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The Indo-Gangetic Plains (IGP) in north-west (NW) India are facing a severe decline in ground water due to prevalent rice-based cropping systems. To combat this issue, conservation agriculture (CA) with an alternative crop/s, such as maize, is being promoted. Recently, surface drip fertigation has also been evaluated as a viable option to address low-nutrient use efficiency and water scarcity problems for cereals. While the individual benefits of CA and sub-surface drip (SSD) irrigation on water economy are well-established, information regarding their combined effect in cereal-based systems is lacking. Therefore, we conducted a two-year field experiment in maize, under an ongoing CA-based maize-wheat system, to evaluate the complementarity of CA with SSD irrigation through two technological interventions–– CA+ (residue retained CA + SSD), PCA+ (partial CA without residue + SSD) – at different N rates (0, 120 and 150 kg N ha-1) in comparison to traditional furrow irrigated (FI) CA and conventional tillage (CT) at 120 kg N ha-1. Our results showed that CA+ had the highest grain yield (8.2 t ha-1), followed by PCA+ (8.1 t ha-1). The grain yield under CA+ at 150 kg N ha-1 was 27% and 30% higher than CA and CT, respectively. Even at the same N level (120 kg N ha-1), CA+ outperformed CA and CT by 16% and 18%, respectively. The physiological performance of maize also revealed that CA+ based plots with 120 kg N ha-1 had 12% and 3% higher photosynthesis rate at knee-high and silking, respectively compared to FI-CA and CT. Overall, compared to the FI-CA and CT, SSD-based CA+ and PCA+ saved 54% irrigation water and increased water productivity (WP) by more than twice. Similarly, a greater number of split N application through fertigation in PCA+ and CA+ increased agronomic nitrogen use efficiency (NUE) and recover efficiency by 8–19% and 14–25%, respectively. Net returns from PCA+ and CA+ at 150 kg N ha-1 were significantly higher by US$ 491 and 456, respectively than the FI-CA and CT treatments. Therefore, CA coupled with SSD provided tangible benefits in terms of yield, irrigation water saving, WP, NUE and profitability. Efforts should be directed towards increasing farmers' awareness of the benefits of such promising technology for the cultivating food grains and commercial crops such as maize. Concurrently, government support and strict policies are required to enhance the system adaptability. [Display omitted] • Effect of conservation agriculture (CA) combined with SSD (CA+) was evaluated for maize physiological performance and water economy. • CA+ (CA+SSD) increased the grain yield by 27% and 30% than furrow irrigated CA and conventional tillage (CT), respectively. • The CA+ saved 54% irrigation water and increased the water productivity by more than 2.5 times over CA and CT. • CA+ increased the agronomic nitrogen use efficiency by 14–25% than CT. [ABSTRACT FROM AUTHOR]

Estimation of evapotranspiration (ET) and yield over cropland is essential for water resources management and food security. Particularly the estimation at long-term and regional scales still needs to be investigated. In this study, a remotely sensed and water-carbon coupled model was combined with a process-based crop growth simulation method to simultaneously estimate ET and yield. The developed model was tested for two of the most important crops (wheat and maize) with years of observations. Leaf area index determined by various remote sensing indices and individually calibrated parameters for wheat and maize were considered to improve crop ET and gross primary production (GPP) estimates. The parameters well reflected different physiological properties that C4 maize has a smaller stomatal conductance coefficient and a larger sensitivity in response to initial light than C3 wheat. Comparing with 20 years of measurements, the root mean square error (RMSE) of ET and GPP for winter wheat was 0.57 mm d−1 and 1.65 g C m−2 d−1, and for maize were 0.80 mm d−1 and 2.92 g C m−2 d−1, respectively. Besides, crop growth simulation including biomass accumulation and allocation agreed well with the measurements. Coefficient of determination was mostly larger than 0.66, and RMSE of yield was 554.7 and 1346.6 kg hm−2 for wheat and maize, respectively. Finally, the spatiotemporal crop water productivity (WP) of winter wheat and summer maize in the North China Plain during 2001–2018 were quantified. The increased WP of winter wheat while the larger WP of maize than that of wheat were discovered. The developed model helps to examine regional crop ET and yield and provides critical information on agricultural water management. • Combining a remotely sensed and water-carbon coupled model with a crop growth simulation method. • Three modelling experiments were conducted to improve ET and GPP estimates. • Simultaneously estimated ET, GPP and yield were evaluated by years of observations. • ET and yield of wheat and maize over the NCP from 2001 to 2018 were examined. • Wheat water productivity with a significantly increased trend was generally lower than that of maize. [ABSTRACT FROM AUTHOR]

