Khichar, M.L.Amit Singh2017-04-122017-04-122016http://krishikosh.egranth.ac.in/handle/1/5810007161The present study entitled “Effect of fertility levels and plant spacing on light interception and its efficiency in Bt cotton”, was conducted at the Research Farm of Cotton Section, Department of Genetics & Plant Breeding, CCS HAU, Hisar (Lat 290 10' N, Long 750 46' E and 215.2 m msl) during kharif season of 2015. The experiment was conducted in split split plot design with three replications. The experiment consist of three varieties viz.V1=RCH 602, V2= RCH 650 and V3= Bunty were kept in main plots while three spacing viz. S1= 67.5 cm x 75 cm, S2=67.5 cm x 60 cm and S3= 67.5 cm x 45 cm with three fertilizer levels i.e.F1= RDF,F2= 125% of RDF and F3= 150% of RDF application of the recommended dose were kept in subplots. Recommended dose of fertilizer is (RDF) N:P:K=175:60:60 kg ha-1. Maximum plant height and leaf area index was recorded with narrow spacing of 67.5 cm x 45 cm which was significantly higher than rest of spacing. However, wider spacing (67.5 cm x 75 cm) had lesser plant density resulted into higher dry matter accumulation. Significantly higher number of sympodial branches plant-1 was recorded with RDF but further increase in fertilizer had on significant effect sympodial branches plant-1. Number of bolls plant-1 increased with increasing levels of fertilizer from RDF to 150 % of RDF. Seed cotton yield was found highest with 125% of RDF followed by 150% of RDF and RDF. Periodic growth parameters viz. plant height and leaf area index were increased significantly with increasing levels of fertilizer up to 150% of RDF. The cultivar RCH 602 consumed highest thermal and radiation indices. Radiation and heat use efficiency were also highest in this cultivar as compared to RCH 650 and Bunty. Cotton cultivar, RCH 602 consumed highest heat units, heliothermal units and photothermal units as compared to RCH 650 and Bunty under different treatments. Among spacing, wider spacing 67.5 cm x 75 cm consumed highest heat units, heliothermal units and photothermal units as compared to narrow spacing 67.5 cm x 60 and 67.5 cm x 45 cm. However, the radiation use efficiency is maximum in spacing 67.5 cm x 75 cm as compared to 67.5 cm x 60 cm and 67.5 cm x 45 cm. But maximum IPAR observed in narrow spacing 67.5 cm x 45 cm as compared to 67.5 cm x 60 cm and 67.5 cm x 75 cm. In case of fertilizer levels, 150% of RDF consumed highest heat units, heliothermal units, photothermal units, thermal and radiation indices as compared to 125% of RDF and RDF.enThesis