 ) Fig. 2 Revival Effects of different treatments on dry matter accumulation amount in winter wheat ( )

5 Table 3 Effects of different treatments on dry matter distribution in different organs at maturity in winter wheat Treatment Grain Spike axis + glume Stem + sheath + leaf Amount (g) Ratio (%) Amount (g) Ratio (%) Amount (g) Ratio (%) W0 1.48±0.04 c 50.51±1.02 c 0.39±0.02 a 13.17±0.73 a 1.06±0.02 c 36.31±0.84 a W1 1.78±0.02 a 54.98±0.55 a 0.35±0.01 b 10.93±0.34 b 1.10±0.02 b 34.09±0.57 b W2 1.67±0.01 b 52.88±0.32 b 0.35±0.02 b 10.99±0.60 b 1.14±0.01 a 36.13±0.23 a W3 1.66±0.01 b 53.06±0.54 b 0.34±0.01 b 10.93±0.26 b 1.13±0.02 ab 36.01±0.41 a W0 1.27±0.10 d 54.61±2.68 c 0.27±0.04 c 11.59±1.82 b 0.79±0.02 c 33.73±1.79 a W1 1.72±0.03 a 57.70±1.06 a 0.34±0.02 b 11.47±0.73 b 0.92±0.04 a 30.83±1.19 c W2 1.66±0.02 b 56.10±0.75 b 0.38±0.01 a 12.94±0.41 a 0.92±0.03 a 30.97±0.86 c W3 1.49±0.05 c 55.47±1.36 c 0.34±0.02 b 12.58±0.84 a 0.86±0.03 b 31.94±1.22 b Data are the averages based on a single stalk. Values followed by the same letter with a column are not significantly different at P < anthesis were presented as W0 > W3 > W2 > W1, with significant difference among treatments, and contribution of dry matter accumulation amount after anthesis to grain as W1 > W2 > W3 > W0, with significant difference among treatments (Table 4). The results indicated that treatment W1 improved accumulation capacity of dry matter after anthesis and increased dry matter ratio of grain after anthesis, which was the physical basis to obtain high yield. 2.4 Effects of different treatments on grain filling Grain-filling rate showed a single peak of slow fast slow pattern from 7 DAA to 35 DAA with the maximum value at 21 DAA in all treatments. Grain-filling rate in W0 was significantly higher than those in other treatments before 21 DAA. However, it was decreased rapidly after 21 DAA. The declines of grain-filling rates were slowly in other treatment after 21 DAA, and there were no significant differences among irrigation treatments from 7 DAA to 28 DAA. From 28 DAA, treatment W1 had a significantly higher grain-filling rate than treatments W2 and W3 (Fig. 3). Treatment W1 remained a high grain-filling rate at the end of filling stage, and thus had a potential of high grain weight ultimately. 2.5 Effects of different treatments on grain yield and WUEs The grain yields were ranked as W1 > W2 > W3 > W0 in the growing season and W1 and W2 > W3 > W0 in the growing season (Table 5). Although the WUE value was higher in W0 than in other treatments, the grain yield of W0 was the lowest in all treatments. With the increase of irrigation amount, the values of WUE I, WUE P, and irrigation benefit were decreased significantly. The WUE S was the largest in W3 and the lowest in W1 in both growing seasons, but the ranks of W0 and W2 were different in both growing seasons. With the synthetic consideration of grain yield, WUE I, and irrigation benefit, W1 regime was recommended as the optimum scheme under conditions similar to this study. As a result, the grain yields reached kg ha 1 and kg ha 1 in and growing seasons, respectively, which were the highest in the 4 treatments. Besides, the WUE I and WUE P were also the highest in W1. Table 4 Effects of different treatments on accumulation and translocation amount of vegetative organ after anthesis in winter wheat Treatment DMTAA (kg ha 1 ) DMTRA (%) CDMTAATG (%) DMAAA (kg ha 1 ) CDMAAATG (%) W ±77.74 a 26.34±2.41 a 50.76±1.71 a ±56.61 d 49.24±1.71 d W ±30.86 d 11.06±3.03 d 12.94±0.99 d ±49.29 a 87.06±0.99 a W ±71.98 c 15.42±0.63 c 19.20±0.94 c ± b 80.80±0.94 b W ±85.98 b 20.19±0.65 b 29.75±1.21 b ± c 70.25±1.21 c W ±21.96 a 27.61±0.21 a 39.74±0.43 a ±32.94 d 60.26±0.43 d W ±26.26 d 14.72±0.23 d 17.26±0.32 d ±39.39 a 82.74±0.32 a W ±41.62 c 18.39±1.77 c 20.87±1.59 c ±77.43 c 79.13±1.59 b W ±49.50 b 24.74±1.67 b 25.57±1.21 b ±73.75 b 74.43±1.21 c DMTAA: Dry matter translocation amount after anthesis; DMTRA: Dry matter translocation ratio after anthesis; CDMTAATG: Contribution of dry matter translocation amount after anthesis to grains; DMAAA: Dry Matter accumulation amount after anthesis; CDMAAATG: Contribution of dry matter accumulation amount after anthesis to grains. Values followed by the same letter are not significantly different at P < 0.05.

