Evaluation of the Nitrification Inhibitor 3,4-Dimethylpyrazole Phosphate in Two Chilean Soils

Two Chilean soils were used to evaluate the performance of the nitrification inhibitor 3,4-dimetilpirazol phosphate (DMPP) added to ammonium-sulfate-nitrate (ASN) in comparison with traditional nitrogen (N) sources and different N-application forms. Two experiments were conducted: In the first, broccoli (Brassica oleracea var. italica) plants were cultivated in pots under greenhouse conditions, and received a N-fertilization equivalent to 150 Kg N ha−1 as ASN+DMPP (one application), urea (two splits), and sodium-potassium nitrate (three splits). In the second, ryegrass (Lolium spp.) plants were grown in pots under shading conditions. In this case, ASN+DMPP and urea were applied at N rates equivalent to 150 and 300 Kg N ha−1 in a single application. In the first experiment, ASN+DMPP increased dry-matter production, maintained a higher N content in the soil (at least until the middle of the growing period), and improved fertilizer N-use efficiency (FUE) in one soil. There were no significant differences in N-leaching losses. In the ryegrass experiment, ASN+DMPP increased dry-matter production and FUE, while N-leaching losses were reduced. Treatments with ASN+DMPP maintained higher N levels in soil throughout the growing period, and there were no significant differences in the available N fraction between the two N rates. The use of DMPP-containing fertilizers may be a good alternative for increasing FUE.