Salt-affected soils have poor structure and physicochemical properties, which affect soil nitrogen cycling process closely related to the environment, such as denitrification and ammonia volatilization. Biochar and polyacrylamide (PAM) have been widely used as soil amendments to improve soil physicochemical properties. However, how they affect denitrification and ammonia volatilization in saline soils is unclear. In this study, the denitrification and ammonia volatilization rates were measured in a saline soil field ameliorated with three biochar application rates (0%, 2%, and 5%, w/w) and three PAM application rates (0‰, 0.4‰, and 1‰, w/w) over 3 years. The results showed that denitrification rates decreased by 23.63–39.60% with biochar application, whereas ammonia volatilization rates increased by 9.82–25.58%. The denitrification and ammonia volatilization rates decreased by 9.87–29.08% and 11.39–19.42%, respectively, following PAM addition. However, there was no significant synergistic effect of biochar and PAM amendments on the denitrification and ammonia volatilization rates. The addition of biochar mainly reduced the denitrification rate by regulating the dissolved oxygen and electrical conductivity of overlying water and absorbing soil nitrate nitrogen. Meanwhile, biochar application increased pH and stimulated the transfer of NH₄⁺–N from soil to overlying water, thus increasing NH₃ volatilization rates. Hence, there was a tradeoff between denitrification and NH₃ volatilization in the saline soils induced by biochar application. PAM reduced the denitrification rate by increasing the infiltration inorganic nitrogen and slowing the conversion of ammonium to nitrate. Moreover, PAM reduced the concentration of NH₄⁺–N in the overlying water through absorbing soil ammonium and inhibiting urea hydrolysis, thereby decreasing NH₃ volatilization rate.

盐害土壤结构和理化性质较差，影响与环境密切相关的土壤氮循环过程，如反硝化、氨挥发等。生物炭和聚丙烯酰胺（PAM）已广泛用作土壤改良剂以改善土壤理化性质。然而，它们如何影响盐渍土中的反硝化和氨挥发尚不清楚。本研究在盐渍土田中测定了三种生物炭施用量（0%、2%和5%，w/w）和三种PAM施用量（0%、0.4%、和 1‰，w/w) 超过 3 年。结果表明，施用生物炭后，反硝化率降低了23.63%~39.60%，氨挥发率提高了9.82%~25.58%。添加PAM后，反硝化率和氨挥发率分别降低了9.87-29.08%和11.39-19.42%。然而，生物炭和PAM改良剂对反硝化和氨挥发率没有显着的协同作用。生物炭的添加主要通过调节上覆水的溶解氧和电导率以及吸收土壤硝态氮来降低反硝化率。同时，生物炭的施用增加了pH值并刺激NH ₄ ⁺ –N从土壤转移到上覆水中，从而增加了NH ₃挥发率。因此，在生物炭施用引起的盐渍土壤中，反硝化和NH ₃挥发之间存在权衡。 PAM通过增加渗透无机氮并减缓铵向硝酸盐的转化来降低反硝化率。 此外，PAM通过吸收土壤铵、抑制尿素水解，降低上覆水中NH ₄ ⁺ –N浓度，从而降低NH ₃挥发率。