Biochar decreased N loss from paddy ecosystem under alternate wetting and drying in the Lower Liaohe River Plain, China

Abstract

Biochar addition to soil is widely utilized to enhance carbon sequestration and reduce fertilizer N losses. However, little research has been studied on the effect of biochar on reactive gaseous N losses, N leaching and grain yield in paddy ecosystems under water stress, especially in the Lower Liaohe River Plain with a higher water percolation. Our experiment was carried out in 2020 and 2021 utilizing a split-plot design with continuously flooding irrigation and alternate wetting and drying irrigation as main plots and without biochar addition and with 20 t·ha⁻¹ rice husk-derived biochar addition as sub-plots. The results showed that alternate wetting and drying irrigation respectively, decreased N leaching and reactive N losses by 15.9 % and 11.3 % but also respectively, increased seasonal cumulative NH₃ volatilization and N₂O emissions by 5.0 % and 210 % on average. Rice husk-derived biochar addition significantly mitigated seasonal cumulative NH₃ volatilization and N₂O emissions by 8.8 % and 19.7 % in 2020, 20.7 % and 19.2 % in 2021, respectively, and decreased inorganic N leaching and reactive N losses by 8.3 % and 14.1 % in 2021. Biochar addition coupling with alternate wetting and drying respectively, mitigated cumulative NH₃ volatilization and N₂O emissions by 7.3 % and 19.3 % in 2020, and, 22.7 % and 22.0 % in 2021 as compared to that without biochar. Biochar did not differ from without biochar in inorganic N leaching under alternate wetting and drying irrigation in both years but significantly reduced reactive N losses by 17.8 % in 2021, which efficiently inhibited the alternate wetting and drying induced negative effects on the increase in reactive N losses. Therefore, biochar addition to paddy ecosystems under alternate wetting and drying could realize sustainable utilization of water resources, increase soil N fixation, and mitigate N losses.