Effect of 1-naphthaleneacetic acid concentrations and the number of applications on the yield components, yield, and fibre properties of Egyptian cotton (Gossypium barbadense L.)

Abstract

Field experiments were performed in 2 successive seasons at the experimental station, Faculty of Agriculture, Cairo University, Giza, Egypt, on the Egyptian cotton cultivar Giza 75 (Gossypium barbadense L.). Cotton plants were sprayed with the growth regulator 1-naphthaleneacetic acid (NAA) once (after 90 days), twice (90 and 105 days), or 3 times (90, 105, and 120 days after sowing), during the square initiation and bolling stage, at concentrations of 5, 10, 15, 20 or 25 mg/L, respectively. The volume of solution was the same for all treatments, 960 L/ha. The control plants were sprayed with water only. The effect of the previous treatments on yield components, lint yield, and fibre properties was studied. The application of NAA increased the number of opened bolls per plant, boll weight, seed index, and lint yield per ha. Lint percentage, fibre length parameters, and micronaire value were not significantly affected by NAA. Flat bundle strength was significantly increased when NAA was applied once at 10-25 mg/L. The application of NAA twice or 3 times at 15-20 mg/L tended to give the best results on yield components and lint yield of the Egyptian cotton plants.