Response of onion (Allium cepa L.) to crop residue mulch and irrigation regimes in a sandy loam soil
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Date
2016
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Punjab Agricultural University, Ludhiana
Abstract
Onion requires light, frequent and high number of irrigations because most of the roots are concentrated in upper surface. Moreover depleting groundwater resources in Punjab, demands for optimum irrigation schedule and water saving techniques. Onion productivity is constrained by high soil evaporation and soil temperature during latter part of the growing season. These can be altered through the straw mulching and irrigation. A field experiment was conducted during rabi 2015-16 at the research farm of Punjab Agricultural University, Ludhiana to evaluate the response of onion to crop residue mulch and different irrigation regimes in a sandy loam soil. Main plots comprised of two mulch rates: No mulch (M0) and rice straw mulch @ 6 t ha-1 (M6) and sub plots included three irrigation regimes based on IW/Pan-E=2.0, 1.4 and 0.8 ratios. Results revealed that the 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 based on IW/Pan-E=0.8 over frequently irrigated IW/Pan-E=2.0. Mulch improved onion bulb yields by 5.5 t ha-1 (24 per cent) over no mulch plots (23.0 t ha-1). Irrigation based on IW/Pan-E ratio of 2.0 and 1.4 significantly enhanced average yield of onion by 5.34 and 4.23 t ha-1 over the restricted irrigation with 0.8 ratio (22.6 t ha-1). Onion in mulched plots with IW/Pan-E=0.8 produced same yield as that recorded in no mulch plots with IW/Pan-E=2.0 demonstrating a saving of six irrigations during growing season. Weed infestation was lower by 92 per cent in mulched plots as compared to no mulch plots. With increase in irrigation frequency the weed biomass also increased significantly. Mulch also improved total water use efficiency by 11.09 kg bulb ha-1 mm-1 over no mulch plots (34.8 kg bulb ha-1 mm-1). Water use efficiency progressively increased with decrease in irrigation water inputs and it was 17 and 8.2 kg bulb ha-1 mm-1 higher with 0.8 and 1.4 ratios over the frequently irrigated plots. Mulch recorded more per cent of larger size (>50 mm) bulbs on mass basis.