Enhancing Maize Yield and Resource Efficiency through Controlled-Release Nitrogen Fertilization on the Semiarid Loess Plateau

Drought stress is one of the premier limitations to global agricultural production. Increasing water and nitrogen (N) use efficiencies in dryland agroecosystems to maintain high agricultural output are key responsibilities to assure food security, especially on the semiarid Loess Plateau region of China, as it is one of the important grain production areas in China. The impact of controlled-release urea (CRU) on the soil water content, soil enzyme activities, soil N content, biomass accumulation, grain yield, water use efficiency (WUE), and agronomic use efficiency of N fertilizer (AEN) were examined on the maize production of the rainfed Loess Plateau during 2020–2021. Two-growing-season field treatments at the Zhengyuan Agri-ecological Station, Qingyang, Gansu, including six N treatments, were investigated for maize: a control without N fertilization (CK) and five application proportions of CRU (i.e., 0, 30, 50, 70, and 100%CRU) under a N rate of 225 kg ha−1. Results showed that compared with common urea (0%CRU), on average, CRU applications significantly increased soil enzyme activity related to N conversion and improved biomass accumulation by 4–11% at the silking stage and by 2–12% at the maturity stage, respectively. As the proportion of CRU increased, the grain no. per ear, 100-grain weight, and harvest index first increased and then decreased. Grain yield was increased by 5.3, 11.4, 20.1, and 5.7% under 30, 50, 70 and 100%CRU, respectively, compared to common urea. Compared to common urea, 70%CRU combined with 30% common urea achieved the highest yield. These results indicate that optimal controlled-release N fertilization increases the yield and water and nitrogen use efficiencies of maize, and 70%CRU combined with 30% common urea under a single application of nitrogen fertilizer at sowing was the optimal application proportion of controlled-release urea for increasing water and nitrogen use efficiencies in dryland agroecosystems. The results of this study can provide a theoretical basis for the efficient fertilization of maize on the semiarid Loess Plateau of China.