Effect of phosphorus fertilization and foliar application of chelated zinc and calcium on seed, protein and oil yields and oil properties of cotton

Abstract

Field experiments were conducted during two successive seasons in the Agricultural Research Center, Giza, Egypt (a clay loam soil), to study the effects of phosphorus fertilization (addition at rates of 44 and 74kg of P2O5/ha) and foliar application of zinc (at 0·0 and 40ppm of Zn applied twice, 75 and 90 days after planting) and calcium (at 0·0, 20, 40, and 60ppm of Ca applied twice, 80 and 95 days after planting) on seed, protein and oil yields and oil properties of the Egyptian cotton cultivar Giza 75. Application of P at the high rate and spraying plants with zinc and calcium at any concentration increased cottonseed yield/ha, seed index, seed oil content, oil and protein yields/ha, seed oil unsaponifiable matter, and total unsaturated fatty acids (oleic and linoleic). Conversely, decreases in oil acid value, saponification value and total saturated fatty acids occurred. The seed protein and oil refractive index tended to increase when the high P rate and Zn were applied. Seed protein content tended to decrease slightly with Ca application. Regardless of the slight decrease in protein content as a result of Ca application, the yield of protein increased, due to the fact that there was an obvious increase in seed yield which counterbalanced the negative effect of the decrease in protein content. The highest Ca concentration (60ppm) gave the highest values of cottonseed yield/ha, seed index, seed oil and protein yields/ha and oil unsaponifiable matter, followed by the concentration of 40ppm. The concentration of 40ppm gave the lowest total saturated fatty acids. The effect of Ca concentrations on oil refractive index was very limited.