Abstract:This experiment was conducted using aerobic incubation to study the nitrification inhibition effect of dicyandiamide(DCD) on ammonium bicarbonate in red soils with different textures.The results indicated that adding DCD significantly increased ammonium content and decreased nitrate nitrogen content at the same time.The nitrification of ammonium bicarbonate took 7 weeks in sandy loam soil and 5 weeks in light clay soil.These processes were 2 weeks longer if dicyandiamide was applied in light clay soil.However,the content of ammonium was still high after aerobic incubation was over,no matter DCD was added or not,so more studies were needed to study the transformations of ammonium bicarbonate in light clay soil.Nitrification inhibition of dicyandiamide on ammonium bicarbonate in medium loam soil was better than that in sandy loam soil and light clay soil.It was concluded that DCD could significantly inhibit the nitrification of treatments with less NH4+-N rate in sandy loam soil and light clay soil,but had better effect on treatments with high NH4+-N rate in medium loam soil.