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Long-term continuous cropping, excessive nitrogen input, and low nitrogen use efficiency are prevalent issues in wheat production in the Northwest Oasis irrigation area. This study examined the compensatory mechanism on grain yield and nitrogen utilization by reducing nitrogen input in wheat and multi-cropping of green manure after wheat harvest. The goal was to provide a theoretical basis for developing efficient wheat production technologies with reduced nitrogen input. This long-term field experiment, initiated in 2018, collected data from 2020 to 2022. The main plot included four green manures: multi-cropped common vetch mixed with hairy vetch (HCV), common vetch (CV), rapeseed (R), and fallow (F) after the previous wheat harvest. Subplots applied three nitrogen rates: the local conventional rate (N3, 180 kg hm-2), reduced by 20% (N2, 144 kg hm-2), and reduced by 40% (N1, 108 kg hm-2). Our results indicated that reducing conventional nitrogen by 20% and 40% significantly decreased both grain yield and nitrogen uptake. However, multi-cropped hairy vetch mixed with common vetch after wheat harvest could compensate for the yield and nitrogen uptake losses caused by a 40% nitrogen reduction. When combined with a 20% nitrogen reduction, grain yield and nitrogen uptake increased by 21.4% and 6.9%, respectively (P < 0.05). Additionally, this cropping pattern compensated for the decreased nitrogen use efficiency resulting from a 40% nitrogen reduction and, when combined with a 20% nitrogen reduction, enhanced nitrogen use efficiency by 13.4% (P < 0.05). The compensation mechanism was attributed to: (1) Under a 40% nitrogen reduction, multi-cropped hairy vetch mixed with common vetch compensated for nitrogen uptake rate, increased net nitrogen assimilation rate by 34.3% (P < 0.05), maintained nitrogen distribution in the ear, and enhanced the nitrogen transportation rate from the stem by 6.6% (P < 0.05). (2) Compared with fallow after wheat harvest and the conventional nitrogen application rate, multi-cropped hairy vetch mixed with common vetch under a 20% nitrogen reduction increased mean nitrogen uptake efficiency and net nitrogen assimilation rate by 7.2% and 34.1%, respectively (P < 0.05). It also improved nitrogen distribution in the ear from early filling to maturity stages by 6.7% (P < 0.05) and enhanced the contribution rate of nitrogen transportation from stem and leaf to ear by 17.8% and 8.9%, respectively (P < 0.05). Therefore, multi-cropped hairy vetch mixed with common vetch after wheat harvest is a viable measure to reduce nitrogen fertilizer input. When combined with a 20% nitrogen reduction, it can increase grain yield and nitrogen use efficiency in wheat by improving nitrogen uptake rate, net nitrogen assimilation rate, and the contribution rate of nitrogen transportation from leaf and stem to ear, thereby promoting nitrogen distribution in the ear in arid oasis irrigated areas. [ABSTRACT FROM AUTHOR]

Aiming at the production and ecological problems of the lack of water resources and excessive chemical nitrogen fertilizer input in arid oasis irrigation areas, the effect of increased planting density to compensate for the loss of maize yield caused by reducing water and nitrogen inputs was analyzed under reduced water and nitrogen inputs, which could provide theoretical and technical support for the efficient production of maize with water and nitrogen reduction. Based on a split-plot field experiment conducted in 2016, the main plot was divided into two irrigation quotas: reduced irrigation by 20% (W1, 3240 m³ hm-2) and traditional irrigation (W2, 4050 m³ hm-2), and the split-plot was divided into two nitrogen application rates: reduced nitrogen (N1, 270 kg hm-2) by 25% and traditional nitrogen (N2, 360 kg hm-2) were applied, and the sub-split plot was divided into three maize densities: traditional planting density (D1, 75,000 hm-2 plants), increased density by 30% (D2, 97, 500 hm-2 plants) and increased density by 60% (D3, 120,000 hm-2 plants). We measured grain yield and biological yield of maize in 2020 and 2021, analyzed the characteristics of dry matter accumulation, distribution, and transport characteristics, quantified the yield composition factors, and clarified the compensation effect and mechanism of densification on maize yield with water and nitrogen reduction. The study showed that water and nitrogen reduction inputs decreased the grain yield and biological yield in maize, but the increased density by 30% can compensate for the loss of yield due to reducing water and nitrogen inputs and improve maize yield under reduced water while maintaining traditional nitrogen. The grain yield and biological yield of W1N1D1 (reduced water and nitrogen and traditional density) was 9.1%-15.0% and 10.0%-11.0% lower than W2N2D1 (comparison: traditional irrigation, traditional nitrogen application, and traditional density), but there was no significant difference in W1N1D2 (reduced irrigation, reduced nitrogen, and increased density by 30%) compared with W2N2D1. Compared with W2N2D1, W1N2D2 (reduced irrigation, traditional nitrogen, and increased density by 30%) increased grain yield and biological yield by 12.9%--15.4% and 6.4%-12.0%, respectively. Increased density by 30% compensated for the negative effect of water and nitrogen reduction mainly attributed to improving spike number of W1N1D2, which further increased dry matter accumulation from the early-filling stage to the maturity stage in maize, population growth rate and dry matter remobilization at pre-anthesis from seeding stage to the flare opening stage. Increasing spike number of W1N2D2 improved dry matter accumulation and population growth rate, promoted dry matter distribution in the ear, and increased dry matter remobilization. In addition, the dry matter remobilization efficiency and contribution of dry matter remobilization to grain at pre-anthesis were the main reasons for increasing maize yield with the increased density by 30% under water and nitrogen reduction inputs. Therefore, increasing density by 30% was a feasible measure for simultaneous reduction of water and nitrogen in oasis irrigation area to stabilize and increase maize yield. [ABSTRACT FROM AUTHOR]

