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 (P₁), two (P₂), and four (P₄) runs of a tine cultivator in ponded water after a common pre-puddling tillage; with two irrigation regimes, viz., continuous submergence (I₁) throughout the growing season, and intermittent submergence (I₂) 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 (D₁) and end June (D₂) 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 P₁ to P₂ 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 I₁ over I₂ ranged between 0.3 and 0.6 Mg ha^?1. Interaction effect between puddling and irrigation indicate that yield benefit with I₁ over I₂ was greatest in P₁ 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 P₂ or P₄ regime with I₁ regime, but water-use efficiency was greater with I₂ compared to I₁ 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 P₁, P₂, and P₄ regimes suggesting that yield gain with P₄ did not match energy input for additional puddling. Further, there was a greater risk of yield reduction of succeeding wheat with P₄ (by 0.2–0.3 Mg ha^?1) compared to P₁ or P₂ regime.