File 2527 (17).qxd Bangladesh J. Sci. Ind. Res. 41(1-2), 109-112, 2006 Short communication Introduction Onion (Allium cepa L.) is the main spice crop grown in Bangladesh. It is used in almost all food preparation and is an integral part of Bangladesh diet.1 Onion is grown in 35,000 hactre land and its total production is 1.40 lac ton.2 It is grown more or less in all the districts of Bangladesh but the average yield is 4.17 t/ha2 which is very low as compared to other developed countries like USA (42 t/ha), Japan (44.7 t/ha) and South Korea (53 t/ha) as reported by Pathak.3 The average world production at present is about 15 t/ha.3 Among various factors affecting its produc- tion, the role of irrigation assumes greater significance. Onion needs frequent irrigation but it does not tolerate water logging condi- tion. Recently the climatological approach has come out to be the most reliable device for scheduling irrigation. The present study was therefore, undertaken to find out opti- mum irrigation schedule and water require- ment of onion. Materials and Methods The field experiment was conducted at Grey Terrace Soil of Gazipur (AEZ-28) during rabi seasons of 1990-2000 and 2000-2001. Five regimes of irrigation (control, 0.50, 0.75, 1.00 and 1.25 IW/CPE ratio with 4 cm depth of irrigation water at each irrigation) were tried in randomized complete block design (RCBD) with four replications. One common irrigation of 4 cm depth was given just after transplanting and the subsequent irrigations were timed on the basis of different IW/CPE ratios. The total number of irrigations includ- ing a common irrigation, irrigation schedules of control, 0.50, 0.75, 1.00 and 1.25 IW/CPE ratio were 1, 3, 4, 5 and 6, in both years respectively. Five week old seedling of line ON-0193 were transplanted on 6th and 1st December, 1999 and 2000, respectively and the crop was harvested on 20th and 12th March, 2000 and 2001, respectively. Unit plot size was 2m x 1m. The spacing was 20 cm between rows and 10 cm between plants. Uniform dose of 120 kg N/ha as urea, 90 kg P2O2/ha as TSP, 90 kg K2O/ha as MP and 20 kg S/ha as gypsum were applied. Half urea and all other fertilizer were applied as basal and rest of urea was applied at 45 DAT. The water table depth was below 3m through out the experimentation. Hence the contribution of ground water was considered to be Effect of Different Soil Moisture Regime on the Yield and Yield Components of Onion R. Sen, A. T. M. A. I. Mondal, S. Brahma and M. S. Khan Soil Science Division, Bangladesh Agricultural Research Institute, Gazipur-1701, Bangladesh negligible. The total rainfall during cropping season were 6.5 cm in 2000 and 5.8 cm in 2001, the bulk of which was received in the March in both year. There was practically no rain during active growth period of the crop in both the year. Five representative plants were harvested from each plot for recording yield attributes of onion. Results and Discussion The yield, yield components and water use efficiency of onion as responded to different soil moisture regime are presented in Table I and Table II. Bulb diameter, bulb length, individual bulb weight and bulb yield/ha increasing upto 1.25 IW/CPE ratio of soil moisture regime, but data obtained from 1.00 IW/CPE ratio and 1.25 IW/CPE ratio are statistically similar. Maximum bulb diameter (5.96 cm in 2000 and 6.08 cm in 2001) obtained from 1.25 IW/CPE ratio which was statistically similar with 1.00 IW/CPE ratio and comparatively higher from all other treatment. Highest bulb length (5.64 cm in 2000 and 5.68 cm in 2001) obtained from 1.25 IW/CPE ratio which was significantly higher than all other treatment. Maximum individual bulb weight (67.55 g in 2000 and 69.86 g in 2001) was obtained from 1.25 IW/CPE ratio which was identical with bulb