Starter fertilizer and the method and rate of potassium fertilizer effects on cotton grown on soils with and without winter grazing by cattle1

Abstract

A three‐year field study was conducted on a Decatur silt loam (clayey, kaolinitic, thermic Rhodic Paleudult) in North Alabama. The objective of the study was to evaluate the effects of winter grazing by cattle on the potassium (K) and starter fertilizer needs of cotton (Gossypium hirsutum L.) the following season. Grazed and non‐grazed treatments were established by planting a wheat (Triticum aestivum L.) cover crop in the fall and allowing cattle to graze half of the treatment area for 35 to 65 days in late winter‐early spring. After grazing, the grazed and non‐grazed wheat was killed and cotton was planted using a strip‐tillage system. Test areas had medium to high soil test ratings for K. Fertility treatments consisted of three rates of K (0, 37, and 74 kg K ha‐1), three methods of K application (surface broadcast; in‐row, band application at a depth of 30.5 cm; and surface banding using a spacing of 50.8 cm) and two rates of starter fertilizer (no starter and 168 kg#lbha‐l of a liquid 15–15–0). Seed cotton yields were affected by grazing of the winter cover crop prior to planting, but not by the method of K fertilizer application. During the two years that a yield reduction was observed, winter grazing reduced seed cotton yields by an average of 14%. Cotton responded to K rate only under the ungrazed system. During the first and second year of the test, an application of 37 kg K ha‐1 increased seed cotton yields by an average of 351 kg#lbha‐1. Starter fertilizer consistently gave slightly higher yields with a significant response occurring in two out of the three years.