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Root vertical distribution is important to improve water use efficiency and grain yield of wheat
Field Crops Research 214 (2017) 131–141
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Root vertical distribution is important to improve water use efficiency and grain yield of wheat
MARK
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Suwei Feng, Shubo Gu1, Hongbo Zhang, Dong Wang
College of Agronomy, Shandong Agricultural University, State Key Laboratory of Crop Biology, Key Laboratory of Crop Ecophysiology and Farming System, Ministry of Agriculture, Taian, Shandong 271018, People’s Republic of China
A R T I C L E I N F O
A B S T R A C T
Keywords: Vertical root distribution Gas exchange characteristics Dry matter redistribution Water use efficiency Winter wheat
The winter wheat (Triticum aestivum L.) production of the North China Plain is threatened by increasing water shortages. Therefore, the invention of effective irrigation techniques is crucial to maintain high yields of winter wheat through improved water use efficiency (WUE). In this study, field experiments were carried out in the North China Plain region in 2012–2013 and 2013–2014. Based on the soil moisture regulation at sowing to ensure the normal emergence of the winter wheat, four supplemental irrigation (SI) regimes were set up: noirrigation after emergence (T1), SI at jointing and anthesis (T2), SI at sowing, jointing and anthesis (T3), and SI at pre-wintering, jointing and anthesis (T4). The results showed that the root length density (RLD), root surface area density (RAD), and root weight density (RWD) in the 0–0.2 m soil layer from T2 increased rapidly after jointing and were significantly higher than those from T3 and T4 at anthesis. Those of T2 in the 0.6–0.8 m and 0.8–1.0 m soil layers were also significantly higher at anthesis. T2 was significantly higher than T1 in the photosynthetic rate (Pn) and instantaneous water use efficiency (WUEleaf) of flag leaves, post-anthesis dry matter accumulation (DMA), contribution of DMA to grain (CDMA), grain yield and WUE, but lower than T1 in the preanthesis dry matter remobilization efficiency (DMRE) and contribution of DMR to grain (CDMR). T2 had significantly lower plant populations and dry matter at jointing, Pn and WUEleaf at 28 days after anthesis, DMA and CDMA, but higher dry matter increase rate after jointing, tiller survival rate, DMR, DMRE, CDMR and WUE. The combined effect of these differences enabled T2 to have yield that was not significantly different to T4. In summary, SI at joining and anthesis that was based on suitable soil water content at sowing increased the absorbing area of roots in both deep and surface soil layers; accelerated the dry matter accumulation after jointing; increased the Pn and WUEleaf of flag leaves, DMA and DMR; and finally achieved a high grain yield and higher WUE. However, excessive irrigation reduced the WUE by inhibiting the redistribution of dry matter, although the WUEleaf of flag leaves was still increased.
1. Introduction Winter wheat (Triticum aestivum L.) is a major crop in the North China Plain (NCP), accounting for greater than 70% of the national wheat production (Zhang et al., 2013a). The annual rainfall of the NCP ranges from 470 to 910 mm, but only 150–180 mm occurs during the winter wheat growing season, which is approximately 25–40% of the total water requirement of winter wheat (Wang et al., 2008; Liu et al., 2011). Irrigation is required for achieving high grain yield. However, multiple irrigations applied during wheat growing season has significantly reduced groundwater table (Sun et al., 2006; Wang et al., 2008; Chen et al., 2010). Wheat production is threatened by increasing water shortages (Wang et al., 2007; Zhang et al., 2010, 2013b).
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Therefore, it is important to develop appropriate water-saving strategies to improve water use efficiency (WUE) and maintain a high level of wheat production. The roots of winter wheat are plastic and affected by soil water status (Zhang et al., 2015), and the enhancement of soil water use efficiency mainly depends on the development of the root system (Guan et al., 2015; Hochholdinger, 2016). The root system of winter wheat determines its ability to capture available water and nutrients (Yadav et al., 2009; White and Kirkegaard, 2010; Bengough et al., 2011), which plays an important role in the plant-soil ecosystem (Zhang et al., 2009a; Wang et al., 2014a; Xu et al., 2016). The root weight density (RWD) in the 0–1.0 m soil layer reached a maximum at the flowering stage and mostly distributed in the 0–0.4 m soil layer (Wang et al., 2014a).
Corresponding author at: College of Agronomy, Shandong Agricultural University, 61 Daizong Street, Taian 271018, Shandong Province, People’s Republic of China. E-mail address: [email protected] (D. Wang). This author equally contributed to this work and should be considered co-first author.
http://dx.doi.org/10.1016/j.fcr.2017.08.007 Received 26 April 2017; Received in revised form 5 August 2017; Accepted 9 August 2017 0378-4290/ © 2017 Published by Elsevier B.V.
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Table 1 Soil nutrition status and soil bulk density in the 0–0.2 m soil layer of the experimental field before sowing in 2012–2013 and 2013–2014. years
Organic matter (g kg−1)
Total nitrogen (g kg−1)
Hydrolysable nitrogen (mg kg−1)
Available phosphorous (mg kg−1)
Available potassium (mg kg−1)
Soil bulk density (t m−3)
2012–2013 2013–2014
16.50 16.39
1.09 1.03
103.91 105.63
29.24 30.42
121.96 122.95
1.60 1.40
(116°41′E, 35°42′N), Shandong Province, China. This experimental area belongs to temperate, continental, monsoon climate with an average annual temperature of 13.6 °C and an annual precipitation of 621.2 mm. Approximately 40% of the precipitation occurs during the winter wheat growing season which is from October to June. The average annual groundwater level is 25 m. The soil of the experimental field was silty loam, and the previous crop was corn (Zea mays L.). The organic matter, total nitrogen, hydrolysable nitrogen, available phosphorous, and available potassium in the 0–0.2 m soil layer of the experimental field before sowing were 16.50 g kg−1, 1.09 g kg−1, 103.91 mg kg−1, 29.24 mg kg−1, and 121.96 mg kg−1 in 2012–2013 and 16.39 g kg−1, 1.03 g kg−1, 105.63 mg kg−1, 30.42 mg kg−1, and 122.95 mg kg−1 in 2013–2014, respectively. The soil bulk density of 0.2 m soil layer was 1.60 t m−3 in 2012–2013 and 1.40 t m−3 in 2013–2014 (Table 1). The field capacity and relative water content in the 0–2.0 m soil layers of the experimental field before sowing are listed in Table 2. The precipitation amount in different growth stages of winter wheat and the seasonal precipitation in 2012–2013 and 2013–2014 are shown in Table 3.
Irrigation regimes strongly influence the density and depth of roots (Wang et al., 2004). Water stress will restrict root growth and distribution in the soil (Gajri et al., 1989), and reduce the root length density (RLD) (Li et al., 2010). It has been found that total root dry weight, volume, length and number of branches reduce with decreasing irrigation times (Zhang et al., 2009a). However, limited irrigation can stimulate roots to grow into deeper soil layers and thus enhanced the uptake of soil-stored water from the subsoil layers (Wang et al., 2014a). Li et al. (2010) reported that one-time irrigation at jointing resulted in the highest RLD in > 0.3 m deep soil layers. Greater root biomass was significantly associated with greater shoot biomass, which contributed to higher grain yields and WUE (Zhang et al., 2009b). However, the relationships between the morphology and distribution of root and the grain yield and WUE of wheat remains an important topic of discussion. WUE is a key physiological parameter indicating the ability of crops to conserve water in a water-scarce region because it combines drought resistance and high potential yield (Fang et al., 2010; Zhang et al., 2010; Xu et al., 2016). Appropriate deficit irrigation does not necessarily reduce crop production and can result in high grain yield and WUE in wheat (Zhang et al., 2006; Fereres and Soriano, 2007). Xu et al. (2016) suggested that 60 mm irrigation applied at elongation was the best irrigation scheme for efficient water use and relatively high yield in winter wheat, but others argued that 120 mm irrigation during the winter wheat growing season could produce a reasonable grain yield and WUE (Bian et al., 2016). Du et al. (2010) reported that the maximum grain yield of winter wheat was achieved when 84% of maximum crop-water requirements were applied. Therefore, the frequency and amount of irrigation could be reduced to increase dry matter accumulation, promote grain-filling rate, and improve the yield and WUE of wheat (Zhang et al., 2006). Many studies attributed the yield and WUE improvement to the increase of water uptake and utilization from the deep soil layers (Johnson and Davis, 1980; Guo et al., 2016) because limited irrigation can stimulate roots to grow into deeper soil layers (Wang et al., 2014a; Xu et al., 2016). However, the shallow root system is required for absorption of nutrients that are mostly concentrated in the upper layers of soil (Manske and Vlek, 2002); furthermore, the superficial root parts may also be beneficial for capturing rainfall that does not infiltrate to the deeper soil layers (Ehdaie et al., 2012). Simultaneously promoting the absorption and utilization of the water from the deep soil layers and the rich nutrition from the upper soil layers is crucial for increasing in WUE. In this study, a method for determining the amount of supplemental irrigation (SI) required of wheat to achieve high grain yield and WUE was adopted, in which, the amount of SI is based on the soil water content before SI, which reflects both the precipitation and water consumption by the crop (Wang et al., 2013). Four SI regimes were designed to (1) determine the effects of the SI regimes on root growth and distribution; (2) clear the response of gas exchange characteristics of leaves, dry matter accumulation and redistribution, grain yield and WUE to SI regimes; and (3) clarify the relationships between wheat root distribution and wheat production.
2.2. Experimental design Jimai 22, one of the most widely planted commercial winter wheat cultivars in the NCP, was used for this study. Four SI regimes were set up (Table 4) in 2012–2013: no-irrigation after emergence (T1), SI at jointing and anthesis (T2), SI at sowing, jointing and anthesis (T3), and SI at pre-wintering, jointing and anthesis (T4). The SI brought soil water content in the 0–1.4 m soil layer to 85% of field capacity at sowing and pre-wintering stages, and to 70% of field capacity at jointing and anthesis stages in 2012–2013, according to our previously published method (Wang et al., 2013). In 2013–2014, the irrigation period of four SI regimes was consistent with previous year, but the SI brought soil water content in the 0–0.2 m soil layer to 100% of field capacity at prewintering, jointing and anthesis stages. This was based on the distribution of wheat root and infiltration rule of irrigation water in soil, in order to save the time and manpower required for measuring the soil water content before irrigation and to facilitate the application of SI technology in wheat production. In 2013–2014, irrigation was applied Table 2 Field capacity and relative soil water content in the 0–2.0 m soil layers of the experimental field before sowing.
2. Materials and methods 2.1. Experimental site The field experiment was performed from 2012 to 2014 in Yanzhou 132
Soil layer
2012–2013
2013–2014
(m)
Field capacity (%)
Relative soil water content (%)
Field capacity (%)
Relative soil water content (%)
0–0.2 0.2–0.4 0.4–0.6 0.6–0.8 0.8–1.0 1.0–1.2 1.2–1.4 1.4–1.6 1.6–1.8 1.8–2.0 mean
24.57 22.81 27.20 23.66 24.52 21.75 22.76 22.90 22.70 22.81 23.57
64.13 70.30 64.06 71.76 75.65 94.97 95.25 94.31 96.94 98.06 82.54
29.04 27.82 26.09 26.43 27.71 26.90 24.08 25.08 24.48 24.28 26.19
32.62 31.12 46.82 62.28 71.23 71.26 75.20 73.86 76.46 77.82 61.87
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the oven-drying method (Gardner, 1986). The amount of irrigation water was calculated based on the soil water content before irrigation as described by Wang et al. (2013). Calculation of total water consumption of winter wheat was based on the equation used by Zhang et al. (2013a):
Table 3 Precipitation amount in different growth stages of winter wheat and seasonal precipitation (mm). years
Sowing to prewintering
Prewintering to jointing
Jointing to anthesis
Anthesis to maturity
Seasonal precipitation
2012–2013 2013–2014
22.0 38.0
51.0 14.0
9.0 37.0
135.5 54.0
217.5 143.0
ET = S + I + P − Dr − Sr + Cr
(1)
where ET is the total water consumption of winter wheat during growing period (mm), S is the soil water consumption for the 2 m depth (mm), I is the irrigation amount (mm), P is the available precipitation amount (mm), Dr is the deep percolation, Cr is the capillary rise to the root zone, and Sr is the surface runoff. When the groundwater table is lower than 2.5 m below the ground surface, the capillary rise is negligible according to Darcy's equation (de Azevedo et al., 2003; Ali et al., 2007). The deep percolation and surface runoff are ignored in the North China Plain (Lv et al., 2011).
at sowing in all treatments because the relative soil water content in the 0–0.2 m soil layer was below 40% of field capacity before sowing. SI brought soil water content in the 0–0.2 m soil layer to 100% of field capacity in T3 treatment, and to 80% of field capacity in the other treatments at sowing (Table 4). A randomized block design with three replications was used, where the area of each plot was 46 m2 (2 m × 23 m). The average relative soil water content of each treatment in main root layers before and after SI at each growth stage are shown in Table 5. Well water was obtained using a submersible pump and uniformly sprayed in the field with micro-sprinkling hoses (Man et al., 2017). The water metre and valve on the hoses were used to measure and control the amount of irrigation. Nitrogen, phosphorus (P2O5) and potassium (K2O) were applied as base fertilizer at 105 kg ha−1, 150 kg ha−1 and 150 kg ha−1, respectively, with the depth of 0.1 m, alternating with two rows of winter wheat at the same time of seeding. Before fertilizing and seeding, rotary tillage and harrowing were carried out after returning the straw of the preceding crop maize into cropland. Topdressing N was 135 kg ha−1 at the jointing stage. The types of fertilizer were urea (N content: 46.4%), diammonium phosphate (P2O5 and N contents: 46% and 18%) and potassium chloride (K2O content: 52%). Wheat was sown on October 10th, 2012 and October 9th, 2013, and harvested on June 14th, 2013 and May 30th, 2014, respectively. A seed rate of 180 seeds per m−2 was used in all treatment regimes. Additional protective measures were taken to assure the healthy growth of the wheat, such as the spraying of herbicides at the regreening period, and insecticides before flowering. No significant incidence of pest, diseases or weeds was observed in any of the treatment sites during the experiment.
