Cottonseed,protein and oil yields and oil properties as affected by nitrogen and phosphorus fertilization and growth regulators

Two experiments were carried out at our research center during the 1981 and 1982 seasons on cotton cultivar Giza 75 (Gossypium barbadense L.) to investigate the influence of nitrogen fertilization rates (72, 144 or 216 kg/ha.), phosphorus levels (36 or 72 kg P₂O₅/ha.) and three growth regulators (IAA, IBA or NAA) applied to cotton plants at 10 ppm and sprayed three times (70, 85 and 100 days after sowing) on protein and oil yields, and oil properties. A randomized complete block design with four replications treatment combinations was used. The combined analysis of the results of the two seasons revealed that yields of cottonseed, oil and protein increased by raising nitrogen and phosphorus levels and under the application of growth regulators. Seed index increased by raising the added nitrogen and the applied growth regulants. No detectable effect of phosphorus levels was observed. The seed oil percentage decreased, although the protein percentage increased, when the nitrogen application rate was raised. Application of growth regulators and a high phosphorus level increased the seed oil percentage, but the seed protein percentage was not affected. The seed oil properties, i.e., acidity, saponification and iodine values, tended to decrease slightly by increasing the nitrogen application rate and the application of growth substances, but the trend reversed when the phosphorus level was raised. The mean values of oil specific gravity and refractive index did not show any definite responses.