In the arid irrigated areas of northwest China, monoculture cropping systems, high dependence on nitrogen fertilizer, and inadequate farmland protection have led to degraded soil quality and reduced farmland productivity, severely constraining crop yield improvement and sustainable production. This study integrated intercropping with leguminous crop, nitrogen reduction, and biochar application to investigate their synergistic effects on maize dry matter accumulation and distribution characteristics, maize yield, and yield stability, aiming to provide a theoretical basis and technical support for establishing a green and efficient sustainable maize production model in this region.

The experiment was conducted from 2022 to 2024 at the Oasis Agriculture Comprehensive Experimental Station of Gansu Agricultural University. A split-split-plot field experiment was employed, with the main plots assigned to cropping patterns (maize ǁ fresh-edible pea, IM; sole maize, SM), the subplots to nitrogen application levels (conventional rate N₁, 360 kg·hm^-2; reduced nitrogen by 30% N₂, 250 kg·hm^-2), and the sub-subplots to biochar treatments (application, C, 15 t·hm^-2; no application, B). Indicators including maize dry matter accumulation and distribution, grain yield, and yield stability were systematically measured.

Compared with monocropping, the intercropping pattern significantly increased maize grain yield, dry matter accumulation, and yield stability. Reducing nitrogen by 30% significantly decreased maize dry matter accumulation, maximum growth rate, ear dry matter allocation ratio, and grain yield, but biochar application effectively mitigated these negative effects. Biochar increased the maximum aboveground dry matter growth rate by 6.7%-33.7% for maize ǁ fresh-edible pea and by 9.4%-24.1% for sole maize, respectively. Under intercropping conditions, the treatment with 30% nitrogen reduction combined with biochar application (IMN₂C) showed no significant differences in grain yield, dry matter accumulation dynamics, and yield stability compared to the full nitrogen rate treatment (IMN₁C) and was significantly superior to other treatment combinations, and compared to the conventional nitrogen application without biochar in monocropped maize (SMN₁B), this treatment increased grain yield by 17.0%-19.2%. The underlying mechanism primarily involved biochar promoting maize root growth by increasing soil organic carbon and total nitrogen content, optimizing the root-to-shoot ratio, thereby ensuring efficient dry matter accumulation throughout the entire growth period. Particularly during the critical grain-filling stage, it maintained a high growth rate and promoted the preferential allocation of dry matter to the ears.

In the arid irrigated areas of northwest China, the integration of maize fresh-edible pea intercropping and biochar application, along with a 30% reduction in nitrogen fertilizer input, can effectively maintain maize yield and yield stability by improving soil fertility, promoting root development, and optimizing dry matter partitioning. This approach represents a feasible agronomic strategy for achieving synergistic reduction of chemical nitrogen fertilizer use and stable maize production in the region.

To address water scarcity in oasis irrigation areas and issues such as excessive nitrogen fertilizer application and low water use efficiency in maize production, this study investigated the effects of biochar combined with slow-release fertilizers on maize soil water use characteristics under reduced nitrogen application, so as to provide the practical evidence for high maize yields and efficient water resource utilization.

A split-plot design was employed. The main plots featured soil conditioner (biochar (B)) and no conditioner (C). Split plots included two nitrogen fertilizer types: traditional chemical nitrogen fertilizer (T) and slow-release nitrogen fertilizer (S). Sub-split plots tested two nitrogen application rates: traditional nitrogen application rate (N2: 360 kg·hm^-2), and a 30% reduced traditional nitrogen application rate (N1: 252 kg·hm^-2). This study investigated the effects of biochar combined with slow-release fertilizer on maize yield, water consumption, and water use efficiency under reduced nitrogen application during the 2023-2024 growth season.

Applying biochar with slow-release fertilizer to reduce nitrogen application (BSN1) increased pre-sowing soil water storage capacity in nitrogen-reduced maize and lowered maize water consumption throughout its entire growth stage. Regarding pre-sowing soil water storage, biochar increased by 5.3%-6.5% compared with no conditioner; no significant differences were observed between slow-release fertilizer and traditional chemical nitrogen fertilizer, nor between reducted nitrogen application and traditional nitrogen application rates (P>0.05). Compared with traditional chemical nitrogen fertilizer application rate without soil conditioner (CTN2), BSN1 increased pre-sowing soil water storage by 11.1%-12.5%. Biochar reduced water consumption during the maize sowing to jointing stage and the big flare to flowering stage by 6.4%-6.7% and 4.6%-5.5%, respectively, though the evapotranspiration modulus showed no significant differences. Slow-release fertilizer reduced maize water consumption from sowing to maturity by 8.1%-10.0%, but only lowered the evapotranspiration modulus during the sowing to flowering stage. Reduced nitrogen application decreased water consumption during the big flare stage to flowering stage by 6.3%-7.5%, with no significant difference in the evapotranspiration modulus. Comprehensive analysis of soil conditioner, nitrogen fertilizer type, and nitrogen application rate showed that BSN1 reduced maize water consumption by 21.4%-29.5% and the evapotranspiration modulus by 6.3%-7.6% compared with CTN2 during the sowing to flowering stage, water consumption decreased by 8.0%-9.9% during flowering to maturity stage, while the evapotranspiration modulus showed an upward trend. The combination of biochar and slow-release fertilizer effectively coordinated water supply and demand during different growth stages of nitrogen-reduced maize. Consequently, maize under BSN1 exhibited a 13.6%-14.8% reduction in total water consumption compared with CTN2, with grain yield and water use efficiency increasing by 8.6%-9.1% and 24.1%-24.7%, respectively.

