Hydro-thermal conditions and their impact on irradiance and hygro-thermal use efficiency of wheat in central Punjab

The experiments were conducted to develop indices to provide critical insights into crop phenology and yield responses of wheat to thermal and moisture conditions during rabi 2021-22 and 2022-23 at PAU, Ludhiana, Punjab. The wheat variety Unnat PBW was sown on three dates (D1: 27th October, D2: 17th November, D3: 8th December) under three irrigation regimes (I1: irrigations at CRI, Jointing, 50% Flowering, Soft dough stages, I2: irrigations at CRI, Flag leaf emergence, soft dough stage, I3: irrigations at Jointing, Soft dough stage). Results revealed that the crop sown on 27th October acquired maximum number of calendar days and various heat indices viz. growing degree days (GDD), solar thermal degree days (STDD) and hygrothermal units (HGTU) for attaining physiological maturity while 8th December sown crop resulted in lowest accumulation. However, late sown crop was observed to accumulate more STDD. Wheat sowing before 17th November resulted in higher grain yield and energy use efficiencies. Four irrigations at critical stages took highest GDD, STDD and HGTU for attaining maturity which was at par with two irrigations. Application of four irrigations resulted in significantly higher yield and energy use efficiencies. Similar performance of three irrigations was observed when irrigation was not skipped at anthesis stage.