2.3.2. Root distribution and morphological characteristics Root samples were collected from soil samples taken from each plot at four growing stages: pre-wintering, regreening, jointing, and anthesis. The sampling followed procedures described by Bǒhm (1979). An auger with an internal diameter of 0.1 m was used to obtain cores, and each core was obtained at 0.2 m increments down to 1.0 m. The core sections and associated roots were soaked in plastic buckets filled with water and gently disaggregated by hand. Collected samples were loaded into 80 mesh bags to remove impurities and roots from other plants. Wheat root from every layer was put in methyl blue solution (4 °C) to dye for 12 h and then tiled upon glass plate (0.24 m × 0.32 m) for scanning with a root scanner (HP Scanjet 8200: Hewlett-Packard, Palo Alto, CA, USA). Pictures were saved as pixel 600api. Root system analysis software (Delta-T Area Meter Type AMB2; Delta-T Devices Ltd., Cambridge, UK) was used to measure root length and root surface area in different soil layers (Zhang et al., 2009a). The roots were dried with absorbent paper and placed in the oven with 80 °C until they reached a constant weight. The root dry weight density (RWD, kg m−3), root length density (RLD, km m−3) and root surface area density (RAD, m2 m−3) were calculated by the following formulas (Mosaddeghi et al., 2009; Li et al., 2010; Wang et al., 2014a; Guan et al., 2015):
M V
2.3. Measurements
RWD =
2.3.1. Soil water content and water consumption of winter wheat The soil water content measurement samples were collected using a soil corer at 0.2-m intervals to a depth of 2.0 m in all experimental plots before sowing, at maturity, on the day before irrigation, and on the third day after irrigation. The soil water content was determined using
where M is the root dry weight (kg) and V is the volume of the soil sample (m3).
RLD =
(2)
L V
(3)
Table 4 Plan wetting layer, targeted soil relative water content at different stages and the amount of each supplemental irrigation in four treatments: no-irrigation after emergence (T1), supplemental irrigation at jointing and anthesis (T2), supplemental irrigation at sowing, jointing and anthesis (T3), and supplemental irrigation at pre-wintering, jointing and anthesis (T4) in 2012–2014. Irrigation treatments
Plan wetting layer (m)
Targeted soil relative water content (%)
Irrigation amount (mm)
Sowing
Pre-wintering
Jointing
Anthesis
Sowing
Pre-wintering
Jointing
Anthesis
2012–2013 T1 T2 T3 T4
— 0–1.4 0–1.4 0–1.4
— — 85 —
— — — 85
— 70 70 70
— 70 70 70
— — 48.6 —
— — — 39.3
— 41.5 39.2 31.8
— 68.6 66.8 51.6
2013–2014 T1 T2 T3 T4
0–0.2 0–0.2 0–0.2 0–0.2
80 80 100 80
— — — 100
— 100 100 100
— 100 100 100
37.5 37.5 53.7 37.5
— — — 18.2
— 58.9 60.1 60.4
— 55.7 50.2 54.0
“—” means no irrigation.
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Table 5 Average relative soil water content in main root layers at each growth stage before and after supplemental irrigation in four treatments: no-irrigation after emergence (T1), supplemental irrigation at jointing and anthesis (T2), supplemental irrigation at sowing, jointing and anthesis (T3), and supplemental irrigation at pre-wintering, jointing and anthesis (T4) in 2012–2014. Growth stage
Treatments
0–0.2 m
0–0.4 m
0–1.4 m
θb (%)
θar (%)
θb (%)
θar (%)
θb (%)
θar (%)
T1 T2 T3 T4
64.1 64.1 64.1 64.1
— — 96.1 —
67.2 67.2 67.2 67.2
— — 91.4 —
76.6 76.6 76.6 76.6
— — 85.1 —
Pre-wintering
T1 T2 T3 T4
63.7 63.7 83.0 63.7
— — — 95.2
68.2 68.2 84.4 68.2
— — — 91.7
75.9 75.9 85.7 75.9
— — — 84.7
Jointing
T1 T2 T3 T4
38.5 38.5 40.6 42.1
— 74.7 80.7 80.9
46.3 46.3 44.4 51.8
— 69.8 73.4 75.7
62.3 62.3 62.7 64.1
— 69.1 69.4 71.3
Anthesis
T1 T2 T3 T4
32.9 40.6 40.3 40.3
— 74.5 80.4 80.6
38.6 44.4 47.2 49.2
— 71.8 78.7 74.6
53.6 57.9 56.9 60.9
— 68.6 67.4 69.7
T1 T2 T3 T4
33.8 33.8 33.8 33.8
65.2 65.2 73.0 65.2
32.2 32.2 32.2 32.2
53.1 53.1 58.7 53.1
57.3 57.3 57.3 57.3
62.5 62.5 66.2 62.5
Pre-wintering
T1 T2 T3 T4
77.5 77.5 81.6 77.5
— — — 85.7
64.1 64.1 74.4 64.1
— — — 71.5
72.4 72.4 72.8 72.4
— — — 74.5
Jointing
T1 T2 T3 T4
27.5 27.5 26.0 25.6
— 69.2 70.7 68.9
31.2 31.2 29.7 31.0
— 63.6 57.4 63.2
56.4 56.4 58.4 56.7
— 66.7 67.2 66.4
Anthesis
T1 T2 T3 T4
30.6 31.3 38.2 33.5
— 66.1 62.0 61.7
29.1 31.5 32.7 30.5
— 61.3 51.3 54.2
55.5 60.8 56.6 56.1
— 68.8 64.2 65.5
2012–2013 Sowing
2013–2014 Sowing
θb and θar are the average relative soil water content before and after supplemental irrigation, respectively. “—” means no irrigation.
draft oven immediately and dried at 75 °C until a constant weight was obtained to determine aboveground biomass (Xu et al., 2005). Various parameters for the dry matter accumulation and remobilization after anthesis were calculated as follows (Ma et al., 2015):
where L is the root length (m).
A RAD = V
(4) 2
where A is the root surface area (m ).
Pre-anthesis dry matter remobilization (DMR, kg ha−1) = dry matter of vegetative organs at anthesis − dry matter of vegetative organs (stem, sheath, leaves, spike axis and glume) at maturity. (5)
2.3.3. Net CO2 assimilation rates (Pn) and instantaneous water use efficiency (WUEleaf) Net CO2 assimilation rates (Pn) and transpiration rates of the flag leaves were measured at 0, 14 and 28 days after anthesis using a Li6400 portable photosynthesis system (LI-Cor, Inc., Lincoln, Nebraska, USA) during 9:00–11:00 a.m. and 2:00–4:00 p.m. Fifteen replicate flag leaves chosen randomly were used for measurements of each treatment. Pn divided by transpiration rates were calculated as the WUEleaf (Wang et al., 2014b).
DMR efficiency (DMRE, %) = (DMR × 100)/dry matter of vegetative organs at anthesis. (6) Contribution of DMR to grain (CDMR, %) = (DMR × 100)/Grain yield. (7) Post-anthesis dry matter accumulation (DMA, kg ha−1) = dry matter at maturity − dry matter at anthesis. (8) Contribution of DMA to grain (CDMA, %) = (DMA × 100)/Grain yield. (9)
2.3.4. Dry matter accumulation and remobilization Plant samples were collected to determine dry matter on five occasions: at pre-wintering, regreening, jointing, anthesis and maturity stages. The whole plants were sampled through removing the roots at pre-wintering, regreening and jointing. Thirty consecutive plants were cut manually at ground level from each plot at anthesis and maturity stages. Plants were separated into the stem plus sheath, leaves and spikes at anthesis, and into the stem plus sheath, leaves, spike axis plus glume and grain at maturity. Plant samples were placed into a forced
2.3.5. Yield and water use efficiency The spike number per square metre was investigated by manual counting. The 1000-grain weight was measured by taking the average of three samples of 1000 grains. Grain yield (kg ha−1) was determined from one 3 m2 quadrat from each plot and was reported at a 12.5% wet 134
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3.3. Gas exchange characteristics of flag leaves
basis through natural air drying. The WUE of winter wheat was defined as follows (Guan et al., 2015):
WUE =
Y ET
The Pn and WUEleaf of flag leaves determinated at 0, 14 and 28 days after anthesis (DAA) are shown in Fig. 5. T1 was lower than the other treatments. There were no significant differences between T3 and T4. Compared with T3 and T4, T2 has no significant difference in the Pn and WUEleaf at 0 DAA and has no significant difference in the WUEleaf at 14 DAA but was lower in the Pn and WUEleaf at 28 DAA for two years. These results indicate that SI at jointing and anthesis with no irrigation before jointing or less SI at sowing reduced the Pn and WUEleaf of flag leaves in the late grain filling stages.
(10)
where WUE (kg ha−1 mm−1) is the water use efficiency for grain yield, Y (kg ha−1) is the grain yield and ET is the water consumption amount during the growing season (mm).
2.4. Statistical analysis
3.4. Dry matter remobilization after anthesis
The data shown are averages. Statistical analysis employed standard analysis of variance (ANOVA assumptions of homogeneity) using SPSS (Statistical Product and Service Solutions, IBM) and mapping by SigmaPlot 12.5 (Systat Software Inc, Dundas, CA, GER). The relationships between RWD, RLD, and RAD in different soil layers and DAJ, DMJ, grain yield, and WUE were analyzed by linear correlation analysis. The DAJ and DMJ represent the increasing rate of dry matter at anthesis and maturity, respectively, relative to jointing. The least significant difference (LSD) method was used to determine if significant differences existed between treatments in their mean RWD, RLD, RAD, WUE, yield, etc. at a probability level of P ≤ 0.05.
Various parameters for the dry matter accumulation and remobilization after anthesis are shown in Table 6. Compared with T1, T2 was lower in the DMRE and CDMR but higher in the DMA and CDMA. Compared with T3 and T4, T2 was higher in the DMR, DMRE and CDMR but lower in the DMA and CDMA. There were no significant differences between T3 and T4 in the DMR, DMRE, CDMR, DMA and CDMA. There were no significant differences between T1 and T2 in the DMR for two years. 3.5. Grain yield and water use efficiency The grain yield, yield components and WUE of winter wheat are shown in Table 7. T2 was higher than T1 in the yield components, grain yield, water consumption and WUE. There were no significant differences between T3 and T4. Compared with T3, T2 has no significant difference in the spike number and 1000-grain weight but was lower in the grain yield and water consumption for both years. T2 had higher WUE than T3 for both years, and the difference was significant in 2012–2013. Compared with T4, T2 was lower in the water consumption but higher in the WUE. There were no significant differences between T2 and T4 in the spike number, 1000-grain weight and grain yield for both years. These results indicate that SI at joining and anthesis based on suitable soil water content at sowing could achieve both high gain yield and WUE.
3. Results 3.1. Spatial and temporal distribution of root T1 was lower than the other treatments in the RLD, RAD and RWD of winter wheat in the 0–0.2 m soil layer after jointing (Fig. 1). The RLD, RAD and RWD in the 0–0.2 m soil layer from T2 were lower than those from T4 at regreening, but increased rapidly after jointing and finally higher than those from T3 and T4 at anthesis by 23%, 22% and 18%, respectively. There were no significant differences of RLD, RAD, and RWD between T3 and T4 at anthesis. The RLD, RAD and RWD of winter wheat declined with increasing soil depth in the 0–1.0 m soil layer at anthesis, and those in the 0–0.6 m soil layers accounted for more than 80% of the total (Fig. 2). T2 was higher than T3 and T4 in the RLD, RAD and RWD of the 0.6–0.8 and 0.8–1.0 m soil layers. There were no significant differences between T3 and T4 in the 0–1.0 m soil layers, and there were no significant differences between T1 and T2 in the 0.4–1.0 m soil layers for two years.
3.6. Relationship between root distribution and wheat production The DAJ showed positive correlations with RLD, RAD and RWD in the 0–0.2 m soil layer at anthesis but had no significant correlations with RLD, RAD and RWD in other soil layers (Table 8). The DMJ and WUE had very significant positive correlations with RLD, RAD and RWD in the 0–0.2 m soil layer but had no significant correlations with RAD and RWD in other soil layers. The grain yield and WUE positively correlated with RLD in the 0.2–0.4 m soil layer.
