ABSTRACT

ABSTRACT

Use of foliar applied potassium has recently been demonstrated to increase fiber strength and yields of varieties of average strength. Historically, the most widely accepted means of producing high strength fiber was by selecting a variety with that trait. Many of the varieties that have above average strength have full season growth and maturity pattern, requiring different management of the crop. Incorporating these two approaches into a management strategy for fiber strength demands more information regarding the response of "high strength" and standard strength varieties to foliar fertilization and other cultural inputs. The objective of this study was to determine the fiber quality and yield response of standard and high strength cotton varieties to application of foliar potassium, nitrogen and mepiquat chloride. Two field studies were carried out during 1991 and 1992. A small plot study evaluated 4 varieties (DPL 50, DPL 5415, HS 46, SG 1001) and treatments of foliar applied potassium and nitrogen, mepiquat chloride, and a combination of mepiquat chloride and foliar fertilizer. A large plot field study evaluated 2 varieties (DPL 50 and SG1001) with and without a foliar K and N fertilizer treatment. Seasonal environments varied greatly between the two seasons. During 1991 growing season, almost 2500 heat units (DD60's) were accumulated, while the total 1992 accumulation was just over 2000. This caused a large delay in the maturity of all the varieties in 1992, and resulted in a different yield and fiber response in 1992 for the full season, high strength varieties. In 1991, the only differences found were changes in fiber strength due to variety. There was also a significant variety x foliar interaction in fiber strength in 1991. The foliar treatment of DPL 50 resulted in higher fiber strength, while SG1001 had no differences in fiber strength. In 1992, factors that improved earliness also improved yields, including variety and mepiquat chloride. A variety by treatment interaction occurred for yield in 1992. Yield increased for DPL 50 treated with both mepiquat chloride and foliar fertilizer, while none of the high strength varieties showed this response. In the large plot test, there was also a variety x foliar treatment interaction, but in this season the SG 1001 variety evidenced increased fiber strength when treated with the foliar K and N, while the DPL 50 did not show that difference. Under the conditions encountered in these tests, the most consistent method to improve fiber strength is varietal selection, but some varieties may respond better to foliar fertilizer than others, dependent on the season and boll development. If fiber strength is a value-added trait in a grower's marketing plan, then selecting a high strength variety that also yields high is probably that most dependable method of producing high strength lint. However, a high strength variety may require a different management strategy to be able to mature the crop timely. The risk of a late maturing crop, especially in the northern Delta, must be weighed against the potential value of higher fiber strength.