Effect of crop residue management on nitrogen loss and balance from urea in a lowland rice cropping system
2001
Sakorn Phongpan(Department of Agriculture, Bangkok (Thailand). Agricultural Chemistry Div. Nuclear Research in Agriculture Group) | Mosier, Arvin R.(United States Department of Agriculture (USA). Agricultural Research Service) | Jenvith Sookthongsa(Department of Agriculture, Bangkok (Thailand). Rice Research Institute. Suphanburi Rice Experimental Station)
Maximum rate of ammonia volatilization losses from urea (11.2 kg N/rai Broadcast into floodwater shortly after transplanting occurred 2-4 days after fertilization. The cumulative NH3 losses during the 11 days following urea application were 0.74, 1.30 and 0.90 kg N/rai from no residue, burned residue and residue treated plots which corresponded to 7, 12 and 8 percent of the applied N, respectively, At nearly that time N2+N2O emissions were first detected 3 days after urea application. From day 3 to 12 following urea addition, N2+N2O emission rates averaged 190, 110 and less than 10 micro g N/square m/hr from no residue burned residue and residue treated plots, respectively or the cumulative percent of N2+N2O emission due to urea addition corresponded to 10, 4.3 and nil. The 15N balance study at grain maturity of the dry season rice showed that fertilizer N recovered by the grain, straw and roots did not show significant differences among residue treatments. Fertilizer N recovery by the grain was low, only 9 to 11 percent of the N applied. Fifty to 53 percent of the applied 15N remained in the soil after rice harvest, mainly in the upper 0-5 cm layer. The unaccounted for 15N was probably lost by gasous N emissions which ranged from 27 to 33 percent of the applied N and was unaffected by residue treatments. Only 4 to 5 percent of the initial 15N-labeled urea applied to the dry season rice crop was taken up by the succeeding rice crop in the wet season to which no additional N fertilizer was applied. Grain yield and N uptake were significantly increased (P=0.05) by N application in the dry season but not significantly affected by residue treatment in either season.
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