Abstract
Abstract. The concept of high yield with a goal of minimum environmental cost has become widely accepted. However, the trade-offs and complex linkages among agronomic, economic, and environmental factors are not yet well understood. In this study, reactive nitrogen (Nr) losses were estimated using an empirical model, and an economic indicator and an evaluation model were used to account for the environmental costs of N fertilizer production and use. The minimum N rate to achieve the maximum yield benefit (agronomically optimal N rate), maximum economic benefit (economically optimal N rate: economic benefit was defined as yield benefit minus N fertilizer cost), and maximum net benefit (ecologically optimal N rate: net benefit was defined as yield benefit minus N fertilizer and environmental costs) were estimated based on 91 on-farm experiment sites with five N levels for summer maize production on the North China Plain. Across all experimental sites, the agronomically, economically, and ecologically optimal N rates (Nagr, Neco, and Necl, respectively) averaged 289, 237, and 171 kg N ha−1, respectively. Necl management increased net benefit by 53% with a 46% decrease in total environmental costs, and a 51% decrease in Nr loss intensity from N fertilizer use (47, 65, and 38% for N2O emission, N leaching, and NH3 volatilization, respectively) and maintained grain yield, compared with Nagr management. Compared with Neco management, Necl increased net benefit by 12%, with a 31% decrease in total environmental costs and a 33% decrease in Nr loss intensity from N fertilizer use, and maintained economic benefit and grain yield. No differences in Necl were observed between soil types or years, but significant variation among counties was revealed. Necl increased with the increase in N-derived yield with an R2 of 0.83. In conclusion, Necl was primarily affected by N-derived yield and could enhance profitability as well as reduce Nr losses associated with the maize grain yield.
Highlights
Nitrogen (N) is a crucial nutrient that requires careful management in intensive cropping systems because of its diverse beneficial and detrimental effects (Ju and Christie, 2011)
It is necessary to resolve the contradictions among grain yield, economic benefit, and environmental cost, forming solutions to improve N management strategies agronomically, economically, and environmentally
Under the 50 % median N rate (MN) treatment, grain yield decreased by 8.5 %, while it decreased by 7.5 % under the 200 % MN treatment
Summary
Nitrogen (N) is a crucial nutrient that requires careful management in intensive cropping systems because of its diverse beneficial and detrimental effects (Ju and Christie, 2011). The massive amounts of N that have leached into water bodies, or been lost into the atmosphere through ammonia volatilization or nitrification–denitrification (Zhu and Chen, 2002), have contributed to various environmental problems, such as the greenhouse effect, eutrophication, and soil acidification (Davidson, 2009; Guo et al, 2010; Ju et al, 2009; Reay et al, 2012; Zhang et al, 1996). It is necessary to resolve the contradictions among grain yield, economic benefit, and environmental cost, forming solutions to improve N management strategies agronomically, economically, and environmentally.
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