Role of nitrification inhibitors on nitrous oxide emissions in a fertilized alluvial clay loam under different moisture regimes

Fertilized soil is considered to be a major source of nitrous oxide (N2O) in the atmosphere. In a laboratory incubation experiment, emission of N2O was studied from a clay loam soil fertilized with urea alone and urea combined with nitrification inhibitors, viz, dicyandiamide (DCD) and thiosulphate, at different moisture regimes. Emission of N2O was observed from day 1 and was appreciable during the first 2 weeks and decreased subsequently. Soil at 80% max. mater holding capacity (WHC) had highest total N2O-N emission followed by soil at field capacity and submergence. Total emissions from control (no N), urea, urea combined with DCD (urea-DCD) and thiosulphate (urea-thiosuiphate) were 78.88, 744.39, 415.63 and 653,75 mu g N2O-N kg(-1) soil, respectively at 80% max, WHC, while total emissions from the corresponding treatments under submergence and at field capacity were 31.7, 298.5, 138.4, 272.8 and 54.6, 333,7, 217.8, 313.5 mu g N2O-N kg(-1) soil, respectively. Of the applied N, nitrogen lost through total N2O emissions was 1.06, 0.53 and 0.92% at 80% max. WHC; 0.45, 0.26 and 0.41% at field capacity and 0.43, 0.17 and 0.39% under submergence from urea, urea-DCD and urea-thiosulphate, respectively. Thus, addition of DCD reduced total N2O-N emission to the extent of 60, 41.5 and 49.4% under submergence, at field capacity and at 80% max. WHC, respectively, when compared to urea atone, while the corresponding reductions on addition of thiosulphate were 9.6, 7.2 and 13.5%.