Increasing Irrigation Amount Research Articles

Deep vertical rotary tillage reduced soil salinity and improved seed cotton yield and water productivity under limited irrigation in saline-alkaline fields

Water scarcity and soil salinization severely limit cotton production in arid areas on the globe. A two-season (2020 and 2021) field experiment was performed on cotton under film-mulched drip irrigation in south Xinjiang of China to explore the responses of soil moisture, soil salinity, root growth, seed cotton yield and water productivity to deep vertical rotary tillage (DVRT) depth (T20: 20 cm, T40: 40 cm, T60: 60 cm, Tck: 20 cm, traditional rotary tillage) in saline-alkaline fields under two irrigation amounts (W1:360 mm, W2: 480 mm, local irrigation amount). It was found that the soil moisture storage (0–120 cm) increased with as irrigation amount increased and decreased with increasing DVRT depth. Soil electrical conductivity in the root zone (0–60 cm) and 0–120 cm soil layer declined as irrigation amount and DVRT depth increased. Irrigation amount and DVRT depth had significant effects on root length density, root mass density, root/shoot ratio, and seed cotton yield, all of which increased with increasing irrigation amount and DVRT depth. Under W2, T20, T40 and T60 increased seed cotton yield by 23.3 %, 45.3 %, 65.6 % in 2020, and by 38.9 %, 62.0 % and 84.1 % in 2021 compared with TCK, respectively. Both water productivity and irrigation water productivity increased with increasing DVRT depth. There were significant positive correlations among seed cotton yield and leaf area index, dry matter accumulation, harvest index, root length density, root mass density, root/shoot ratio, water productivity and irrigation water productivity. W1T60 was suggested for cotton production in the saline regions of southern Xinjiang. The DVRT offset the decrease in seed cotton yield under limited irrigation, which indicates that DVRT is promising to reduce soil salinity and improve seed cotton yield and water productivity in saline-alkaline fields for coping with water scarcity and soil salinization.

Dynamics of soil water and nitrate within the vadose zone simulated by the WHCNS model calibrated based on deep learning

Excessive application of water and nitrogen fertilizer during farmland management practices leads to serious groundwater nitrate pollution. A field experiment was conducted during the spring maize growth period in Alxa, Inner Mongolia, China. The soil Water Heat Carbon Nitrogen Simulator (WHCNS) model was calibrated by the ensemble smoother method (ES(DL)) based on the field experiment. Then dynamics of soil water content, soil water percolation flux, soil nitrate concentration and soil nitrate leaching flux were simulated with the calibrated WHCNS model under different water and nitrogen fertilization treatments within the vadose zone. The main conclusions are as follows: ES(DL) is feasible for the calibration of the WHCNS model. RMSE_Maximum a posteriori (RMSE_MAP) of soil water content are 0.0301 cm3 cm−3 and 0.0302 cm3 cm−3 for model calibration and model validation, respectively. RMSE_MAP of soil nitrate concentration are 5.49 mg N kg−1 and 3.86 mg N kg−1 for model calibration and model validation, respectively. Both average soil nitrate concentration and average nitrate leaching flux increase with increasing irrigation amount under the same nitrogen fertilization level for the depths of 1.2 m and 1.8 m. However, average soil nitrate concentration decreased and leaching flux increased with increasing irrigation amount under the same nitrogen fertilization level for the depths of 10 m and 20 m. The study of nitrate dynamics in the deep vadose zone contributes to better understand the procedure of nitrate pollution in groundwater caused by excessive water and nitrogen application.

Appropriate water and fertilizer supply can increase yield by promoting growth while ensuring the soil ecological environment in melon production

Water and fertilizer management in sustainable agricultural development needs to balance crop yield, quality, and soil ecological environment. Therefore, we conducted trials with nine treatments over two growing seasons in 2020 and 2021. The treatments included the three irrigation levels W1 (75% Ep), W2 (100% Ep), and W3 (125% Ep) and the three fertilization levels F1 (758.44 kg/hm2), F2 (948.05 kg/hm2), and F3 (1137.66 kg/hm2) with a N/P/K ratio of 2:1:3. The net photosynthetic rate (Pn) gradually decreased with the plant growing period, and was significantly (*) affected by fertilization at the flowering and fruiting stages. The chlorophyll content increased by 43.75% from the vine to flowering and fruiting stages and decreased by 12.50% in the mature stage, reaching a maximum following W1 application. W2F2 was the most effective in promoting total dry mass (TDM) during the vine and mature stages. Irrigation, fertilization and the interaction exerted a highly significant effect on the fruit quality and yield. Soluble solids performed best under W1F1, while free amino acid reached a maximum under W3F2. Moreover, water use efficiency increased with the fertilization amount, and was maximized in W1F3. At the same fertilizer level, soil nitrate N and available P content exhibited an increasing then decreasing trend with the increasing irrigation amount, while soil available K content increased with irrigation at all growth stages. Structural equation models of yield and quality formation were then established based on the co-occurrence analysis. Pn indirectly regulated the melon growth by TDM (0.87) (***), while growth was identified as the most important direct factor affecting the yield and quality of melon. Furthermore, soil residues indirectly affected yield and quality composition through efficiency. This study indicates that the sustainable practices for water and fertilizer management are essential to improve melon yield and quality in arid and semi-arid regions, and contribute to reducing the risk of soil contamination from agricultural production.

