PUDDLING AND N MANAGEMENT EFFECTS ON CROP RESPONSE IN A RICE-WHEAT CROPPING SYSTEM

Coarse-textured soils are puddled to reduce high percolation losses of irrigation water under rice (Oryza sativa L.). This practice, however , reduces yield of succeeding wheat (Triticum aestivum L.) owing to de terioration in soil physical conditions. The 6 year field study report ed in this paper evaluated the effects of puddling level and integrate d N management on the development of subsurface compaction and growth and yield of rice and the following spring wheal grown in 1 year seque nce on a sandy loam soil. Treatments were combinations of three puddli ng levels: low (one discing and one planking), medium (two discings an d one planking), and high ( four discings and one planking), and three nitrogen sources: (1) 120 kg N ha(-1) from urea, (2) 60 kg N ha(-1) f rom urea plus sesbania (Sesbania aculeata Pers.) green manure, and (3) 60 kg N ha(-1) from urea plus 20 Mg ha(-1) farmyard manure. Percolati on rate decreased from 14 mm day(-1) with low puddling to 10 mm day(-1 ) with high puddling, with a corresponding reduction in irrigation wat er requirement of rice of about 20%. Bulk density pro files in the 0-3 0 cm soil layer showed the formation of a compact layer at 15-20 cm de pth, and bulk density increased with puddling level and cropping seaso n. The impact of organic amendments in reducing bulk density was immed iate, but the rate of increase in bulk density with time was the same in all the nitrogen sources. Organic amendments did not affect percola tion rate and irrigation requirement of rice. Rice yields were not sig nificantly affected by puddling and N source treatments throughout the study period. Residual effects of treatments on wheat yield were obse rved from the second season onwards. Interactive effects of puddling a nd N source on yields of rice and succeeding wheat were not significan t. Yield differences in wheat between high and low puddling were 8% an d 11% during the second and the fifth cropping season, respectively. T his study indicates that medium puddling was optimum, as it reduced pe rcolation without decreasing yield of succeeding wheat.