Impact of Long-Term Inhibitors and Organic Materials Addition on Soil Microbial Carbon Use Efficiency in a Corn Field

The addition of inhibitors and organic materials in corn fields is an important measure to ensure yield and improve soil fertility. Understanding the effects of the addition of inhibitors and organic material on soil microbial carbon use efficiency (CUE) and microbial mechanisms is crucial for promoting carbon (C) sequestration in agricultural systems. This study explored the effects of the addition of inhibitors (N-(nbutyl) thiophosphoric triamide (NBPT) and 3,4-dimethylpyrazole phosphate (DMPP)) and organic materials (corn stalks and pig manure (PM)) on soil microbial CUE through a field experiment with the continuous addition of inhibitors, corn stalks, and PM incorn fieldss for 7 years. Overall, the application of inhibitors reduced soil microbial CUE by 39.20% by reducing microbial immobilization C and promoting microbial respiration, but did not affect the microbial community structure. Under inhibitor application conditions, the addition of PM improved soil microbial CUE by 37.38%, which was mainly achieved by increasing microbial immobilization C, fungal, and bacterial copies. Long-term addition of organic materials and fertilizers was beneficial to the increase in soil microbial CUE, because the input of nutrients stimulates microbial growth. Although high soil microbial CUE was beneficial to soil C sequestration, it also required appropriate exogenous organic matter addition to ensure soil organic carbon (SOC) increase. In this study, when fertilizer-containing inhibitors were used, combined application with PM was beneficial to improve soil microbial CUE and promote SOC sequestration.