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Nitrification inhibitors applied to soil can reduce nitrogen (N) fertilizer losses by delaying the nitrification process and reducing nitrate losses to environment with enhanced N-fertilizer management. In this study, laboratory-scale experiments were carried out in order to evaluate the efficiency of nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) applied on urea and ammonium sulfate nitrate (ASN) sources under three tropical soils (Typic Quartzipsamment, Typic Hapludox and Rhodic Hapludox – contrasting soil textures). Soil samples were incubated over 60 days and the content of nitrate (N-NO3−), ammonium (N-NH4+) and pH variations were assessed periodically. In addition, N-NO3− and N-NH4+ percentage and nitrification inhibition were assessed. 3,4-Dimethylpyrazole phosphate application delays the nitrification process across all three tropical soil types, being more evident in the sandy-textured soils (Typic Quartzipsamment > Typic Hapludox > Rhodic Hapludox). DMPP application reduced the N-NO3− and N-NH4+ percentage in both ASN and urea sources, mainly between 15 and 30 (ASN) and between 7 and 30 days after N fertilization (urea). However, 45 days after N fertilization, inhibition of the nitrification process by DMPP is unlikely, regardless of N source. The nitrification process tended to be more intense when conventional urea was applied compared to conventional ASN. Therefore, the use of DMPP would benefit more urea than ASN mainly in sandy-textured soils, where the nitrification was observed to be increased. [ABSTRACT FROM AUTHOR]

Purpose: The use of nitrification inhibitors could be an interesting alternative when applied to enhance nitrogen (N) fertilizer use efficiency in annual crops such as cotton under tropical soil conditions. Thus, our aim was to evaluate the efficiency of the nitrification inhibitor 3,4-Dimethylpyrazole phosphate (DMPP) in a typical tropical soil by evaluating the fate of nitrogen (N-NO3−, N-NH4+ and total N in soil and leached water), N accumulation and N recovery by cotton plants and soil. Methods: Leaching columns with cotton plants were used to assess N-NO3− and N-NH4+ losses in drainage water. The treatments consisted of three N levels applied in side-dressing (corresponding to 50, 100 and 150 kg N ha−1) as 15N-urea with and without DMPP application. An additional treatment (absence of N application in side-dressing) was used as a control. Results: 3,4-Dimethylpyrazole phosphate efficiently improved N recovery after urea fertilizer was applied to plants and in the soil by reducing NO3− leaching, leading to enhanced N acquisition from fertilizer and soil and augmenting N accumulation in plants, mainly when high N levels above 100 kg N ha−1 were applied. We found that total N recovery increased 31% when 150 kg N ha−1 was applied as a urea + DMPP source compared to the application of conventional urea. In addition, DMPP application reduced NO3− leaching losses (by approximately 11 to 20%), although it had no significant effect on the shoot or root dry matter yields. Conclusion: The reduction in NO3− leaching losses obtained herein highlights the potential of DMPP to mitigate the impact of increased urea inputs on leaching losses, thereby improving N use efficiency and N uptake in cotton crops. [ABSTRACT FROM AUTHOR]