3.2. Dynamics of plant population and dry matter at different growing stages
4. Discussion
The plant population dynamics of wheat are shown in Fig. 3. There were no significant differences between T2 and T1 before jointing, but T2 was higher than T1 at anthesis and maturity. T3 and T4 were higher than T2 and T1 at jointing, but there were no significant differences among T2, T3 and T4 at maturity. The tiller survival rate (population at maturity/population at jointing) of T2 was 75–78% higher than that of T3 and T4 for two years. For dry matter accumulation, there were no significant differences between T2 and T1 before jointing both in 2012–2013 and 2013–2014 (Fig. 4). There were also no significant differences between T3 and T4 from jointing to maturity. T3 and T4 were higher than T2 and T1 from jointing to maturity. The dry matter of T2 was increased by 65–66% from jointing to anthesis and by 64–67% from anthesis to maturity, which was higher than those of T1. The dry matter increase rate of T3 was only 13–45% from jointing to anthesis, and 60–64% from anthesis to maturity. The dry matter increase rate of T4 was only 6–52% from jointing to anthesis, and 60–61% from anthesis to maturity.
4.1. Relation of SI to root growth and distribution As an integral part of plant organs, roots are involved in the acquisition of nutrients and water (Yang et al., 2004; Wu and Cheng, 2014). The amount of soil water absorbed by plant roots mainly depends on soil water supply, morphological and physiological characteristics of roots, and so on (Wang et al., 2014a; Li et al., 2017). The morphology of roots is affected by the soil water supply (Chu et al., 2014). Root morphological traits in drying soil media included increased deep root biomass, longer seminal roots, and increased production of small diameter roots at depth (Becker et al., 2016). In this paper, the treatments without SI before jointing increased the RLD, RAD and RWD in the soil below 0.6 m at anthesis (Fig. 2) because the extreme arid condition in the shallow soil layer (Table 5) encouraged the growth of deeper roots (Asseng et al., 1998). However, the relative 135
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Fig. 1. Root length density, surface area density and dry weight density of winter wheat in the 0–0.2 m soil layer in four treatments: no-irrigation after emergence (T1), supplemental irrigation at jointing and anthesis (T2), supplemental irrigation at sowing, jointing and anthesis (T3), and supplemental irrigation at pre-wintering, jointing and anthesis (T4) in 2012–2014. Vertical bars indicate the standard deviation.
before jointing (Fig. 1). However, the differences among these treatments in the relative soil water content of the 0–0.4 m soil layer were small during this period. It can be speculated that the local abundant water supply in the upper soil layer after drought stimulated the
soil water content in the 0–0.2 and 0.2–0.4 m soil layers was greatly increased when the first SI was supplied at jointing (Table 5). The RLD, RAD and RWD in the 0–0.2 m soil layer increased rapidly from jointing to anthesis and were finally higher than those of the treatments with SI 136
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Fig. 2. Root length density, surface area density and dry weight density of winter wheat in the 0–1.0 m soil layers at anthesis stage in four treatments: no-irrigation after emergence (T1), supplemental irrigation at jointing and anthesis (T2), supplemental irrigation at sowing, jointing and anthesis (T3), and supplemental irrigation at pre-wintering, jointing and anthesis (T4) in 2012–2014. Transversal bars indicate the standard deviation, and different letters on the right error bars indicate significant differences between treatments at P < 0.05 by the LSD test.
certain depth of the soil layer. Root morphological development is based on shoot development; the pattern of root development and shoot growth is closely associated (Aguirre and Johnson, 1991). In this study, compared with T3 and T4,
compensatory physiological responses of wheat (Xu et al., 2010; Steinemann et al., 2015), which induced the growth of the topsoil roots. The periodical change of the soil water content in the upper soil layer caused by SI changed the distribution pattern of the root system in a 137
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Fig. 3. Populations of winter wheat at different growth stages in four treatments: noirrigation after emergence (T1), supplemental irrigation at jointing and anthesis (T2), supplemental irrigation at sowing, jointing and anthesis (T3), and supplemental irrigation at pre-wintering, jointing and anthesis (T4) in 2012–2014. Vertical bars indicate the standard deviation.
layers for high-yielding wheat production, and the grain yield was negatively correlated with RWD in the deep soil layers. Similar views were clarified by Xue et al. (2003), who stated that root depth did not contribute to the increased grain yield and WUE in irrigated treatments. The roots near the soil surface are known to be a primary location of moisture and nutrient uptake in well-watered conditions (Hopkins and Hüner, 2009; Becker et al., 2016). However, the moisture in the upper soil layers is rapidly consumed and drastically reduced due to root uptake and ground evaporation, which significantly reduces the effectiveness of soil nutrients and affects the water and nutrients absorption of roots. In this study, the root growth of T2 in the soil both at 0–0.2 m and below 0.6 m was promoted (Fig. 2), which increased the absorbing area of roots in both deep and surface soil layers. It can be inferred that this kind of root distribution pattern together with appropriate water supply in the upper soil layer after jointing, was conducive to the absorption of water from deep soil layer and rich nutrition from upper soil layer and then improved the dry matter increase rate (Fig. 4 and Table 8). Finally, it enabled high grain yield and high WUE of winter wheat (Table 7).
T2 was lower in the plant population (Fig. 3) and dry matter (Fig. 4) at jointing due to lower water supply before jointing (Table 5), but higher in the tiller survival rate (Fig. 3) and root growth rate in the 0–0.2 m soil layer from jointing to anthesis (Fig. 1). This differs from the previous study, in which the mild drought prior to the jointing stage controls excessive vegetative growth, increasing the distribution of photosynthetic products to the roots of winter wheat (Liu et al., 2016). It was more likely that less invalid tillers caused by drought before jointing relieved the contradiction of dry matter demand between the above-ground and underground of plant after jointing, thus prompting more dry matter to be transported into the roots and enhancing the root growth in the surface layers where the soil moisture was appropriate after jointing (Table 5). 4.2. Roles of root distribution in grain yield and WUE improvement The root growth, especially deep roots, had a significant effect on the stable yield and absorbed larger amounts of deep water from the soil under drought condition (White and Kirkegaard, 2010). Some other studies also suggest that smaller root sizes in the upper soil layer might be more economical in terms of production efficiency (Zhang et al., 2009a). However, the shallow root system is required for absorption of nutrients that are mostly concentrated in the upper layers of soil (Manske and Vlek, 2002). Furthermore, the superficial root parts may also be beneficial for capturing rainfall that does not infiltrate to deeper soil layers (Ehdaie et al., 2012). Wang et al. (2014a) pointed that it should not be attempt to enhance root development in the deep soil
4.3. The key to achieving high yield and WUE The highest yield of winter wheat is usually obtained with moderate irrigation, more than the threshold, the yield of winter wheat was not increased, and the WUE was significantly reduced (Zhang et al., 2015). The WUE at yield level was positively related to seasonal WUEleaf (Qiu et al., 2008), while the WUEleaf was connected with the soil water Fig. 4. Dry matter accumulation of winter wheat at different growth stages in four treatments: no-irrigation after emergence (T1), supplemental irrigation at jointing and anthesis (T2), supplemental irrigation at sowing, jointing and anthesis (T3), and supplemental irrigation at pre-wintering, jointing and anthesis (T4) in 2012–2014. Vertical bars indicate the standard deviation.
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Fig. 5. Net CO2 assimilation rates (Pn) and instantaneous water use efficiency (WUEleaf) of winter wheat after anthesis in four treatments: no-irrigation after emergence (T1), supplemental irrigation at jointing and anthesis (T2), supplemental irrigation at sowing, jointing and anthesis (T3), and supplemental irrigation at pre-wintering, jointing and anthesis (T4) in 2012–2014. Vertical bars indicate the standard deviation, and different letters above error bars indicate significant differences between treatments at P < 0.05 by the LSD test.
content at the time the measurements were taken (Wang et al., 2016). In this study, the grain yield and WUE were simultaneously increased along with an increased WUEleaf of flag leaves after anthesis, DMA and CDMA, and decreased DMRE and CDMR (Fig. 5, Tables 6 and 7) by the appropriate SI. However, further decreasing the DMR, DMRE and CDMR with extra SI at the pre-wintering stage reduced the WUE, even though the WUEleaf of flag leaves in the late grain filling stages and DMA and CDMA were further increased. It is demonstrated that the inhibition of the recycling of the dry matter assimilated before anthesis limited the WUE improvement as excessive SI is applied.
Table 6 Dry matter accumulation and remobilization after anthesis in four treatments: no-irrigation after emergence (T1), supplemental irrigation at jointing and anthesis (T2), supplemental irrigation at sowing, jointing and anthesis (T3), and supplemental irrigation at pre-wintering, jointing and anthesis (T4) in 2012–2014. Treatments
DMR (kg ha−1)
DMRE (%)
CDMR (%)
DMA (kg ha−1)
CDMA (%)
2012–2013 T1 T2 T3 T4
2535.0a 2498.0a 2022.3b 2124.1b
30.3a 24.4b 16.3c 17.6c
40.1a 27.7b 21.4c 22.8c
3779.8c 6531.3b 7411.0a 7174.2a
59.9c 72.3b 78.6a 77.2a
2013–2014 T1 T2 T3 T4
2308.0a 2363.5a 1759.6b 1883.7b
29.5a 24.1b 15.0c 15.7c
41.4a 26.5b 19.1c 20.5c
3273.5c 6555.7b 7475.3a 7288.7a
58.6c 73.5b 80.9a 79.5a
5. Conclusion The timing and frequency of SI significantly influenced root distribution, gas exchange characteristics of leaves, dry matter remobilization, yield and WUE. Moderate drought at the early growth stage not only promoted the distribution of roots in the deeper soil layer but also reduced the invalid tillers at jointing. Less invalid tillers and appropriate SI at jointing stimulated the growth of roots in the top 0.2 m soil layer after jointing. The increase of roots in both deep and surface soil was conducive to accelerating dry matter accumulation
DMR: Pre-anthesis dry matter remobilization; DMRE: DMR efficiency; CDMR: Contribution of DMR to grain; DMA: Post-anthesis dry matter accumulation; CDMA: Contribution of DMA to grain. The different letters in the same column in 2012–2013 or 2013–2014 are significantly different at P < 0.05 by the LSD test.