Appropriate Water-Nitrogen Regulation Mode to Improve Productivity of Mixed-Sowing Grassland of Bromus inermis and Alfalfa

Scientific selection of appropriate herbage planting management mode is an important guarantee to promote artificial grassland development and grassland productivity. In this study, three-year-old alfalfa (Medicago sativa L.) and bromus inermis were applied to analyze the effects of planting patterns (bromus inermis and alfalfa mixed-sowing D1, bromus inermis mono-sowing D2), nitrogen application (pure nitrogen) level (N1: 60 kg·ha−1, N2: 120 kg·ha−1), and water regulation (upper and lower limits of irrigation are calculated as a percentage of field capacity θf, W1: slight water deficit 65~85% θf, W2: moderate water deficit 55~85% θf, W3: serious water deficit 45~85% θf) on herbage growth and water-nitrogen use efficiency. This research applied the principal component analysis, the TOPSIS model, and the combination evaluation to evaluate each treatment. Results demonstrated that (1) the plant height, leaf area index, and yield of mixed-sowing herbage were 81.63%, 119.52%, and 111.51%, higher than the mono-sowing herbage. Increasing the amount of irrigation and nitrogen application could enhance herbage yield. The herbage yield with the W1N2 treatment was the highest. In this treatment, the mixed-sowing herbage yield was 26,050.73 kg·ha−1, and the mono-sowing herbage yield was 12,186.10 kg·ha−1. (2) The crude protein content of mixed-sowing herbage increased by 41.44%, higher than mono-sowing herbage, and the relative feeding value decreased by 16.34%. Increasing irrigation and nitrogen application could improve the quality of herbage. Meanwhile, the quality of herbage treated with W1N2 was the best. (3) The water use efficiency (WUE), irrigation water use efficiency (IWUE), partial factor productivity of nitrogen (PFPN), and crude protein water use efficiency (CPWUE) of mixed-sowing herbage were significantly higher than mono-sowing herbage. The PFPN and the CPWUE of herbage improved with increasing irrigation amount. Meanwhile, the WUE, the IWUE, and the CPWUE of herbage also improved with increasing nitrogen application amount. The results showed that mixed-sowing of alfalfa and bromus inermis with slight water deficit (upper and lower limit of irrigation was 65~85% θf) and nitrogen application (120 kg·ha−1) could have the best comprehensive production effect. At the same time, it was a planting and management mode of high yield, high quality, and high efficiency of artificial herbage in the oasis-desert interlacing area of Hexi, Gansu Province, China, and areas with similar climates.

Effect of Irrigation Water Amount and Planting Pattern on Water Use and Yield of Cotton in Northern Xinjiang, China

This study aimed to clarify the effect of irrigation water amount and planting pattern on water use and yield of cotton in Northern Xinjiang. A field experiment was conducted during 2020–2021 comprising four irrigation water amounts (360, 450, 540, and 630 mm) and two planting patterns (same row spacing, R1; and wide-narrow row planting, R2). The results showed that the evapotranspiration (ET), soil evaporation (Es), and plant transpiration (T) of cotton under both planting patterns increased with the increasing irrigation amount. During the entire growth period, the annual average daily ET and T under R2 were higher than those under R1, but the annual average daily Es under R2 were lower than those under R1. The daily Es was highest between one and four days after irrigation. The Es/ET under R1 was approximately 27.45%–31.82%, and that under R2 was approximately 24.52%–28.56% under the four irrigation treatments. The relationship between the Es/ET and leaf area index was fitted based on an exponential equation (R2>0.85). The yield increased with an increase in the irrigation amount, although there was no significant difference between the yields obtained with 540 mm and 630 mm irrigation amounts. The water use efficiency (WUE) increased first and then decreased with an increase in irrigation water amount, with the highest WUE observed under the 540 mm condition and the lowest under the 630 mm condition.

Quantifying source-sink relationships of drip-fertigated potato under various water and potassium supplies

