Effect of various plant growth regulators on yield of American cotton (Gossypium hirsutum)

The field experiment was conducted during Kharif season of 2012-13 at the Agronomy Instructional Farm, Chimanbhai Patel College of Agriculture, Sardarkrushinagar Dantiwada Agricultural University, Sardarkrushinagar, and District: Banaskantha (North Gujarat). The experiment was laid in factorial randomized block design with three replications. Eighteen treatment combinations comprised of the foliar spray of growth regulators and nutrients viz. 30 ppm NAA, 50 ppm GA3, 200 ppm Mepiquat chloride, 2 % Urea and control were applied at 60 and 80 days after sowing. Foliar application of NAA @ 30ppm significantly gave early and higher number of flowers opening compared to other treatments. The application of NAA increased the flowering percentage, reduced the abscission and increased the flower retention percentage, which in turn helped in getting higher seed cotton yield. Higher seed cotton yield was obtained with application of NAA @ 30 ppm i.e. 1213.27 kg/ha., maximum biological yield i.e. 241.66 gm., maximum harvest index i.e. 37.10 %, which leads to interpret that higher seed cotton yield obtained because HI having significant positive effect on yield.