Effects of nitrification/urease inhibitors and biochar on nitrogen conversion in soil irrigated with digested slurry

The addition of nitrification/urease inhibitor or biochar to chemical nitrogen fertilizer can reduce nitrate leaching loss or gas loss, but the application of new fertilizers based on organic nitrogen and inorganic nitrogen compound systems to reduce nitrogen loss is relatively rare. In this study, different types of inhibitors and combinations of inhibitors were set under the premise of the same amount of nitrogen application:Single application of digested slurry (CK), single application of urea (U), digested slurry+dicyandiamide (DCD), digested slurry+hydroquinone (HQ), digested slurry+dicyandiamide+hydroquinone (DCD+HQ), and digested slurry+biochar (B) to explore the extent of nitrogen conversion in soil irrigated with digested slurry after nitrification/urease inhibitor or biochar application. The results showed that the cumulative emission inhibition rate of soil N2O-N was in the order DCD+HQ > HQ > DCD > B, and the inhibition rates were 21.97%, 19.39%, 18.55%, and 10.71%, respectively. The soil nitrogen mineralization rate was in the order DCD+HQ > DCD > HQ > B > CK > U, and the soil nitrogen nitrification rate from high to low was in the order CK > HQ > B > DCD+HQ > DCD > U. It is suggested that the combined model of DCD+HQ inhibitors is more conducive to preventing and controlling the loss of soil nitrogen in the process of digested slurry irrigation.