Water and fertilizer supply can affect the processes of assimilate production (source) and assimilate accumulation (sink), thereby causing differences in potato yield. However, little is known about the coupling effects of irrigation amount and potassium rate on potato tuber yield and its potential source-sink relationships. The objective of this study was to quantify how water and potassium supplies affected the source-sink relationships of drip-fertigated potato after tuber emergence. A two-year field experiment was conducted during the potato growing seasons of 2019 and 2020, with three irrigation levels (W1: 60% ET c , W2: 80% ET c and W3: 100% ET c , where ET c is the crop water requirements) and four potassium rates (K0: 0 kg ha -1 , K1: 135 kg ha -1 , K2: 270 kg ha -1 and K3: 405 kg ha -1 ). The results showed that compared with K0, the treatments viz ., K1, K2 and K3 increased average tuber yield by 1.3%, 17.3% and 15.5% in 2019 and 10.7%, 24.0% and 19.3% in 2020, respectively. However, compared with W3, the treatments viz ., W1 and W2 reduced the average tuber yield by 8.0% and 12.9% in 2019 and 8.9% and 14.7% in 2020, respectively. The beta sigmoid growth function well fitted the relationship of source capacity and sink capacity. The source capacity and source activity increased with the increase of potassium rate under W2 and W3 in 2019 and under W3 in 2020, while the sink capacity and sink activity first increased and then declined with the increasing potassium rate. Increasing water and potassium supply generally increased the vegetative growth and tuber growth time. The tuber growth rate first increased and then decreased with the increase of potassium rate, while it increased with the increasing irrigation amount. The sink-source ratio decreased with the increase of potassium rate, but there was no significant difference between K1 and K2, and the sink-source ratio under K3 was significantly lower than that in the other potassium treatments. It was concluded that potato was in source-sink balance under K1 and K2, but not under K3. The quantitative approach produced parameters that characterized the differences of source and sink capacity in response to various water and potassium supplies. Sufficient irrigation (W3) with moderate potassium application (K2) increased potato yield mainly by maintaining its source-sink balance. • A model approach was proposed to quantify source-sink relationships of potato under various water and potassium supplies. • The mechanism analysis of yield difference from various water and potassium supplies was conducted by source-sink balance. • Source-sink capacity was affected by different water and potassium management practices. • The sink-source ratio was not significantly different between 135 and 270 kg ha -1 , indicating the source-sink balance. • Various water and potassium application amounts influenced plant potassium absorption and tuber yield.

Assessing the Applicability of Biodegradable Film Mulching in Northwest China Based on Comprehensive Benefits Study

Biodegradable film is a promising alternative to polyethylene film in arid regions, but its use is usually inhibited by its high cost and elusive effects on soil and crop yield. A two-year field experiment was carried out to explore the impact of biodegradable film on soil hydrothermal dynamics, yield, water productivity and economic benefits under three irrigation strategies (full, medium and low irrigation amount) compared with non-mulching and polyethylene film. The comprehensive benefits (economic, technical and ecological) of different film mulching patterns were evaluated using analytic hierarchy process and gray relational analysis methods. The results indicated that increasing irrigation amount could accelerate the degradation of the biodegradable film, with the highest film weight loss rate of 38.8% obtained under full irrigation. Film mulching could mitigate the negative impact of water deficit on crop yield, with the yield of biodegradable film and polyethylene film enhanced by 11.6% and 18.6% compared with non-mulching under low irrigation. Although polyethylene film showed the highest economic benefits, non-mulching showed the highest comprehensive benefits. Only when the price of biodegradable film material dropped to less than 1.37 times that of polyethylene film did the economic benefit of biodegradable film outcompete non-mulching and become a more acceptable and promising farming solution to boosting environmental sustainability.

Exploration of Water-Saving and High-Yield Irrigation Model for Tomato under Microsprinkler Irrigation with Plastic Film in a Greenhouse Based on Spatial Analysis

The purpose of this study was to analyse the suitability of the frequency and amount of microsprinkler irrigation under plastic film technology (MSPF) in a greenhouse. This study was aimed at determining the effects of different irrigation frequency and irrigation amount of the MSPF on the quality, yield (Y), and water use efficiency (WUE) of tomato, and the optimal irrigation period and irrigation amount of tomato with MSPF were determined by spatial analysis method. Irrigation frequency was set 3 levels, 3 d (F1), 5 d (F3), and 7 d (F3), respectively. Irrigation amount was set 3 levels, 0.7 E pan (I1), 1.0 E pan (I2), and 1.2 E pan (I3) ( E pan is the diameter of 20 cm standard pan evaporation, mm), respectively. The results show that increase in the single fruit weight (SFW), transverse diameter (TD), vertical diameter (VD), total soluble solids (TSS), total soluble sugar (TSU), soluble solid content (SSC), sugar-acid ratio (SAR), soluble protein (SP), vitamin C (VC), lycopene (L), Y, and WUE of spring and autumn tomatoes was observed initially with decreasing irrigation frequency; however, decrease in all these variables was observed thereafter. Similarly, SFW, TD, VD, and SAR of spring and autumn tomatoes first added and then reduced with increasing irrigation amount, whereas TSS, SP, TSU, VC, L, and WUE exhibited an overall decreasing trend. On the basis of spatial analysis, the comprehensive score, Y, and WUE of F2I2 tomato were predicted to simultaneously reach more than 95% of the maximum, which is consistent with the earlier studies on comprehensive evaluation of yield and WUE.