The application of biochar combined with slow-release fertilizer and reduced nitrogen rates significantly increased maize grain yield and water use efficiency compared with traditional chemical nitrogen fertilizers without soil conditioners at traditional nitrogen application levels. This approach served as a viable technology for nitrogen-saving, yield-enhancing, and water-efficient maize production in the Hexi Oasis irrigation areas.

Aiming at the issues of insufficient input of organic matters and high reliance on nitrogen fertilizers of wheat production in the Qinghai Plateau, the study investigated the influences of different incorporation methods of green manure after wheat combing nitrogen fertilizer reduction on wheat yield and soil quality, so as to provide the theoretical basis and practical guidance of efficiently and sustainably producing wheat in this area.

The experiment was conducted in the experimental field of the Academy of Agriculture and Forestry Sciences of Qinghai University from 2022 to 2023. A split plot design was adopted, and three nitrogen application levels were set up in the main plot of wheat season: conventional nitrogen application (225 kg·hm^-2, N2), nitrogen reduction by 30% (158 kg·hm^-2, N1), and no nitrogen application (N0). The subplot was setup as three green manure incorporation methods in the previous season: only green manure root returning (RR), overground straw returning via sheep digest combined with root returning (SDRR), and overground straw and root returning (OSRR).

The content of soil organic matter, total nitrogen, ammonium nitrogen, available phosphorus, and available potassium of treatment nitrogen reduction by 30% and overground straw returning via sheep digest combined with root returning (N1SDRR) were increased by 10.3%, 8.6%, 23.8%, 9.1%, and 8.4%, respectively, than those under nitrogen reduction by 30% and overground straw and root returning (N1OSRR). Meanwhile, the content of soil nitrate nitrogen under N1SDRR was 4.4% and 11.3% lower than that of treatment conventional nitrogen application and overground straw returning via sheep digest combined with root returning (N2SDRR) and N1OSRR, respectively. Additionally, the activities of soil alkaline phosphatase, sucrase, and urease under N1SDRR treatment were increased by 8.5%, 10.2%, and 3.7%, respectively, compared with the N1OSRR treatment; however, the activity of soil catalase was 7.1% and 10.0% lower than that under N2SDRR and N1OSRR, respectively. The soil quality index of the N1SDRR treatment was the highest (0.79), showing no significant difference from the N2SDRR treatment, but significantly increasing by 72.0% compared with the N1OSRR treatment. Furthermore, SDRR significantly enhanced the grain yield of wheat by 28.1% and 7.3% compared with RR and OSRR, respectively, and no yield reduction occurred even 30% nitrogen fertilizer was reduced. Linear regression analysis demonstrated a significant positive correlation between the soil quality index and yield. The random forest model indicated that the main factors influencing soil quality index were soil organic matter, available phosphorus, ammonium nitrogen, and total nitrogen, while the main factors influencing grain yield of wheat were soil organic matter, total nitrogen, ammonium nitrogen, available phosphorus, and urease activity.

Under the condition of 30% reduction of nitrogen fertilizer, the overground straw returning via sheep digest combined with root returning could effectively improve soil quality and wheat grain yield by reducing soil bulk density, increasing soil organic matter, total nitrogen, ammonium nitrogen, available phosphorus, available potassium content and alkaline phosphatase, urease and sucrase activity, which was a suitable management measure for sustainable wheat production in this area.

In the oasis irrigated agricultural region, the low resource utilization efficiency and the ratio of output/input are the most prominent constraints for crop production. In this study, the characteristics of light use efficiency, irrigation water productivity and economic benefit in different cropping patterns were investigated in the areas. Research on the sustainability of different cropping patterns would benefit crop production to save cost and increase income in this region.

A field experiment was carried out in a typical arid irrigation area, Wuwei, Gansu province, from 2018 to 2020, to determine the effects of different cropping patterns on leaf area duration, grain yields light utilization efficiency, irrigation water productivity and economic benefit of crops. The sustainability of different cropping patterns was evaluated based on the above indexes.