Soil water deficits limit the photosynthetic productivity of crops, resulting in reduced yields. However, the effects of soil water stress on leaf gas exchange parameters, actual quantum efficiency (Φ PSII), photosynthetic capacity (maximum electron transfer rate ETRmax, maximum photosynthetic rate An max , maximum carboxylation rate Vc max25) and environmental parameters, such as photosynthetic active radiation (PAR), vapour pressure deficit (VPD), remains unclear. Especially, the dynamic responses of crops with different canopy structure types and phenological stages to water stress needs to be further clarified. In this study, we conducted a field experiment using wheat and maize under complete rainfall isolation to study the effects of coupled water stress and environmental factors on leaf gas exchange processes and photosynthetic capacity. Our results showed that the Φ PSII - PAR relationship in the wheat leaves(a C 3 plant) was more sensitive to water stress than was that in the maize leaves (a C 4 plant) and significantly differed with phenological stage. The coupling of water stress with VPD had a more pronounced effect on the gas exchange parameters (net photosynthetic rate (An), stomatal conductance (g sw), transpiration efficiency (TE), intrinsic water use efficiency (WUEi)) than coupling with PAR, especially for wheat, where the coupling effect of soil water content (SWC) with VPD was more pronounced as the degree of water stress increased. The SWC status did not significantly alter the wheat An -PAR relationship, in contrast to that in maize, wherein a strong effect of SWC on the An -PAR relationship was observed. Water stress had a more pronounced limiting effect on ETR max in wheat than in maize. An max showed a weaker relationship with SWC in both wheat and maize, whereas Vc max25 exhibited a stronger relationship with SWC. Additionally, the physiological response process should take into account the differences between phenological periods. Our study can be used as a reference for precise field irrigation. ● The response mechanism of the Φ PSII -PAR relationship to soil water stress was established. ● The mechanism of coupling soil water stress and environmental parameters on leaf gas exchange was clarified. ● Contribution of soil moisture and photosynthetic pigment content to leaf photosynthetic capacity. ● The effect of potential phenological stages on physiological characteristics under soil water stress. [ABSTRACT FROM AUTHOR]

Increasing dryland cropping system intensity in the semi-arid central Great Plains by reducing frequency of fallow can add diversity to cropping systems and decrease erosion potential. However elimination of the periodic fallow phase has been shown to reduce yields of subsequent crops in this region. The objective of this experiment was to determine how productivity of a 4-yr WCMF rotation [wheat (W, Triticum aestivum L.); corn (C, Zea mays L.); proso millet (M, Panicum miliaceum L.); fallow (F)] was affected when the fallow phase was replaced with pea (P, Pisum sativum L.). The effect of this intensification of the WCMF rotation on the available soil water content at planting, the water use, and the yield of each crop, and on total system productivity and net income was quantified by analyzing data over a 20-yr period from a long-term crop rotation experiment at Akron, CO. Large year-to-year variations were found for available soil water at planting, water use, and yield for all four crops. Pea water use resulted in significant reductions in available soil water at planting, water use, and yield for wheat and corn, but had little effect on those quantities in the millet crop. Total production on a seed mass basis was not different between the WCMF and WCMP rotations, but system net income for the WCMP rotation was 32% lower than for WCMF. Intensification of the WCMF rotation by replacing the fallow phase with pea production could be recommended as an alternative production method if pea seed costs and nitrogen fertilizer applied to the subsequent wheat crop can be reduced. [ABSTRACT FROM AUTHOR]

Intercropping is commonly used in the Hetao irrigation district, upper Yellow River basin, where the main crops are wheat, maize and sunflower. For a better use of land, water, radiation energy, and nutrients, spring wheat is traditionally intercropped with maize (W–M) and, more recently, with sunflower (W–S). Considering the need to reduce diversions of water for irrigation in Hetao, this study aims to assess crop water use of W–M and W–S intercropping systems in comparison to the same crops in monocropping. The dual crop coefficient approach was adopted with the SIMDualKc model, which allows partitioning crop evapotranspiration into crop transpiration and soil evaporation. A new model approach was tested to compute a combined basal crop coefficient for the intercropping, K cb inter , which uses the daily values of the K cb of the component crops together with the respective heights and fractions of ground covered by the crops. SIMDualKc was first calibrated and validated for wheat, maize and sunflower as single crops using field data of 2010–2012 and was later used with the new developed approach, which was validated with W–M and W–S field data of 2010–2011. The K cb values calibrated for wheat, maize and sunflower compared well with literature and goodness of fit indicators have shown high accuracy of simulations used for calibration and validation. Results evidenced the importance of groundwater contribution in Hetao, and that soil evaporation is there low under surface irrigation. Moreover, it was found that actual evapotranspiration, crop transpiration, irrigation water use and groundwater contribution of intercropping systems were larger than those of the component sole crops, which led to significantly higher yields of intercropping relative to those of single crops. [ABSTRACT FROM AUTHOR]

Drought is a natural hazard that may decrease agricultural production. To investigate crop growth and yield responses to drought conditions are vital for drought prevention during crop growth periods. This study aims to analyze the impacts of meteorological and agricultural droughts on wheat/maize yields from multiple perspectives and to select the key parameters which describe the best relationship between crop yield and drought indices. Using standardized precipitation evapotranspiration index (SPEI) and soil moisture deficit index (SMDI) at 1- to 9-month timescales, the drought characteristics of different crop growth periods at the selected 98 sites in different subregions were analyzed. DSSAT-CERES-Wheat/Maize models were used to simulate the leaf area index (LAI), biomass and yield of spring wheat, spring and summer maize over 1961 − 2018. The relationships between yield related factors and SPEI/SMDI 0–10 at different timescales were investigated using Pearson correlation. The key timescale and growth period which showed the best correlations between crop yield/growth and SPEI/SMDI were determined and used to obtain the yield/growth equations using multivariable linear regression. The results showed that: (1) The temporal variations of SPEI and SMDI 0–10 differed with different timescales, months and subregions. DSSAT-CERES generally performed well in simulating growth and yields of wheat and maize over 1961–2018. (2) For spring wheat, the correlations of yield and SMDI were highest at 3-month timescale in July, at 5-month timescale in July and at 3-month timescale in June in subregions I, II and IV, respectively. For spring maize, in subregion I, yield correlated with 1-month SPEI in June best), while yield was correlated largest with 4-month SPEI in August in subregion III and IV. For summer maize, the best correlations occurred in August between yield and 4-month SPEI. Therefore, different crop had varying key parameters for drought prevention measures. (3) The multivariable linear equations described yield/growth vs. drought indices relationship well for different crops. The results are referable for providing measures for agricultural production practice under drought. • Agricultural drought index SMDI (soil moisture deficit index) can better identify drought in spring wheat growth period, and meteorological drought index SPEI (standardized precipitation evapotranspiration index) has a greater correlation with maize yield. • The continuous drought during jointing-tasseling period has the greatest influence on the spring maize yield. • For summer maize, drought had the greatest effect on yield during the anthesis period, the significant positive correlation between yield SPEI and at the 4-month timescale in August was the best. • The linear slopes of SMDI has greater influence on the linear slopes of yield related factors of spring wheat than that of SPEI，but the opposite was true for maize. [ABSTRACT FROM AUTHOR]

