3,4-Dimethylpyrazole Phosphate (DMPP) Reduces Nitrogen Leaching in Three Tropical Soils and Improves the Agronomic Efficiency of Nitrogen Fertilizers Applied to Cotton

Nitrification inhibitors applied to soil could reduce nitrogen (N) fertilizer leaching losses by delaying the nitrification process via enhanced N fertilizer management. Thus, we investigated the agronomic efficiency of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) applied in three tropical soils (Typic Quartzipsamment, Typic Hapludox and Rhodic Hapludox) cultivated with cotton plants, evaluating the fate of N (NH 4 + -N, NO 3 − -N, and total N in leached water and soil), N accumulation and N use efficiencies (agronomic, physiological, and recovery efficiencies). Five treatments were tested with each treatment consisting of two N sources applied, urea (U) and ammonium sulfate nitrate (ASN), either with or without DMPP application; an additional control treatment (absence of N application) was also tested. Leaching columns were used to assess NH 4 + -N and NO 3 − -N losses. DMPP improved the recovery efficiency from applied U and ASN fertilizers by reducing NO 3 − -N and NH 4 + -N leaching, leading to enhanced N acquisition from fertilizer and augmenting plant N accumulation and biomass. We found that agronomic efficiency in cotton plants increased from 4 to 52% with the DMPP + ASN source relative to ASN along the soil types. In addition, DMPP use increased agronomic efficiency from urea application from 32 to 91% relative to conventional urea. The use of DMPP would benefit from more urea than ASN mainly in sandy-textured soils, where the leaching losses were observed to be increased. The reduction in NO 3 − -N and NH 4 + -N losses highlights the potential of DMPP to mitigate the impact of N-based fertilizer application on N leaching, thereby improving agronomic efficiency, N uptake, and cotton growth–related responses under tropical soil conditions.