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

•Oil content and yield in cottonseed kernel were more sensitive to phosphorus (P) than protein.•P altered cottonseed kernel yield and quality mainly by altering those of oil.•Protein content in cottonseed kernel decreased because of the dilution effect of higher biomass.•There were critical mean P concentrations in the leaf that subtends the boll for cottonseed kernel, oil, and protein yields.•Cottonseed kernel yield and quality of cultivars responded to P variedly.