Biochar one-off application for paddy soil 15N loss improvement: Evidence from a two-year experiment

Jiping Gao^1,2Yanghui Sui³Zhongcheng Zhang²Kai Zhang¹Hongfang Jiang²Yuzhuo Liu¹Zhongcheng Sun¹Xinyue Bing¹Yanze Zhao¹Wenzhong Zhang^1*

• ¹College of Agronomy, Shenyang Agricultural University, Shenyang, China
• ²Shenyang Agricultural University, Shenyang, China
• ³Corn Research Institute, Liaoning Academy of Agricultural Sciences, Shenyang, China

This study aimed to quantify the impact of one-time application of biochar on split application of nitrogen fertilizers. We used the 15N tracer technique to explore the effects of biochar on greenhouse gas (GHG) emissions and nitrogen use efficiency (NUE) during three growth stages (tillering, panicle growth, ripening). Total nine treatments incorporated three biochar treatments (0, C0; 15, C1; 45 t ha-1, C2) with three N levels (0, N0; 168, N1; conventional N fertilization, 210 kg N ha−1, N2). The high N2O emission rate during the tillering stage was significantly affected by biochar and its interaction with N fertilization in two years, with the tillering stage of 2016 yielding higher N2O emissions, constituting 15.8–65.2% of the overall emissions. Optimizing biochar focused on the tillering and panicle growth stages can help mitigate global warming potential (GWP) in the initial application. The highest rice yields in two years were N2C0 and N2C2 treatments, which were 13.0% and 8.5% higher than yield in N1C0, respectively. The base fertilizers in two years reduced the 15N loss rate (NLR) in N1C2 treatment by 49.5% and 38.6% compared with N1C0, respectively. In the This is a provisional file, not the final typeset article first year, the N recovery efficiency (NRE) of N1C2 treatment decreased by 55.2%, 44.0%, and 21.4% in base, tiller, and panicle fertilizers, respectively, compared to N1C0. Compared with the N1C0 treatment, the N2C1 significantly decreased NRE of the base fertilizers by 27.9% in the next year. No significant differences in the NRE of tiller and panicle fertilizers were observed between the N1C1 and N2C1 treatments in the next year. This study demonstrates the potential of biochar as a sustainable soil amendment for nitrogen loss in rice systems. Furthermore, this study highlights the role of biochar in mitigating GHG emissions, particularly different fertilization periods of rice, contributing to more environmentally friendly agricultural practices.