Phosphorus application affected cottonseed kernel yield and nutritional quality by improving oil yield and quality of two cotton (Gossypium hirsutum L.) cultivars differing in phosphorus sensitivity

Context: Cottonseed is rich in oil and protein and can provide high-quality raw materials for food, feed, and biodiesel production, but phosphorus deficiency reduces its utilization value.Objective: The purpose of this study was to evaluate the effects of phosphorus application on the yield and nutritional quality of cottonseed.Methods: A three-year field experiment was carried out with Lu 54 (low-phosphorus sensitive) and Yuzaomian 9110 (low-phosphorus tolerant) to study the changes in the contents and yields of cottonseed kernel oil and protein, and the compositions of fatty acid and amino acid under three phosphorus rates (0, 100, and 200 kg P2O5 ha- 1).Results: (1) Phosphorus application significantly enlarged the cottonseed kernel, oil, and protein yields, among which oil yield exhibited higher phosphorus sensitivity than protein. (2) Phosphorus application markedly increased the contents of total phosphorus, phytic acid, and inorganic phosphorus in the cottonseed kernel, resulting in increased oil content and decreased protein content. Notably, the decrease in protein content was attributed to the dilution effect caused by the greater accumulation of oil than protein but not the weak accu-mulation of nitrogen. (3) Phosphorus application markedly altered the fatty acid composition of cottonseed kernel by decreasing palmitic acid content and increasing oleic acid and linoleic acid contents. This significant improvement in the ratio of unsaturated fatty acid content to saturated fatty acid content of cottonseed further lowered the atherogenicity index and thrombogenicity index while elevating the health-promoting index, thereby improving the oil nutritional quality. Phosphorus application slightly decreased the amino acid content and protein nutritional value of cottonseed kernel. (4) The changing amplitudes of cottonseed kernel yield and quality in Lu 54 were higher than Yuzaomian 9110. When the mean phosphorus concentration in the leaf that subtends the cotton boll reached 0.43%, 0.44%, and 0.42% for Lu 54, respectively, further increasing phosphorus rate had a mild influence on the cottonseed kernel, oil, and protein yields, versus 0.37%, 0.37%, and 0.36% for Yuzaomian 9110.Conclusion: Phosphorus application improved cottonseed kernel yield by significantly increasing oil and protein yields and improved cottonseed kernel quality by significantly increasing oil quality while having less effect on protein quality.Implication: The results of this study are conducive to evaluating the effects of phosphorus application on cot-tonseed kernel yield and quality to make full use of its oil and protein in future production processes.