The field experiments was carried out for three years (2015 to 2017) at the Research Farm, Department of Climate Change and Agricultural Meteorology, Punjab Agricultural University, Ludhiana with maize variety PMH-1 sown on three dates (D1-Third week of May, D2-Second week of June and D3- First week of July) under two irrigation regimes (I1 = IW:CPE 1.0 and I2 IW:CPE 0.75) and mulch application (M1: straw mulch @ 5 tha-1 and M2: without mulch) in a split plot design.Results revealed that the early sown crop(third week of May) took higher number of days and heat units to attain various phenophases. Maize variety PMH-1 consumed maximum heat units of 1952oC days for maturity under early sown condition. The heat use efficiency was highest (3.04 kg ha-1oCday-1)for the crop sown during June. Among irrigation regimes, the HUE was higher (2.89 kg ha-1oC day-1) in IW: CPE = 0.75 level of irrigation as compared to IW: CPE = 1.00 (2.81 kg ha-1oCday-1) and higher HUE was obtained with mulch application (M1) (2.92 kg ha-1oCday-1) as compared to without mulch (M2) (2.76 kg ha-1oCday-1). The sowing of maize crop during second week of June with irrigation of IW: CPE 0.75 under mulch application have been found to be the most efficient for heat utilisation.