Cassava (Manihot Esculenta Crantz) Yields, Soil Nitrous Oxide Emission, and Soil Nitrogen Transformation Affected by Nitrification Inhibitors in Loamy Sand Soil in Thailand

Abstract

The effects of nitrification inhibitors (NIs) on soil nitrous oxide (N2O) emission, soil ammonium (NH4+) and nitrate (NO3−), and cassava (Manihot esculenta Crantz) yields were investigated in a loamy sand soil in eastern Thailand. Treatments were chemical fertilizer (CF) and CF plus dicyandiamide (DCD) or neem (Azadirachta indica) oil at two rates of 5% and 10%. DCD had a greater reduction of soil N2O flux than the neem oil (P<0.10). DCD and neem oil retained NH4+-N in the soil by 79% and 63% (P ≤ 0.10), respectively. The NI effect on soil NO3−-N was small due to a low N fertilizer rate. The cassava root yield and N uptake were increased 4–11% and 2–18%, respectively, by use of NIs, but they were only significant for DCD (P ≤ 0.10). These findings suggest that NIs application may be a promising method for minimizing nitrogen loss and enhancing crop yields in a tropical cassava field.