Influence of Integrated Nano-Calcium and K-Humate Foliar Spray on Growth, Yield and Fiber Quality of Cotton Grown in Alluvial Non-Saline Soil

Calcium (Ca 2+ ) is one of the essential elements for plants and the changes in soil properties reduce its availability for plants as a result of forming insoluble compounds. The aim of this study was to evaluate the effect of foliar application of Nano-Ca (N-Ca) combined with potassium humate (K-H) on improving the cotton growth parameters, yield components and fiber quality. Two split-plot design field experiments (2019 and 2020) in a randomized complete block design arrangement with four replicates were laid out. Three cotton cultivars (Giza 92, 94 and 95) and six fertilizers treatments (control; traditional-CaO (T-Ca); Nano-CaO (N-Ca); K-H; T-Ca+K-H; and N-Ca+K-H) were applied. The foliar spray was performed four times (30 days after sowing, at squaring, beginning of flowering and 15 days later). Results indicated the superiority of Giza 95 was in the yield while Giza 92 and 94 cotton cultivars were in the quality of fiber. Individual foliar applications of N-Ca and K-H had a significant increase in plant height, yield components (sympodial branches, total and open bolls, boll weight, seed index, lint% and seed cotton yield) and fiber quality (fiber length, uniformity index, fiber strength, fiber fineness and reflectance (Rd %)) and decrease yellowness (+b) compared with the control. Foliar N-Ca was more efficient as fertilizer than T-Ca. N-Ca combined with K-H achieved a higher increase of most previous traits than T-Ca with K-H. Application of N-Ca combined with K-H could be recommended to improve cotton production and fiber quality.