Effect of high density planting and growth retardant spray on growth and yield of Bt cotton variety (Gossypium hirsutum L.)

A field experiment was conducted at Cotton Research Station, Nanded to evaluate the effect of high density planting and number of PGR sprays on crop growth and yield of Bt cotton straight variety during Kharif 2024 season under rainfed condition. The experiment was laid out in a split plot design comprising twelve treatment combinations and three replications. Four plant densities i.e., D1: 55,555 plants ha-1, D2: 83,333 plants ha-1, D3: 1,11,111 plant ha-1, D4: 1,66,666 plants ha-1 were evaluated in main plot with spacing of 60 cm x 30 cm, 60 cm x 20 cm, 60 cm x 15 cm and 60 cm x 10 cm, respectively. Three treatments of number of PGR spray, P1: One spray of PGR, P2: Two sprays of PGR, P0: Control (water spray) were evaluated in sub plot. Plant growth retardant (PGR) Mepiquat chloride @ 25 g a.i. per ha was sprayed to retard plant growth. First spray was done at square formation and second at 15 days after first spray as per treatment schedule. The results showed that increase in plant density has reduced number of monopodial branches plant-1, dry matter accumulation plant-1 and AGR whereas, plant height, number of sympodial branches plant-1, CGR and leaf area index were increased with increase in plant density. The plant density of 1.66 lakh plants ha-1 (spacing 60 cm x 10 cm) resulted in higher seed cotton yield (2109 kg ha-1), whereas lower plant density exhibited greater value of harvest index (27.34). Application of two sprays of PGR has reduced plant height, dry matter accumulation plant-1 significantly over control. Number of monopodia were increased in two sprays of PGR (P2) over control. Whereas number of sympodia were reduced in number of PGR sprays. Absolute growth rate, Crop growth rate and leaf area index were greater in control. Two sprays of Mepiquat chloride @ 25 g a.i. ha-¹, first at square formation stage and followed by 15 days has increased number of bolls m-2, seed cotton yield (2116 kg ha-1), and harvest index of Bt hirsutum cotton variety over control.