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The application of nitrogen (N) improves the winter wheat yield. Excessive N application affects winter wheat yields, leading to low net incomes and negative environmental impacts, therefore, optimizing N application is essential. In this study, the effects of N rates on crop growth yield, net income (NI), water use efficiency (WUE), and nitrogen use efficiency (NUE) in the irrigated districts of the eastern loess plateau, China, were investigated using seven N application rates (N0, N90, N180, N210, N240, N270, and N300 kg ha−1) during the 2016–2017 and 2017–2018 seasons. N application significantly increased the total water consumption at 0–200 cm during the growth period, the aboveground dry matter at maturity, the grain nitrogen accumulation, yield, NI, and WUE. However, N exceeding 240 kg ha−1 did not favor dry matter and nitrogen accumulation or translocation from the anthesis stage to the maturity stage, thus leading to reduced yield, NI, and WUE. The transpiration rate and stomatal conductance N240 was highest 21–28 day after anthesis, at 187–276 kg ha−1, which can achieve a high yield and profitability with relatively low environmental costs. [ABSTRACT FROM AUTHOR]

Precipitation is the major cause of crop yield variation in rainfed agriculture production in the Loess Plateau. As over fertilization is economically and environmentally undesirable, and crop yield and the resulting returns for N input are uncertain when rainfall variability is high, optimizing N management according to precipitation during fallow season is vital for efficient crop water use and high yield in dryland rainfed farming systems. Results show that the nitrogen treatment rate of 180 treatment significantly increased the tiller percentage rate, and the leaf area index at anthesis, the jointing anthesis, anthesis maturity dry matter, and nitrogen accumulation was closely related to yield. N150 treatment compared to N180 treatment significantly increased the percentage of ear-bearing tiller by 7%, dry substance accretion from jointing to anthesis by 9%, and yield by 17% and 15%, respectively. Our study has important implications for the assessment of the effects of fallow precipitation, as well as for the sustainable development of dryland agriculture in the Loess Plateau. Our results indicate that adjusting N fertilizer inputs based on summer rainfall variation could enhance wheat yield in rainfed farming systems. [ABSTRACT FROM AUTHOR]

Background: About 60% of the annual precipitation in the Loess Plateau occurs during the summer fallow season, and does not align with the wheat growing season. In addition, the nitrogen use efficiency is low in this area because nutrient availability is affected by drought. As a result, rainwater storage during the summer fallow season is very important to increasing nitrogen use efficiency, and to the stable production of dryland wheat in the Loess Plateau. Methods: A 3-year field experiment in the eastern part of the Loess Plateau was conducted with two tillage methods (no tillage (NT) and deep ploughing (DP)) and five N rates (0, 120, 150, 180, and 210 kg N ha-1) to study the effect of tillage on soil water utilization, plant nitrogen utilization, and wheat yield. Result: Compared to NT, DP showed a larger increase in soil water storage (SWSf) and precipitation storage efficiency (PSEf) during the two dry summer fallow seasons than in the normal summer fallow season. DP substantially increased the pre-anthesis soil water consumption (SWCpre) and N translocation. The average yield under DP was 12.46% and 14.92-18.29% higher than under NT in the normal and dry seasons, respectively. A 1 mm increase in SWCpre could increase grain yield by 25.28 kg ha-1, water use efficiency (WUE) by 0.069 kg ha-1 mm-1, and nitrogen utilization efficiency (NUtE) by 0.029 kg kg-1. DP could reduce the N rate by 11.49-53.34% in the normal seasons and 40.97-65.07% in the dry seasons compared to the same highest point of yield, WUE, and NUtE under NT. Conclusion: Deep ploughing in the summer fallow season, paired with optimized N application, could help increase wheat yield and nitrogen efficiency in dryland. [ABSTRACT FROM AUTHOR]

Wheat (Triticum aestivum L.) is a staple crop worldwide, and its yield has improved since the green revolution, which was attributed to chemical nitrogen (N) fertilizer application. However, regular N application decreases N use efficiency (NUE, the ratio of grain dry matter yield to N supply from soil and fertilizer). Various practices have been implemented to maintain high crop yield and improve NUE. Nowadays, the enhanced sowing method, i.e., wide space sowing (WS), has improved the productivity of wheat crops. However, how the sowing method and N application rate affect N use and yield productivity has not been fully elucidated. Field experiments with treatments using two sowing methods (WS, and drill sowing, DS) and four N application rates (0, 180, 240, and 300 kg ha-1, represented as N0, N180, N240, and N300, respectively) were conducted from 2017 to 2019. The results showed that grain yield under WS was 13.57-16.38% higher than that under DS. The yield advantage under WS was attributed to an increased ear number. Both the higher stem and productive stem percentage accounted for the increased ear number under WS. Higher total N quantity and larger leaf area index at anthesis under WS contributed to higher dry matter production, resulting in higher grain yield. Higher dry matter production was due to pre-anthesis dry weight and post-anthesis dry weight. The wheat crop under WS had a 12.44-15.00% higher NUE than that under DS. The increased NUE under WS was attributed to higher N uptake efficiency (the ratio of total N quantity at maturity to N supply from soil and fertilizer), which was the result of greater total N quantity. The higher total N quantity under WS was due to both higher pre-anthesis N uptake and post-anthesis N uptake. Remarkably, compared to DS with 240 kg N ha-1, WS with 180 kg N ha-1 had almost equal grain yield, dry matter, and total N quantity. Therefore, wheat crops under WS could achieve both high NUE and grain yield simultaneously with only moderate N fertilizer in South Shanxi, China. [ABSTRACT FROM AUTHOR]

Precipitation is the major cause of crop yield variation in rainfed agriculture production on the Loess Plateau. As overfertilization is economically and environmentally undesirable, and crop yield and the resulting returns for N input are uncertain when rainfall variability is high, optimizing N management according to the precipitation of fallow season is vital for efficient crop water use and high yield in dryland/rainfed farming systems. Thus, this study established a reference range describing wheat cultivation year types based on fallow season precipitation over 37 years. We conducted an 8-year field experiment using seven different N input rates, to focus on soil water content and its vertical distribution in the 0–300 cm soil layers and to assess the relationship between soil water utilization and yield formation. The final objective was to evaluate how the optimal N input affects crop water consumption, with the aim of maximizing yields. Eight experimental years (2009–2017) were classified as dry and normal years (four of each), with optimum N application rates of 150 and 180 kg N ha−1, respectively. Compared with that used by farmers (210 kg N ha−1), optimum N input saved 26.8% and 12.3% of N fertilizer, increased grain yield by 5.0% and 5.2%, and improved crop water productivity (CWP) by 6.1% and 8.5% in dry and normal years, respectively. Optimized N inputs reduced soil water consumption before the jointing stage and increased the soil water available for grain yield production. Soil water depletion occurred from deeper soil layers with crop development, and soil water storage (SWS) at 80–240 and 200–300 cm depth played an important role in increasing spike number and grain filling, respectively. Furthermore, soil water conservation treatment (increasing rainwater storage via deep plowing at start of the summer fallow season) was unable to eliminate the variability in soil water storage at sowing, and as "drought at sowing" effects on yield were more adverse than "drought in growing season" effects in dryland systems, our results indicate that adjusting N fertilizer inputs based on summer rainfall variation could enhance wheat yield and CWP in the rainfed farming system. • N input was optimized to match year type based on fallow season precipitation. • Soil water storage in 80–300 cm depth was important for yield formation. • Optimized N input regulated water consumption during wheat development. • Optimizing N input for dryland wheat production was feasible and economical. [ABSTRACT FROM AUTHOR]