Excessive use of water resources is threatening agriculture, other business and populations in China, India and USA, and crop production is expected to play a critical role in the sustainable use of water. In China, plastic mulching is widely employed in crop production, but its impact on agricultural water footprint has not been properly described. A meta-analysis was performed to examine how plastic mulching influences volumetric water availability (VWA), global stress-weighted water footprint per unit of output energy (WFo), and per unit of net economic return in crop production (WFe). Data extracted from 394 published studies in maize (Zea mays L.), wheat (Triticum aestivum L.), and potato (Solanum tuberosum L.) were used in the meta-analysis on crop production at the regional scale and across a range of N fertilization gradients in China. Plastic mulching reduced VWA by 15.3%, 14.1%, and 16.3% in maize, wheat, and potato, respectively, when compared to non-mulching practice, with corresponding reductions of WFo by 33.3%, 28.1%, and 32.1% and of WFe by 14.8%, 31.1%, and 31.0% in maize, wheat, and potato, respectively. Water footprint for crop production increased first and then decreased over the past four decades in China, and was greater in northwest and north central regions of China than in other regions. Under moderate and high N fertilization (>100 kg N ha−1) in dry regions, plastic mulching increased the impact on VWA, thereby reducing WFo and WFe. Water footprint for the production in potato and maize was lower than that in wheat. The meta-analysis demonstrated that plastic mulching practices reduced water footprint while lowering VWA. Therefore, plastic mulching has potential for saving water resource when appropriate growing region and N fertilizer applications are considered. • Plastic mulching (PM) significantly reduced crop's water footprint. • Under moderate and high N input, PM had greater effect on water footprint. • PM was more effective in reducing water footprint in relatively drought environments. [ABSTRACT FROM AUTHOR]

Climate change impacts crop productivity as atmospheric conditions and water supply change, particularly in intensive cropping areas. This study used the validated AquaCrop Model, which was run with downscaled daily climate data produced by SDSM and CanESM2. The changes in the potential grain yield of winter wheat and summer maize and water budget during the cropping seasons were estimated for the Huang-Huai-Hai Plain (3H Plain) under RCP4.5 and RCP8.5 scenarios. The results show that the potential yield of winter wheat is increasing with similar spatial patterns in the 2030s, 2050s, and 2080s, with much of the increase is distributed in Shandong and northeastern parts of Henan. During the winter wheat growth period, the water budget deficit will likely improve from −210 mm in the 2030s to −202 mm in 2080s under RCP4.5 and from −206 mm in the 2030s to −191 mm in 2080s under RCP8.5 across the 3H Plain. The water budget during the winter wheat period will continue to be in deficit in the north 3H Plain and improvements are estimated mostly in the lower southern areas of the Plain. The summer maize potential yield is estimated to increase from the baseline period, but yields will decrease by 0.81%, 1.19%, and 2.10% in the 2030s, 2050s, and 2080s, respectively, under RCP8.5 compared to RCP4.5. During the summer maize growth period, the water budget is also estimated to improve from 109 mm in 2030s to 126 mm in 2080s under RCP4.5 and 107 mm in the 2030s to 163 mm in 2080s under RCP8.5. This increase is mainly estimated in the central and south of the 3H Plain. The estimated ET c of winter wheat shows no significant decrease, while the reduction of 6 mm and 13 mm for summer maize is observed under RCP4.5 and RCP8.5, respectively. The study provides scientific evidence to devise adaptation and mitigation climate change strategies for agricultural productivity and water resource management. • The potential winter wheat yield will increase under RCP4.5 and RCP8.5 scenarios. • The increase in wheat yield follows a similar spatial pattern under both RCP scenarios. • The potential summer maize yield will decrease under RCP8.5 as compared to RCP4.5. • Water deficit for wheat will remain similar to the present with increased temperature. • Water budget during summer will significantly improve in the latter half of this century. [ABSTRACT FROM AUTHOR]

