Estimation of crop coefficient of Bt cotton hybrid (gossypium hirsutum L.) NHH-44 by using lysimeter
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Date
2020-12-11
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Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani
Abstract
The research trial was conducted during Kharif season 2019-20 on experimental farm of Department of Agricultural Meteorology, College of Agriculture, Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani, entitled “Estimation of Crop Coefficient of Bt. Cotton hybrid (Gossypium hirsutum L.) NHH-44 by using Lysimeter” to find out the crop coefficient values of Bt. Cotton hybrid NHH-44 and the effect of weather parameters on cotton varieties under different dates of sowing.
An experiment was conducted in Split plot design with 12 treatments under 3 replications. Treatments under study were four sowing dates i.e. D1 (25th MW), D2 (26th MW), D3 (27th MW) and D4 (28th MW) and four varieties of Bt. Cotton i.e. V1 (NHH-44), V2 (Ajeet-155) and V3 (PKV Hy-2) having spacing 120 cm x 45 cm. The gross plot size was 7.2 x 4.5 m2 and net plot size was 4.8 x 3.6 m2. The sowing of cotton seeds were done by dibbling method on respective dates of sowing. Accurate estimation of crop water requirement in cotton is an important aspect with respect to increase in production and productivity in any area. The use of onsite climatological data and known values of crop coefficients enables the determination of crop water use at different critical growth stages of cotton and also helps in dissemination of such information to farmers in a reliable, usable and affordable format.
Results of this investigation showed that all the biometric observations were significantly highest in D2 (26th MW) followed by D1 (25th MW), D3 (27th MW) and D4 (28th MW) sowings. Among the varieties, Ajeet-155 (V1) recorded significantly highest number of branches and bolls per plant, dry matter accumulation (plant-1) and seed cotton yield (1267 kg/ha). Most optimum date of sowing Bt cotton at Parbhani station was found to be 26th MW (D2) which produced significantly highest seed cotton yield (1449.8 kg/ha) and other yield attributing characters. The accumulated GDD, PTU and HTU were obtained maximum in D1 (25th MW) and decreased by delay in sowing dates. In case of crop weather relationship of all bt cotton varieties, rainfall and rainy days were positively correlated with seed cotton yield at P3 and P7 stages. The maximum temperature was positively correlated with seed cotton yield at P2 and P6 stages whereas minimum temperature was positively correlated at P2, P3, P4, P6 and P7 stages, respectively. BSS was positively correlated at P5 stage and wind velocity was positively correlated at P2, P3, P4, P6, P7 and P8 stage of crop.
By using mechanical lysimeter, the total water requirement of bt cotton i.e. ETc recorded during the crop growth season 2019 was obtained to be 801.9 mm. Crop coefficients of cotton were estimated by using different methods such as PM method, Turc, FAO Modified Penman, Pristley-Taylor, Makkink, Christansen method, Hargeaves and Hargeaves-Samani method. Among these methods, FAO Penman monteith is widely used for the estimation of ETc. The Kc values of Bt cotton hybrid NHH-44 (V1) were estimated to be 0.49, 1.55 and 1.07 for initial (0-30 DAS), mid (31-111 DAS) and end (112-166 DAS) stage respectively by using PM method. Kc value was at the maximum level during boll formation stage and then started declining, which indicates the increase in crop water demand of the crop. All the estimated Kc values of cotton by PM method were higher than the Kc values those suggested in FAO-56 Irrigation and Drainage paper (Allen et al., 1998). Among the all methods, Hargreaves is the best method showing lower magnitude of average error, MAE and RMSE, for the estimation ETc and crop coefficients at Parbhani location if the climatological data is limited.