Abstract
A long-term field and lysimeter experiment under different amount of fertilizer-N application was conducted to explore the optimal N application rates for a high productive rice–wheat system and less N leaching loss in the Yangtse Delta region. In this region excessive applications of N fertilizer for the rice–wheat production has resulted in reduced N recovery rates and environment pollution. Initial results of the field experiments showed that the optimal N application rate increased with the yield. On the two major paddy soils (Hydromorphic paddy soil and Gleyed paddy soil) of the region, the optimal N application rate was 225–270 kg N hm−2 for rice and 180–225 kg N hm−2 for wheat, separately. This has resulted in the highest number of effective ears and Spikelets per unit area, and hence high yield. Nitrogen leaching in the form of NO −3 -N occurs mainly in the wheat-growing season and in the ponding and seedling periods of the paddy field. Its concentration in the leachate increased with the N application rate in the lysimeter experiment. When the application rate reached 225 kg N hm−2, the concentration rose to 5.4–21.3 mgN l−1 in the leachate during the wheat-growing season. About 60% of the leachate samples determined contained NO −3 -N beyond the criterion (NO −3 -N 10 mg l−1) for N pollution. In the field experiment, when the N application rate was in the range of 270–315 kg hm−2, the NO −3 -N concentration in the leachate during the wheat-growing season ranged from 1.9 to 11.0 mg l−1. About 20% of the leachate samples reached close to, and 10% exceeded, the criterion for N pollution. Long-term accumulation of NO −3 -N from leaching will no doubt constitute a potential risk of N contamination of the groundwater in the Yangtse Delta Region.
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Wang, D., Liu, Q., Lin, J. et al. Optimum Nitrogen Use and Reduced Nitrogen Loss for Production of Rice and Wheat in the Yangtse Delta Region. Environmental Geochemistry and Health 26, 221–227 (2004). https://doi.org/10.1023/B:EGAH.0000039584.35434.e0
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DOI: https://doi.org/10.1023/B:EGAH.0000039584.35434.e0