Effect of different nitrogen sources and nitrification inhibitors on soil nitrogen distribution in Kinnow orchard

A field experiment was conducted on 2-year-old Kinnow mandarin to find out effect of different nitrogen sources and nitrification inhibitors on ammonical and nitrate nitrogen distribution in Kinnow young plants during 2011–12. There were 13 treatments comprising four nitrogen sources (ammonium sulphate, calcium nitrate, mixture of ammonium sulphate and calcium nitrate and urea), two nitrification inhibitor (dicyandiamide 5% of fertilizers, meliacin 0.1% of fertilizers) and control. Recommended fertilizers dose was applied in three splits, i.e. in February, June and September. Nitrification inhibitors were mixed with different nitrogenous fertilizers before application and then applied in the field. The process of nitrification slow down when N-fertilizers (ammonium sulphate, mixture of ammonium sulphate & calcium nitrate and urea) treated with DCD and meliacins. Thus the inhibitory effect of DCD and meliacins on the nitrification process resulted in more NH₄⁺ accumulation in soil. The concentration of NH₄⁺-N in soil at 0–30 (44.1, 55.7, 42.7 mg kg⁻¹ soil below drippers and 37.8, 41.9, 36.0 mg kg⁻¹ soil at 30 cm away from drippers) and 30–60 cm depth (24.2, 20.2, 23.2 mg kg⁻¹ soil below drippers and 20.0, 23.5, 23.6 mg kg⁻¹ soil at 30 cm away from drippers) in all three split applications respectively, was significantly higher when ammonium sulphate followed by urea fertilizers treated with DCD than they are in alone form. Due to nitrification inhibitors, NO₃⁻-N availability remains high on surface level, reduced NO₃⁻ leaching and increase N fertilizer utilization efficiency in Kinnow production.