DEGREE DAYS, HEAT USE EFFICIENCY AND BIOMASS ACCUMULATION IN WHEAT UNDER VARYING GROWING ENVIRONMENTSS.K. Tomar, S.K. Yadav D. P. Singh, Vinay, Vipin Kumar and Ajay Kumar
The major constraint of low wheat productivity of wheat in eastern Uttar Pradesh is high temperature during reproductive phase of the crop. It is due to late sowing of wheat after long duration rice varieties, spending more time for field preparation and improper tillage. Influence of temperature on phenology, accumulation of growing degree days(GDD), biomass, grain yield and heat use efficiency (HUE) in wheat crop studied under field condition through the accumulated heat unit system. An on farm trial in farmer participatory mode were conducted at 5 location by selecting cooperator and well equipped farmers in Gorakhpur, (U.P.). Trials were conducted under irrigated ecosystem during Rabi season 2010 -2011 and 2011-2012. The treatment comprises four sowing dates (3 November, 18 November, 3 December and 18 December) and 3 tillage practices (zero tillage, conventional tillage and reduced tillage). Highest accumulation of GDD (1904 & 1907), lowest phenol thermal index (PTI)(10.0 and 9.2) and highest grain yield was recorded with early sowing (3 November.) of wheat in both the years but highest HUE (2.52 and 2.48 kg grain/ha/ GDD) was recorded with 18th November sowing of wheat in both the years. Among the tillage practices highest accumulated GDD and HUE with low PTI was recorded with zero till sowing of wheat. Yield reduction after 3rd November sown crop varied with tillage practices. Calculated for delays after the optimum date, grain yield decreased at the rate of 29.1, 35.3 and 44.8 kg /ha/day delayed sowing with ZT, CT and RT sown crop, respectivelyduring 2010-11. While during 2011-12 it was 30.9, 32.3 and 32.3 kg/ha/day. Corresponding values on a relative basis for these tillage practices were 0.60, 0.76 and 0.99 per cent /day during 2010-11 and during 2011-12 it was 0.62, 0.67 and 0.70 per cent /day, respectively.
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