Water shortage and high fertilizer input have become the dominant factors restraining maize production in arid oasis irrigation area, it is urgent to study the technology of stable yield and increasing yield of crops with reduced water and fertilizer. To provide basis for establishing the efficient technology of stable and high yield of maize with water and nitrogen reduction, the effects of increasing density on dry matter accumulation, grain yield and yield components of maize were investigated under reduced water and nitrogen supply. A split-split plot field experiment was conducted in 2020 and 2021. Under two irrigation levels on local conventional irrigation reduced by 20% (W1) and local conventional irrigation (W2), and two levels of nitrogen fertilizer at a local conventional nitrogen reduced by 25% (N1) and local conventional nitrogen (N2), the response characteristics of dry matter accumulation and yield of maize were studied when maize density increased from 75,000 plants·hm-2 (low density, D1) by 30% (medium density D2), and by 60% (high density D3). The results showed that the grain yield of maize was significantly decreased with the reduced water and nitrogen supply, and increasing planting density by 30% could compensate the negative effect on the decrease of yield. Under the reduced water supply while maintaining N application rate, the dense planting density could significantly increase grain yield. In the two experimental years, the yield of W1 was 3.0% lower than W2. The grain yield of N1 was 12.9% lower than N2. Compared with D1, D2, and D3 increased grain yield by 12.9% and 9.2%, respectively. Compared with W2N2D1, the grain yield of W1N1D1 was decreased by 12.3%, but there was no significant difference between W2N2D1 andW1N1D2 treatments. Under the reduced water and nitrogen supply, increasing density could compensate the negative effect on the decrease of yield was mainly attributed to promoting the dry matter accumulation from early-filling to maturing stage and improving panicle number significantly. Compared with W2N2D1, the dry matter accumulation of W1N1D2 was increased by 5.8% from the early-filling to maturing stage of maize, but there were no significant differences on Vmax (maximum rate of dry matter accumulation), Vmean (mean increase rate of dry matter accumulation), Tm (the days of the maximum rate), and HI (harvest index) between W1N1D2 and W2N2D1 treatments. Compared with W2N2D1, the spike number of W1N1D2 was increased by 24.7%, but the number of kernels per spike and 1000-kernel weight of W1N1D2 were decreased by 19.3% and 14.8%, respectively. The grain yield of W1N2D2 was 13.9% higher than W2N2D1. When the nitrogen application rate was unchanged, the main reasons for the reduced irrigation, increasing density, and stable yield were the increase of dry matter accumulation, Vmean, HI, and the panicle number. Compared with W2N2D1, W1N2D2 increased panicle number, dry matter accumulation, Vmean and HI by 24.8%, 10.2%, 8.4%, and 4.7%, respectively, but there was not significant difference in 1000-kernel weight between W1N2D2 and W2N2D1 treatments. In conclusion, increasing planting density by 30% under the simultaneous reduction of water and nitrogen in the experiment was a feasible measure to save water and nitrogen for stable and high yield of maize in oasis irrigation areas. Increasing planting density by 30% was a feasible measure to save water and increase yield of maize when irrigation water was reduced by 20% while maintaining N application rate [ABSTRACT FROM AUTHOR]

Dryland agriculture, with wide distribution and high yield potential, plays an important role in ensuring food security in China. It is currently limited by water scarcity, soil depletion, water and soil loss, and low non-renewable resource-use efficiency. Green manure has the potential to improve growth environment of crops and promote sustainable high-yield crops by increasing soil quality, balancing soil nutrients, and enhancing soil water-storage capacity. In addition, green manure has ecological benefits, including enhancing agroecosystem biodiversity, increasing soil surface cover degree, reducing ineffective nutrient loss to environment, improving air balance of farmland systems, and biological control of diseases, insect pests, and weeds. Under current scenario of intensified global climate change, environmental deterioration, and agricultural product demand changes, the traditional agronomic techniques of using green manure as a fertilizer cannot satisfy the requirements of agricultural development. Thus, it is necessary to strengthen the selection and bree-ding of green manure genetic resources for dryland agriculture, to develop a new regionalization of green manure, and to establish a cropping pattern based on green manure suitable for different regions. Furthermore, it is important to study and optimize the tillage and cultivation techniques to satisfy modern production and to establish an evaluation system for the comprehensive benefits of green manure. It is needed to establish a green manure application pattern that enables resource and ecological protection for improving ecological environment and economic efficiency of dryland agriculture and provides theoretical basis and technical support for exploiting green manure benefits.