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Table 7 Yield components, grain yield and water use efficiency of winter wheat in four treatments: no-irrigation after emergence (T1), supplemental irrigation at jointing and anthesis (T2), supplemental irrigation at sowing, jointing and anthesis (T3), and supplemental irrigation at pre-wintering, jointing and anthesis (T4) in 2012–2014. Spike number (×104 spike ha−1)
Kernel number (grain spike−1)
1000-grain weight (g)
Grain yield (kg ha−1)
Water consumption (mm)
Water use efficiency (kg ha−1 mm−1)
2012–2013 T1 T2 T3 T4
630.4b 688.0a 699.2a 713.7a
27.2c 30.6b 32.5a 32.8a
39.6b 42.0a 42.9a 42.2a
6314.8c 9029.3b 9433.3a 9298.3ab
325.5c 393.3b 434.7a 428.5a
19.4c 23.0a 21.7b 21.7b
2013–2014 T1 T2 T3 T4
403.3b 524.0a 531.2a 528.0a
28.3b 34.4a 35.2a 35.2a
43.5b 48.2a 49.3a 48.8a
5581.5c 8919.2b 9234.9a 9172.4ab
288.5c 367.8b 393.6a 402.0a
19.3c 24.3a 23.5ab 22.8b
Treatments
The different letters in the same column in 2012–2013 or 2013–2014 are significantly different at P < 0.05 by the LSD test. Australia. Field Crops Res. 57, 163–179. Bǒhm, W., 1979. Methods of Studying Root System. Springer-Verlag, Berlin. Becker, S.R., Byrne, P.F., Reid, S.D., Bauerle, W.L., McKay, J.K., Haley, S.D., 2016. Root traits contributing to drought tolerance of synthetic hexaploid wheat in a greenhouse study. Euphytica 207, 213–224. Bengough, A.G., McKenzie, B.M., Hallett, P.D., Valentine, T.A., 2011. Root elongation, water stress, and mechanical impedance: a review of limiting stresses and beneficial root tip traits. J. Exp. Bot. 62, 59–68. Bian, C.Y., Ma, C.J., Liu, X.H., Gao, C., Liu, Q.R., Yan, Z.X., Ren, Y.J., Li, Q.Q., 2016. Responses of winter wheat yield and water use efficiency to irrigation frequency and planting pattern. PLoS One 11, e0154673. http://dx.doi.org/10.1371/journal.pone. 0154673. Chen, C., Wang, E.L., Yu, Q., 2010. Modeling wheat and maize productivity as affected by climate variation and irrigation supply in North China Plain. Agron. J. 102, 1037–1049. Chu, G., Chen, T.T., Wang, Z.Q., Yang, J.C., Zhang, J.H., 2014. Reprint of Morphological and physiological traits of roots and their relationships with water productivity in water-saving and drought-resistant rice. Field Crops Res. 165, 36–48. de Azevedo, P.V., da Silva, B.B., da Silva, V.P.R., 2003. Water requirements of irrigated mango orchards in northeast Brazil. Agric. Water Manage. 58, 241–254. Du, T.S., Kang, S.Z., Sun, J.S., Zhang, X.Y., Zhang, J.H., 2010. An improved water use efficiency of cereals under temporal and spatial deficit irrigation in north China. Agric. Water Manage. 97, 66–74. Ehdaie, B., Layne, A.P., Waines, J.G., 2012. Root system plasticity to drought influences grain yield in bread wheat. Euphytica 186, 219–232. Fang, Q.X., Ma, L., Green, T.R., Yu, Q., Wang, T.D., Ahuja, L.R., 2010. Water resources and water use efficiency in the North China Plain: current status and agronomic management options. Agric. Water Manage. 97, 1102–1116. Fereres, E., Soriano, M.A., 2007. Deficit irrigation for reducing agricultural water use. J. Exp. Bot. 58, 147–159. Gajri, P.R., Prihar, S.S., Arora, V.K., 1989. Effects of nitrogen and early irrigation on root development and water use by wheat on two soils. Field Crops Res. 21, 103–114. Gardner, W.H., 1986. Water content. In: Klute, A. (Ed.), Methods of Soil Analysis: Part 1Physical and Mineralogical Methods-Agronomy Monograph No. 9, 2nd edition. American Society of Agronomy, Madison, WI, pp. 493–544. Guan, D.H., Zhang, Y.S., Mahdi, M.A., Wang, Q.Y., Zhang, M.C., Li, Z.H., 2015. Tillage practices effect on root distribution and water use efficiency of winter wheat under rain-fed condition in the North China Plain. Soil Tillage Res. 146, 286–295. Guo, F., Ma, J.J., Zhang, L.J., Sun, X.H., Guo, X.H., Zhang, X.L., 2016. Estimating distribution of water uptake with depth of winter wheat by hydrogen and oxygen stable isotopes under different irrigation depths. J. Integr. Agric. 15, 891–906. Hochholdinger, F., 2016. Untapping root system architecture for crop improvement. J. Exp. Bot. 67, 4431–4433. Hopkins, W.G., Hüner, N.P.A., 2009. Introduction to Plant Physiology, 4th ed. John Wiley & Sons, Inc, Hoboken. Johnson, W.C., Davis, R.G., 1980. Yield-water relationships of summer-fallowed winter wheat. A precision study in the Texas Panhandle. Science and Education Administration Pub. Arr(Ns-5). pp. 1–43. Li, Q.Q., Dong, B.D., Qiao, Y.Z., Liu, M.Y., Zhang, J.W., 2010. Root growth, available soil water, and water-use efficiency of winter wheat under different irrigation regimes applied at different growth stages in North China. Agric. Water Manage. 97, 1676–1682. Li, X.Y., Šimůnek, J., Shi, H.B., Yan, J.W., Peng, Z.Y., Gong, X.W., 2017. Spatial distribution of soil water, soil temperature, and plant roots in a drip-irrigated intercropping field with plastic mulch. Eur. J. Agron. 83, 47–56. Liu, H.J., Yu, L.P., Luo, Y., Wang, X.P., Huang, G.H., 2011. Responses of winter wheat (Triticum aestivum L.) evapotranspiration and yield to sprinkler irrigation regimes. Agric. Water Manage. 98, 483–492. Liu, E.K., Mei, X.R., Yan, C.R., Gong, D.Z., Zhang, Y.Q., 2016. Effects of water stress on photosynthetic characteristics, dry matter translocation and WUE in two winter wheat genotypes. Agric. Water Manage. 167, 75–85. Lv, L.H., Wang, H.J., Jia, X.L., Wang, Z.M., 2011. Analysis on water requirement and water-saving amount of wheat and corn in typical regions of the North China Plain. Front. Agric. China 5, 556–562.
Table 8 Analysis of correlations between the root dry weight density (RWD), root length density (RLD), and root surface area density (RAD) in different soil layers and the DAJ, DMJ, grain yield, and water use efficiency. Soil layer (m)
DAJ
DMJ
Grain yield
Water use efficiency
RLD 0–0.2 0.2–0.4 0.4–0.6 0.6–0.8 0.8–1.0
0.72* 0.21 −0.49 −0.24 0.43
0.82** 0.39 −0.37 −0.29 0.31
0.60 0.88** 0.48 −0.16 −0.53
0.86** 0.83** 0.01 −0.41 −0.07
RAD 0–0.2 0.2–0.4 0.4–0.6 0.6–0.8 0.8–1.0
0.73* 0.04 −0.46 −0.10 0.05
0.83** 0.18 −0.40 −0.21 −0.06
0.61 0.59 0.29 −0.43 −0.37
0.83** 0.54 −0.15 −0.54 −0.43
RWD 0–0.2 0.2–0.4 0.4–0.6 0.6–0.8 0.8–1.0
0.76* −0.50 −0.45 −0.21 −0.20
0.85** −0.42 −0.43 −0.25 −0.23
0.62 0.36 0.11 −0.08 −0.07
0.83** −0.11 −0.29 −0.34 −0.31
The DAJ and DMJ represent the increasing rate of dry matter at anthesis and maturity, respectively, relative to jointing. * p < 0.05. ** p < 0.01.
after jointing. However, excessive irrigation inhibited the redistribution of the dry matter after anthesis. In addition to high WUEleaf of leaves, elevated dry matter increase rates after jointing and unimpeded dry matter remobilization after anthesis were important factors for improving grain yield and WUE. In the NCP, SI at joining and anthesis based on suitable soil water content at sowing is an important way to simultaneously increase grain yield and WUE. Acknowledgements This work was supported by the Special Fund for Agro-scientific Research in the Public Interest (201503130), and the National Natural Science Foundation of China (31271660). References Aguirre, L., Johnson, D.A., 1991. Root morphological development in relation to shoot growth in seedlings of four range grasses. J. Range Manage. 44, 341–346. Ali, M.H., Hoque, M.R., Hassan, A.A., Khair, A., 2007. Effects of deficit irrigation on yield water productivity, and economic returns of wheat. Agric. Water Manage. 92, 151–161. Asseng, S., Keating, B.A., Fillery, I.R.P., Gregory, P.J., Bowden, J.W., Turner, N.C., Palta, J.A., Abrecht, D.G., 1998. Performance of the APSIM-wheat model in western
140
Field Crops Research 214 (2017) 131–141
S. Feng et al.
White, R.G., Kirkegaard, J.A., 2010. The distribution and abundance of wheat roots in a dense: structured subsoil-implications for water uptake. Plant Cell Environ. 33, 133–148. Wu, W.M., Cheng, S.H., 2014. Root genetic research: an opportunity and challengeto rice improvement. Field Crops Res. 165, 111–124. Xu, Z.Z., Yu, Z.W., Wang, D., Zhang, Y.L., 2005. Nitrogen accumulation and translocation for winter wheat under different irrigation regimes. J. Agron. Crop Sci. 191, 439–449. Xu, Z.Z., Zhou, G.S., Shimizu, H., 2010. Plant responses to drought and rewatering. Plant Signal. Behav. 5, 649–654. Xu, C.L., Tao, H.B., Tian, B.J., Gao, Y.B., Ren, J.H., Wang, P., 2016. Limited-irrigation improves water use efficiency and soil reservoir capacity through regulating root and canopy growth of winter wheat. Field Crops Res. 196, 268–275. Xue, Q., Zhu, Z., Musick, J.T., Stewart, B.A., Dusek, D.A., 2003. Root growth and water uptake in winter wheat under deficit irrigation. Plant Soil 257, 151–161. Yadav, B.K., Mathur, S., Siebel, M.A., 2009. Soil moisture flow modeling with water uptake by plants (wheat) under varying soil and moisture conditions. J. Irrig. Drain. Eng. 135, 375–381. Yang, C.M., Yang, L.Z., Yang, Y.X., Ouyang, Z., 2004. Rice root growth and nutrient uptake as influenced by organic manure in continuously and alternately flooded paddy soils. Agric. Water Manage. 70, 67–81. Zhang, B.C., Li, F.M., Huang, G.B., Cheng, Z.Y., Zhang, Y.H., 2006. Yield performance of spring wheat improved by regulated deficit irrigation in an arid area. Agric. Water Manage. 79, 28–42. Zhang, X.Y., Chen, S.Y., Sun, H.Y., Wang, Y.M., Shao, L.W., 2009a. Root size: distribution and soil water depletion as affected by cultivars and environmental factors. Field Crops Res. 114, 75–83. Zhang, H., Xue, Y.G., Wang, Z.Q., Yang, J.C., Zhang, J.H., 2009b. Morphological and physiological traits of roots and their relationships with shoot growth insuper rice. Field Crops Res. 113, 31–40. Zhang, X.Y., Chen, S.Y., Sun, H.Y., Wang, Y.M., Shao, L.W., 2010. Water use efficiency and associated traits in winter wheat cultivars in the North China Plain. Agric. Water Manage. 97, 1117–1125. Zhang, X.Y., Wang, Y.Z., Sun, H.Y., Chen, S.Y., Shao, L.W., 2013a. Optimizing the yield of winter wheat by regulating water consumption during vegetative and reproductive stages under limited water supply. Irrig. Sci. 31, 1103–1112. Zhang, X.Y., Wang, S.F., Sun, H.Y., Chen, S.Y., Shao, L.W., Liu, X.W., 2013b. Contribution of cultivar, fertilizer and weather to yield variation of winter wheat over three decades: a case study in the North China Plain. Eur. J. Agron. 50, 52–59. Zhang, X.Y., Zhang, X.Y., Liu, X.W., Shao, L.W., Sun, H.Y., Chen, S.Y., 2015. Incorporating root distribution factor to evaluate soil water status for winter wheat. Agric. Water Manage. 153, 32–41.
Ma, S.C., Duan, A.W., Wang, R., Guan, Z.M., Yang, S.J., Ma, S.T., Shao, Y., 2015. Rootsourced signal and photosynthetic traits dry matter accumulation and remobilization, and yield stability in winter wheat as affected by regulated deficit irrigation. Agric. Water Manage. 148, 123–129. Man, J.G., Wang, D., White, P.J., 2017. Photosynthesis and drymass production of winter wheat in response to micro-sprinkling irrigation. Agron. J. 109, 549–561. Manske, G.G.B., Vlek, P.L.G., 2002. Root architecture-wheat as a model plant. In: Waisel, Y., Eshel, A., Beeckman, T., Kafkafi, U. (Eds.), Plant Roots: the Hidden Half. Marcel Dekker, Inc., New York-Basel, pp. 249–259. Mosaddeghi, M.R., Mahboubi, A.A., Safadoust, A., 2009. Short-term effects of tillage and manure on some soil physical properties and wheat root growth in a sandy loam soil in western Iran. Soil Tillage Res. 104, 173–179. Qiu, G.Y., Wang, L.M., He, X.H., Zhang, X.Y., Chen, S.Y., Chen, J., Yang, Y.H., 2008. Water use efficiency and evapotranspiration of winter wheat and its response to irrigation regime in the north China plain. Agric. For. Meteorol. 148, 1848–1859. Steinemann, S., Zeng, Z.H., McKay, A., Heuer, S., Langridge, P., Huang, C.Y., 2015. Dynamic root responses to drought and rewatering in two wheat (Triticum aestivum) genotypes. Plant Soil 391, 139–152. Sun, H.Y., Liu, C.M., Zhang, X.Y., Shen, Y.J., Zhang, Y.Q., 2006. Effects of irrigation on water balance, yield and WUE of winter wheat in the North China Plain. Agric. Water Manage. 85, 211–218. Wang, F.H., Wang, X.Q., Sayre, K., 2004. Comparison of conventional, flood irrigated, flat planting with furrow irrigated, raised bed planting for winter wheat in China. Field Crops Res. 87, 35–42. Wang, X.B., Cai, D.X., Hoogmoed, W.B., Oenema, O., Perdok, U.D., 2007. Developments in conservation tillage in rainfed regions of North China. Soil Tillage Res. 93, 239–250. Wang, E.L., Yu, Q., Wu, D.R., Xia, J., 2008. Climate, agricultural production and hydrological balance in the North China Plain. Int. J. Climatol. 28, 1959–1970. Wang, D., Yu, Z.W., Philip, J.W., 2013. The effect of supplemental irrigation after jointing on leaf senescence and grain filling in wheat. Field Crops Res. 151, 35–44. Wang, C.Y., Liu, W.X., Li, Q.X., Ma, D.Y., Lu, H.F., Feng, W., Xie, Y.X., Zhu, Y.J., Guo, T.C., 2014a. Effects of different irrigation and nitrogen regimes on root growth and its correlation with above-ground plant parts in high-yielding wheat under field conditions. Field Crops Res. 165, 138–149. Wang, W.H., Chen, J., Liu, T.W., Chen, J., Han, A.D., Simon, M., Dong, X.J., He, J.X., Zheng, H.L., 2014b. Regulation of the calcium-sensing receptor in both stomatal movement and photosynthetic electron transport is crucial for water use efficiency and drought tolerance in Arabidopsis. J. Exp. Bot. 65, 223–234. Wang, Y.Z., Zhang, X.Y., Zhang, X.Y., Shao, L.W., Chen, S.Y., Liu, X.W., 2016. Soil water regime affecting correlation of carbon isotope discrimination with yield and wateruse efficiency of winter wheat. Crop Sci. 56, 760–772.
