IRRIGATION OF SUNFLOWER (HELIANTHUS-ANNUUS) IN RELATION TO TILLAGE AND MULCHING

For sustainable sunflower production in semi-arid sub-tropical regions , it is essential to increase its water use efficiency. Field studies were conducted for three years on deep alluvial loamy sand (Typic Usti psamment) and sandy loam (Typic Ustochrept) soils at Punjab Agricultur al University, Ludhiana, India, to evaluate the interactive effects of three irrigation regimes (irrigation water to net open pan evaporatio n ratios, I-1, I-2, I-3) on sunflower yield in relation to tillage (co nventional tillage, CT, and deep-tillage, DT) and mulching (no mulch, M-0, and residue mulch, Both deep tillage and mulch significantly incr eased crop yield irrespective of soil type and year. Increase in mean achene yield across soils during three years with DT over CT varied be tween 10 and 16% and that with mulch over no mulch by 8 to 17%. Deep t illage and/or mulching helped the crop in efficient utilization of wat er by increasing leaf area index (LAI) and the depth and density of ro oting. Irrigation and tillage interacted for their effects on yield on loamy sand, as the crop responded to higher level of irrigation with CT than with DT. On loamy sand, mean achene yield increased with incre ase in water supply up to IW/PE = 1.5 in a dry year and upto IW/PE = 1 .2 in relatively wetter years. On sandy loam, mean yield response to i rrigations was observed upto IW/PE = 1.0 in all the three years. Regre ssion analysis of relative yield against water supply during the three years on both the soils, showed that for 80% relative yield the crop required 105 cm water in CTM0, 90 cm in CTM or DTM0 and only 80 cm in DTM. The study suggests that deep tillage or straw mulch may be used t o achieve higher water use efficiency in sunflower on coarse textured soils in semi-arid, sub-tropical regions. (C) 1997 Elsevier Science B. V.