Reasonable cropping pattern can improve resource utilization efficiency, reduce environmental risks in agricultural production, and achieve the goal of resource saving coupled with high production and efficiency. We evaluated the production effects of typical cropping patterns in an arid irrigation region from several aspects, including resource utilization, carbon emissions, economic benefit, emergy self-sufficiency ratio and net emergy yield ratio, with the method of emergy theory, to provide theoretical and practical basis for the establishment of efficient cropping with lower resource investment and carbon emissions but higher yield and resource utilization efficiency combined with the sustainability of agricultural production. The results showed that, high-efficient wheat-maize intercropping production pattern (integration of no tillage with 25 to 30 cm height of wheat straw covering in the wheat strip and two-year plastic mulching in the maize strip, NTSI) had the best performance in grain yield boosting, with the yields 13.5% to 16.9% and 13.8% to 17.1% higher than that in local traditional production patterns (i.e., wheat-maize intercropping, CTI, and monoculture maize, CTM), respectively. Moreover, NTSI increased water use efficiency and solar energy use efficiency by 12.4% to 17.2% and 6.1% to 8.1%, compared to CTI, respectively. Compared to CTI and CTM, NTSI improved the effect on carbon emission reduction by decreasing total soil CO 2 emission by 618 to 895 kg·hm -2 and 1804 to 2002 kg·hm -2 with the ratio of 12.1% to 16.4% and 28.6% to 31.0%, but increased carbon emission efficiency by 29.3% to 40.1% and 58.9 to 71.4%, respectively. Meanwhile, the NTSI pattern had obvious resources saving potential. Compared with CTI and CTM, NTSI reduced total input by 1424 to 1431 yuan·hm -2 and 501 to 1547 yuan·hm -2 , with the proportional reduction being 12.6% to 13.6% and 4.9% to 14.6%; however, increased total output by 4309 to 4603 yuan·hm -2 and 8439 to 11057 yuan·hm -2 , the increased ratio was 11.2% to 11.8% and 24.4% to 36.3%; also, increased net return by 5740 to 6027 yuan·hm -2 and 9544 to 11558 yuan·hm -2 , and the improved percentage was 19.6% to 22.4% and 40.1% to 57.7%, respectively. Therefore, the high-efficient NTSI pattern had greater input-output ratio by 27.9% to 29.0% and 40.5% to 45.6% than CTI and CTM, respectively, similarly, greater benefit per cubic meter of water by 19.9% to 23.2% and 27.7% to 39.3%, respectively. The emergy self-sufficiency ratio of NTSI pattern was 57.2%, being 4.0% and 12.2% higher than CTI and CTM, respectively. NTSI pattern's net emergy yield ratio was 0.173, being 10.0% greater than CTI but 11.7% lower than CTM. With respect to resource utilization, carbon emission reduction, economic benefits and the sustainable development of high-efficient intercropping pattern, the integration of no tillage with straw covering and two-year plastic film mulching measures had higher economic activity, better function of agricultural system, greater production efficiency, and higher returns on energy value. We concluded that NTSI could be a high-efficiency farming system pattern on resources saving, carbon emission reduction, high yield and efficiency in arid oasis irrigation areas.