The traditional monocropping system in the Longdong Loess Hilly Region suffers from low production efficiency and underutilization of water and thermal resources. To address these limitations, this study introduced an early-maturing potato-maize rotation model aimed at breaking through the constraints of the original cropping system and fully leveraging the region's water and thermal resource potential. To further optimize the productivity and sustainability of this new model, this research focused on investigating the effects of different tillage and fertilization practices on the photosynthetic characteristics, water use, yield, and economic benefits of the potato-maize double cropping system. These findings were expected to provide the key technical support for enhancing annual farmland productivity.

During the 2023-2024 growing season, using early-maturing potato (cv. Helan 15) and early-maturing maize (cv. Kewo 028) as test materials, four treatments were established: traditional tillage (TT), traditional tillage+organic fertilizer (TTO), vertically rotary sub-soiling (VT), and vertically rotary sub-soiling + organic fertilizer (VTO). Aboveground and belowground biomass, photosynthetic characteristics, yield and yield components were measured, and water use efficiency and economic benefits were calculated too.

Compared with TT, VT and VTO treatments significantly increased aboveground biomass and tuber yield at potato maturity, as well as stalk weight and ear weight at maize maturity. VT and VTO also increased the number of tubers per plant, tuber weight per plant, and marketable tuber rate in potato, while enhancing the number of kernels per row and 100-kernel weight in maize. Under VTO, potato and maize yields reached 32 853-33 879 and 8 289-9 860 kg·hm^-2, respectively, resulting in an annual total yield (converted to grain equivalent) of 15 065-16 431 kg·hm^-2. Compared with TT, VT and VTO increased potato yield by 21.5%-24.5% and 30.4%-36.2%, maize yield by 4.2%-10.3% and 9.3%-16.2%, and total annual yield by 11.2%-15.4% and 17.8%-23.5%, respectively. Furthermore, VT and VTO synergistically enhanced photosynthetic capacity. During key growth stages of both crops, these treatments significantly increased leaf SPAD values, net photosynthetic rate, stomatal conductance, and transpiration rate, while decreasing intercellular carbon dioxide (CO₂) concentration and improving instantaneous water use efficiency. Specifically, VT and VTO improved water use efficiency in potato by 15.4%-19.6% and 21.3%-32.5%, and in maize by 7.3%-10.4% and 13.4%-15.3%, respectively. Annual precipitation use efficiency increased by 3.0%-3.1% under VTO and 2.7%-3.4% under VT. Economically, VTO and VT increased net income by 19.9%-31.8% and 32.7%-40.5% compared with TT, though VTO was 6.3%-9.6% lower than VT. With the exception of economic returns, VTO outperformed VT in all other metrics evaluated and demonstrated greater potential for soil improvement, supporting its role in advancing agricultural sustainability.

In promoting the early-maturing potato–maize double cropping system in the Longdong Loess Hilly Region, the combination of vertically rotary sub-soiling with organic fertilizer (VTO) represented the most effective approach for synergistically enhancing crop productivity and ecological benefits. This practice not only provided robust support for the stable implementation of the potato–maize double cropping system but also contributed to achieving the high-yield goal of an annual "ton-grain hectare" (10 000 kg·hm^-2). Although the economic return of VTO was slightly lower than that under VT in the short term, it demonstrated significant technical value and long-term potential in promoting efficient and sustainable use of resources in regional dryland farming systems.

The field experiment was conducted from 2018 to 2020, in order to determine the optimized fertilization amount and methods of spring wheat, and to improve yield and water use efficiency on rain-fed area of northwest China.

The spring wheat (Longchun 35) was selected as test material. Three fertilization depths with nitrogen reduction application included shallow application (PM-N), deep application (PMD), and layered application (PMA), and the control was traditional nitrogen shallow application (PM). The soil water content in 0-300 cm profile, aboveground biomass, leaf SPAD value, canopy temperature and leaf area index (LAI) in different growth stages, as well as grain yield of wheat were recorded. The soil water storage (SWS), periodical evapotranspiration (ET), water use efficiency (WUE), plant nitrogen accumulation (PNA) and nitrogen partial productivity (PFPN) were calculated to understand the effects of the deeper and layered application of chemical fertilizer on nutrient and water utilization from the aspect of soil moisture, canopy development and grain yield.

PMA and PMD significantly regulated the process of water consumption during the growth period of spring wheat. From seedling to jointing stage, the water consumption in 0-300 cm profile of PMA and PMD increased by 11.8-20.4 mm and 15.1-25.4 mm compared with PM, respectively, and increased by 10.7-14.6 mm and 9.3-20.0 mm compared with PM-N, respectively. From heading to filling stage, the water consumption increased by 15.1-39.8 mm and 16.5-26.5 mm compared with PM, increased by 18.1-48.7 mm and 19.5-35.4 mm compared with PM-N, respectively. Correspondingly, the average SPAD value, LAI and biomass during the growth period of spring wheat of PMA and PMD were increased by 7.2% and 4.2%, 23.0% and 19.4%, 34.6% and 17.8% compared with PM, respectively, and increased by 7.6% and 5.4%, 17.7% and 10.8%, 38.5% and 23.4% compared with PM-N, respectively. However, the canopy temperature of PMA after jointing, and that of PMD after heading was decreased by 8.5% and 4.5% compared with PM, respectively, and decreased by 8.6% and 4.8% compared with PM-N, respectively. The grain number was increased by 4.3% and 4.0% compared with PM, respectively, and increased by 4.8% and 4.2% compared with PM-N, respectively. The spike number was increased by 10.1% and 6.2% compared with PM, respectively, and increased by 11.0% and 7.8% compared with PM-N, respectively. The yield, WUE, PNA and PFPN of PMA and PMD were increased by 10.5% and 5.1%, 11.8% and 6.2%, 48.0% and 35.7%, 38.2% and 31.3% compared with PM, respectively, and increased by 15.7% and 10.0%, 14.1% and 8.0%, 51.8% and 40.4%, 15.7% and 10.0% compared with PM-N, as compared with PM-N, respectively. The yield, WUE and PFPN of PMA were increased by 5.2%, 4.8% and 5.2% compared to PMD, respectively. The significant difference of the indices between PM-N and PM were not observed, except the PFPN of PM-N was significantly increased by 21.0% compared to PM.

While the amount of chemical N application was reduced from 150 kg·hm^-2 to 120 kg·hm^-2, both PMD and PMA could increase the grain yield, nitrogen and water utilization, which should be widely extend on the northwest loess plateau.