Biochar modified water-retaining agent polyacrylamide reduced NO but not N2O emissions from Camellia oleifera plantation soil

Camellia oleifera , an important woody oil crop, is primarily grown in the acidic laterite regions. As an economic plantation distributed in subtropical area where characterized by seasons with high temperature and low precipitation, ensuring adequate soil moisture is pivotal for achieving high and stable yields in C. oleifera plantation soil, which potentially impact soil gaseous nitrogen emissions associated with global climate change. However, few studies have been reported on the impact of modified water-retaining agents on soil nitrous oxide (N 2 O) and nitric oxide (NO) emissions. This study aims to investigate the effects of water-retaining agent polyacrylamide (PAM) and C. oleifera fruit shell-derived biochar-modified PAM (MP) on soil water retention ability and the emissions of N 2 O and NO from C. oleifera plantation soil. Specifically, the effects of PAM (0.4 ‰PAM, and 1 ‰PAM) and biochar-modified PAM (4 %MP, 10%MP) on the emissions of N 2 O and NO, soil physicochemical properties, and the abundance of relevant microbial functional genes in C. oleifera plantation soil was examined. The results indicated that both PAM and biochar modified PAM significantly altered soil moisture, soil physicochemical properties, and the abundance of associated microbial functional genes. Soil NO emissions were reduced by 15.90 %, 18.54 %, 16.01 %, and 30.34 % by the application of 0.4‰, 1‰, 4 % ModiPAM, and 10 % ModiPAM, respectively. The application of the modified water-retaining agents increased soil moisture, reduced soil NO emissions by affecting the abundance of functional genes involved in nitrification and denitrification processes via increases in soil pH. The application of water-retaining agents, especially MP, offers a beneficial approach to soil moisture management and the regulation of greenhouse gas emissions. The optimal ratio and application methods of water-retaining agents should be explored by future studies to maximize benefits. • Biochar modified PAM reduced NO but not N 2 O emissions from C. oleifera plantation. • Mixing biochar with PAM altered surface area, and functional groups of biochar. • Soil NH 4 + , DOC, and pH were increased by 10 % modified water-retaining agent.