Response of cowpea (Vigna unguiculta (L).Walp) to varying water table conditions in tarai soil of Uttarakhand
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Date
2017-06
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
An experiment was conducted at N. E. Borlaug Crop Research Center of G. B. Pant University of Agriculture and Technology, Pantnagar (Latitude 290N, Longitude 79030’ E and Altitude 243.84 m above MSL) during summer season of 2016 to study the growth, development, root length and root length density and major nutrients leached with percolation water, yield and yield attributes, evapotranspiration, water requirement, water use efficiency and crop coefficients of Cowpea (Vigna unguiculta (L.) Walp)) cv. Pant Lobia-1 under three irrigation schedules viz. CPE 100, 150 and 200 mm, two irrigation methods viz. flood and sprinkler in lysimeters filled with silty clay loam soil and associated with 30±1.5, 60±1.5 and 90±1.5 cm water table depths during the season. The experiment was under three factorial RBD with eighteen irrigation treatment combinations. The analyzed data of the experiment has indicated that maximum plant height of 84.72 cm of Cowpea crop was obtained in lysimeters associated with 60±1.5 cm water table depth. However, maximum number of leaves per plant (62.5), and maximum number of branches per plant (8.16) were obtained in lysimeters in which 30±1.5 cm water table depth was maintained. Cowpea crop receiving 6 irrigations at CPE 100 gave maximum plant height (82.37 cm), number of leaves per plant (56.70) and number of branches per plant (7.28). Sprinkler method of irrigation gave better results of all growth and development parameters over flood method of irrigation. Number of grains per pod, number of pod per plant, length of pod and 100 seed weight were more under 60±1.5 cm water table depth. Root length (179.68 cm) and root length density (0.35 cm cm-3) were found to be maximum in lysimeters in which 60±1.5 cm water table depth was maintained. Results also indicated maximum grain yield of 1017.57 kg ha-1 of Cowpea in irrigation treatment in which irrigations were scheduled based on CPE 100 mm using sprinkler method and in lysimeters associated with 60±1.5 cm water table depth. Maximum water use efficiency (WUE) of Cowpea (1.20 kg ha-1mm-1) in lysimeters was obtained as when irrigations were given based on CPE 100 mm under medium (60±1.5 cm) water table conditions. Results also showed remarkably higher grain yield and yield attributes in lysimeters, when crop was irrigated at CPE 100 mm receiving a total of 6 irrigations using sprinkler method of irrigation. Total water use varied from 705.81 to 1134.75 mm among various irrigation treatment combinations and water table depths. Crop coefficient (Kc) for cowpea crop as calculated from potential evapotranspiration and actual evapotranspiration measured from lysimeters ranged from 0.42 at one week after sowing to 0.83 at flowering stage during mid season and then declined to 0.48 as crop approached towards maturity. However, the average value of Kc was found to be 0.57 during the crop season. At the time of harvesting of crop, the minimum bulk density of lysimeter soil was 1.35 Mg m-3 and its maximum hydraulic conductivity of 17.84 cm day-1 was observed under shallow water table of 30±1.5 cm. After at harvesting time surplus amount of available N (254273 kg ha-1), P205 (15.04-17.47 kg ha-1) and K2O (169.71-198.61 kg ha-1) remained in the soil. Significant losses of nitrate-N (9.28-14.09 mg L-1), ammonical-N (2.80-3.95 mg L-1), P205 (1.15- 1.56 mg L-1) and K2O (1.43- 1.75 mg L-1) in drained water were observed due to variations in water table depth, irrigation schedules and methods of irrigation.
Thus it can be concluded from this study that scheduling of irrigation to Cowpea crop under conditions of medium water table (60±1.5 cm) based on CPE 100 mm using sprinkler method of irrigation is most favorable technique for better yield and maximum WUE of Cowpea c.v. Pant Lobia-1 in tarai conditions of Uttarakhand. Cowpea crop can be taken as an additional crop during summer season for economic benefits. It is a need of the hour to produce more per drop of water due to scarcity of water due to drying of water resources and rainfall variability due to climate change.