HEAT-UNIT REQUIREMENT OF RAIN-FED SOYBEAN (GLYCINE-MAX)

A field experiment was conducted at Jabalpur during 1987-93 to study t he heat-unit requirement during different phenophases of soybean [Glyc ine max (L.) Merr.]. Two varieties of soybean ('Gaurav' and 'Durga') w ere sown on 3 dates (early, normal and delayed). The growing degree-da ys. heliothermal units and photo-thermal units were worked out for eac h phenophase. Analysis showed that the requirement of these characters were more for 'Gaurav' than 'Durga'. Photo-thermal indices were const ant for both the varieties sown on 3 dates of sowing. Heat-use efficie ncy was mom for 'Gaurav' than for 'Durga'. For these varieties under 3 dates of sowing, total requirement of heliothermal units was 23 232 ( for early sowing) and 19 279 (for normal sowing). whereas that of accu mulated growing degree-days was 1 956-1 733 and of photo-thermal units was 7 492-8 286.