Cottonseed, Protein and Oil Yields, and Oil Properties as Affected by Nitrogen and Phosphorus Fertilization and Growth Regulators

Two experiments were carried out at Giza Agric. Res. St., Agric. Res. Centre, Ministry of Agric, Egypt, during 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 N/ha), phosphorus levels (36 or 72 kg P₂O₅/ha) and three growth regulators (IAA, IBA or NAA), each was applied to cotton plants at 10 ppm and sprayed three times (70, 85 and 100 days after sowing), on cotton seed, 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, cottonseed, oil and protein yields/ha increased by raising N- and P-levels and under the application of growth regulators. Seed index increased by raising the added-N and the applied growth regulants. No detectable effect of P-levels was observed. The seed oil percentage decreased, while the protein percentage increased by raising N-rate. Application of growth regulators and high P-level increased the seed oil percentage, while the seed protein percentage was not affected. The seed oil properties, i.e. acidity, saponification and iodine values, tended to decrease slightly by increasing N-rate and the application of growth substances, while a reverse trend was noticed by raising P-level. The mean values of oil specific gravity and refractive index did not show any definite response.