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Determining the optimal nitrogen rate for summer maize in China by integrating agronomic, economic, and environmental aspects
oleh: G. L. Wang, Y. L. Ye, X. P. Chen, Z. L. Cui
Format: | Article |
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Diterbitkan: | Copernicus Publications 2014-06-01 |
Deskripsi
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 (N<sub>r</sub>) 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 (N<sub>agr</sub>, N<sub>eco</sub>, and N<sub>ecl</sub>, respectively) averaged 289, 237, and 171 kg N ha<sup>−1</sup>, respectively. N<sub>ecl</sub> management increased net benefit by 53% with a 46% decrease in total environmental costs, and a 51% decrease in N<sub>r</sub> loss intensity from N fertilizer use (47, 65, and 38% for N<sub>2</sub>O emission, N leaching, and NH<sub>3</sub> volatilization, respectively) and maintained grain yield, compared with N<sub>agr</sub> management. Compared with N<sub>eco</sub> management, N<sub>ecl</sub> increased net benefit by 12%, with a 31% decrease in total environmental costs and a 33% decrease in N<sub>r</sub> loss intensity from N fertilizer use, and maintained economic benefit and grain yield. No differences in N<sub>ecl</sub> were observed between soil types or years, but significant variation among counties was revealed. N<sub>ecl</sub> increased with the increase in N-derived yield with an <i>R</i><sup>2</sup> of 0.83. In conclusion, N<sub>ecl</sub> was primarily affected by N-derived yield and could enhance profitability as well as reduce N<sub>r</sub> losses associated with the maize grain yield.