Puddling, irrigation, and transplanting-time effects on productivity of rice-wheat system on a sandy loam soil of Punjab, India

Rice-wheat productivity in irrigated tract of the Indo-Gangetic plains is constrained by water and energy limitations. In order to minimize unproductive soil water evaporation and percolation loss at a field scale, management practices include soil puddling, water-economizing irrigation schedule, and matching growth cycle with periods of low evaporative demand. This 3-year field study examines combined effects of these options on rice-wheat productivity and water-use efficiency (WUE) and energy-use efficiency (EUE) on a sandy loam soil in an irrigated semi-arid sub-tropical environment. Treatments included combinations of three puddling intensities, viz., one (P-1), two (P-2) and four (P-4) runs of a tine cultivator in ponded water after a common pre-puddling tillage; with two irrigation regimes, viz., continuous submergence (I-1) throughout the growing season, and intermittent submergence (I-2) with continuous submergence for 2 weeks after transplanting followed by 2-day interval between successive irrigations, and two transplanting dates, viz., first fortnight of June (D-1) and end June (D-2) to impose variation in seasonal evaporative demand. Residual effect of puddling in rice on succeeding wheat was also evaluated during the 3 years. Intensive puddling and water-economizing schedule caused a significant reduction in seasonal percolation loss primarily due to puddling-induced changes in soil bulk density and hydraulic behavior. Increasing puddling intensity from P-1 to P-2 enhanced mean rice yield by 0.2-0.3 Mg ha(-1), but additional puddling did not improve yield significantly. Mean grain yield increase with I-1 over I-2 ranged between 0.3 and 0.6 Mg ha(-1). Interaction effect between puddling and irrigation indicate that yield benefit with I-1 over I-2 was greatest in P-1 regime (0.6 Mg ha(-1)), and the effect decreased with increase in puddling intensity. Delayed transplanting caused a decline of 0.3-0.5 Mg ha(-1) in rice yield. Although maximum yield was realized with combination of P-2 or P-4 regime with I-1 regime, but water-use efficiency was greater with I-2 compared to I-1 regime by 1.1 kg ha(-1) mm(-1) in 2000 and by 0.3 kg ha(-1) mm(-1) in 2001. It indicates that yield gain with additional irrigation were not commensurate with additional water input. Energy analysis also showed that energy-use efficiency was 6.8, 7.2, and 6.6 kg kWh(-1) for P-1, P-2, and P-4 regimes suggesting that yield gain with P-4 did not match energy input for additional puddling. Further, there was a greater risk of yield reduction of succeeding wheat with P-4 (by 0.2-0.3 Mg ha(-1)) compared to P-1 or P-2 regime. (C) 2005 Elsevier B.V. All rights reserved.