weight derived from 1.00 IW/CPE ratio (58.14 g in 2000 and 60.77 g in 2001). Both of above two bulb weight were significantly higher than bulb weight of rest three treat- ments. Bulb yield/ha increasing significantly with the increase of soil moisture regime upto 1.00 IW/CPE ratio. Bulb yield /ha was highest in 1.25 IW/CPE ratio (16.32 t/ha in 2000 and 16.59 t/ha in 2001) which was identical with 1.00 IW/CPE ratio (15.08 t/ha in 2000 and 15.36 t/ha in 2001). Percent increase in bulb yield due to 1.25, 1.00, 0.75, 0.50 IW/CPE 110 Effect of Different Soil Moisture 41(1-2) 2006 Table I. Effect of different soil moisture regimes on the yield, yield components and water use efficiency of onion during rabi season of 1999-2000 Soil moisture regimes (IW/ CPE ratio) Control 0.50 0.75 1.00 1.25 LSD CV(%) No. of irriga- tion 1 2 3 4 5 - - Bulb diameter (cm) 1.81d 2.47c 4.56b 5.48a 5.96a ** 6.3 Bulb length (cm) 2.13e 3.33d 4.45c 5.21b 5.64a ** 4.8 Bulb weight (g) 12.52d 29.49c 44.32b 58.14a 67.55a ** 14.4 Bulb yield (t/ha) 5.48d 8.72c 12.06b 15.08a 16.32a ** 8.8 % Yield increase over control - 59.12 120.07 175.18 197.81 - - Total water applied includ- ing rainfall (cm) 10.50 18.50 22.50 26.50 30.50 - - Water use efficiency (kg/ha/cm) 521.90 471.35 536.00 569.06 535.06 - - ratio over control were 197.81, 175.18, 120.07 and 59.12 in 2000 and 192.59 170.90, 116.58 and 56.79 in 2001, respectively. Liberal water supply (1.25 or 1.00 IW/CPE ratio) increased bulb diameter, bulb length and individual bulb weight which resulted increased bulb yield of onion, confirming the results of Singh and Sharma4; Hegde5 and Palled et al.6 Total water use for onion varied from 10.50 to 30.50 cm in 2000 and 9.80 to 29.80 cm in 2001. Highest water use efficiency (569.06 kg/ha/cm in 2000 and 595.35 kg/ha cm in 2001) was obtained from soil moisture regimes of 1.25 IW/CPE ratio which received 6 irrigations giving bulb yield of 15.08 t/ha in 2000 and 15.36 t/ha in 2001. Conclusion Soil moisture regime 1.00 IW/CPE ratio (5 irrigations 1, 20, 35, 55 and 70 days after transplanting) was found optimum for onion production in Grey Terrace Soil of Gazipur. References 1. A. K. M. Hossain and J. Islam. Status of Allium cepa production in Bangladesh. Hort. Abst. 358 (1994) 33-36. 2. B. B. S. The year Book of Agricultural Statistics of Bangladesh. Statistics Division, Ministry of Plannning. Goverment of the Peoples Republic of Bangladesh (1997). 3. C. S. Pathak. Allium improvement for the tropics: Problem and AVRDC Strategy. Hort. Abst. 358 (1994) 23-93. 4. D. Singh and R. P. Sharma. Effect of soil moisture regimes and nitrogen fertilization on onion. Indian J. of Agronomy. 36(1) (1991) 125-126. Sen, Mondal, Brahma and Khan 111 Table II. Effect of different soil moisture regimes on the yield, yield components and water use efficiency of onion during rabi season of 2000-2001 Soil moisture regimes (IW/ CPE ratio) Control 0.50 0.75 1.00 1.25 LSD CV(%) No. of irriga- tion 1 2 3 4 5 - - Bulb diameter (cm) 1.87d 2.51c 4.65b 5.59a 6.08a ** 7.0 Bulb length (cm) 2.16e 3.39d 4.53c 5.28b 5.68a ** 6.2 Bulb weight (g) 13.14d 30.55c 46.41b 60.77a 69.86a ** 9.7 Bulb yield (t/ha) 5.67d 8.89c 12.28b 15.36a 16.59a ** 7.9 % Yield increase over control - 59.79 116.58 170.90 192.59 - - Total water applied includ- ing rainfall (cm) 9.80 17.80 21.80 25.80 29.80 - - Water use efficiency (kg/ha/cm) 578.57 499.44 563.30 595.35 556.71 - - 5. D. M. Hegde. Effect of irrigation and N fertilization on water relations, canopy temperature, yield. N uptake and water use of onion. Indian J. Agric. Sci. 56(12) (1986) 858-867. 6. Y. B. Palled, M. D. Kachpur, A. M. Chandrasekharan and A. S. Prabhakar. Response of onion to irrigation and nitro- gen. Indian J. Agron. 33(1) (1988) 22-25. 112 Effect of Different Soil Moisture 41(1-2) 2006