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Root vertical distribution is important to improve water use efficiency and grain yield of wheat
MARK
⁎
Suwei Feng, Shubo Gu1, Hongbo Zhang, Dong Wang
College of Agronomy, Shandong Agricultural University, State Key Laboratory of Crop Biology, Key Laboratory of Crop Ecophysiology and Farming System, Ministry of Agriculture, Taian, Shandong 271018, People’s Republic of China
A R T I C L E I N F O
A B S T R A C T
Keywords: Vertical root distribution Gas exchange characteristics Dry matter redistribution Water use efficiency Winter wheat
The winter wheat (Triticum aestivum L.) production of the North China Plain is threatened by increasing water shortages. Therefore, the invention of effective irrigation techniques is crucial to maintain high yields of winter wheat through improved water use efficiency (WUE). In this study, field experiments were carried out in the North China Plain region in 2012–2013 and 2013–2014. Based on the soil moisture regulation at sowing to ensure the normal emergence of the winter wheat, four supplemental irrigation (SI) regimes were set up: noirrigation after emergence (T1), SI at jointing and anthesis (T2), SI at sowing, jointing and anthesis (T3), and SI at pre-wintering, jointing and anthesis (T4). The results showed that the root length density (RLD), root surface area density (RAD), and root weight density (RWD) in the 0–0.2 m soil layer from T2 increased rapidly after jointing and were significantly higher than those from T3 and T4 at anthesis. Those of T2 in the 0.6–0.8 m and 0.8–1.0 m soil layers were also significantly higher at anthesis. T2 was significantly higher than T1 in the photosynthetic rate (Pn) and instantaneous water use efficiency (WUEleaf) of flag leaves, post-anthesis dry matter accumulation (DMA), contribution of DMA to grain (CDMA), grain yield and WUE, but lower than T1 in the preanthesis dry matter remobilization efficiency (DMRE) and contribution of DMR to grain (CDMR). T2 had significantly lower plant populations and dry matter at jointing, Pn and WUEleaf at 28 days after anthesis, DMA and CDMA, but higher dry matter increase rate after jointing, tiller survival rate, DMR, DMRE, CDMR and WUE. The combined effect of these differences enabled T2 to have yield that was not significantly different to T4. In summary, SI at joining and anthesis that was based on suitable soil water content at sowing increased the absorbing area of roots in both deep and surface soil layers; accelerated the dry matter accumulation after jointing; increased the Pn and WUEleaf of flag leaves, DMA and DMR; and finally achieved a high grain yield and higher WUE. However, excessive irrigation reduced the WUE by inhibiting the redistribution of dry matter, although the WUEleaf of flag leaves was still increased.
1. Introduction Winter wheat (Triticum aestivum L.) is a major crop in the North China Plain (NCP), accounting for greater than 70% of the national wheat production (Zhang et al., 2013a). The annual rainfall of the NCP ranges from 470 to 910 mm, but only 150–180 mm occurs during the winter wheat growing season, which is approximately 25–40% of the total water requirement of winter wheat (Wang et al., 2008; Liu et al., 2011). Irrigation is required for achieving high grain yield. However, multiple irrigations applied during wheat growing season has significantly reduced groundwater table (Sun et al., 2006; Wang et al., 2008; Chen et al., 2010). Wheat production is threatened by increasing water shortages (Wang et al., 2007; Zhang et al., 2010, 2013b).
⁎
1
Therefore, it is important to develop appropriate water-saving strategies to improve water use efficiency (WUE) and maintain a high level of wheat production. The roots of winter wheat are plastic and affected by soil water status (Zhang et al., 2015), and the enhancement of soil water use efficiency mainly depends on the development of the root system (Guan et al., 2015; Hochholdinger, 2016). The root system of winter wheat determines its ability to capture available water and nutrients (Yadav et al., 2009; White and Kirkegaard, 2010; Bengough et al., 2011), which plays an important role in the plant-soil ecosystem (Zhang et al., 2009a; Wang et al., 2014a; Xu et al., 2016). The root weight density (RWD) in the 0–1.0 m soil layer reached a maximum at the flowering stage and mostly distributed in the 0–0.4 m soil layer (Wang et al., 2014a).
Corresponding author at: College of Agronomy, Shandong Agricultural University, 61 Daizong Street, Taian 271018, Shandong Province, People’s Republic of China. E-mail address: [email protected] (D. Wang). This author equally contributed to this work and should be considered co-first author.
http://dx.doi.org/10.1016/j.fcr.2017.08.007 Received 26 April 2017; Received in revised form 5 August 2017; Accepted 9 August 2017 0378-4290/ © 2017 Published by Elsevier B.V.
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Table 1 Soil nutrition status and soil bulk density in the 0–0.2 m soil layer of the experimental field before sowing in 2012–2013 and 2013–2014. years
Organic matter (g kg−1)
Total nitrogen (g kg−1)
Hydrolysable nitrogen (mg kg−1)
Available phosphorous (mg kg−1)
Available potassium (mg kg−1)
Soil bulk density (t m−3)
2012–2013 2013–2014
16.50 16.39
1.09 1.03
103.91 105.63
29.24 30.42
121.96 122.95
1.60 1.40
(116°41′E, 35°42′N), Shandong Province, China. This experimental area belongs to temperate, continental, monsoon climate with an average annual temperature of 13.6 °C and an annual precipitation of 621.2 mm. Approximately 40% of the precipitation occurs during the winter wheat growing season which is from October to June. The average annual groundwater level is 25 m. The soil of the experimental field was silty loam, and the previous crop was corn (Zea mays L.). The organic matter, total nitrogen, hydrolysable nitrogen, available phosphorous, and available potassium in the 0–0.2 m soil layer of the experimental field before sowing were 16.50 g kg−1, 1.09 g kg−1, 103.91 mg kg−1, 29.24 mg kg−1, and 121.96 mg kg−1 in 2012–2013 and 16.39 g kg−1, 1.03 g kg−1, 105.63 mg kg−1, 30.42 mg kg−1, and 122.95 mg kg−1 in 2013–2014, respectively. The soil bulk density of 0.2 m soil layer was 1.60 t m−3 in 2012–2013 and 1.40 t m−3 in 2013–2014 (Table 1). The field capacity and relative water content in the 0–2.0 m soil layers of the experimental field before sowing are listed in Table 2. The precipitation amount in different growth stages of winter wheat and the seasonal precipitation in 2012–2013 and 2013–2014 are shown in Table 3.
Irrigation regimes strongly influence the density and depth of roots (Wang et al., 2004). Water stress will restrict root growth and distribution in the soil (Gajri et al., 1989), and reduce the root length density (RLD) (Li et al., 2010). It has been found that total root dry weight, volume, length and number of branches reduce with decreasing irrigation times (Zhang et al., 2009a). However, limited irrigation can stimulate roots to grow into deeper soil layers and thus enhanced the uptake of soil-stored water from the subsoil layers (Wang et al., 2014a). Li et al. (2010) reported that one-time irrigation at jointing resulted in the highest RLD in > 0.3 m deep soil layers. Greater root biomass was significantly associated with greater shoot biomass, which contributed to higher grain yields and WUE (Zhang et al., 2009b). However, the relationships between the morphology and distribution of root and the grain yield and WUE of wheat remains an important topic of discussion. WUE is a key physiological parameter indicating the ability of crops to conserve water in a water-scarce region because it combines drought resistance and high potential yield (Fang et al., 2010; Zhang et al., 2010; Xu et al., 2016). Appropriate deficit irrigation does not necessarily reduce crop production and can result in high grain yield and WUE in wheat (Zhang et al., 2006; Fereres and Soriano, 2007). Xu et al. (2016) suggested that 60 mm irrigation applied at elongation was the best irrigation scheme for efficient water use and relatively high yield in winter wheat, but others argued that 120 mm irrigation during the winter wheat growing season could produce a reasonable grain yield and WUE (Bian et al., 2016). Du et al. (2010) reported that the maximum grain yield of winter wheat was achieved when 84% of maximum crop-water requirements were applied. Therefore, the frequency and amount of irrigation could be reduced to increase dry matter accumulation, promote grain-filling rate, and improve the yield and WUE of wheat (Zhang et al., 2006). Many studies attributed the yield and WUE improvement to the increase of water uptake and utilization from the deep soil layers (Johnson and Davis, 1980; Guo et al., 2016) because limited irrigation can stimulate roots to grow into deeper soil layers (Wang et al., 2014a; Xu et al., 2016). However, the shallow root system is required for absorption of nutrients that are mostly concentrated in the upper layers of soil (Manske and Vlek, 2002); furthermore, the superficial root parts may also be beneficial for capturing rainfall that does not infiltrate to the deeper soil layers (Ehdaie et al., 2012). Simultaneously promoting the absorption and utilization of the water from the deep soil layers and the rich nutrition from the upper soil layers is crucial for increasing in WUE. In this study, a method for determining the amount of supplemental irrigation (SI) required of wheat to achieve high grain yield and WUE was adopted, in which, the amount of SI is based on the soil water content before SI, which reflects both the precipitation and water consumption by the crop (Wang et al., 2013). Four SI regimes were designed to (1) determine the effects of the SI regimes on root growth and distribution; (2) clear the response of gas exchange characteristics of leaves, dry matter accumulation and redistribution, grain yield and WUE to SI regimes; and (3) clarify the relationships between wheat root distribution and wheat production.
2.2. Experimental design Jimai 22, one of the most widely planted commercial winter wheat cultivars in the NCP, was used for this study. Four SI regimes were set up (Table 4) in 2012–2013: no-irrigation after emergence (T1), SI at jointing and anthesis (T2), SI at sowing, jointing and anthesis (T3), and SI at pre-wintering, jointing and anthesis (T4). The SI brought soil water content in the 0–1.4 m soil layer to 85% of field capacity at sowing and pre-wintering stages, and to 70% of field capacity at jointing and anthesis stages in 2012–2013, according to our previously published method (Wang et al., 2013). In 2013–2014, the irrigation period of four SI regimes was consistent with previous year, but the SI brought soil water content in the 0–0.2 m soil layer to 100% of field capacity at prewintering, jointing and anthesis stages. This was based on the distribution of wheat root and infiltration rule of irrigation water in soil, in order to save the time and manpower required for measuring the soil water content before irrigation and to facilitate the application of SI technology in wheat production. In 2013–2014, irrigation was applied Table 2 Field capacity and relative soil water content in the 0–2.0 m soil layers of the experimental field before sowing.
2. Materials and methods 2.1. Experimental site The field experiment was performed from 2012 to 2014 in Yanzhou 132
Soil layer
2012–2013
2013–2014
(m)
Field capacity (%)
Relative soil water content (%)
Field capacity (%)
Relative soil water content (%)
0–0.2 0.2–0.4 0.4–0.6 0.6–0.8 0.8–1.0 1.0–1.2 1.2–1.4 1.4–1.6 1.6–1.8 1.8–2.0 mean
24.57 22.81 27.20 23.66 24.52 21.75 22.76 22.90 22.70 22.81 23.57
64.13 70.30 64.06 71.76 75.65 94.97 95.25 94.31 96.94 98.06 82.54
29.04 27.82 26.09 26.43 27.71 26.90 24.08 25.08 24.48 24.28 26.19
32.62 31.12 46.82 62.28 71.23 71.26 75.20 73.86 76.46 77.82 61.87
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the oven-drying method (Gardner, 1986). The amount of irrigation water was calculated based on the soil water content before irrigation as described by Wang et al. (2013). Calculation of total water consumption of winter wheat was based on the equation used by Zhang et al. (2013a):
Table 3 Precipitation amount in different growth stages of winter wheat and seasonal precipitation (mm). years
Sowing to prewintering
Prewintering to jointing
Jointing to anthesis
Anthesis to maturity
Seasonal precipitation
2012–2013 2013–2014
22.0 38.0
51.0 14.0
9.0 37.0
135.5 54.0
217.5 143.0
ET = S + I + P − Dr − Sr + Cr
(1)
where ET is the total water consumption of winter wheat during growing period (mm), S is the soil water consumption for the 2 m depth (mm), I is the irrigation amount (mm), P is the available precipitation amount (mm), Dr is the deep percolation, Cr is the capillary rise to the root zone, and Sr is the surface runoff. When the groundwater table is lower than 2.5 m below the ground surface, the capillary rise is negligible according to Darcy's equation (de Azevedo et al., 2003; Ali et al., 2007). The deep percolation and surface runoff are ignored in the North China Plain (Lv et al., 2011).
at sowing in all treatments because the relative soil water content in the 0–0.2 m soil layer was below 40% of field capacity before sowing. SI brought soil water content in the 0–0.2 m soil layer to 100% of field capacity in T3 treatment, and to 80% of field capacity in the other treatments at sowing (Table 4). A randomized block design with three replications was used, where the area of each plot was 46 m2 (2 m × 23 m). The average relative soil water content of each treatment in main root layers before and after SI at each growth stage are shown in Table 5. Well water was obtained using a submersible pump and uniformly sprayed in the field with micro-sprinkling hoses (Man et al., 2017). The water metre and valve on the hoses were used to measure and control the amount of irrigation. Nitrogen, phosphorus (P2O5) and potassium (K2O) were applied as base fertilizer at 105 kg ha−1, 150 kg ha−1 and 150 kg ha−1, respectively, with the depth of 0.1 m, alternating with two rows of winter wheat at the same time of seeding. Before fertilizing and seeding, rotary tillage and harrowing were carried out after returning the straw of the preceding crop maize into cropland. Topdressing N was 135 kg ha−1 at the jointing stage. The types of fertilizer were urea (N content: 46.4%), diammonium phosphate (P2O5 and N contents: 46% and 18%) and potassium chloride (K2O content: 52%). Wheat was sown on October 10th, 2012 and October 9th, 2013, and harvested on June 14th, 2013 and May 30th, 2014, respectively. A seed rate of 180 seeds per m−2 was used in all treatment regimes. Additional protective measures were taken to assure the healthy growth of the wheat, such as the spraying of herbicides at the regreening period, and insecticides before flowering. No significant incidence of pest, diseases or weeds was observed in any of the treatment sites during the experiment.
