Effect of nitrification and urease inhibitors on nitrous oxide and methane emissions from an oat crop in a volcanic ash soil

Abstract

Nitrous oxide (N2O) emissions from the Chilean agricultural sector are primarily associated with the use of nitrogen (N) fertilizers, so that the use of nitrification and urease inhibitors may represent a potential mitigation option. However, their effectiveness in volcanic ash soils with high organic matter is still uncertain. In this study, the effect of Dicyandiamide (DCD) and N-(n-butyl) thiophosphoric triamide (NBPT) on soil N2O and CH4 emissions from an oat crop was determined using a fully automated greenhouse gas measuring system. Three urea treatments were evaluated: 120kgNha−1, 120kgNha−1+DCD and 120kgNha−1+NBPT (n=3). A zero treatment (-N) was also considered. Annual N2O emissions ranged from 0.36 to 1.00kgN2O-Nha−1 (P>0.05) whereas the net uptake of CH4 ranged from 6.72 to 7.00kg CH4-C ha‐1 (P>0.05). Increases in N2O emissions were associated with rainfall events, as characteristic of Mediterranean rain fed ecosystems. Soil CH4 uptake did not vary among treatments but had a significant role offsetting N2O emissions, resulting in total emissions ranging from −17.1 to 239.0kg CO2eq ha−1 (P<0.001). There was no significant effect of DCD or NBPT on average soil mineral N concentration, and total N2O and CH4 emissions. NBPT significantly increased crop yield and crop N uptake by 27% and 33% respectively (P<0.05), resulting in greater N use efficiency. The use of DCD did not increase productive parameters, but resulted in a 35% reduction of the N2O-N emission intensity (P<0.05). The study shows that volcanic ash soils have a relatively low N2O emission potential due to physic-chemical characteristics and that NBPT could be used to increase N use efficiency in crops, while DCD has a potential to reduce N2O losses per unit yield.