Submitted to: Journal of Production Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 21, 1998
Publication Date: N/A
Interpretive Summary: A lack of potassium in the soil is being reported throughout cotton fields in the southern USA. Cotton yield and quality can be reduced if this nutrient is deficient. New production technologies, like planting cotton after wheat harvest, cause boll development to occur later in the season when temperatures are cooler. Like potassium deficiency, cool temperatures during boll development can lower the yield and quality of the lint. We conducted this experiment to determine the effect of potassium fertilization and planting date on cotton yield and fiber properties. We found that potassium fertilization affects the yield of normal- and late-developing cotton to the same degree. We also found that late-planted cotton had fibers that were longer, thinner, and less-mature than cotton planted at the normal time. Although long thin fibers are desirable, fibers that are not mature can cause problems when the lint is processed into fabric. This information is important to scientists and growers who are developing and testing new production systems. It indicates low soil potassium and cool temperatures during boll development do not interact to worsen the yield or quality of cotton beyond the individual effects of these stresses. However, adequate potassium fertility will be necessary for optimizing these new systems. It also points out to scientists the need to monitor cotton fiber maturity when developing systems where the crop will develop late in the season.
Technical Abstract: Potassium deficiency and cool temperatures during boll development together may affect the yield and fiber quality of cotton (Gossypium hirsutum L.) beyond the individual effects of these stresses. Our objective was to determine the effect of K fertilization on normal- and late-planted cotton. In 1991, 1992, and 1993, three cotton genotypes were seeded in late-April and late-May on a Hornsville loamy sand (clayey, kaolinitic, thermic Aquic Hapludult) soil with and without annual applications of 100 lb K/ac. Surface soil K was 95 lb/ac before applying treatments in 1991. No interactions between planting date and K occurred for lint yield. In 1991 and 1992, applied K level did not affect lint yield. In 1993, the 100-lb K/ac treatment averaged 104 lb lint/ac more than the 0-lb K/ac treatment. In that year, fiber from cotton plants receiving 100-lb K/ac was shorter, thicker, and less mature than fiber from plants receiving no fertilizer K. Planting date influenced lint yield in 1991 and 1992 only, but the response was small and not consistent across genotypes. Each year, micronaire was higher for the late-April planting date than for the late-May. In two of three years, the late-May planting treatment had higher yarn strength, elongation, and fiber length, but lower fiber maturity. Additional attention to K fertility is not needed in production systems where the boll maturation period is delayed.