Sunday, June 12, 2011

Quantifying economically and ecologically optimum nitrogen rates for rice production in south-eastern China
Abstract: China consumes 32% of the world's total synthetic fertilizer nitrogen (N). Overuse of fertilizer N has become widespread, resulting in severe environmental problems. Based on a set of statistical models, we quantified the optimum N rates for rice production in terms of economic and ecological benefits. Model fitting results suggested that the dependence of rice yield, N uptake and N loss on fertilizer N application rates can be well determined by a quadratic polynomial function, a logistic function and a power function, respectively. Using these functions, the economically optimum and ecologically optimum N rates in south-eastern China were estimated to be 180–285 kg ha−1 and 90–150 kg ha−1, respectively, depending on rice subspecies, varieties and cropping systems. A case study in Jiangsu Province, where single rice with conventional japonica varieties is dominated, suggested that current N rates (not, vert, similar390 kg ha−1) could be cut by 26% and 61% when the economically and ecologically optimum N rates, respectively, are adopted, saving 189 × 103 and 442 × 103 metric tons per year, respectively. Cutting one-third of the N use would not reduce rice yield but is expected to mitigate negative environmental impact in this province.

by Jing Chen 1, Yao Huang 1 and 2 and Yonghua Tang 3
1. College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China
2. State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
3. Shanghai Agricultural Science and Technology Service Center, Shanghai 200335, China
Agriculture, Ecosystems & Environment via Elsevier Science Direct
Article in Press, Corrected Proof; Available online 31 May 2011.
Keywords: Fertilizer nitrogen use; Rice production; Economically optimum; Ecologically optimum; Environment; China

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