ISSN 2360-7971
Abstract
Accepted 14th April, 2018.
Onion (Allium cepa L.) is one of the most important spices as well as vegetable crop of the world. It requires light and frequent irrigation owing to most of the roots are concentrated in upper surface. Moreover depleting groundwater resources in Punjab demands for optimum irrigation schedule and water saving technique. Onion productivity is constrained by high soil evaporation and temperature during second half of the growing periods. These can be altered through the mulching and irrigation. Mulching with surplus rice residue is likely to provide favorable hydrothermal regime, check weed infestations, economize irrigation water use and enhance onion bulb yield. This study examined the combined effects of residue mulching and irrigation regimes on onion bulb yield and water productivity in a semi-arid sub-tropical environment of north-west India. Treatment included two mulch rates viz., No mulch (M0) and rice straw mulch @ 6 t ha-1 (M6) in main plots and sub plots comprised of three irrigation regimes based on IW/Pan-E=2.0, 1.4 and 0.8 ratios with four replicates. Onion was transplanted in first week of January with recommended doses of N, P2O5 and K2O and harvested in second fortnight of May.Results revealed that residue mulch improved onion bulb yields by 17 per cent over no mulch plots (24.2 t ha-1). Response of onion to irrigation regimes was observed significantly up to I2.0 irrigation regime. Irrigation based on I 2.0 and I1.4 significantly enhanced average yield of onion bulb by 5.3 and 3.7 t ha-1 over the restricted irrigation with I0.8 ratio (23.3 t ha-1). Mulching benefits were more in drier year 2016 (24%) than in wet year 2015 (10%). For a similar bulb yield, mulching saved 175 mm of irrigation water. Soil moisture storage was higher in mulch plots throughout the growing period. Mulch lowered the maximum soil temperature by 1.8 to 8.8 °C over no mulch plots and also changed the minimum soil temperature during the growing season. The maximum soil temperature was higher by 0.1 to 4.5 °C with the irrigation regime IW/Pan-E=0.8 over IW/Pan-E=2.0. Weed infestation was lower by 92 per cent in mulched plots. Increase in frequency of irrigation weed biomass also increased. Mulch enhanced water use efficiency and these effects were greater in less-frequent irrigations. Mulch recorded more per cent of larger size (>50 mm) bulbs on mass basis. Both mulching and irrigation frequency improved total N uptake. Mulching effects on bulb yield and irrigation economy are attributed to its effect on moderation of soil temperature, reduction in soil water evaporation and weed infestation.
Keywords: Onion, residue mulching, irrigation, water productivity, bulb yield