Reduced groundwater use and increased grain production by optimized irrigation scheduling in winter wheat–summer maize double cropping system—A 16-year field study in North China Plain

Optimizing irrigation strategies to increase water utilization efficiency and achieve higher yield is vital for balancing groundwater use and improving food security during water shortage in the North China Plain (NCP). Based on a 16-year field experiment (2003–2018) using seven irrigation schedules from W0M0 to W4M3 (numbers are irrigation times in wheat (W) and maize (M) season, 75 mm each) in the winter wheat–summer maize double cropping system, we analyzed annual total water consumption ( ET a ) and groundwater table change in terms of net groundwater depletion, annual total grain yield, water productivity (WP), irrigation water productivity (IWP) and marginal benefit of the whole wheat–maize system. Relationship between yield or WP and irrigation or ET a were also revealed. Results showed that (1) total ET a increased as irrigation input increased, ranging from 427.3 mm (Rainfed, W0M0) to 891.0 mm (W4M3). Soil water storage contributed nearly 30% to ET a for winter wheat under water deficit conditions. Pre-sowing soil water storage played an important role in improving the annual yield and WP of both wheat and maize by promoting germination, seedling emergence and root growth; (2) the rainfed treatment (W0M0) was best for mitigating the groundwater table decline (0.1 m yr -1 ), followed by W1M1 (0.5 m yr -1 ) and W2M1 (0.8 m yr -1 ). Groundwater table decline in M2W2 almost overlapped the observed data at the station (1.1 m yr -1 ). In W3M2, the farmers’ traditional practice, the groundwater table declined by 1.4 m yr -1 , obviously over exploitation, while W4M2 and W4M3 declined by almost 2.0 m yr -1 ; (3) the relationship between total annual yield and irrigation (or ET a ) followed a quadratic curve. Total annual yield significantly increased from W0M0 to M1W1 (25%) to M2M1 (5%) and then kept stable. Average annual WP decreased as irrigation increased, from 2.4 kg m -3 (W0M0) to 1.6 kg m -3 (W4M3). Average annual IWP and marginal benefit also declined as irrigation increased. These results over 16 years indicated that the W2M1 is the most balanced irrigation regime for wheat– maize rotation to mitigate groundwater decline, maintain grain production, and improve water use efficiency in the NCP. ● A 16 - year field experiment of seven irrigation regimes for wheat-maize was conducted. ● ET a increased and water productivity decreased with increasing irrigation amount. ● W2M1 was the best optimized irrigation regime for balancing groundwater use and yield.

Evaluation of cotton N nutrition status based on critical N dilution curve, N uptake and residual under different drip fertigation regimes in Southern Xinjiang of China

Irrigation and fertilization are the two most important measures to ensure the agricultural development in arid regions. However, there is still a lack of reasonable irrigation and fertilization strategy in Xinjiang, the largest cotton producing area in China, which causes a waste of resources and a reduction in cotton yield and pollutes the environment. This study investigated the effects of four irrigation amounts (W0.6: 60% ETc, W0.8: 80% ETc, W1.0: 100% ETc and W1.2: 120% ETc, where ETc is the crop evapotranspiration) and four nitrogen rates (N250-250 kg N ha-1, N300-300 kg N ha-1, N350-350 kg N ha-1 and N400-400 kg N ha-1) on seed cotton yield, nitrogen nutrition status and soil nitrogen residue, so as to explore the optimal water-nitrogen coupling strategy to increase cotton production and water-fertilizer use efficiency while reducing environmental pollution. The nitrogen dilution curves were built to assess the nitrogen nutrition status of cotton. The results showed that increasing irrigation amount increased dry matter and seed cotton yield, but decreased harvest index. Nitrogen application enhanced the nitrogen concentration and accumulation in cotton. Irrigation decreased the nitrogen concentration, but increased the nitrogen accumulation by increasing the dry matter. The highest total plant nitrogen accumulation was obtained under W1.2N400, 223.88 kg ha-1 in 2018 and 242.77 kg ha-1 in 2019. With the increase of irrigation amount, agronomic nitrogen utilization efficiency (aNUE) first increased and then decreased. Increasing irrigation amount increased nitrogen recovery efficiency (NRE), but reduced physiological nitrogen utilization efficiency (pNUE). pNUE and aNUE decreased with the increasing nitrogen rate, while NRE first increased and then decreased. Soil NO3−-N content increased with the increase of nitrogen rate. Irrigation reduced NO3−-N content in the surface soil (0–30 cm), while increased that in the deeper soil (40–80 cm). The optimal nitrogen nutrition status was found under W1.0N300, followed by W1.0N350. Furthermore, the optimal dry matter, seed cotton yield, NRE and total nitrogen accumulation were obtained under W1.0N350, which was considered as the optimal combination of irrigation amount and nitrogen rate in this study.

