Comparative effectiveness of zeolite and rice husk biochar in mitigating NH₃ and N₂O emissions as linked to the nitrogen use efficiency of pig slurry during the vegetative growth of Brassica napus

Abstract Ammonia (NH 3 ) and nitrous oxide (N 2 O) emitted from the pig slurry (PS)-applied soil lead not only to the risk of environmental pollution, but also to the loss of plant nutritional nitrogen (N). This study aimed to compare the effectiveness of zeolite and rice husk biochar (RHB) in mitigating the N losses via NH₃ and N 2 O emissions from PS-amended soils, and N use efficiency (NUE) for vegetative growth of oilseed rape ( Brassica napus L.). Both zeolite and RHB application significantly reduced NH 3 and N 2 O emissions from the PS-applied soil and improved the NUE for the vegetative growth. When compared the effectiveness of two materials, RHB application has more positive effectiveness in soil pH buffering, urease activity, organic acid content and NH 4 + content in soil throughout the experimental period, resulting in a higher mitigation of NH 3 and N 2 O emissions as well as NUE for dry matter (DM) and crude protein (CP) production. The enhanced NH 4 + content in soil closely related to the reduction of NH 3 and N 2 O emissions, and with improved NUE for DM and CP production. A superior performance of RHB relative to zeolite is attributed mainly to a stronger capacity of NH 4 + adsorption by higher oxygen-containing functional groups on its surface, and in part to the supply of bioavailable carbon derived from RHB leading to an increase in urease activity and soil organic acid content. Therefore, RHB can be considered a more promising amendment than zeolite for simultaneously mitigating gaseous N losses and enhancing NUE in oilseed rape cultivation. Graphical abstract