Analysis of Emergy–Economy Coupling in Maize Farmland Ecosystems Under Nitrogen and Phosphorus Reduction and Optimization of Fertilization Schemes

This study optimizes fertilization schemes through the emergy analysis of different nutrient reduction treatments in maize cropping ecosystems in Xinjiang, thereby providing technical support for improving chemical fertilizer use efficiency and maintaining the stability of farmland ecosystems. The study was conducted in 2024 at Huaxing Farm in Changji Hui Autonomous Prefecture, Xinjiang Uyghur Autonomous Region. The experiment used the local conventional nitrogen and phosphorus fertilization rates as the control treatment N0P0 (applying P 183 kg·hm−2 and N 246 kg·hm−2), with eight different N and P nutrient reduction treatments: N0P1 (10% reduction in P only), N0P2 (20% reduction in P only), N1P0 (10% reduction in N only), N2P0 (20% N reduction), N1P1 (10% N and P reduction), N1P2 (10% N and 20% P reduction), N2P1 (20% N and 10% P reduction), and N2P2 (20% N and P reduction). Each treatment was replicated three times. Based on biomass data of maize plant components under different fertilization treatments, emergy analysis of farmland ecosystems and integration of economic benefit indicators led to the optimization of an optimal fertilization scheme. Results indicate that the N0P1 treatment performed optimally: maize plant biomass reached 251.09 g, significantly higher than other treatments. The N0P1 treatment exhibited the highest energy output (3.23 × 1016 sej·hm−2), the highest net energy yield ratio (EYR) of 1.45, and an energy sustainability index (ESI) of 3.34, representing a high level. It also delivered the highest economic benefit, with a net profit of 8571.95 CNY·hm−2 and a production–investment ratio of 1.71. In conclusion, the N0P1 treatment (10% reduction in phosphorus alone) demonstrated superior performance in biomass yield, energy utilization efficiency, ecological sustainability, and economic benefits, making it the optimal fertilization strategy for maize fields in this region.