Nitrogen, potassium and plant growth retardant effects on oil content and quality of cotton seed

The aim of this field experiment was to investigate the effect of nitrogen, potassium and a plant growth retardant (PGR) on seed yield and protein and oil content of an Egyptian cotton cultivar (Gossypium barbadense Giza 86). Treatments consisted of: soil application of N (95 and 143 kg N ha(-1) in the form ammonium nitrate), foliar application of potassium (0, 319, 638 or 957 g K ha-1 as potassium sulfate) and foliar application of mepiquat chloride (MC) (0 and 48 + 24 g active ingredient ha-1) on seed, protein and oil yields and oil properties of Egyptian cotton cultivar "Giza 86" (Gossypium barbadense). After applying the higher N-rate, foliar application of potassium and plant growth retardant MC significantly increased seed yield and the content of seed protein and oil, seed oil refractive index, unsaponifiable matter and total unsaturated fatty acids (oleic and linoleic). In contrast, oil acid and saponification value as well as total saturated fatty acids were decreased by foliar application of potassium and MC. The seed oil content was decreased with soil application of N.