Leaching of Nitrogen Applied as Urea from Undisturbed Alluvial Soil Columns under Continuous and Intermittent Flooding

Leaching of N applied as urea on undisturbed soil columns was studied under conditions of continuous and intemittent flooding. Soil columns were 50 cm long with 9.6 cm internal diameter. Soil was nonsaline and sandy loam in texture. Under continuous flooding treatment, total urea-N loss was 1.01 per cent and that of NH₄⁺-N was 1.75 per cent of the applied N (130 mg N column⁻¹) with 16.1 cm leachate. There was no loss of NO₃⁻-N under continuous flooding. Total loss of urea-N under intemittent flooding was 0.91 per cent of the applied N, and that of NH₄⁺-N was 0.66 per cent with 15.5 cm leachate. Loss of NO₃⁻-N under intemittent flooding depended on split number; 0.05, 1.18 and 5.35 per cent of the applied N leached after the application of first, second and third split of urea, respectively. At the conclusion of the study after 85 days, residual urea-N was zero but residual NH₄⁺-N was 65.57 and 38.28 per cent and residual NO₃⁻-N was 0.00 and 19.03 per cent of the applied N under continuous and intermittent flooding treatments, respectively. Leaching loss of total N from puddled soil under continuons flooding (2.67%) was comparatively lesser than under intemittent flooding (8.14%).