2.3.2. Root distribution and morphological characteristics Root samples were collected from soil samples taken from each plot at four growing stages: pre-wintering, regreening, jointing, and anthesis. The sampling followed procedures described by Bǒhm (1979). An auger with an internal diameter of 0.1 m was used to obtain cores, and each core was obtained at 0.2 m increments down to 1.0 m. The core sections and associated roots were soaked in plastic buckets filled with water and gently disaggregated by hand. Collected samples were loaded into 80 mesh bags to remove impurities and roots from other plants. Wheat root from every layer was put in methyl blue solution (4 °C) to dye for 12 h and then tiled upon glass plate (0.24 m × 0.32 m) for scanning with a root scanner (HP Scanjet 8200: Hewlett-Packard, Palo Alto, CA, USA). Pictures were saved as pixel 600api. Root system analysis software (Delta-T Area Meter Type AMB2; Delta-T Devices Ltd., Cambridge, UK) was used to measure root length and root surface area in different soil layers (Zhang et al., 2009a). The roots were dried with absorbent paper and placed in the oven with 80 °C until they reached a constant weight. The root dry weight density (RWD, kg m−3), root length density (RLD, km m−3) and root surface area density (RAD, m2 m−3) were calculated by the following formulas (Mosaddeghi et al., 2009; Li et al., 2010; Wang et al., 2014a; Guan et al., 2015):
M V
2.3. Measurements
RWD =
2.3.1. Soil water content and water consumption of winter wheat The soil water content measurement samples were collected using a soil corer at 0.2-m intervals to a depth of 2.0 m in all experimental plots before sowing, at maturity, on the day before irrigation, and on the third day after irrigation. The soil water content was determined using
where M is the root dry weight (kg) and V is the volume of the soil sample (m3).
RLD =
(2)
L V
(3)
Table 4 Plan wetting layer, targeted soil relative water content at different stages and the amount of each supplemental irrigation in four treatments: no-irrigation after emergence (T1), supplemental irrigation at jointing and anthesis (T2), supplemental irrigation at sowing, jointing and anthesis (T3), and supplemental irrigation at pre-wintering, jointing and anthesis (T4) in 2012–2014. Irrigation treatments
Plan wetting layer (m)
Targeted soil relative water content (%)
Irrigation amount (mm)
Sowing
Pre-wintering
Jointing
Anthesis
Sowing
Pre-wintering
Jointing
Anthesis
2012–2013 T1 T2 T3 T4
— 0–1.4 0–1.4 0–1.4
— — 85 —
— — — 85
— 70 70 70
— 70 70 70
— — 48.6 —
— — — 39.3
— 41.5 39.2 31.8
— 68.6 66.8 51.6
2013–2014 T1 T2 T3 T4
0–0.2 0–0.2 0–0.2 0–0.2
80 80 100 80
— — — 100
— 100 100 100
— 100 100 100
37.5 37.5 53.7 37.5
— — — 18.2
— 58.9 60.1 60.4
— 55.7 50.2 54.0
“—” means no irrigation.
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Table 5 Average relative soil water content in main root layers at each growth stage before and after supplemental irrigation in four treatments: no-irrigation after emergence (T1), supplemental irrigation at jointing and anthesis (T2), supplemental irrigation at sowing, jointing and anthesis (T3), and supplemental irrigation at pre-wintering, jointing and anthesis (T4) in 2012–2014. Growth stage
Treatments
0–0.2 m
0–0.4 m
0–1.4 m
θb (%)
θar (%)
θb (%)
θar (%)
θb (%)
θar (%)
T1 T2 T3 T4
64.1 64.1 64.1 64.1
— — 96.1 —
67.2 67.2 67.2 67.2
— — 91.4 —
76.6 76.6 76.6 76.6
— — 85.1 —
Pre-wintering
T1 T2 T3 T4
63.7 63.7 83.0 63.7
— — — 95.2
68.2 68.2 84.4 68.2
— — — 91.7
75.9 75.9 85.7 75.9
— — — 84.7
Jointing
T1 T2 T3 T4
38.5 38.5 40.6 42.1
— 74.7 80.7 80.9
46.3 46.3 44.4 51.8
— 69.8 73.4 75.7
62.3 62.3 62.7 64.1
— 69.1 69.4 71.3
Anthesis
T1 T2 T3 T4
32.9 40.6 40.3 40.3
— 74.5 80.4 80.6
38.6 44.4 47.2 49.2
— 71.8 78.7 74.6
53.6 57.9 56.9 60.9
— 68.6 67.4 69.7
T1 T2 T3 T4
33.8 33.8 33.8 33.8
65.2 65.2 73.0 65.2
32.2 32.2 32.2 32.2
53.1 53.1 58.7 53.1
57.3 57.3 57.3 57.3
62.5 62.5 66.2 62.5
Pre-wintering
T1 T2 T3 T4
77.5 77.5 81.6 77.5
— — — 85.7
64.1 64.1 74.4 64.1
— — — 71.5
72.4 72.4 72.8 72.4
— — — 74.5
Jointing
T1 T2 T3 T4
27.5 27.5 26.0 25.6
— 69.2 70.7 68.9
31.2 31.2 29.7 31.0
— 63.6 57.4 63.2
56.4 56.4 58.4 56.7
— 66.7 67.2 66.4
Anthesis
T1 T2 T3 T4
30.6 31.3 38.2 33.5
— 66.1 62.0 61.7
29.1 31.5 32.7 30.5
— 61.3 51.3 54.2
55.5 60.8 56.6 56.1
— 68.8 64.2 65.5
2012–2013 Sowing
2013–2014 Sowing
θb and θar are the average relative soil water content before and after supplemental irrigation, respectively. “—” means no irrigation.
draft oven immediately and dried at 75 °C until a constant weight was obtained to determine aboveground biomass (Xu et al., 2005). Various parameters for the dry matter accumulation and remobilization after anthesis were calculated as follows (Ma et al., 2015):
where L is the root length (m).
A RAD = V
(4) 2
where A is the root surface area (m ).
Pre-anthesis dry matter remobilization (DMR, kg ha−1) = dry matter of vegetative organs at anthesis − dry matter of vegetative organs (stem, sheath, leaves, spike axis and glume) at maturity. (5)
2.3.3. Net CO2 assimilation rates (Pn) and instantaneous water use efficiency (WUEleaf) Net CO2 assimilation rates (Pn) and transpiration rates of the flag leaves were measured at 0, 14 and 28 days after anthesis using a Li6400 portable photosynthesis system (LI-Cor, Inc., Lincoln, Nebraska, USA) during 9:00–11:00 a.m. and 2:00–4:00 p.m. Fifteen replicate flag leaves chosen randomly were used for measurements of each treatment. Pn divided by transpiration rates were calculated as the WUEleaf (Wang et al., 2014b).
DMR efficiency (DMRE, %) = (DMR × 100)/dry matter of vegetative organs at anthesis. (6) Contribution of DMR to grain (CDMR, %) = (DMR × 100)/Grain yield. (7) Post-anthesis dry matter accumulation (DMA, kg ha−1) = dry matter at maturity − dry matter at anthesis. (8) Contribution of DMA to grain (CDMA, %) = (DMA × 100)/Grain yield. (9)
2.3.4. Dry matter accumulation and remobilization Plant samples were collected to determine dry matter on five occasions: at pre-wintering, regreening, jointing, anthesis and maturity stages. The whole plants were sampled through removing the roots at pre-wintering, regreening and jointing. Thirty consecutive plants were cut manually at ground level from each plot at anthesis and maturity stages. Plants were separated into the stem plus sheath, leaves and spikes at anthesis, and into the stem plus sheath, leaves, spike axis plus glume and grain at maturity. Plant samples were placed into a forced
2.3.5. Yield and water use efficiency The spike number per square metre was investigated by manual counting. The 1000-grain weight was measured by taking the average of three samples of 1000 grains. Grain yield (kg ha−1) was determined from one 3 m2 quadrat from each plot and was reported at a 12.5% wet 134
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3.3. Gas exchange characteristics of flag leaves
basis through natural air drying. The WUE of winter wheat was defined as follows (Guan et al., 2015):
WUE =
Y ET
The Pn and WUEleaf of flag leaves determinated at 0, 14 and 28 days after anthesis (DAA) are shown in Fig. 5. T1 was lower than the other treatments. There were no significant differences between T3 and T4. Compared with T3 and T4, T2 has no significant difference in the Pn and WUEleaf at 0 DAA and has no significant difference in the WUEleaf at 14 DAA but was lower in the Pn and WUEleaf at 28 DAA for two years. These results indicate that SI at jointing and anthesis with no irrigation before jointing or less SI at sowing reduced the Pn and WUEleaf of flag leaves in the late grain filling stages.
(10)
where WUE (kg ha−1 mm−1) is the water use efficiency for grain yield, Y (kg ha−1) is the grain yield and ET is the water consumption amount during the growing season (mm).
2.4. Statistical analysis
3.4. Dry matter remobilization after anthesis
The data shown are averages. Statistical analysis employed standard analysis of variance (ANOVA assumptions of homogeneity) using SPSS (Statistical Product and Service Solutions, IBM) and mapping by SigmaPlot 12.5 (Systat Software Inc, Dundas, CA, GER). The relationships between RWD, RLD, and RAD in different soil layers and DAJ, DMJ, grain yield, and WUE were analyzed by linear correlation analysis. The DAJ and DMJ represent the increasing rate of dry matter at anthesis and maturity, respectively, relative to jointing. The least significant difference (LSD) method was used to determine if significant differences existed between treatments in their mean RWD, RLD, RAD, WUE, yield, etc. at a probability level of P ≤ 0.05.
Various parameters for the dry matter accumulation and remobilization after anthesis are shown in Table 6. Compared with T1, T2 was lower in the DMRE and CDMR but higher in the DMA and CDMA. Compared with T3 and T4, T2 was higher in the DMR, DMRE and CDMR but lower in the DMA and CDMA. There were no significant differences between T3 and T4 in the DMR, DMRE, CDMR, DMA and CDMA. There were no significant differences between T1 and T2 in the DMR for two years. 3.5. Grain yield and water use efficiency The grain yield, yield components and WUE of winter wheat are shown in Table 7. T2 was higher than T1 in the yield components, grain yield, water consumption and WUE. There were no significant differences between T3 and T4. Compared with T3, T2 has no significant difference in the spike number and 1000-grain weight but was lower in the grain yield and water consumption for both years. T2 had higher WUE than T3 for both years, and the difference was significant in 2012–2013. Compared with T4, T2 was lower in the water consumption but higher in the WUE. There were no significant differences between T2 and T4 in the spike number, 1000-grain weight and grain yield for both years. These results indicate that SI at joining and anthesis based on suitable soil water content at sowing could achieve both high gain yield and WUE.
3. Results 3.1. Spatial and temporal distribution of root T1 was lower than the other treatments in the RLD, RAD and RWD of winter wheat in the 0–0.2 m soil layer after jointing (Fig. 1). The RLD, RAD and RWD in the 0–0.2 m soil layer from T2 were lower than those from T4 at regreening, but increased rapidly after jointing and finally higher than those from T3 and T4 at anthesis by 23%, 22% and 18%, respectively. There were no significant differences of RLD, RAD, and RWD between T3 and T4 at anthesis. The RLD, RAD and RWD of winter wheat declined with increasing soil depth in the 0–1.0 m soil layer at anthesis, and those in the 0–0.6 m soil layers accounted for more than 80% of the total (Fig. 2). T2 was higher than T3 and T4 in the RLD, RAD and RWD of the 0.6–0.8 and 0.8–1.0 m soil layers. There were no significant differences between T3 and T4 in the 0–1.0 m soil layers, and there were no significant differences between T1 and T2 in the 0.4–1.0 m soil layers for two years.
3.6. Relationship between root distribution and wheat production The DAJ showed positive correlations with RLD, RAD and RWD in the 0–0.2 m soil layer at anthesis but had no significant correlations with RLD, RAD and RWD in other soil layers (Table 8). The DMJ and WUE had very significant positive correlations with RLD, RAD and RWD in the 0–0.2 m soil layer but had no significant correlations with RAD and RWD in other soil layers. The grain yield and WUE positively correlated with RLD in the 0.2–0.4 m soil layer.
