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Optimized fertigation maintains high yield and mitigates N2O and NO emissions in an intensified wheat–maize cropping system

Zhang, Xin, Meng, Fanqiao, Li, Hu, Wang, Ligang, Wu, Shuxia, Xiao, Guangmin, Wu, Wenliang
Agricultural water management 2019 v.211 pp. 26-36
Triticum aestivum, Zea mays, agricultural soils, corn, crop yield, cropping systems, denitrification, emissions factor, fertigation, field experimentation, flood irrigation, greenhouse gas emissions, irrigation water, microirrigation, nitric oxide, nitrification, nitrogen, nitrogen fertilizers, nitrous oxide, nutrient use efficiency, water conservation, water use efficiency, winter wheat, China
Agricultural soil is a major source of N2O and NO. In this study, we tested whether optimized N fertigation and water-saving irrigation methods could improve nutrient and water use efficiency while maintaining productivity in the intensified farmed winter wheat (Triticum aestivum L.)–summer maize (Zea mays L.) cropping system of northern China. A field experiment was conducted to test different flood irrigation (FN600, conventional N fertilization of 600 kg N ha−1 yr−1 and flood irrigation; FN0, no N input and flood irrigation) and drip fertigation (N0, no N input and drip irrigation; N420, optimized N fertilization of 420 kg N ha−1 yr−1 and drip irrigation; N600, conventional N fertilization of 600 kg N ha−1 yr−1 and drip irrigation) treatments. Compared with the FN600 treatment, the N600 treatment reduced water use by 62.5% (wheat season) and 36.4% (maize season). The N600 treatment significantly reduced N2O emissions (by 19.9%) during the maize season, but not during the wheat season. The N600 treatment increased NO emissions by 20.9% and 11.0% during the wheat and maize seasons, respectively. Compared with the N600 treatment, the N420 treatment significantly decreased N2O and NO emissions by 21.8% and 29.8%, respectively, during the wheat season, and by 31.5% and 41.6%, respectively, during the maize season, while achieving higher crop yield. The direct emission factors (ratio of the cumulative N2O or NO emissions of fertilized treatment minus CK to N rate) of N2O and NO were 0.19%–0.25% and 0.21%–0.27% for the wheat season and 0.38%–0.63% and 0.34%–0.42% for the maize season, respectively. Optimal fertilization (N420) significantly increased the water use efficiency, intrinsic water use efficiency, partial factor productivity, and apparent nitrogen use efficiency in both the wheat and the maize seasons. In addition to nitrification, nitrifier denitrification contributed to the generation and diffusion of N2O and NO, especially during the summer maize season. Considering the higher productivity, more efficient use of irrigation water and nitrogen, and lower N2O and NO emissions, drip irrigation combined with optimized N fertilization is recommended in northern China.