Nitrapyrin is primarily used as a nitrification inhibitor in agricultural practices. It is applied to soil to slow down the conversion of ammonium nitrogen into nitrate nitrogen, which helps in reducing nitrogen loss through leaching and denitrification. This ensures that crops have a more sustained supply of nitrogen, improving fertilizer efficiency and promoting healthier plant growth. Additionally, by minimizing nitrate runoff, it contributes to reducing environmental pollution, particularly in water bodies where excess nitrates can lead to issues like eutrophication.