The Guanzhong Plain is a critical food production area in the Yellow River Basin that frequently suffers from water shortages. In this study, long-term (June 2013 to June 2018) water and energy fluxes were observed, and path analysis was conducted over an irrigated winter wheat (Triticum aestivum L.) / summer maize (Zea mays L.) rotation field to identify the controlling factors of evapotranspiration (ET). Total ET for each crop year ranged from 627 to 775 mm, with an average growing season ET of 398 mm for wheat and 310 mm for maize. There is significant seasonal variation in both ET and surface conductance (G s). Daily ET varied from 0.0 to 6.0 mm d–1 for wheat and 0.0 to 6.7 mm d–1 for maize. The peak daily values of G s were 29.5 mm s–1 for wheat and 19.5 mm s–1 for maize. The direct and indirect effects of environmental and biological factors—net radiation (R n), surface conductance (G s), saturation vapor pressure deficit (VPD), leaf area index (LAI), air temperature (T air), and volumetric soil water content (VWC)—on ET were calculated using the path analysis method. R n was determined to be the primary controlling factor of ET for both the summer maize and winter wheat growing seasons. Also, G s was found to be another controlling factor that has more controlling power in the summer maize growing season than in the winter wheat season. VPD had a significant positive and direct effect on ET for both of the crop seasons, while it had a significant negative and indirect effect on ET through G s in the summer maize season. VWC and T air only directly affected the wheat ET. In addition, VWC had two significant paths that can indirectly affect ET through LAI and G s. The revealed seasonal patterns and controlling factors of evapotranspiration in this agroecosystem provide a theoretical basis for optimizing water resources management of the Yellow River. • A 5-year dataset of energy fluxes in winter wheat/summer maize system is presented. • Seasonal variations in evapotranspiration (ET) and energy partitioning are investigated. • Net radiation and surface conductance (G s) control the ET directly. • Vapor pressure deficit have a significant indirect effect on ET through G s. [ABSTRACT FROM AUTHOR]

Abstract: Groundwater irrigation consumes considerable energy as well as water resources across the globe. Using a case study from Iran, this paper explores how enhanced farm water management can help in reducing groundwater exploitation and subsequently limiting energy consumption and the carbon footprint of the groundwater economy. Groundwater use for irrigated agriculture in Iran has increased vastly over the last three decades. We estimate that groundwater pumping consumes 20.5billionkWh electricity and 2 billion liters of diesel and contributes to 3.6% of the total carbon emission of the country. Thus there is an opportunity to reduce energy use and carbon emissions by pumping less water. However, groundwater use remains important for food security. To identify opportunities for water conservation within agricultural fields, the SWAP model was applied to simulate crop growth and field water balance for three major irrigated crops, i.e. wheat, maize, and sugar beet in the Gamasiab River Basin, one of the highest groundwater using irrigated areas of Iran. The model simulations showed that by adopting improved irrigation schedules and improving farm application efficiencies, water productivity will increase, and irrigation water withdrawals from groundwater can be reduced significantly with no reduction in yields. While these improvements may or may not result in water saving and retarding the ground water decline, depending on the fate of excess application, they will have significant water quality, energy, and carbon implications. Such reduction in irrigation application can result in 40% decline in energy consumption and subsequently carbon emission of groundwater use. [Copyright &y& Elsevier]

Abstract: Plant water status is a key factor impacting crop growth and agricultural water management. Crop water stress may alter canopy temperature, the energy balance, transpiration, photosynthesis, canopy water use efficiency, and crop yield. The objective of this study was to calculate the Crop Water Stress Index (CWSI) from canopy temperature and energy balance measurements and evaluate the utility of CWSI to quantify water stress by comparing CWSI to latent heat and carbon dioxide (CO2) flux measurements over canopies of winter wheat (Triticum aestivum L.) and summer maize (Zea mays L.). The experiment was conducted at the Yucheng Integrated Agricultural Experimental Station of the Chinese Academy of Sciences from 2003 to 2005. Latent heat and CO2 fluxes (by eddy covariance), canopy and air temperature, relative humidity, net radiation, wind speed, and soil heat flux were averaged at half-hour intervals. Leaf area index and crop height were measured every 7 days. CWSI was calculated from measured canopy-air temperature differences using the Jackson method. Under high net radiation conditions (greater than 500Wm−2), calculated values of minimum canopy-air temperature differences were similar to previously published empirically determined non-water-stressed baselines. Valid measures of CWSI were only obtained when canopy closure minimized the influence of viewed soil on infrared canopy temperature measurements (leaf area index was greater than 2.5m2 m−2). Wheat and maize latent heat flux and canopy CO2 flux generally decreased linearly with increases in CWSI when net radiation levels were greater than 300Wm−2. The responses of latent heat flux and CO2 flux to CWSI did not demonstrate a consistent relationship in wheat that would recommend it as a reliable water stress quantification tool. The responses of latent heat flux and CO2 flux to CWSI were more consistent in maize, suggesting that CWSI could be useful in identifying and quantifying water stress conditions when net radiation was greater than 300Wm−2. The results suggest that CWSI calculated by the Jackson method under varying solar radiation and wind speed conditions may be used for irrigation scheduling and agricultural water management of maize in irrigated agricultural regions, such as the North China Plain. [Copyright &y& Elsevier]

Abstract: In the present study, water and nitrogen interaction on soil profile water extraction and evapo-transpiration (ET) was investigated taking a field experiment on a clay loam soil (Typic Haplustept) at the Indian Agricultural Research Institute, New Delhi with four consecutive crops (maize–wheat–maize–wheat) taken from July 2002 to April 2004. Three levels of water regime, namely W1, W2 and W3 referring to limited, medium and maximum irrigation were applied to each crop depending on the seasonal rainfall and the critical crop growth stage. The three water regimes were used with five nitrogen levels from T1 to T5, (T1, 0% N; T2, 75% N; T3, 100% N; T4, 150% N; T5, 100% N from organic source) in a split plot design for the four crops grown in sequence. Significant water and nitrogen interaction was observed for ET and soil profile water extraction pattern. Averaged across nitrogen treatments, ET in W2 and W3 were higher by 17 and 26%, respectively than W1 in maize 2002 and by 12 and 19% in maize 2003. In case of wheat, ET in W2 and W3 were higher by 27 and 58% than W1 in 1st crop and by 37 and 70% in 2nd crop. The effect of nitrogen regime, however, was prominent in both crops of maize and wheat, with significantly higher profile soil moisture depletion in T4 of each water regime. In all cases, lowest water depletion was observed in control plots receiving 0% N. In both crops, water extraction from surface 60cm was highest in W3 followed by W2 and W1. In maize, the % extraction from 0 to 60cm layer varied from 71 to 76% (W1), 70–79% (W2) and 75–82% (W3), whereas the values for wheat were 70–77, 72–79 and 75–83% for W1, W2 and W3, respectively. The 90–120cm layer contributed only 3–14% to total water extraction in both the crops. From 90 to 120cm layer, higher extraction was observed in W1 as compared to W3. The extraction values in W1, W2 and W3 in maize were 9–13, 7–14 and 3–9, respectively, whereas the corresponding values in wheat were 8–14, 5–12 and 3–7% for the three water regimes. Effect of nitrogen treatments on water extraction from deeper layer was observed with higher extraction in highest fertilized treatment (T4) as compared to other treatments. [Copyright &y& Elsevier]

