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

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.

Automated summary

Increasing rates of nitrogen fertilizer use result in increased nitrogen losses, mainly in the forms of ammonia and nitrous oxide, to the atmosphere. This study evaluated the effects of foliar application of nitrogen-based nanoformulations on nitrogen gas emissions from grasslands. Results showed that nitrate-based fertilizers had lower nitrogen gas emissions compared to ammonium-based nanoformulations. Ammonia volatilization was the main pathway for nitrogen losses, and indirect nitrogen oxide emissions exceeded direct emissions. There were no significant effects of the nitrogen treatments on soil available nitrogen or pasture yield.