Joint application of urease and nitrification inhibitors to diminish gaseous nitrogen losses under different tillage systems

Abstract

Urea fertilization is a widely spread source of nitrogen (N) for agriculture because of its easy accessibility. However, its use is highly inefficient, since a large amount of the applied N is lost to the environment mainly in the form of ammonia (NH3) volatilization, causing serious environmental and economic damages. Although there are simple strategies to reduce these losses, as the subsurface application, this practice cannot be adopted in all types of cultivations and tillage systems. To address this problem, combinations of urease and nitrification inhibitors (double inhibitors) have been developed to close all possible N escape routes, which is not achieved when these inhibitors are applied individually. The objective of this work was to evaluate the potential of a new double inhibitor combining N-(n-butyl) thiophosphoric triamide (NBPT) and 2-(3,4-dimethylpyrazole-1-YL)-succinic acid (DMPSA) to mitigate N losses in a rapeseed crop established in conventional tillage (CT) and no-tillage (NT) soils under Humid Mediterranean conditions. To do so, N losses in form of NH3 volatilization and nitrous oxide (N2O) emissions were determined through the Dräger-Tube method (DTM) and closed chamber method respectively. The specific weather conditions present during the experiment promoted great losses, mostly in form of NH3 volatilization. The treatments receiving urea without inhibitors or urea with DMPSA lost up to 57.3 and 59.9 kg N ha−1 in CT and NT respectively. Nonetheless, the application of the double inhibitor was able to diminish these losses by more than 50%, reducing the losses to a minimum of 18.8 kg N ha−1 (CT) and 25 kg N ha−1 (NT). As a whole, a CT system fertilized with a single application of urea with the double inhibitor showed the lowest global warming potential (GWP) (3.93 Mg CO2-eq ha−1), at the same level of the unfertilized treatment.