Evaluating Organic Materials Coating on Urea as Potential Nitrification Inhibitors for Enhanced Nitrogen Recovery and Growth of Maize (Zea mays)

Abstract

To slow down the urea hydrolysis and inhibition of nitrification process is a promising approach for enhancing crop production and reducing environmental risk of nitrogen (N). Two separate (incubation and pot) experiments were conducted to estimate the nitrification inhibition potential of coated urea and maize growth. The applied treatments included control, ordinary urea, neem (Azadirachta indica) oil coated urea (NOCU1%) and NOCU2%, moringa (Moringa oleifera) oil coated urea (MOCU1%) and MOCU2% and pomegranate (Punica granatum) leaves extract coated urea (PLECU0.5%) and PLECU1%. In incubation experiment, changes in mineral-N were studied for 40 days by analyzing NH4+-N and NO3--N contents in soil samples taken at 10-days intervals. The application of coated urea delayed the nitrification up to 30 days and increased the plant available N pool compared to un-coated urea. Highest N losses (40–48%) were observed in case of un-coated urea, while minimum NO3--N (7.40 mg kg-1) concentrations were recorded where, 2% NOCU was applied. Maize was sown as a test crop in pot experiment with same treatments plan. Apparent N recovery ranged from 61–84% between coated urea treatments than ordinary urea. Similarly, growth related parameters i.e. plant height, dry matter yield, chlorophyll a and b significantly (P ≤ 0.05) increased with the application of natural nitrification inhibitors (NNIs) coated urea than ordinary urea, respectively. Correspondingly, the relative growth rate (RGR) was increased by 11–89% and 30–70% in all NNIs coated urea than control and ordinary urea, respectively. In conclusion, application of NNIs seemed highly effective to reduce N losses and sustaining better crop productivity.