Heat unit requirement and its utilisation efficiency in wheat under different hydrothermal environments

Abstract

A field experiment was conducted at the Research Farm, School of Climate Change and Agricultural
Meteorology, Punjab Agricultural University, Ludhiana during rabi 2013-14. Wheat variety PBW
621 was sown on three dates viz. D1 (29th October), D2 (12th November) and D3 (28th November) and
four irrigation levels namely I1 (Irrigation at CRI stage), I2 (Irrigation at CRI and Flag leaf emergence
stage), I3 (Irrigation at CRI, flag leaf emergence and soft dough Stage) and I4 (Recommended 4 post
sowing irrigations) in randomized block design. D1 took 157 days to attain maturity followed by
151 days taken by D2 and 142 days taken by D3 sown crop. The AGDD and APTU at physiological
maturity were higher under D1 (1759.9°C day and 19403.2°C day hr) followed by D2 (1695.3°C day
and 18992.6°C day hr) and D3 (1623.2°C day and 18570.2°C day hr) respectively, where as AHTU
were higher under D2 (11897.8°C day hr) followed by D1 (11386.9°C day hr) and D3 (11234.2°C day
hr). Heat use efficiency w.r.t. straw and grain yield were higher under D1 followed by D2 and D3.
Phenophasic models explained 96 to 99% variation in crop phenology due to heat units under D1,
94 to 98% under D2 89 to 97% variation under D3. Heat use efficiency also exhibited positive linear
relationship with dry matter production (R2 = 0.99) and grain yield (R2 = 0.87). The study concluded
that timely sowing of wheat improves heat use efficiency, which is essentially required under climate
warming scenarios