Laser land levelling is expanding rapidly in the rice-wheat (RW) and maize-wheat (MW) systems of the Indo-Gangetic Plains of India and Pakistan. Current practice is to level to zero (0%) gradient, whereas a small gradient (e.g. 0.1%) is typically used in developed countries. Therefore, experiments were conducted in farmers' plots (~15 m x 40 m) in the Eastern Gangetic Plains to evaluate laser levelling with a 0.1% gradient in comparison with 0% and farmer levelling practice (FL). The study was conducted over two years in RW and MW systems. In the MW system, raised beds in plots lasered with 0% and 0.1% gradients were also evaluated. Laser levelling with 0% gradient significantly reduced irrigation amount and/or increased irrigation water productivity (WPi) in all crops/systems grown on the flat compared to FL except for wheat in the MW system. While there was a consistent trend for higher yield with a 0% gradient compared with FL, the differences were not significant in any crop/system. For the RW system, the results suggest no to marginal benefits in irrigation amount and WPi from levelling with a 0.1% gradient in comparison with 0% gradient. In that system, by far the bigger gains were from changing from FL to laser levelling with 0% gradient. This resulted in substantial reductions in irrigation amount, which greatly increased WPi in both crops (by ~40%), while yield was not affected. Rice grown with FL was not profitable, but lasering with 0% gradient significantly increased gross margin for rice, wheat and the total RW system. As for the RW system, levelling to 0% with a flat configuration significantly increased WPi of both crops in the MW system compared to FL, but by a lesser proportion. Raised beds significantly increased yield of maize by 8% (0.5 t ha−1), reduced irrigation amount by 20% (40 mm) and increased WPi by 34% (1.0 kg m−3) in comparison with the laser levelled flat plots. Gross margin of the MW system on beds was 17–20% higher than FL, and gross margin with beds on a 0.1% gradient was significantly higher than either gradient on the flat. The results suggest that the gains from levelling with a 0.1% gradient compared to 0% are marginal; however, this may change if the goal of consolidation of small farmer plots into larger fields becomes a reality provided there is a proportionate increase in irrigation flow rates, and ability to drain. • Land gradient (0, 0.1%) and configuration (flats, beds) were tested in non-puddled rice-wheat (RW) and maize-wheat (MW) systems. • 0% gradient with flat configuration did not increase yield but increased gross margin of RW system than farmer practice. • 0.1% gradient with flats increased yield, WPi and gross margin of all crops compared with farmer levelling. • In MW, beds increased WPi of maize over flats with the same gradient, and had the highest gross margin regardless of gradient. • Gross margin of the MW system was 2–4 times that of the RW system. [ABSTRACT FROM AUTHOR]

Abstract: Irrigation water supplies are decreasing in many areas of the US Great Plains, which is requiring many farmers to consider deficit-irrigating corn (Zea mays L.) or growing crops like winter wheat (Triticum aestivum L.) that require less water, but that are less profitable. The objectives of this study were to: (1) quantify the yield response of corn to deficit irrigation, and (2) determine which of several seasonal water variables correlated best to corn yield in a semiarid climate. Eight (T1–T8) and nine (T1–T9) deficit-irrigated treatments (including dryland), were compared in 2003 and 2004 in North Platte, Nebraska. The actual seasonal crop evapotranspiration (ETd) (calculated with procedures in FAO-56) for the different treatments was 37–79% in 2003 and 63–91% in 2004 compared with the seasonal crop evapotranspiration when water is not limited (ETw). Quantitative relationships between grain yield and several seasonal water variables were developed. Water variables included, irrigation (I), total water (W all), rain+irrigation (W R+I ), evaporation (E), crop evapotranspiration (ETd), crop transpiration (T d), and the ratios of ETd and T d to evapotranspiration and transpiration when water is not limited (ETw and T w). Both years, yield increased linearly with seasonal irrigation, but the relationship varied from year to year. Combining data from both years, ETd had the best correlation to grain yield (yield=0.028ETd–5.04, R 2 =0.95), and the water variables could be ranked from higher to lower R 2 when related to grain yield as: . Crop water productivity (CWP) (yield per unit ETd) linearly increased with ETd/ETw (R 2 =0.75), which suggests that trying to increase CWP by deficit-irrigating corn is not a good strategy under the conditions of this study. [Copyright &y& Elsevier]