Optimal irrigation amount and nitrogen rate improved seed cotton yield while maintaining fiber quality of drip-fertigated cotton in northwest China

Improving the quality of cotton fiber is an important way to increase the competitiveness of cotton in the international market. However, how to improve fiber quality as much as possible without significantly reducing seed cotton yield is still a challenge to the cotton industry. A two-year field experiment was conducted in 2018 and 2019 to investigate the effects of irrigation amount and nitrogen rate on seed cotton yield and fiber quality traits of drip-fertigated cotton in northwest China. A comprehensive evaluation model was also developed to determine the optimal supply range of water and nitrogen to simultaneously improve seed cotton yield and fiber quality. There were four irrigation amounts (W0.6-60 % ETc, W0.8-80 % ETc, W1.0-100 % ETc and W1.2-120 % ETc, ETc was the crop evapotranspiration) and four nitrogen rates (N250-250 kg N ha−1, N300-300 kg N ha−1, N350-350 kg N ha−1 and N400-400 kg N ha−1). Increasing irrigation amount and nitrogen rate had positive effects on seed cotton yield. However, there was no significant difference in seed cotton yield between W1.0 and W1.2 and between N350 and N400. The optimal seed cotton yield was obtained under W1.0N350 in both 2018 (6655.58 kg ha−1) and 2019 (6309.3 kg ha−1). Water use efficiency (WUE) increased with the increase of nitrogen rate, and decreased with the increasing irrigation amount. Nitrogen partial factor productivity (PFPN) increased with the increase of irrigation amount, and decreased with the increasing nitrogen rate. There was a positive correlation between irrigation amount and fiber length, fiber strength, fiber quality index (FQI) and textile parameter, but a negative correlation with micronaire and short-fiber index. Fiber length, fiber strength, FQI and textile parameter first increased and then decreased with the increasing nitrogen rate. Irrigation amount and nitrogen rate had no significant effect on maturity index. There were strong correlations between the results of various evaluation methods, but the ranking differed among the methods. Based on the comprehensive evaluation model, the optimal combination of irrigation amount and nitrogen rate was W1.0N350. Through the combination of multiple regression and spatial analysis, the optimal supply range of irrigation amount of 334∼450 mm and nitrogen rate of 320∼400 kg ha−1was able to obtain over 90 % of the optimal seed cotton yield and 80 % of the optimal fiber quality.

Improving winter wheat grain yield and water-/nitrogen-use efficiency by optimizing the micro-sprinkling irrigation amount and nitrogen application rate

Available irrigation resources are becoming increasingly scarce in the North China Plain (NCP), and nitrogen-use efficiency of crop production is also relatively low. Thus, it is imperative to improve the water-use efficiency (WUE) and nitrogen fertilizer productivity on the NCP. Here, we conducted a two-year field experiment to explore the effects of different irrigation amounts (S60, 60 mm; S90, 90 mm; S120, 120 mm; S150, 150 mm) and nitrogen application rates (150, 195 and 240 kg ha–1; denoted as N1, N2 and N3, respectively) under micro-sprinkling with water and nitrogen combined on the grain yield (GY), yield components, leaf area index (LAI), flag leaf chlorophyll content, dry matter accumulation (DM), WUE, and nitrogen partial factor productivity (NPFP). The results indicated that the GY and NPFP increased significantly with increasing irrigation amount, but there was no significant difference between S120 and S150; WUE significantly increased first but then decreased with increasing irrigation and S120 achieved the highest WUE. The increase in nitrogen was beneficial to improving the GY and WUE in S60 and S90, while the excessive nitrogen application (N3) significantly reduced the GY and WUE in S120 and S150 compared with those in the N2 treatment. The NPFP significantly decreased with increasing nitrogen rate under the same irrigation treatments. The synchronous increase in spike number (SN) and 1 000-grain weight (TWG) was the main reason for the large increase in GY by micro-sprinkling with increasing irrigation, and the differences in SN and TGW between S120 and S150 were small. Under S60 and S90, the TGW increased with increasing nitrogen application, which enhanced the GY, while N2 achieved the highest TWG in S120 and S150. At the filling stage, the LAI increased with increasing irrigation, and greater amounts of irrigation significantly increased the chlorophyll content in the flag leaf, which was instrumental in increasing DM after anthesis and increasing the TGW. Micro-sprinkling with increased amounts of irrigation or excessive nitrogen application decreased the WUE mainly due to the increase in total water consumption (ET) and the small increase or decrease in GY. Moreover, the increase in irrigation increased the total nitrogen accumulation or contents (TNC) of plants at maturity and reduced the residual nitrate-nitrogen in the soil (SNC), which was conducive to the increase in NPFP, but there was no significant difference in TNC between S120 and S150. Under the same irrigation treatments, an increase in nitrogen application significantly increased the residual SNC and decreased the NPFP. Overall, micro-sprinkling with 120 mm of irrigation and a total nitrogen application of 195 kg ha–1 can lead to increases in GY, WUE and NPFP on the NCP.

