Neem oil and pomegranate leaf extract coating on urea to reduced nitrous oxide emission; improved nitrogen use efficiency and crop yield: A step towards sustainable N use and green production

Abstract

Nitrogen (N) is widely regarded as the most important essential plant nutrient in agricultural cropping systems. However, the use efficiency of applied N fertilizer is as low as 20-30% from farm to fork, due to losses including runoff, leaching and emission of nitrous oxide (N2O) which has huge environmental and economic consequences. The use of synthetic nitrification inhibitors (NIs), such as dicyandiamide (DCD) has been suggested to minimize N emission significantly and enhance N recovery in cereals. But the use of natural plant products that may act as NIs has been less studied so far. Field experiments were conducted in central Punjab, Pakistan, to assess the impact of neem oil and pomegranate leaf extract coating on urea, and urea plus dicyandiamide (DCD) on N2O emission, N recovery efficiency and grain yield, in wheat and rice crops. All NIs reduced N2O emission compared with the inorganic fertilizer (urea treatment), with emission reductions from 21 to 88% in wheat and 25 to 72% in rice. The maximum reduction in N2O emission was with the DCD treatment (72-88%). The application of all NIs (natural and synthetic) improved grain yield compared with inorganic fertilizer, by 3 to 10% in wheat and 4 to 12% in rice. Neem oil-coated urea gave the maximum increase in grain yields and N recovery in both the crops. Thus, it is recommended that neem oil and pomegranate leaf extract coated urea may be used for mitigating N2O emission along with increased N recovery and optimum yield benefits.