Abstract: The wheat- (Triticum aestivum L.) and corn- (Zea mays L.) rotation system is important for food security in Northwest China. Grain yield and water-use efficiency [WUE: grain yield/estimated evapotranspiration (ET)] were recorded during a 24-year fertilization trial in Pingliang (Gansu, China). Mean yields of wheat for the 16 years, starting in 1981, ranged from 1.29Mgha−1 for unfertilized plots (CK) to 4.71Mgha−1 for plots that received manure (M) annually with nitrogen (N) and phosphorus (P) fertilizers (MNP). Corn yields for the 6 years, starting in 1979, averaged 2.29 and 5.61Mgha−1 for the same respective treatments. Whether the years were dry, normal or wet, average grain yields and WUEs for both crops were consistently highest in the MNP and lowest in the CK treatment, and were always lower in the N than in the M treatment and in all others treatments that received N along with P fertilizers. More importantly, WUEs for MNP and for straw along with N annually and P every second year (SNP) were always higher than the other fertilized treatments in dry years. Compared to yield data, coefficients of variance (CV) for WUEs were consistently low for all treatments, suggesting that WUEs were relatively stable from year to year. Yields and WUEs declined over time, except in the CK and MNP treatments for wheat. Declined yields of wheat for the N and M treatments were comparable, and the decline for the NP treatment was similar to that for the SNP treatment. Likewise, corn yields and WUEs declined for all treatments. Grain yields were significantly correlated with ET, with slopes ranging from 0.5 to 1.27kgm−3 for wheat and from 1.15 to 2.03kgm−3 for corn. Balanced fertilization and long-term addition of organic material to soil should be encouraged in this region to maximize the use of stored soil water, arrest grain yields decline, and ensure sustainable productivity using this intensive cereal cropping system. [Copyright &y& Elsevier]

Continuous cropping of winter wheat and summer maize is the main cropping pattern in North China Plain lying in a seasonal frost area. Irrigation scheduling of one crop will influence soil water regime and irrigation scheduling of the subsequent crop. Therefore, irrigation scheduling of winter wheat and maize should be studied as a whole. Considering the meteorological and crop characteristics of the area lying in a seasonal frost area, a cropping year is divided into crop growing period and frost period. Model of simultaneous moisture and heat transfer (SMHT) for the frost period and model of soil water transfer (SWT) for the crop growing period were developed, and used jointly for the simulation of soil water dynamics and irrigation scheduling for a whole cropping year. The model was calibrated and validated with field experiment of winter wheat and maize in Beijing, China. Then the model was applied to the simulation of water dynamics and irrigation scheduling with different precipitation and irrigation treatments. From the simulation results, precipitation can meet the crop water requirement of maize to a great extent, and irrigation at the seeding stage may be necessary. Precipitation and irrigation had no significant influence on evaporation and transpiration of maize. On the other hand, irrigation scheduling of winter wheat mainly depends on irrigation standard. Irrigation at the seeding stage and before soil freezing is usually necessary. For high irrigation standard, four times of irrigation are required after greening. While for medium irrigation, only once (rainy year) or twice (medium and dry years) of irrigation is required after greening. Transpiration of winter wheat is very close for high and medium irrigation, but it decreases significantly for low irrigation and will result in a reduction of crop yield. Irrigation with proper time and amount is necessary for winter wheat. Considering irrigation quota and crop transpiration comprehensively, medium irrigation is recommended for the irrigation of winter wheat in the studying area, which can reduce the irrigation quota of over 150 mm with little water stress for crop growth. [Copyright &y& Elsevier]

• Drip fertigation with urea and (NH 4) 2 SO 4 performed better than NH 4 NO 3 and Ca(NO 3) 2. • (NH 4) 2 SO 4 reduced N loss by 25 %–31 % than other N fertilizers during wheat season. • Urea reduced N loss by 69 %–77 % than other N fertilizers during maize season. Fertigated areas of wheat and maize in the North China Plain (NCP) have grown rapidly during recent years, but little information is available on the effects of different nitrogen (N) fertilizers applied through drip fertigation on wheat and maize. A field experiment was conducted in the NCP during 2012−2016 to evaluate the effects of urea, ammonium nitrate, ammonium sulfate and calcium nitrate applied by drip fertigation (no N as the control, CK) on grain yield, water use efficiency (WUE), N use efficiency (NUE) and N loss in wheat and maize. A total of 250 kg N ha−1 and 205.5 kg N ha−1 were split into six and four applications and applied by drip fertigation at key growth stages during the wheat and maize growing seasons, respectively. The results showed that urea and calcium nitrate produced higher yields (p < 0.05) than ammonium nitrate and ammonium sulfate in the first year of the study in both wheat and maize, whereas in subsequent years, ammonium sulfate increased the yield of wheat by 11.3 %–25.1 %, 13.7 %–46.1 % and 16.4 %–32.7 % compared with urea, ammonium nitrate and calcium nitrate, respectively. Urea and ammonium sulfate averagely produced higher maize yields than ammonium nitrate and calcium nitrate, but no significant difference in maize yield was found between urea and ammonium sulfate. Similar trends in WUE and NUE were recorded in both crops. Ammonium sulfate contributed to higher WUE and NUE in wheat compared to the other N fertilizers except in the first year, while urea contributed to higher WUE and NUE in maize. The total apparent N loss in urea was 13.9 %, 15.4 % and 15.8 % lower (p < 0.05) than those in ammonium nitrate, ammonium sulfate and calcium nitrate after three cycles of the rotation (2012–2015), respectively. Considering both yield and NUE, and based on the results of apparent N loss for the four N fertilizers under field conditions, ammonium sulfate was recommended as the superior N source for wheat under drip fertigation, while urea was the optimal N source for maize under drip fertigation. [ABSTRACT FROM AUTHOR]