Effects of water quality, irrigation amount and nitrogen applied on soil salinity and cotton production under mulched drip irrigation in arid Northwest China

Understanding the interaction effects of water, fertilizer, and salinity is of great environmental importance to mitigate soil salinization and improve crop production. Field experiments were conducted to evaluate the effects of water quality, irrigation amount, and nitrogen application rate on soil salt accumulation, root water and nitrogen uptake, lint yield, and water productivity during 2018 and 2019 growing seasons of cotton (Gossypium hirsutum L.) in arid region of Xinjiang, China. Four irrigation levels 75%, 100%, 125%, and 150% of crop water requirement (ETc) and four nitrogen levels 195, 255, 315, and 375 kg ha−1 were applied with groundwater and brackish water irrigation. Results demonstrated that, brackish water irrigation significantly increased the root-zone soil salt accumulation (SSA). Either increasing irrigation amount during the squaring stage or decreasing irrigation amount during the flower boll stage with higher nitrogen application rate can reduce the SSA. And with an increase in brackish water irrigation amount, a corresponding increase in nitrogen application rate is required to reduce the possible soil salt accumulation during the flower boll stage. Highest irrigation amount (150% ETc) and nitrogen application rate (375 kg ha−1) at the flower boll stage and during the whole growing season resulted in significant higher nitrogen uptake increment with an increasing rate of 25–74% and 39–65%, respectively. The integration of higher irrigation amount and highest nitrogen application rate with groundwater irrigation produced higher lint yield and water productivity. Considering soil salinity and lint yield as well as water productivity, the appropriate integration modes of water and nitrogen are higher irrigation amount and highest nitrogen application rate (125% ETc and 375 kg ha−1) for groundwater and lowest irrigation amount and lower nitrogen application rate (75% ETc and 255 kg ha−1) for brackish water.

Responses of growth, fruit yield, quality and water productivity of greenhouse tomato to deficit drip irrigation

Agriculture is the largest consumer of scarce water resources and irrigation serves as the sole source of water for greenhouse tomato production. It is an urgent task to seek an appropriate deficit irrigation strategy that is beneficial for high marketable yield, fruit quality, saving irrigation water and ultimately improving water use efficiency. A four-season experiment was conducted on drip-irrigated greenhouse tomato during Autumn 2015-Spring 2017 with three irrigation regimes, i.e., 100 %ETc (crop evapotranspiration) (W1), 75 %ETc (W2) and 50 %ETc (W3). The results showed that aboveground biomass, leaf area index (LAI), plant height and fruit yield increased with increasing irrigation amount. However, soluble solids, vitamin C and soluble sugar of tomato fruits were lowest under W1. W2 markedly reduced unmarketable fruits and more small-sized fruits were harvested at the late stage under W1. Through fitting the relationship between cumulative temperature and aboveground biomass using logistic equations, it was found that average duration of the rapid growth period (td) and the time when growth rate reached the maximum value (tm) increased as irrigation amount decreased. Conversely, the maximum growth rate during the rapid growth period (vm) decreased with the increase of water deficit. The highest total water consumption (278.05 mm), lowest total yield water use efficiency (25.12 kg m−3) and marketable yield water use efficiency (22.87 kg m−3) were obtained under W1. The smallest total water consumption (27.01–50.75 mm) occurred at the blooming and setting stage. Based on the results of path analysis, aboveground biomass and average fruit weight were important indexes affecting yield positively. It is concluded that deficit drip irrigation with 75 %ETc has the potential of supporting tomato growth, improving marketable yield and WUE as a result of less unmarketable yield and bigger fruit size.

Double-Double Row Planting Mode at Deficit Irrigation Regime Increases Winter Wheat Yield and Water Use Efficiency in North China Plain

Low water availability coupled with poor planting method has posed a great challenge to winter wheat (Triticum aestivum L.) productivity. To improve productivity and water use efficiency (WUE) under deficit irrigation, an effective water-saving technology that is characterized by three planting modes has been developed (uniform with 30-cm row spacing (U), double-double row spacing of 5 cm (DD), and furrow-ridge row spacing of alternated 20 cm and 40 cm (F)) combined with three irrigation regimes (50 mm water each at growth stage 34 (GS34) and GS48 (W1), and 100 mm water at GS48 (W2), or 100 mm each water at GS34 and GS48 (W3)). Results showed that DD increased yield by 9.7% and WUE by 12.6% due to higher soil water status and less soil water depletion and evapotranspiration compared with U. Although the soil water status, soil water depletion, evapotranspiration, and yield increased with increasing irrigation amount, more soil water depletion and evapotranspiration resulted in low WUE. The deficit irrigation was beneficial for improving WUE as W1 had significantly increased yield by 5.4% and WUE by 7.1% compared with W2. Yield and evapotranspiration showed a quadratic dynamic equation indicating that yield increased with increasing evapotranspiration. Considering WUE and relatively higher yield under deficit water, W1 combined with DD is suggested to be a good management strategy to be applied in winter wheat of water-scarce regions.