3.2. Dynamics of plant population and dry matter at different growing stages
4. Discussion
The plant population dynamics of wheat are shown in Fig. 3. There were no significant differences between T2 and T1 before jointing, but T2 was higher than T1 at anthesis and maturity. T3 and T4 were higher than T2 and T1 at jointing, but there were no significant differences among T2, T3 and T4 at maturity. The tiller survival rate (population at maturity/population at jointing) of T2 was 75–78% higher than that of T3 and T4 for two years. For dry matter accumulation, there were no significant differences between T2 and T1 before jointing both in 2012–2013 and 2013–2014 (Fig. 4). There were also no significant differences between T3 and T4 from jointing to maturity. T3 and T4 were higher than T2 and T1 from jointing to maturity. The dry matter of T2 was increased by 65–66% from jointing to anthesis and by 64–67% from anthesis to maturity, which was higher than those of T1. The dry matter increase rate of T3 was only 13–45% from jointing to anthesis, and 60–64% from anthesis to maturity. The dry matter increase rate of T4 was only 6–52% from jointing to anthesis, and 60–61% from anthesis to maturity.
4.1. Relation of SI to root growth and distribution As an integral part of plant organs, roots are involved in the acquisition of nutrients and water (Yang et al., 2004; Wu and Cheng, 2014). The amount of soil water absorbed by plant roots mainly depends on soil water supply, morphological and physiological characteristics of roots, and so on (Wang et al., 2014a; Li et al., 2017). The morphology of roots is affected by the soil water supply (Chu et al., 2014). Root morphological traits in drying soil media included increased deep root biomass, longer seminal roots, and increased production of small diameter roots at depth (Becker et al., 2016). In this paper, the treatments without SI before jointing increased the RLD, RAD and RWD in the soil below 0.6 m at anthesis (Fig. 2) because the extreme arid condition in the shallow soil layer (Table 5) encouraged the growth of deeper roots (Asseng et al., 1998). However, the relative 135
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Fig. 1. Root length density, surface area density and dry weight density of winter wheat in the 0–0.2 m soil layer in four treatments: no-irrigation after emergence (T1), supplemental irrigation at jointing and anthesis (T2), supplemental irrigation at sowing, jointing and anthesis (T3), and supplemental irrigation at pre-wintering, jointing and anthesis (T4) in 2012–2014. Vertical bars indicate the standard deviation.
before jointing (Fig. 1). However, the differences among these treatments in the relative soil water content of the 0–0.4 m soil layer were small during this period. It can be speculated that the local abundant water supply in the upper soil layer after drought stimulated the
soil water content in the 0–0.2 and 0.2–0.4 m soil layers was greatly increased when the first SI was supplied at jointing (Table 5). The RLD, RAD and RWD in the 0–0.2 m soil layer increased rapidly from jointing to anthesis and were finally higher than those of the treatments with SI 136
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Fig. 2. Root length density, surface area density and dry weight density of winter wheat in the 0–1.0 m soil layers at anthesis stage in four treatments: no-irrigation after emergence (T1), supplemental irrigation at jointing and anthesis (T2), supplemental irrigation at sowing, jointing and anthesis (T3), and supplemental irrigation at pre-wintering, jointing and anthesis (T4) in 2012–2014. Transversal bars indicate the standard deviation, and different letters on the right error bars indicate significant differences between treatments at P < 0.05 by the LSD test.
certain depth of the soil layer. Root morphological development is based on shoot development; the pattern of root development and shoot growth is closely associated (Aguirre and Johnson, 1991). In this study, compared with T3 and T4,
compensatory physiological responses of wheat (Xu et al., 2010; Steinemann et al., 2015), which induced the growth of the topsoil roots. The periodical change of the soil water content in the upper soil layer caused by SI changed the distribution pattern of the root system in a 137
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Fig. 3. Populations of winter wheat at different growth stages in four treatments: noirrigation after emergence (T1), supplemental irrigation at jointing and anthesis (T2), supplemental irrigation at sowing, jointing and anthesis (T3), and supplemental irrigation at pre-wintering, jointing and anthesis (T4) in 2012–2014. Vertical bars indicate the standard deviation.
layers for high-yielding wheat production, and the grain yield was negatively correlated with RWD in the deep soil layers. Similar views were clarified by Xue et al. (2003), who stated that root depth did not contribute to the increased grain yield and WUE in irrigated treatments. The roots near the soil surface are known to be a primary location of moisture and nutrient uptake in well-watered conditions (Hopkins and Hüner, 2009; Becker et al., 2016). However, the moisture in the upper soil layers is rapidly consumed and drastically reduced due to root uptake and ground evaporation, which significantly reduces the effectiveness of soil nutrients and affects the water and nutrients absorption of roots. In this study, the root growth of T2 in the soil both at 0–0.2 m and below 0.6 m was promoted (Fig. 2), which increased the absorbing area of roots in both deep and surface soil layers. It can be inferred that this kind of root distribution pattern together with appropriate water supply in the upper soil layer after jointing, was conducive to the absorption of water from deep soil layer and rich nutrition from upper soil layer and then improved the dry matter increase rate (Fig. 4 and Table 8). Finally, it enabled high grain yield and high WUE of winter wheat (Table 7).
T2 was lower in the plant population (Fig. 3) and dry matter (Fig. 4) at jointing due to lower water supply before jointing (Table 5), but higher in the tiller survival rate (Fig. 3) and root growth rate in the 0–0.2 m soil layer from jointing to anthesis (Fig. 1). This differs from the previous study, in which the mild drought prior to the jointing stage controls excessive vegetative growth, increasing the distribution of photosynthetic products to the roots of winter wheat (Liu et al., 2016). It was more likely that less invalid tillers caused by drought before jointing relieved the contradiction of dry matter demand between the above-ground and underground of plant after jointing, thus prompting more dry matter to be transported into the roots and enhancing the root growth in the surface layers where the soil moisture was appropriate after jointing (Table 5). 4.2. Roles of root distribution in grain yield and WUE improvement The root growth, especially deep roots, had a significant effect on the stable yield and absorbed larger amounts of deep water from the soil under drought condition (White and Kirkegaard, 2010). Some other studies also suggest that smaller root sizes in the upper soil layer might be more economical in terms of production efficiency (Zhang et al., 2009a). However, the shallow root system is required for absorption of nutrients that are mostly concentrated in the upper layers of soil (Manske and Vlek, 2002). Furthermore, the superficial root parts may also be beneficial for capturing rainfall that does not infiltrate to deeper soil layers (Ehdaie et al., 2012). Wang et al. (2014a) pointed that it should not be attempt to enhance root development in the deep soil
4.3. The key to achieving high yield and WUE The highest yield of winter wheat is usually obtained with moderate irrigation, more than the threshold, the yield of winter wheat was not increased, and the WUE was significantly reduced (Zhang et al., 2015). The WUE at yield level was positively related to seasonal WUEleaf (Qiu et al., 2008), while the WUEleaf was connected with the soil water Fig. 4. Dry matter accumulation of winter wheat at different growth stages in four treatments: no-irrigation after emergence (T1), supplemental irrigation at jointing and anthesis (T2), supplemental irrigation at sowing, jointing and anthesis (T3), and supplemental irrigation at pre-wintering, jointing and anthesis (T4) in 2012–2014. Vertical bars indicate the standard deviation.
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Fig. 5. Net CO2 assimilation rates (Pn) and instantaneous water use efficiency (WUEleaf) of winter wheat after anthesis in four treatments: no-irrigation after emergence (T1), supplemental irrigation at jointing and anthesis (T2), supplemental irrigation at sowing, jointing and anthesis (T3), and supplemental irrigation at pre-wintering, jointing and anthesis (T4) in 2012–2014. Vertical bars indicate the standard deviation, and different letters above error bars indicate significant differences between treatments at P < 0.05 by the LSD test.
content at the time the measurements were taken (Wang et al., 2016). In this study, the grain yield and WUE were simultaneously increased along with an increased WUEleaf of flag leaves after anthesis, DMA and CDMA, and decreased DMRE and CDMR (Fig. 5, Tables 6 and 7) by the appropriate SI. However, further decreasing the DMR, DMRE and CDMR with extra SI at the pre-wintering stage reduced the WUE, even though the WUEleaf of flag leaves in the late grain filling stages and DMA and CDMA were further increased. It is demonstrated that the inhibition of the recycling of the dry matter assimilated before anthesis limited the WUE improvement as excessive SI is applied.
Table 6 Dry matter accumulation and remobilization after anthesis in four treatments: no-irrigation after emergence (T1), supplemental irrigation at jointing and anthesis (T2), supplemental irrigation at sowing, jointing and anthesis (T3), and supplemental irrigation at pre-wintering, jointing and anthesis (T4) in 2012–2014. Treatments
DMR (kg ha−1)
DMRE (%)
CDMR (%)
DMA (kg ha−1)
CDMA (%)
2012–2013 T1 T2 T3 T4
2535.0a 2498.0a 2022.3b 2124.1b
30.3a 24.4b 16.3c 17.6c
40.1a 27.7b 21.4c 22.8c
3779.8c 6531.3b 7411.0a 7174.2a
59.9c 72.3b 78.6a 77.2a
2013–2014 T1 T2 T3 T4
2308.0a 2363.5a 1759.6b 1883.7b
29.5a 24.1b 15.0c 15.7c
41.4a 26.5b 19.1c 20.5c
3273.5c 6555.7b 7475.3a 7288.7a
58.6c 73.5b 80.9a 79.5a
5. Conclusion The timing and frequency of SI significantly influenced root distribution, gas exchange characteristics of leaves, dry matter remobilization, yield and WUE. Moderate drought at the early growth stage not only promoted the distribution of roots in the deeper soil layer but also reduced the invalid tillers at jointing. Less invalid tillers and appropriate SI at jointing stimulated the growth of roots in the top 0.2 m soil layer after jointing. The increase of roots in both deep and surface soil was conducive to accelerating dry matter accumulation
DMR: Pre-anthesis dry matter remobilization; DMRE: DMR efficiency; CDMR: Contribution of DMR to grain; DMA: Post-anthesis dry matter accumulation; CDMA: Contribution of DMA to grain. The different letters in the same column in 2012–2013 or 2013–2014 are significantly different at P < 0.05 by the LSD test.