• A comprehensive review on the effects of farming practices on various crops such as wheat, maize and potato • RFFM performed better than RF and FM in increasing crop yield and crop water productivity. • Potato obtained the greatest increases in yield and WP under ridge-furrow planting or film mulching. • For clay soils and high altitude regions, the two film mulching practices (FM and RFFM) attained greater yield increases. • Under the two ridge-furrow treatments (RFFM and RF), it is better to plant crops in the furrow than on the ridge Crop yields are significantly restricted by the shortage of water resources in semi-arid and semi-humid regions around the world. Farming practices like ridge-furrow planting with plastic film mulching (RFFM) can effectively improve crop yield and crop water productivity (WP) by enhancing soil moisture and temperature availability. This meta-analysis study collected and analyzed the data of 964 observations published in 90 peer-reviewed papers to investigate the effects of various farming practices, i.e., RFFM, ridge-furrow planting without film mulching (RF) and flat planting with film mulching (FM) in comparison with conventional flat planting without film mulching (F), on yield and WP of three major crops (wheat, maize and potato) in China, in terms of planting region, climatic condition, altitude, soil type and seeding method. The results showed that RFFM, RF and FM improved mean crop yields by 33.8 %, 16.6 % and 27.0 %, and increased mean WP of crops by 35.8 %, 17.5 % and 27.8 % compared with F, respectively. Increases in crop yields under RFFM, RF and FM were greater in regions with seasonal rainfall <400 mm than in regions with seasonal rainfall>400 mm. RFFM, RF and FM performed better in Northwest China than in North-central and other regions of China. Among the three crops, potato obtained the greatest increases in yield and WP under ridge-furrow planting or film mulching. For clay soils and high altitude regions, the two film mulching practices (FM and RFFM) attained greater yield increases. With regards to the two ridge-furrow practices (RFFM and RF), it is better to plant crops in the furrow than on the ridge. In short, RFFM was most effective to improve yield and WP of wheat, maize and potato among the farming practices. These findings have important implications for choosing appropriate field management practices to improve crop yield and crop water productivity in China. [ABSTRACT FROM AUTHOR]

• Future climate warming led to advance in wheat and maize phenology. • Future climate change had negative impact on maize but positive impact on wheat. • Crop water consumption was largely decreased under future climate scenarios. • Future climate change could mitigate groundwater overdraft across NCP. Climate change has already and will continue to exert a vital impact on crop yield and water use in the North China Plain (NCP). Currently, this plain is facing a dilemma between groundwater depletion and grain production demand. It is urgent to identify the impact of future climate change on crop yield and water consumption and then develop efficient adaptation strategies in the region. In this study, we used statistically downscaled daily climate data from 33 global climate models (GCMs) and two Representative Concentration Pathways (RCP4.5 and RCP8.5) for 61 stations distributed across the NCP and drove the well-validated APSIM model to simulate crop yield and water use for two future periods of 2031–2060 (2040s) and 2071–2100 (2080s). Data from all 33 GCMs show an increase in annual mean temperature and almost all the GCMs also show increases in annual mean solar radiation and annual total precipitation across the NCP. Future climate warming led to an advance in phenology for both winter wheat and summer maize, two typical crops in the NCP. However, the length of the reproductive growth period (RGP) of winter wheat was prolonged while that of summer maize was shortened under future climate scenarios across the NCP. Our simulated results show that future climate change had negative impacts on maize yield but positive impacts on wheat yield across the NCP. Mainly due to the shortening of the whole growth period, crop water consumption was largely decreased under future climate scenarios. The amount of irrigation required was also reduced mainly due to increased precipitation and decreased ET. Although future climate change would likely mitigate groundwater overdraft in most part of NCP, some areas in the northern NCP still had groundwater over-pumping in the future. Therefore, we suggest that it might be a good choice to change cropping system for reducing planting area of water-consuming crop (e.g. winter wheat) in those over-pumping areas to balance groundwater use and crop yield. [ABSTRACT FROM AUTHOR]

• Quantified irrigation's role in stabilizing U.S. agricultural yields. • Irrigation-Induced Reduction in Yield Variability (IIRYV) computed for nine crops. • Derived from 220,000 historical records, mean U.S IIRYV was 41 % (range: 0–90 %). • Maize and cotton demonstrated the highest and lowest IIRYV. • IIRYV increased during 1950–2015 for most crops, albeit crop and space variation. Irrigation contributes to enhance and sustain agricultural production in the U.S. across all aridity regimes, via mitigation against interannual environmental variability. Currently, a quantitative understanding of the role of irrigation in stabilizing agricultural yields is lacking, limiting the realization of irrigation-adoption impacts. Here we use >220,000 historical (1950–2015) county-year irrigated and rainfed yield records for the top-nine U.S. crops [maize (Zea mays L.), soybean (Glycine max (L.) Merr.), spring wheat (Triticum aestivum L.), winter wheat (Triticum aestivum L.), alfalfa (Medicago sativa L.), sorghum (Sorghum bicolor (L.) Moench), cotton (Gossypium hirsutum), barley (Hordeum vulgare L.) and oats (Avena sativa)]. To comprehensively quantify the "Irrigation-Induced Reduction in Crop Yield Variability" (IIRYV, defined as the percent reduction in crop yield variability when irrigated with respect to rainfed yield variability). Averaged across all crops, national-level IIRYV was 41 %, which varied from 0 to 90 % across various regions and crops. IIRYV was highly crop-specific, and maize and cotton crops demonstrated the highest and least magnitudes. IIRYV substantially varied spatially within the constituent growing regions for each crop, and thus national scale assessments masked significant spatial differences. IIRYV was subject to interannual (temporal) variability; however, in general, IIRYV increased over time (1950–2015) for most crops. These findings will help in the evaluation of the contribution of historical irrigation development policy and adoption in the U.S in mitigating external shocks (variability) in U.S. agricultural productivity. The demonstration of spatial and temporal dynamics in IIRYV will aid in irrigation-water allocations and adoption by prioritizing irrigation development for vulnerable crops and regions. [ABSTRACT FROM AUTHOR]