Determining irrigation amount and fertilization rate to simultaneously optimize grain yield, grain nitrogen accumulation and economic benefit of drip-fertigated spring maize in northwest China

Inappropriate water and fertilizer management can lead to unstable crop yield, and excessive irrigation and fertilization can potentially cause soil degradation and groundwater pollution. A two-year field experiment was conducted on drip-fertigated spring maize (Zea mays L.) in Ningxia of northwest China to explore the effects of four irrigation amounts (I75: 0.75ETc, I90: 0.90ETc, I105: 1.05ETc and I120: 1.20ETc, where ETc is the crop evapotranspiration) and four N-P2O5-K2O fertilization rates (F60-30-30, F120-60-60, F180-90-90 and F240-120-120 in 2016; F150-70-70, F225-110-110, F300-150-150 and F375-180-180 in 2017) on maize growth, grain yield, grain nitrogen accumulation, economic benefit and soil nitrate residue (NO3-N). Considering the goal of conserving both water and fertilizer while maintaining relatively high yields and minimizing soil NO3-N, a management strategy to optimize irrigation and fertilization regimes was developed based on the response surface methodology. The results showed that irrigation amount and fertilization rate significantly affected leaf area index, aboveground biomass, grain yield and harvest index. The irrigation-fertilization interaction significantly affected plant and grain nitrogen accumulation. In 2016 with lower fertilization range, grain yield and grain nitrogen accumulation were highest under I120F240-120-120, reaching 14,440 kg ha-1 and 184.50 kg ha-1, respectively. In 2017 with higher fertilization range, both grain yield and grain nitrogen accumulation initially increased and then decreased with increasing irrigation and fertilization regimes. Grain yield and grain nitrogen accumulation were highest under I90F300-150-150, reaching 16,884 kg ha-1 and 195.09 kg ha-1, respectively. Although plant nitrogen uptake was dramatically higher under I90F375-180-180 than those in the other treatments, grain yield was markedly lower under I90F300-150-150 and nitrogen harvest index was also lower. Soil NO3−-N increased with increasing fertilization rate, but it decreased with increasing irrigation amount. When irrigation amount and fertilization rate increased at the same time, the soil NO3−-N accumulation area moved deeper in the soil profile. Soil NO3--N content and distribution in the 60−100 cm soil layer showed an increasing trend, but this trend was less obvious than that in the 0−60 cm soil layer. When the irrigation amount was 447−452 mm and the N-P2O5-K2O fertilization rate ranged from 290−145-145 to-303−152-152 kg ha-1, grain yield, grain nitrogen accumulation and economic benefit (≥13,688 CNY ha-1) can reach 95 % confidence interval of their maximum values simultaneously. This study can provide a theoretical basis for high-efficient water and fertilizer utilization in sustainable spring maize (Zea mays L.) production in northwest China.

Optimizing irrigation frequency and amount to balance yield, fruit quality and water use efficiency of greenhouse tomato

Vegetable production in many countries relies on irrigation. While increasing irrigation amount normally improves yield, too much water could jeopardize fruit quality and comprise profit. Optimizing irrigation frequency and amount is thus essential to ensuring yield increase without compromising fruit quality. This paper presents a three-year (2011–2013) experimental study on responsive changes in yield, fruit quality and water use efficiency (WUE) of tomato grown in greenhouse to different irrigation frequency and amount under drip irrigation. The irrigation scheduling was based on accumulative evaporation (AE) measured from a standard 20 cm pan. Three irrigation frequencies were considered in which irrigation was resumed when AE was 10 mm (I1), 20 mm (I2) and 30 mm (I3) respectively. Each frequency was associated with four irrigation amounts, which were 50% (Kcp1), 70% (Kcp2), 90% (Kcp3) and 110% (Kcp4) of AE respectively. Water consumption, yield characteristics and fruit quality of the plants in each treatment were measured. The three-year results show that for each irrigation amount, increasing irrigation frequency led to an increase in yield and WUE. Visual fruit-quality traits, including average weight, longitudinal and transverse diameter, increased with irrigation amount but not with irrigation frequency. It was found that a reduction in irrigation amount increased all other fruit quality characteristics except the sugar-organic acid ratio in 2013. Both yield and WUE increased asymptotically with irrigation amount before approaching their plateau when the irrigation amount reached 90% and 70% of AE respectively. While the yield was positively related to fruit size and negatively to soluble solid content, it was independent of WUE. The results from technique for order preference by similarity to ideal solution analysis revealed that among all treatments, I1+Kcp2 was the optimal in terms of best balancing yield, fruit quality and water use efficiency. Principal component analysis found that the comprehensive fruit quality score was closely related to the total soluble solids content.

Effects of irrigation amounts on soil CO2, N2O and CH4 emissions in greenhouse tomato field.