6 0.0 Fig. 3 Effects of different treatments on grain filling rate in winter wheat ( ) 3 Discussion Proper irrigation regimes for wheat production in the NCP region have been studies with numerous experiments, of which most were designed with fixed irrigation amounts. Li et al. [20] suggested 3 irrigation systems: 75 mm of water before sowing, 75 mm of water each at sowing and jointing stages, and 75 mm of water each at sowing, jointing, and at anthesis stages. The total irrigation amount was mm, and the highest yield was 7423 kg ha 1. Fang et al. [21] and Dong et al. [22] conducted irrigation under the condition of sufficient soil moisture at sowing stage, and found that 60 mm of water at jointing and anthesis stages each pushed the grain yield to kg ha 1 ; and total irrigation amount could be reduced to mm, without decreasing yield and WUE, if high-yield and high-wue-type cultivars were used [22]. Wang et al. [23] pointed out that no irrigation needed for winter wheat in wet years and once (at jointing stage) or twice irrigations (at jointing and heading stages) were recommended in normal precipitation and dry years, respectively, with water amount of mm at each time. In this study we improved the irrigation method by considering the original soil moisture content before irrigation. The quantity of irrigation water was estimated after measuring soil moisture content. The 3 irrigation regimes, i.e., W1, W2, and W3, conduced to final grain yields of , , and kg ha 1, respectively, and the supplemental water amounts were 43.8, 83.0, and mm in the growing season and 13.8, 62.9, and mm in the growing season. These results showed that the total irrigation amount during wheat growth was less than 120 mm and the yield was higher than 7500 kg ha 1, indicating the obtainment of water-saving and high-yield cultivation by means of supplemental irrigation based on testing of soil moisture. At certain growth stages of wheat, relative water deficiency or limitation results in more photosynthate translocating to grain and higher harvest index [24, 25]. Moderate water deficit before jointing stage is propitious to the concertation of wheat individual and population, controlling excessive vegetative growth, speeding up development and degeneration of tillers, and increasing the use efficiency of solar energy [26]. Deficit irrigations at jointing and anthesis stages enhance dry matter accumulation in wheat plant, and water deficit at grain-filling stage stimulates the redistribution of dry matter accumulated before anthesis from vegetative organs to grain [24, 27]. Simultaneously, the photosynthetic rate is reduced and the senescence of functional leaves is accelerated [27]. With the increases of irrigation amount and frequency, the dry matter accumulated in vegetative organs before anthesis is distributed Table 5 Effects of different treatments on grain yield, water consumption amount, and WUE in winter wheat Treatment Yield (kg ha 1 ) Water consumption amount (mm) Water use efficiency (kg ha 1 mm 1 ) Total I P SWCA WUE WUE I WUE P WUE S IB W ±188.9 d 329.3±8.0 d 0.0 d ±8.0 b 21.5±0.6 c 31.0±0.8 d 69.8±3.4 c W ±165.4 a 425.5±10.1 a 43.8 c ±10.1 a 20.8±0.5 d 201.6±3.8 a 38.8±0.7 a 57.5±2.3 d 40.3±0.5 a W ±36.0 b 374.3±9.6 b 83.0 b ±9.6 c 22.6±0.5 b 102.0±0.4 b 37.1±0.2 b 133.8±13.9 b 16.8±1.8 b W ±43.0 c 352.5±3.8 c a ±3.8 d 23.1±0.4 a 78.9±0.4 c 35.8±0.2 c 386.6±49.5 a 10.5±1.4 c W ±11.0 c 237.7±11.4 c 0.0 d ±11.4 c 26.2±1.1 ab 44.4±0.1 d 64.0±4.9 b W ±13.1 a 331.0±10.6 b 13.8 c ±10.6 a 27.3±0.8 a 656.5±1.0 a 64.4±1.0 a 51.2±1.9 d 204.4±0.2 a W ±235.8 a 358.2±3.9 a 62.9 b ±3.9 b 25.0±0.7 b 142.2±3.8 b 63.8±1.7 b 57.8±0.9 c 43.3±3.8 b W ±246.3 b 315.2±9.5 b a ±9.5 d 22.5±0.6 c 67.3±2.1 c 56.4±1.8 c 138.5±15.9 a 14.4±2.0 c I: irrigation amount; P: precipitation; SWCA: soil water consumption amount; WUE: water use efficiency; WUE I : irrigation water use efficiency; WUE P : precipitation use efficiency; WUE S : soil water use efficiency; IB: irrigation benefit. Values followed by the same letter are not significantly different at P < 0.05.

