Nitrification inhibitor 3,4-Dimethylpyrazole phosphate improves nitrogen recovery and accumulation in cotton plants by reducing NO.sub.3.sup.- leaching under .sup.15N-urea fertilization

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-NO.sub.3.sup.-, N-NH.sub.4.sup.+ 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-NO.sub.3.sup.- and N-NH.sub.4.sup.+ losses in drainage water. The treatments consisted of three N levels applied in side-dressing (corresponding to 50, 100 and 150 kg N ha.sup.-1) as .sup.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 NO.sub.3.sup.- 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.sup.-1 were applied. We found that total N recovery increased 31% when 150 kg N ha.sup.-1 was applied as a urea + DMPP source compared to the application of conventional urea. In addition, DMPP application reduced NO.sub.3.sup.- 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 NO.sub.3.sup.- 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.