Abstract: Nitrification inhibitors play a critical role in the migration and transformation of nitrogen in agricultural soils. Using soil column simulations, we investigated the effects of different fertilization treatments on nitrogen transformation and leaching potential in typical yellow soil in a karst region. There were five treatments, including conventional nitrogen fertilizer, conventional nitrogen fertilizer with nitrification inhibitor DMPP, 120% nitrogen fertilizer with nitrification inhibitor DMPP, 80% nitrogen fertilizer with nitrification inhibitor DMPP, and conventional nitrogen fertilizer with nitrification inhibitor DMPP and phosphate fertilizer. The results showed that soil nitrification was inhibited by DMPP. Compared to the conventional fertilization condition, nitrate concentration was reduced by 34.8%±4.2%. The nitrogen reduction strategy (80% of the conventional fertilization amount) combined with DMPP application resulted in a 56.4%±6.1% decrease in nitrate leaching compared to conventional fertilization. The addition of phosphate fertilizer increased nitrate concentration in the soil leachate by 56.2%±5.4% compared to the application of urea and DMPP alone, indicating that phosphorus addition has an inhibitory effect on the function of DMPP. In summary, DMPP application in karst regions can inhibit soil nitrification, effectively reduce nitrate leaching and the risk of groundwater nitrogen pollution, which is of great significance for water resource management and ecological environment protection in karst agricultural soils.

Key words: karst, DMPP, reduced nitrogen fertilizer application, nitrogen loss