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Effect of nitrogen fertilizer rates on carbon footprint and ecosystem service of carbon sequestration in rice production

Jiang, Zhenhui, Zhong, Yiming, Yang, Jingping, Wu, Yangxiaoying, Li, Hui, Zheng, Lin
The Science of the total environment 2019 v.670 pp. 210-217
agroecosystems, carbon, carbon footprint, carbon sequestration, ecosystem services, fertilizer rates, field experimentation, grain yield, greenhouse gas emissions, greenhouse gases, harvesting, methane production, nitrogen, nitrogen fertilizers, paddies, paddy soils, rice, sowing, system boundary, China
Optimizing nitrogen (N) fertilizer inputs in agroecosystems may be an effective strategy for reducing greenhouse gas (GHG) emissions and improving carbon (C) sequestration. Using a system boundary that started at seeding and ended at harvesting, a field experiment was established in Zhejiang, Southern China, to evaluate the effects of N fertilizer rates (0, 75, 150, 225, 300, and 375 kg N/ha) on the C footprint and ecosystem service of C sequestration in a single-crop rice production and to identify optimal N fertilizer application rates for balancing low C footprint, high ecosystem service values of C sequestration, and high rice yield. The results showed that increased N fertilizer application improved rice grain yields, but that rates above 225 kg N/ha (grain yield: 9.35 Mg/ha/crop season) had little, or even a negative, impact on rice yield. The C footprint and total GHG emissions of rice production positively correlated with N fertilizer rates. On average, methane emissions from rice paddy soils, as regulated by N fertilizer input, were the main component of total GHG emissions, which accounted for 49.5% of the total C footprint. The ecosystem service values of C sequestration changed from positive (661–233 US$/ha/crop season) to negative (−345 US$/ha/crop season) as N fertilizer rates increased, indicating that paddy fields transitioned from a net C sink at N fertilizer rates between 0 and 300 kg N/ha to a net C source at 375 kg N/ha. Within this limited system boundary, the 225 kg N/ha rate was determined to be a sustainable N fertilizer application rate for achieving high grain yield, mitigating GHG emissions, and improving C sequestration in a single-crop rice production system.