Multiple cropping of green manure after spring wheat harvested significantly increased the leaf area duration of the main-cultivate crops during the whole growth period. W-G//M increased leaf area duration of the main-cultivate crops by 7.7%-7.8%, compared with W//M. Compared with sole cropping and spring wheat-green manure multiple cropping, the intercropping increased the grain yield of main-cultivate crops and the inputs of production cost, simultaneously. There was no significant difference in the total grain yield between W-G//M and W//M in 2018 and 2019. However, W-G//M increased the total grain yield by 8.7% in comparison to W//M in 2020. Compared with M, W-G and W, W-G//M increased net return by 16.7%-26.5%, 78.5%-132.2% and 35.9%-78.8%, respectively. In two intercropping patterns, the net return of the W-G//M decreased by 7.2% in comparison to W//M treatment in 2018. However, the net return of two intercropping treatments showed not significantly different in 2019 and 2020, and the ratio of output/input showed a similar result. Multi-planting green manure after wheat harvested could significantly improve the light use efficiency of crops. W-G//M treatment increased light use efficiency by 7.2%-14.1% compared with W//M. The light use efficiency under W-G was increased by 23.5%-52.1% in comparison to W treatment. Compared with W, the productivity of irrigation water under W-G was significantly reduced by 48.6%-54.3% (irrigation water use efficiency) and 30.9%-39.8% (Economic benefit per cubic meter irrigation water), while there was no significant difference in the productivity of irrigation water under W-G//M and W//M. W-G//M had the highest sustainability index across three years.

Grain yield of main-cultivate crops and economic benefits were improved by intercropping and multiple cropping green manure after wheat harvested. The irrigation water productivity and light utilization efficiency were also increased, thereby improved the sustainability of this cropping pattern. Therefore, multiple cropping green manure after wheat harvested in wheat/maize intercropping could be used as a high-efficient utilization of resources and sustainable cropping pattern in arid irrigation areas.

The problem for film-mulched maize in the oasis irrigation region was an advanced nitrogen (N) requirement and led to the insufficient supply of N at the late growth stages. In this study, the effects of N-fertilizer postponing application on intercropped maize photosynthetic physiological characteristics and grain yield were studied, so as to reveal the photosynthetic mechanism of intercropped maize grain yield advantage in the experimental area.

From 2019 to 2021, the maize was used as experimental materials in Hexi oasis irrigation region. The split-plot experiment design was adopted, among which pea/maize intercropping and maize monoculture were the main factors, and three N fertilizer postponing application (postponing ration 20%, 10%, and traditional practice) were the secondary factors. Then, this field experiment was used to investigate the photosynthetic physiological characteristics and yield performance of maize under N-fertilizer postponing application and intercropping pattern.

The results demonstrated that the grain yield of intercropped maize under the postponing application of 20% N-fertilizer and 10% was increased by 28.5% and 13.8%, and biomass yield by 23.8% and 12.5%, respectively, compared with traditional N management practices. Similarly, compared with traditional N management practice, the grain yield of sole maize under the postponing application of 20% N-fertilizer and 10% was also increased by 29.7% and 13.3%, and biomass yield by 19.6% and 10.3%, respectively. Compared with the monoculture maize, intercropping could increase the grain yield by 33.2%-35.1% and biomass yield by 26.8%-31.5% under the same area. Furthermore, the postponing application of 20% N-fertilizer and 10% increased the population grain yield of intercropping pattern by 27.2% and 12.9%, respectively, compared with the traditional N management practice. The results showed that intercropping pattern could increase the grain yield of maize compared with the sole pattern, and the N fertilizer postponing application also boosted the improvement of grain yield in the intercropping system compared with the traditional N management practice. During the whole growth periods, the intercropping increased the net photosynthetic rate, stomatal conductance, transpiration rate, and decreased intercellular CO₂ concentration. Compared with traditional N management, the net photosynthetic rate under the postponing application of 20% N-fertilizer and 10% was increased by 12.8% and 6.0%, the stomatal conductance by 14.0% and 6.9%, and the transpiration rate by 20.5% and 9.5%, respectively, while the intercellular CO₂ concentration was decreased by 29.8% and 13.1%, respectively. The SPAD value under the postponing application of 20% N-fertilizer and 10% was increased by 7.5% and 3.7%, respectively. The principal component analysis results showed that the N-fertilizer postponing application and intercropping pattern could increase the grain yield via boosting the net photosynthetic rate, the stomatal conductance, the transpiration rate, and leaf SPAD value, and decreasing intercellular CO₂ concentration.

N-fertilizer postponing application 20% treatment (36 kg·hm^-2 N fertilizer was topdressing at maize jointing stage and 108 kg·hm^-2 at 15 d post-silking stage) had the advantage of improving the photosynthetic characteristics of intercropped maize, thereby boosting the grain yield improvement.