7 to grain in smaller amount and lower rate, and its contribution to grain yield is decreased [28, 29]. Zhang et al. [30] revealed that the canopy photosynthetic rate after anthesis was positively correlated with final grain yield in different treatments (75 mm at each time), but there was no significant difference between treatments with 2 and 4 times of irrigation in spring. This might result from population regulation by controlling water before jointing stage, such as improvement of population structure before anthesis, reduction of population respiration, and maintenance of high canopy photosynthetic function after anthesis. However, extremely high or low soil moisture content after anthesis degrades the photosynthetic characteristics of wheat flag leaf, leading to the reduction of grain yield [4]. Ma et al. [4] found that the highest photosynthetic rate, chlorophyll content, and leaf area index appeared when the relative soil moisture content ranged from 60% to 70% after anthesis. In this study, the relative soil moisture content in cm soil layer was controlled at water critical stages (sowing, jointing, and anthesis) of wheat. With increase of relative soil moisture content (irrigation amount), more dry matter amounts accumulated before anthesis was redistributed, and the ratio of redistribution was also increased. However, more dry matter accumulated after anthesis was conserved in the vegetative organs instead of translocated into grain. In comparison with the 4 treatments designed, W1 showed the highest grain yield at maturity. The possible physiological basis might be the high photosynthetic rate at the end of grain-filling stage, which was favorable for increasing the accumulation amount and distribution ratio of dry matter and the grain weight at maturity. In this treatment, the soil moisture content was maintained to proper status at the critical stages of wheat. WUE is a major theme in water-saving cultivation. A key issue is to promote the WUEs of both natural precipitation and irrigation [31]. In wheat field, water consumption amount is composed of precipitation, irrigation water, and soil water. Soil moisture content plays important roles in wheat growth and development, such as boosting absorptions of water and nutrition by roots. Abundant soil moisture at sowing stage may increase WUE S and decrease soil residual moisture at harvest. As a result, the storage capacity of soil reservoir is expanded to hold more water in flood seasons and regulate the soil reservoir [32]. Deficit irrigation at jointing and anthesis stages can promote root growth and increase WUE [27] S. Under dry condition, N fertilizer has positive effects on WUE [33] S and WUE [34] P. Deficit irrigation is beneficial to promoting economic index and WUE, but the grain yield might be reduced in some cases [35]. A moderate water deficit can improve crop yield and WUE simultaneously [27]. In winter wheat, Zhang et al. [36] suggested an irrigation regime for normal precipitation condition, i.e., soil moisture controlled from revival to erecting stage and supplemental irrigation at jointing and heading anthesis stages with mm at each time. In this experiment, we noticed that the grain yield, WUE I, WUE P, and irrigation benefit showed decrease trends in both growing seasons when more water was irrigated. The W1 regime showed the best effects on WUE, WUE P, soil water consumption amount, and final yield, and had a great potential in wheat production in the NCP region. Nevertheless, the method for quantifying irrigation water needs to be improved if this technique is applied in water-saving and high-yield cultivation. 4 Conclusions In and growing seasons, the relative soil moisture contents in wheat fields were regulated to 80% at sowing, 70% at jointing, and 70% at anthesis stage through supplemental irrigating with 43.8 mm and 13.8 mm, respectively. In this irrigation treatment, the amount and distribution ratio of dry matter accumulated after anthesis were increased compared to other treatments, and the grain-filling rate and photosynthetic rate of flag leaf maintained relatively high levels at the end of filling stage. This regime is suggested as the optimal scheme due to its remarkable effects on high yield, WUE, WUE I, WUE P, and irrigation benefit. Acknowledgments We are grateful to the supports from the National Natural Science Foundation of China ( ) and the project of Technology System in Modern Wheat Industry, Chinese Ministry of Agriculture (nycytx-03). References [1] Liu B C, Mei X R, Li Y Z, Yang Y L. The connotation and extension of agricultural water resources security. Sci Agric Sin, 2006, 39: (in Chinese with English [2] Xu Z Z, Li C R, Chen P, Yu Z W, Yu S L. Effect of soil drought on physiological characteristics and dry matter accumulation in winter wheat. Agric Res Arid Areas, 2000,18(1): , 123 (in Chinese with English [3] Fang Q X, Chen Y H, Li Q Q, Yu S Z, Yu S L, Dong Q Y, Luo Y, Yu Q, Ou-Yang Z. Effects of irrigation on photosynthate supply and conversion and related enzymes activity during grain filling period. Acta Agron Sin, 2004, 30: (in Chinese with English [4] Ma D H, Zhao C, Wang Y F, Wu G, Lin Q. 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