Enhancing Use Efficiency of Urea-Nitrogen by Combining Use of Nitrification Inhibitors with Irrigation Sequence in Wheat

摘要

To investigate the fate of fertilizer nitrogen applied to wheat in combination with dicyandiamide (DCD) and neem cake (NC), a field experiment was conducted on Mehrauli loam (Typic Ustochrept) in the Main Block-8B of the Indian Agricultural Research Institute farm, New Delhi. The results indicated that application of urea-N either alone or in various combinations with DCD and NC significantly increased both grain as well as straw yield to wheat. Magnitude of N response varied from 0.96 to 1.28 and 0.09 to 2.05 t ha~(-1) in grain and straw, respectively. Highest grain and straw yield was obtained when urea amended with DCD was applied in two splits of 60+60 kg, with top-dressed N applied just before irrigation. Compared to control, the N content of wheat grain and straw tissues was significantly higher in urea-treated plots. Application of nitrification inhibitors and band placement of urea significantly increased the nitrogen content in grain as well as straw. In all the urea-fertilized treatments, total N uptake varied from 116 to 162 kg ha~(-1). Application of urea amended with DCD showed significantly higher total N uptake than other treatments, when top-dressed N dose was applied half-an-hour before irrigation. Urea + DCD maintained the highest amount of total mineral N in soil during the cropping season; blending urea with DCD was more effective than blending urea with NC. The residual fertilizer nitrogen in soil was significantly lower with urea + DCD and urea + NC than the other treatments. Band placement of urea produced significantly higher residual fertilizer N than the respective top-dressed treatments.