EFFECT OF 1-NAPHTHALENEACETIC ACID CONCENTRATIONS AND THE NUMBER OF ITS APPLICATIONS ON THE YIELD COMPONENTS, YIELD AND FIBER PROPERTIES OFEGYPTIAN COTTON (GOSSYPIUM BARBADENSE L.)

Field experiments were performed in two successive seasons at the Expe rimental Station, Faculty of Agriculture, Cairo University, Giza, Egyp t, on the Egyptian cotton cultivar Giza 75 (Gossypium barbadense L.). Cotton plants were sprayed with the growth regulator 1-naphthaleneace acid (NAA) once (at 90 days), or twice (at 90 and 105 days) or thrice (90, 105 and 120 days) after sowing, during the square initiation and belling stage at the concentrations of 5, 10, 15, 20 or 25 p.p.m. The volume of solution was the same for all treatments, 960 l ha(-1). The control plants were sprayed with water only. The effect of the previou s treatments on yield components, cotton yield and fibre properties wa s studied. The application of NAA increased the number of opened bells plant(-1), bell weight, seed index, seed cotton yield plant(-1) and s eed cotton and lint yields ha(-1). The most significant effects were o btained with the 15 and 20 p.p.m. concentrations. Lint percentage, fib re length parameters and micronaire value were not significantly affec ted by NAA. Flat bundle strength was significantly affected by NAA but with no definite trend. The application of NAA twice or thrice tended to give the best results on yield components and cotton yield compare d with one application The results of this study suggested that 20 p.p .m. of NAA gave the best figures when applied twice on the Egyptian co tton plants.