Dynamics of Nitrogen Gaseous Losses Following the Application of Foliar Nanoformulations to Grasslands

Abstract

Increasing rates of nitrogen (N) conventional fertilizer have led to increasing risks of N losses to the atmosphere, mainly as ammonia (NH3) and nitrous oxide (N2O). The aim of this study was to evaluate the effect of foliar N-based nanoformulations on the dynamics of N2O and NH3 emissions from grasslands. Six N treatments (50 kg N ha−1) plus a control (n = 4) were tested on a completely randomized design: granular urea (Urea-g), dissolved urea (Urea-d), dissolved ammonium nitrate (NH4NO3), and nitrate-, urea-, and ammonium-based nanoformulations (NO3-F, Urea-F, NH4-F) applied as foliar spray to intact soil cores maintained under controlled conditions. In addition, a control N = 0 was included. Cumulative emissions of N2O and NH3 (mg N m−2) were measured using dynamic/static chambers. Effects on yield and soil available N were also quantified. Volatilization of NH3 was the main N loss pathway (ranged from 2 to 51% of the N applied). Higher emissions were observed with NH4-F and low emissions in the nitrate-based fertilizers. Direct N2O losses were low compared to NH3 losses, varying between 0.07 and 0.25% of the N applied. Due to high NH3 losses, indirect N2O losses were 0.3 to 2.8 times greater than direct N2O losses. There was no effect of N treatments on soil available N or pasture yield. The application of a NO3-foliar formulation emerges as a potential alternative for the mitigation of integrated N gaseous emissions. Ammonium-based nanoformulations require improvements in order to reduce losses. Further studies should include yield evaluations under field conditions, cost–benefit analysis, and potential impacts in the agri-food chain.