Mineral Nutrition for Optimum Cotton Yield and Fiber Quality

The deficiencies of secondary nutrients such as sulfur (S) and micronutrients, especially zinc (Zn), are recognized as constraints to crop production and productivity. Symptoms of S and micronutrient deficiencies have been observed in Tennessee cotton in recent years. This study was conducted to investigate the influence of S and Zn on lint yield and fiber properties, and to develop guidelines for correcting deficiencies. This project was implemented from 2007 to 2010 with a small-plot study of response to S and Zn fertilization in field-grown cotton and a study of S deficiency induced in container-grown cotton. The S-Zn response study was conducted in a non-irrigated, no-tilled Dexter loam that had tested low in these essential elements. Sulfur treatments were 0, 10, 20, and 30 lb S/ac broadcast to small plots before planting as main-plot treatments. Sub-treatments consisted of foliar application of 0 or 0.26 lb Zn/ac during squaring. The following measurements were taken on an individual plot basis: Mid-season soil S and Zn levels, leaf S and Zn concentrations, lint yield, gin turnout, seed index, and fiber properties (micronaire, length, uniformity, or strength). The S-deficiency study was conducted on cotton grown in containers placed outdoors, in which groups of plants were fed nutrient solutions with 1 (or 0) or 20 ppm S, plus 11 other essential elements through a drip system. Sulfur treatments were applied from about 29 to 74 days after planting, followed by a recovery phase in which all plants in the 1 (or 0) ppm treatment gradually received S nutrition. Leaf S concentration, concentrations of other essential elements, seedcotton weight per plant at maturity, weight per boll, bolls per plant, proportion of bolls at first position fruiting sites, locules per boll, seeds per locule, and seed index were measured or determined.