EFFECTS OF FREQUENCY AND DEPTH OF IRRIGATION ON GROWTH AND YIELD OF ONION by MD. MUAZZEM HOSSAIN

Abstract

The experiment was conducted at the Horticulture Farm of Bangladesh Agricultural University to study the effects of frequency and depth of irrigation on growth and yield of onion cv. Taherpuri during October, 1990 to April, 1991. There were three different frequencies of irrigation viz. at 15%, 30% and 45% depletion of available soil moisture and three different depths of irrigation viz. 5 mm less than, equal to and 5 mm more than the soil moisture depletion in the root zone. The frequency and depth of irrigation significantly affected the growth and yield of onion. Plant height, average length of leaves and bulb diameter increased significantly with irrigation at 15% depletion of soil moisture regime. Yield of onion bulbs was maximum (12.4 t/ha) by irrigation at 15% depletion of soil moisture regime along with a irrigation depth of 5 mm more’ than the amount of depletion of soil moisture in the root zone. The total water used at that treatment was 264.1 mm. Decreasing the depth of irrigation under same regime significantly decreased the yield. Although bulb yield increased by irrigation, but irrigation induced a higher percentage of splitted bulb. However, higher proportion of large size ‘A’ (>44 mm in diameter) grade bulbs were obtained by irrigation. Maximum A grade bulbs (33.7%) were produced by irrigation at 15% depletion along with a irrigation depth of 5 mm more than the soil moisture depletion.