Impact of Heat Units on the Phenology and Yield of Baby Corn (Zea mays L.) in Western Agro Climate Zone of Tamil Nadu

Field investigation was carried out during winter 2022 at Tamil Nadu Agricultural University, Coimbatore to study the phenological behaviour and yield of baby corn (Zea mays L.) as influenced by heat units. The split-plot design consisting of three dates of sowing viz., D1 – 21st January, D2 – 5th February and D3 – 20th February as a main plot and three spacing viz., 60x45 cm (S1), 60x30 cm (S2) and 60x20 (S3) as a sub plot was adopted and replicated thrice. Growing Degree Days, Helio Thermal Unit and Heat Use Efficiency were calculated for different phenological stages viz., plant emergence to 50% flowering (P1), 50% flowering to cob emergence (P2), cob emergence to harvest (P3), plant emergence to cob emergence (P4), 50% flowering to harvest (P5) and plant emergence to harvest (P6). The results revealed that sowing on 20th Feb. had completed the phenophases early, followed by 5th Feb and 21st Jan. GDD required for attaining physiological maturity was highest in 20th Feb. (1194.6 ºC days)). Except morning relative humidity, wind speed and solar radiation, all other weather parameters had negative correlation with baby corn yield (R2=0.921). The optimum temperature was obtained during D1 (27.2 – 27.5 ºC) along with short-day length (11.7 hours) resulting in higher corn yield (9333.3 kg/ha) as well as higher HUE (5.75).