Effects of different fertilizer application methods on soil water, nitrogen transport and maize growth in sloping farmland

To investigate the effects of different fertilizer application methods on soil water and nitrogen transport and on maize growth in sloping farmland, soil water sensing and soil water sampling devices were set up in the runoff plots to study the characteristics of soil water and nitrogen transport and maize uptake and utilization of nitrogen on different slopes in sloping farmland under the treatments of bare (CK), uniform fertilizer application (UF), and non-uniform fertilizer application (NUF). The results showed that: 1) The average soil moisture content at the footslope was the lowest at the same soil layer depth except for the 40 cm soil layer depth of CK treatment, and the degree of moisture fluctuation was the greatest at the 20 cm soil layer depth at the footslope under the combined effect of rainfall replenishment and evaporation. The coefficients of variation of soil moisture content at most observation points under non-uniform fertilization treatment were smaller than that under uniform fertilization treatment. 2) Nitrogen concentration at 20 cm depth from the surface was higher than that at 40 cm depth under each treatment except at the footslope of CK treatment. Nitrate nitrogen (NO₃⁻-N) and total nitrogen (TN) concentrations under CK treatment were lower than that under UF and NUF treatments. However, ammoniacal nitrogen (NH₄⁺-N) concentration under CK treatment was the highest, and the overall nitrogen change was the smallest. Total nitrogen concentration increased from the hilltop to the footslope under the UF treatment, and there were no significant differences in total nitrogen concentration between the hilltop, the midslope, and the footslope under the NUF treatment. 3) Corn yield, the partial factor productivity from nitrogen and nitrogen absorption rate under UF treatment showed an increasing trend from the hilltop to the footslope. The total nitrogen accumulation at the midslope under NUF treatment reached 31.507 kg∙hm⁻², which was higher than that at the footslope and the hilltop, and the maize yield also showed the highest in the midslope. The partial factor productivity from nitrogen and nitrogen absorption rate increased greatly from the hilltop to the footslope, especially the partial factor productivity from nitrogen and nitrogen absorption rate of the maize at the footslope in the first season increased by more than three times compared with that at thehilltop. 4) Compared with uniform fertilization treatment, the non-uniform fertilization treatment ensured crop yield and substantially increased the partial factor productivity from nitrogen and nitrogen absorption rate (65.0%−69.0% and 43.8%−104.2%) based on a 28.6% reduction in fertilizer application. The non-uniform fertilizer application method in sloping arable land improves crop uptake of nitrogen fertilizer by utilizing the downslope migration of nitrogen, reduces the amount of fertilizer applied while ensuring the yield, and provides a scientific basis for scientifically formulating the fertilizer application system in sloping arable land and effectively controlling the loss of nutrients.