Determining the optimal nitrogen rate for summer maize in China by integrating agronomic, economic, and environmental aspects

[摘要] The concept of high yield with a goal of minimum environmental cost hasbecome widely accepted. However, the trade-offs and complex linkages amongagronomic, economic, and environmental factors are not yet well understood.In this study, reactive nitrogen (N_r) losses were estimated usingan empirical model, and an economic indicator and an evaluation model wereused to account for the environmental costs of N fertilizer production anduse. The minimum N rate to achieve the maximum yield benefit (agronomicallyoptimal N rate), maximum economic benefit (economically optimal N rate:economic benefit was defined as yield benefit minus N fertilizer cost), andmaximum net benefit (ecologically optimal N rate: net benefit was defined asyield benefit minus N fertilizer and environmental costs) were estimatedbased on 91 on-farm experiment sites with five N levels for summer maizeproduction on the North China Plain. Across all experimental sites, theagronomically, economically, and ecologically optimal N rates(N_agr, N_eco, and N_ecl, respectively)averaged 289, 237, and 171 kg N ha⁻¹, respectively. N_eclmanagement increased net benefit by 53% with a 46% decrease intotal environmental costs, and a 51% decrease in N_r lossintensity from N fertilizer use (47, 65, and 38% for N₂O emission,N leaching, and NH₃ volatilization, respectively) and maintained grainyield, compared with N_agr management. Compared withN_eco management, N_ecl increased net benefit by12%, with a 31% decrease in total environmental costs and a 33%decrease in N_r loss intensity from N fertilizer use, andmaintained economic benefit and grain yield. No differences inN_ecl were observed between soil types or years, but significantvariation among counties was revealed. N_ecl increased with theincrease in N-derived yield with an R² of 0.83. In conclusion,N_ecl was primarily affected by N-derived yield and could enhanceprofitability as well as reduce N_r losses associated with themaize grain yield.

[学科分类] 地球化学与岩石