Assessment of thermal heat requirement in wheat (Triticum aestivum) for central plain zone of Uttar Pradesh

Wheat (Triticum aestivum L.) being a temperature sensitive crop, its development and productivity respond significantly to dates of sowing. The sensitive analysis of three wheat cultivars HD 2733, K-307 and K-9107 were grown under irrigated conditions with three sowing dates, viz. 23–29 November (D₁), 8–14 December (D₂) and 23–29 December (D₃) over 5 seasons from 2009–10 to 2013–14 at Kanpur to see the possible change in the grain yield of wheat due to change in maximum and minimum temperature. The potential condition was assumed with congenial weather and adequate management practices. The results revealed that accumulated growing degree days (GDD) was increased with one month delay in sowing (D₃) over D₁, but helio thermal unit (HTU) was higher in D₂ sowing and decreased with delay in sowing till crop reached physiological maturity stage. The grain yield was higher when maximum temperature (Tmax) during anthesis stage remained between 23.2 to 23.6°C and decrease appreciably when Tmax was above 25.0°C during this phase. Maximum temperature revealed that R² was higher during anthesis (84%) and milking (85.9%) phenophases but the association was poor during tillering phase. Results further revealed that the grain yield ofwheat was decreased to the tune of 174 kg ha⁻¹ and 176 kg ha⁻¹ with increase in 1.0°C maximum temperature during anthesis and milking phenophase, respectively. Among the different stages, anthesis and milking were found to be most sensitive stage. The effect of minimum temperature was behaved in a similar manner to that of maximum. Thus it can be suggested that the variety HD-2733 can be recommended among the tested varieties for sowing under both favorable and unfavorable thermal conditions