Objective The coordinated enhancement of nitrogen (N) fertilizer reduction and crop yield in farmland soils is a key technique for achieving agricultural resource conservation and food security. This study aimed to investigate the effects of applying N fertilizer inhibitors combined with organic materials on the availability of effective N and crop yield.

Method A field experiment was conducted in brown earth in Shenyang, Liaoning Province, China, with seven treatments: no fertilization (CK), conventional fertilization (N), conventional fertilization + urease inhibitor (NBPT) + nitrification inhibitor (DMPP) (NY), conventional fertilization + biochar (NC), conventional fertilization + biochar + NBPT + DMPP (NCY), conventional fertilization + straw incorporation (NJ), and conventional fertilization + straw incorporation + NBPT + DMPP (NJY). Ammonium N (NH₄₃-N) and nitrate N (NO₃⁻-N) contents in the 0 - 20 cm soil layer during maize growth, nitrate N content in the 0 - 100 cm soil layer after harvest, and maize yield were measured. The effects of different treatments on soil available N and crop yield were analyzed.

Result Regardless of whether straw or biochar was applied, the addition of inhibitors significantly reduced the NH₄₃-N and NO₃⁻-N contents in the surface soil (0-20 cm) during the early growth period of maize (5 - 35 days after fertilization), and increased the NH₄₃-N and NO₃⁻-N contents in the surface soil (0 - 20 cm) during the later growth period (60 ~ 120 days after fertilization), with the most significant effect observed in the conventional fertilization + inhibitor + straw treatment (NJY). Additionally, the inhibitor + straw treatment (NJY) also significantly increased the NO₃⁻-N content in the 0 - 20 cm soil layer and reduced the NO₃⁻-N content in deeper soil layers. The sequence of soil NO₃⁻-N content from high to low across treatments was: NJY > NCY > NY > NJ > NC. Furthermore, the NJ and NC treatments significantly increased maize yield, with increases of 27.9% and 31.6%. While the corresponding treatments with inhibitors (NJY and NCY) resulted in a slight decrease in maize yield (2.9%-3.6%), they significantly reduced the risk of N leaching.

Conclusion Under conventional fertilization, the combined application of urease/nitrification inhibitors with straw incorporation significantly regulates N availability in soils and enhances maize yield. The results of this study can provide a reference for optimizing N fertilizer management and improving crop yield in agricultural production practices.