To understand the effects of different irrigation amounts on soil CO2, N2O, and CH4 emission characteristics and tomato yield, and further put forward effective reduction measures, we carried out an experiment with three irrigation levels: full irrigation (1.0W, W1.0; W meant irrigation amount needed to provide the adequate water), 20% deficit irrigation (0.8W, W0.8) and 40% deficit irrigation (0.6W, W0.6). We used static closed chamber and gas chromatography method to measure greenhouse gas emission in two consecutive greenhouse tomato rotation cycles from April to December, 2017. The results showed that cumulative soil CO2, N2O and CH4 emissions increased with increasing irrigation amounts in the two growing seasons (W1.0＞W0.8＞W0.6), and significant difference of N2O between W0.6 and W1.0 was observed, while other treatment effects on soil gas emissions were not obvious. Compared to W1.0, cumulative soil CO2 emissions were decreased by 12.2% and 8.3%, cumulative soil N2O emissions were decreased by 19.1% and 8.0%, and cumulative soil CH4 emissions were reduced by 11.0% and 6.2% for W0.6 and W0.8, respectively. Tomato yield and global warming potential of soil N2O and CH4 emissions (GWP) increased as irrigation amount increasing. Compared with W1.0, W0.6 significantly decreased tomato yield by 17.0% and GWP by 22.9%, while the difference between the effects of W0.8 and W1.0 on these two parameters was not significant. Global warming potential per tomato yield presented an increase then a decrease as irrigation amount increasing (W0.8＞W1.0＞W0.6), but without stanificance. Irrigation water use efficiency (IWUE) showed a decrease with increasing irrigation amount. Compared with W1.0, IWUE under W0.6 and W0.8 was increased by 38.3% and 9.4%, respectively. Soil CO2 flux was nega-tively and exponentially correlated with soil moisture. The dependence of soil CH4 flux on soil moisture showed a significantly positive correlation. An exponential negative correlation was observed between the soil N2O ux and soil temperature when soil temperature was below or above 18 ℃. Irrigation increased tomato yield and soil greenhouse gas emissions, but decreased IWUE. Therefore, W0.8 was the best mode of irrigation management when synthetically considering tomato yield, IWUE, and greenhouse effect.

Interactive Effects of Water and Fertilizer on Yield, Soil Water and Nitrate Dynamics of Young Apple Tree in Semiarid Region of Northwest China

Exploring the interactive effect of water and fertilizer on yield, soil water and nitrate dynamics of young apple tree is of great importance to improve the management of irrigation and fertilization in the apple-growing region of semiarid northwest China. A two-year pot experiment was conducted in a mobile rainproof shelter of the water-saving irrigation experimental station in Northwest A&F University, and the investigation evaluated the response of soil water and fertilizer migration, crop water productivity (CWP), irrigation water use efficiency (IWUE), partial factor productivity (PFP) of young apple tree to different water and fertilizer regimes (four levels of soil water: 75%–85%, 65%–75%, 55%–65% and 45%–55% of field capacity, designated W1, W2, W3 and W4, respectively; three levels of N-P2O5-K2O fertilizer, 30-30-10, 20-20-10 and 10-10-10 g plant−1, designated F1, F2 and F3, respectively). Results showed that F1W1, F2W1 and F3W1 had the highest average soil water content at 0~90 cm compared with the other treatments. When fertilizer level was fixed, the average soil water content was gradually increased with increasing irrigation amount. For W1, W2, W3 and W4, high levels of water content were mainly distributed at 50~80 cm, 40~70 cm, 30~50 cm and 10~30 cm, respectively. There was no significant difference in soil water content at all fertilizer treatments. However, F1 and F2 significantly increased soil nitrate-N content by 146.3%~246.4% and 75.3%~151.5% compared with F3. The highest yield appeared at F1W1 treatment, but there was little difference between F1W1 and F2W2 treatment. F2W2 treatment decreased yield by 7.5%, but increased IWUE by 11.2% compared with F1W1 treatment. Meanwhile, the highest CWP appeared at F2W2 treatment in the two years. Thus, F2W2 treatment (soil moisture was controlled in 65–75% of field capacity, N-P2O5-K2O were controlled at 20-20-10 g·tree−1) reached the best water and fertilizer coupling mode and it was the optimum combinations of water and fertilizer saving.

Spatial distribution and simulation of soil moisture and salinity under mulched drip irrigation combined with tillage in an arid saline irrigation district, northwest China

Hetao Irrigation District, a large irrigation district in arid area, northwest China, is suffering from the decreasing water supply and increasing soil salinization. Mulched drip irrigation is widely used for agricultural production in arid area, and tillage management affects soil environment variously. This study aimed to explore combined effects of tillage and mulching modes on soil water and salt transfer under drip irrigation. The experiment included 4 treatments: ridge tillage with full film mulching (RFM), ridge tillage with partial film mulching (RPM), flat tillage with full film mulching (FFM) and flat tillage with partial film mulching (FPM). The results showed that RFM increased soil moisture in root zone (0–40 cm). Soil salt was pushed to the edge of soil wetting front and, RFM and FFM reduced salt accumulation in 0–70 layer significantly than RPM and FPM, indicating that full film mulching could retard the upward movement of soil salt more effectively. Furthermore, the performance of HYDRUS-2D was calibrated and evaluated by comparing the simulated values with observed values, and further verified model by another year dataset, to simulate the spatial distributions of soil water and salt in the two directions under mulched drip irrigation with different irrigation quantity. The simulation showed that the wetted region was expanded to the middle position of the film and the uniformity of irrigation increased with the increasing irrigation amount. In addition, the increasing of assumed irrigation amount induced soil desalination and make soil salinity spatial movement meet a discipline that the direction parallel to the drip line was lower than that perpendicular to the line at the same distance. In all, RFM could be adopted for optimizing soil water-salt regulation under drip irrigation in Hetao Irrigation District, and the model presented here is an efficient approach for investigating the regulation mechanisms of root-zone water and salt dynamics under mulching and/or tillage.