• Modeling yield, evapotranspiration and economic profit in different cropping systems using APSIM under projected climate scenarios. • Maize and wheat yield underwent significant reduction in projected scenarios compared with the baseline data. • Plant transpiration have not changed significantly between scenarios, but evaporation decreased in some conditions markedly. • Lucerne-winter wheat rotation presented the greatest potential of the sustainability under projected scenarios. Agriculture in the semiarid region is undergoing radical changes driven by global warming and increasing incidences of extreme weather events. Predicting and evaluating the responses of crop yield and water use patterns of rainfed cropping systems according to future temperature and precipitation changes could provide important information regarding adoption of climate-smart farming systems that could offer great resilience and sustainability. The objective of this study was to evaluate the potential changes in agronomic productivity, hydrological balance and economic profitability of cropping systems with perennial legumes and rotation on the Loess Plateau of China affected by different future temperature and precipitation scenarios using APSIM-based modeling. Five different cropping systems were investigated: (i) continuous maize (Zea mays) (M), (ii) continuous winter wheat (Triticum aestivum) (W), (iii) continuous lucerne (Medicago sativa) (L), (iv) maize-wheat-soybean (Gyleine max) rotation (MWS) and (v) lucerne (4-yr)-winter wheat (2-yr) rotation (LW) in Xifeng, Gansu, China. Five series of temperature and precipitation changes scenarios (no changes in atmospheric CO 2 concentrations were considered) based on RCPs (representative concentration pathways) were integrated into scenario simulations, including the baseline scenario (1980–2010), mid-century scenarios of RCP4.5 (M45) and RCP8.5 (M85), and end-century scenarios of RCP4.5 (E45) and RCP8.5 (E85). The results showed that, compared with baseline simulations, mean maize yield under RCPs decreased by 6.7 %–37.7 %, and the mean wheat yield decreased by 1.7 %–23.6 %. Lucerne yield consistently increased by 7.2 %–12.3 % under M45 and E45. Although different cropping systems affected the yield to a certain extent, only the difference between the wheat yields of W and MWS was significant (P < 0.05). On a cropping system level of every 6-yr (totally five phases for a scenario of 30-yr), the temperature and precipitation changes did not significantly affect plant transpiration (T c) per phase. For all systems except L [which received its highest soil evaporation (E s) per phase in baseline], the greatest E s per phase was found in the E85. L tended to provide greater T c per phase and evapotranspiration (ET) per phase (ranging from 1219 to 1332 mm and 2910–3034 mm, respectively), followed by LW. L and MWS presented the highest and lowest E s per phase (1636–1724 and 1592–1677 mm), respectively. The gross profit (GP per 6-yr phase) and water productivity (WP per 6-yr phase) of L were the greatest among all cropping systems (11.5–13.7 thousand US$ ha−1 per phase and 3.72–4.41 US$ ha-1 mm-1 per phase, respectively), followed by LW and MWS. For M, W and MWS, the GP per phase and the WP per phase were predicted to be greater under the baseline than under any of the RCPs, whereas M45 and E45 scenarios improved the GP per phase and WP per phase of L and LW compared with those of the baseline. In general, we advocate that LW-based systems have the greatest potential for producing acceptable yield and economic profit under future temperature and precipitation scenarios for this local environment. [ABSTRACT FROM AUTHOR]

• Water conservation is the best way to increase water management efficiency in agriculture and reduce potential negative environmental impacts. • Residue improves soil tilth and adds organic matter to the soil as it decomposes. • Crop residue can reduce the rate of water evaporation and runoff, increase penetration of water and therefore improve soil water conservation. Wheat (Triticum aestivum L.) residues and water management are major problems in southern part of Iran where irrigated wheat-corn (Zea mays L.)-wheat rotation is a common practice. A 2-year (2015–2016) field experiment was conducted as a split plot design with four replications to determine the influence of different irrigation regimes (50, 70, and 100% of water requirement) and wheat residue rates (0, 25, and 50%) incorporation into the soil on sweet corn (Zea mays L V. Saccharata) growth, grain yield, and some soil properties at School of Agriculture, Shiraz University, Shiraz, Iran. The results showed that the highest plant height (187.12 cm) and leaf area index (3.49) were obtained when the crop was normally irrigated (100% of water requirement) and sown into the 25% incorporated wheat residues. Furthermore, canned yield (68%) and water use efficiency (WUE) increased with normal irrigation and 25% residue incorporation compared to the 50% wheat residue rate. The highest grain protein (14.67%) was achieved under incorporation of either 25 or 50% wheat residue into the soil, while the highest grain sugar (2643.5 mg g−1) was obtained when the crop was moderately irrigated (70% of water requirement) with 25% residue incorporation into the soil. The highest soil nitrogen (N) and soil organic carbon (SOC) were achieved with normal irrigation and 50% residue incorporation in both years.In general, adopting an adequate rate of wheat residue (between 25%–50%) accompanied by decreasing irrigation volume to 70% water requirement of corn is recommended in semi-arid agroecosystems. [ABSTRACT FROM AUTHOR]