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Table 7 Yield components, grain yield and water use efficiency of winter wheat in four treatments: no-irrigation after emergence (T1), supplemental irrigation at jointing and anthesis (T2), supplemental irrigation at sowing, jointing and anthesis (T3), and supplemental irrigation at pre-wintering, jointing and anthesis (T4) in 2012–2014. Spike number (×104 spike ha−1)
Kernel number (grain spike−1)
1000-grain weight (g)
Grain yield (kg ha−1)
Water consumption (mm)
Water use efficiency (kg ha−1 mm−1)
2012–2013 T1 T2 T3 T4
630.4b 688.0a 699.2a 713.7a
27.2c 30.6b 32.5a 32.8a
39.6b 42.0a 42.9a 42.2a
6314.8c 9029.3b 9433.3a 9298.3ab
325.5c 393.3b 434.7a 428.5a
19.4c 23.0a 21.7b 21.7b
2013–2014 T1 T2 T3 T4
403.3b 524.0a 531.2a 528.0a
28.3b 34.4a 35.2a 35.2a
43.5b 48.2a 49.3a 48.8a
5581.5c 8919.2b 9234.9a 9172.4ab
288.5c 367.8b 393.6a 402.0a
19.3c 24.3a 23.5ab 22.8b
Treatments
The different letters in the same column in 2012–2013 or 2013–2014 are significantly different at P < 0.05 by the LSD test. Australia. Field Crops Res. 57, 163–179. Bǒhm, W., 1979. Methods of Studying Root System. Springer-Verlag, Berlin. Becker, S.R., Byrne, P.F., Reid, S.D., Bauerle, W.L., McKay, J.K., Haley, S.D., 2016. Root traits contributing to drought tolerance of synthetic hexaploid wheat in a greenhouse study. Euphytica 207, 213–224. Bengough, A.G., McKenzie, B.M., Hallett, P.D., Valentine, T.A., 2011. Root elongation, water stress, and mechanical impedance: a review of limiting stresses and beneficial root tip traits. J. Exp. Bot. 62, 59–68. Bian, C.Y., Ma, C.J., Liu, X.H., Gao, C., Liu, Q.R., Yan, Z.X., Ren, Y.J., Li, Q.Q., 2016. Responses of winter wheat yield and water use efficiency to irrigation frequency and planting pattern. PLoS One 11, e0154673. http://dx.doi.org/10.1371/journal.pone. 0154673. Chen, C., Wang, E.L., Yu, Q., 2010. Modeling wheat and maize productivity as affected by climate variation and irrigation supply in North China Plain. Agron. J. 102, 1037–1049. Chu, G., Chen, T.T., Wang, Z.Q., Yang, J.C., Zhang, J.H., 2014. Reprint of Morphological and physiological traits of roots and their relationships with water productivity in water-saving and drought-resistant rice. Field Crops Res. 165, 36–48. de Azevedo, P.V., da Silva, B.B., da Silva, V.P.R., 2003. Water requirements of irrigated mango orchards in northeast Brazil. Agric. Water Manage. 58, 241–254. Du, T.S., Kang, S.Z., Sun, J.S., Zhang, X.Y., Zhang, J.H., 2010. An improved water use efficiency of cereals under temporal and spatial deficit irrigation in north China. Agric. Water Manage. 97, 66–74. Ehdaie, B., Layne, A.P., Waines, J.G., 2012. Root system plasticity to drought influences grain yield in bread wheat. Euphytica 186, 219–232. Fang, Q.X., Ma, L., Green, T.R., Yu, Q., Wang, T.D., Ahuja, L.R., 2010. Water resources and water use efficiency in the North China Plain: current status and agronomic management options. Agric. Water Manage. 97, 1102–1116. Fereres, E., Soriano, M.A., 2007. Deficit irrigation for reducing agricultural water use. J. Exp. Bot. 58, 147–159. Gajri, P.R., Prihar, S.S., Arora, V.K., 1989. Effects of nitrogen and early irrigation on root development and water use by wheat on two soils. Field Crops Res. 21, 103–114. Gardner, W.H., 1986. Water content. In: Klute, A. (Ed.), Methods of Soil Analysis: Part 1Physical and Mineralogical Methods-Agronomy Monograph No. 9, 2nd edition. American Society of Agronomy, Madison, WI, pp. 493–544. Guan, D.H., Zhang, Y.S., Mahdi, M.A., Wang, Q.Y., Zhang, M.C., Li, Z.H., 2015. Tillage practices effect on root distribution and water use efficiency of winter wheat under rain-fed condition in the North China Plain. Soil Tillage Res. 146, 286–295. Guo, F., Ma, J.J., Zhang, L.J., Sun, X.H., Guo, X.H., Zhang, X.L., 2016. Estimating distribution of water uptake with depth of winter wheat by hydrogen and oxygen stable isotopes under different irrigation depths. J. Integr. Agric. 15, 891–906. Hochholdinger, F., 2016. Untapping root system architecture for crop improvement. J. Exp. Bot. 67, 4431–4433. Hopkins, W.G., Hüner, N.P.A., 2009. Introduction to Plant Physiology, 4th ed. John Wiley & Sons, Inc, Hoboken. Johnson, W.C., Davis, R.G., 1980. Yield-water relationships of summer-fallowed winter wheat. A precision study in the Texas Panhandle. Science and Education Administration Pub. Arr(Ns-5). pp. 1–43. Li, Q.Q., Dong, B.D., Qiao, Y.Z., Liu, M.Y., Zhang, J.W., 2010. Root growth, available soil water, and water-use efficiency of winter wheat under different irrigation regimes applied at different growth stages in North China. Agric. Water Manage. 97, 1676–1682. Li, X.Y., Šimůnek, J., Shi, H.B., Yan, J.W., Peng, Z.Y., Gong, X.W., 2017. Spatial distribution of soil water, soil temperature, and plant roots in a drip-irrigated intercropping field with plastic mulch. Eur. J. Agron. 83, 47–56. Liu, H.J., Yu, L.P., Luo, Y., Wang, X.P., Huang, G.H., 2011. Responses of winter wheat (Triticum aestivum L.) evapotranspiration and yield to sprinkler irrigation regimes. Agric. Water Manage. 98, 483–492. Liu, E.K., Mei, X.R., Yan, C.R., Gong, D.Z., Zhang, Y.Q., 2016. Effects of water stress on photosynthetic characteristics, dry matter translocation and WUE in two winter wheat genotypes. Agric. Water Manage. 167, 75–85. Lv, L.H., Wang, H.J., Jia, X.L., Wang, Z.M., 2011. Analysis on water requirement and water-saving amount of wheat and corn in typical regions of the North China Plain. Front. Agric. China 5, 556–562.
Table 8 Analysis of correlations between the root dry weight density (RWD), root length density (RLD), and root surface area density (RAD) in different soil layers and the DAJ, DMJ, grain yield, and water use efficiency. Soil layer (m)
DAJ
DMJ
Grain yield
Water use efficiency
RLD 0–0.2 0.2–0.4 0.4–0.6 0.6–0.8 0.8–1.0
0.72* 0.21 −0.49 −0.24 0.43
0.82** 0.39 −0.37 −0.29 0.31
0.60 0.88** 0.48 −0.16 −0.53
0.86** 0.83** 0.01 −0.41 −0.07
RAD 0–0.2 0.2–0.4 0.4–0.6 0.6–0.8 0.8–1.0
0.73* 0.04 −0.46 −0.10 0.05
0.83** 0.18 −0.40 −0.21 −0.06
0.61 0.59 0.29 −0.43 −0.37
0.83** 0.54 −0.15 −0.54 −0.43
RWD 0–0.2 0.2–0.4 0.4–0.6 0.6–0.8 0.8–1.0
0.76* −0.50 −0.45 −0.21 −0.20
0.85** −0.42 −0.43 −0.25 −0.23
0.62 0.36 0.11 −0.08 −0.07
0.83** −0.11 −0.29 −0.34 −0.31
The DAJ and DMJ represent the increasing rate of dry matter at anthesis and maturity, respectively, relative to jointing. * p < 0.05. ** p < 0.01.
after jointing. However, excessive irrigation inhibited the redistribution of the dry matter after anthesis. In addition to high WUEleaf of leaves, elevated dry matter increase rates after jointing and unimpeded dry matter remobilization after anthesis were important factors for improving grain yield and WUE. In the NCP, SI at joining and anthesis based on suitable soil water content at sowing is an important way to simultaneously increase grain yield and WUE. Acknowledgements This work was supported by the Special Fund for Agro-scientific Research in the Public Interest (201503130), and the National Natural Science Foundation of China (31271660). References Aguirre, L., Johnson, D.A., 1991. Root morphological development in relation to shoot growth in seedlings of four range grasses. J. Range Manage. 44, 341–346. Ali, M.H., Hoque, M.R., Hassan, A.A., Khair, A., 2007. Effects of deficit irrigation on yield water productivity, and economic returns of wheat. Agric. Water Manage. 92, 151–161. Asseng, S., Keating, B.A., Fillery, I.R.P., Gregory, P.J., Bowden, J.W., Turner, N.C., Palta, J.A., Abrecht, D.G., 1998. Performance of the APSIM-wheat model in western
140
Field Crops Research 214 (2017) 131–141
S. Feng et al.
White, R.G., Kirkegaard, J.A., 2010. The distribution and abundance of wheat roots in a dense: structured subsoil-implications for water uptake. Plant Cell Environ. 33, 133–148. Wu, W.M., Cheng, S.H., 2014. Root genetic research: an opportunity and challengeto rice improvement. Field Crops Res. 165, 111–124. Xu, Z.Z., Yu, Z.W., Wang, D., Zhang, Y.L., 2005. Nitrogen accumulation and translocation for winter wheat under different irrigation regimes. J. Agron. Crop Sci. 191, 439–449. Xu, Z.Z., Zhou, G.S., Shimizu, H., 2010. Plant responses to drought and rewatering. Plant Signal. Behav. 5, 649–654. Xu, C.L., Tao, H.B., Tian, B.J., Gao, Y.B., Ren, J.H., Wang, P., 2016. Limited-irrigation improves water use efficiency and soil reservoir capacity through regulating root and canopy growth of winter wheat. Field Crops Res. 196, 268–275. Xue, Q., Zhu, Z., Musick, J.T., Stewart, B.A., Dusek, D.A., 2003. Root growth and water uptake in winter wheat under deficit irrigation. Plant Soil 257, 151–161. Yadav, B.K., Mathur, S., Siebel, M.A., 2009. Soil moisture flow modeling with water uptake by plants (wheat) under varying soil and moisture conditions. J. Irrig. Drain. Eng. 135, 375–381. Yang, C.M., Yang, L.Z., Yang, Y.X., Ouyang, Z., 2004. Rice root growth and nutrient uptake as influenced by organic manure in continuously and alternately flooded paddy soils. Agric. Water Manage. 70, 67–81. Zhang, B.C., Li, F.M., Huang, G.B., Cheng, Z.Y., Zhang, Y.H., 2006. Yield performance of spring wheat improved by regulated deficit irrigation in an arid area. Agric. Water Manage. 79, 28–42. Zhang, X.Y., Chen, S.Y., Sun, H.Y., Wang, Y.M., Shao, L.W., 2009a. Root size: distribution and soil water depletion as affected by cultivars and environmental factors. Field Crops Res. 114, 75–83. Zhang, H., Xue, Y.G., Wang, Z.Q., Yang, J.C., Zhang, J.H., 2009b. Morphological and physiological traits of roots and their relationships with shoot growth insuper rice. Field Crops Res. 113, 31–40. Zhang, X.Y., Chen, S.Y., Sun, H.Y., Wang, Y.M., Shao, L.W., 2010. Water use efficiency and associated traits in winter wheat cultivars in the North China Plain. Agric. Water Manage. 97, 1117–1125. Zhang, X.Y., Wang, Y.Z., Sun, H.Y., Chen, S.Y., Shao, L.W., 2013a. Optimizing the yield of winter wheat by regulating water consumption during vegetative and reproductive stages under limited water supply. Irrig. Sci. 31, 1103–1112. Zhang, X.Y., Wang, S.F., Sun, H.Y., Chen, S.Y., Shao, L.W., Liu, X.W., 2013b. Contribution of cultivar, fertilizer and weather to yield variation of winter wheat over three decades: a case study in the North China Plain. Eur. J. Agron. 50, 52–59. Zhang, X.Y., Zhang, X.Y., Liu, X.W., Shao, L.W., Sun, H.Y., Chen, S.Y., 2015. Incorporating root distribution factor to evaluate soil water status for winter wheat. Agric. Water Manage. 153, 32–41.
Ma, S.C., Duan, A.W., Wang, R., Guan, Z.M., Yang, S.J., Ma, S.T., Shao, Y., 2015. Rootsourced signal and photosynthetic traits dry matter accumulation and remobilization, and yield stability in winter wheat as affected by regulated deficit irrigation. Agric. Water Manage. 148, 123–129. Man, J.G., Wang, D., White, P.J., 2017. Photosynthesis and drymass production of winter wheat in response to micro-sprinkling irrigation. Agron. J. 109, 549–561. Manske, G.G.B., Vlek, P.L.G., 2002. Root architecture-wheat as a model plant. In: Waisel, Y., Eshel, A., Beeckman, T., Kafkafi, U. (Eds.), Plant Roots: the Hidden Half. Marcel Dekker, Inc., New York-Basel, pp. 249–259. Mosaddeghi, M.R., Mahboubi, A.A., Safadoust, A., 2009. Short-term effects of tillage and manure on some soil physical properties and wheat root growth in a sandy loam soil in western Iran. Soil Tillage Res. 104, 173–179. Qiu, G.Y., Wang, L.M., He, X.H., Zhang, X.Y., Chen, S.Y., Chen, J., Yang, Y.H., 2008. Water use efficiency and evapotranspiration of winter wheat and its response to irrigation regime in the north China plain. Agric. For. Meteorol. 148, 1848–1859. Steinemann, S., Zeng, Z.H., McKay, A., Heuer, S., Langridge, P., Huang, C.Y., 2015. Dynamic root responses to drought and rewatering in two wheat (Triticum aestivum) genotypes. Plant Soil 391, 139–152. Sun, H.Y., Liu, C.M., Zhang, X.Y., Shen, Y.J., Zhang, Y.Q., 2006. Effects of irrigation on water balance, yield and WUE of winter wheat in the North China Plain. Agric. Water Manage. 85, 211–218. Wang, F.H., Wang, X.Q., Sayre, K., 2004. Comparison of conventional, flood irrigated, flat planting with furrow irrigated, raised bed planting for winter wheat in China. Field Crops Res. 87, 35–42. Wang, X.B., Cai, D.X., Hoogmoed, W.B., Oenema, O., Perdok, U.D., 2007. Developments in conservation tillage in rainfed regions of North China. Soil Tillage Res. 93, 239–250. Wang, E.L., Yu, Q., Wu, D.R., Xia, J., 2008. Climate, agricultural production and hydrological balance in the North China Plain. Int. J. Climatol. 28, 1959–1970. Wang, D., Yu, Z.W., Philip, J.W., 2013. The effect of supplemental irrigation after jointing on leaf senescence and grain filling in wheat. Field Crops Res. 151, 35–44. Wang, C.Y., Liu, W.X., Li, Q.X., Ma, D.Y., Lu, H.F., Feng, W., Xie, Y.X., Zhu, Y.J., Guo, T.C., 2014a. Effects of different irrigation and nitrogen regimes on root growth and its correlation with above-ground plant parts in high-yielding wheat under field conditions. Field Crops Res. 165, 138–149. Wang, W.H., Chen, J., Liu, T.W., Chen, J., Han, A.D., Simon, M., Dong, X.J., He, J.X., Zheng, H.L., 2014b. Regulation of the calcium-sensing receptor in both stomatal movement and photosynthetic electron transport is crucial for water use efficiency and drought tolerance in Arabidopsis. J. Exp. Bot. 65, 223–234. Wang, Y.Z., Zhang, X.Y., Zhang, X.Y., Shao, L.W., Chen, S.Y., Liu, X.W., 2016. Soil water regime affecting correlation of carbon isotope discrimination with yield and wateruse efficiency of winter wheat. Crop Sci. 56, 760–772.
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