Dynamics of ammonia volatilization from NBPT-treated urea in tropical acid soils

The urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) reduces NH3 losses from urea (UR) surface-applied to soils, but its efficacy may be lower in acidic soils. period when inhibition occurs efficaciously change with soil pH. This needs clarified tropical soils which are commonly acidic. study evaluated the effectiveness of NBPT-treated delay and reduce ammonia volatilization two at three pH levels. Two experiments were conducted under laboratory conditions different textures (sandy-clay clay). treatments consisted levels N sources (UR UR + NBPT), five replicates. values adjusted reached 4.5, 5.6, 6.4 sandy-clay, 5.4, 6.1 clay soil. Ammonia was measured using glass chambers (1.5 L). In sandy-clay soil, 40-47 % UR-N. 26-32 %. addition NBPT reduced by 18-53 %; decreased all significantly less efficient (pH 4.5). efficiency more evident first few days: 50 total occurred than four days 8-11 above 5.4. rapid loss is a drawback. Using severely showed relatively small advantage over untreated as did not provide extra time for fertilizer incorporation further reduction losses.