Planting Date and Potassium Fertility Effects on Cotton Yield and Fiber Properties

Late planting causes cotton (Gossypium hirsutum L.) to flower later in the season so boll development occurs at lower temperatures. Potassium deficiency elicits some of the same responses in cotton that delayed planting does. Together, these stresses may affect the yield and fiber quality beyond the individual effects of late planting and K deficiency. Our objective was to determine the effect of K fertilization on normal- and late-planted cotton. In 1991, 1992, and 1993, three cotton genotypes (PD 5286, PD 5358, and PD 5472) 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 Ib K 2 O/acre. Soil K in the upper 6-in. was 95 Iblacre at the initiation of the experiment. Soil K did not differ between the two K fertilizer treatments after the 1991 growing season. After the 1992 and 1993 seasons, K in the 0- to 6- and 6- to 12-in. soil layers was greater in the 100 Ib K 2 O/acre treatment than in the 0 Ib K 2 O/acre treatment, but no differences occurred at greater depths. Potassium fertilization did not affect flower production in either planting date in any year. Potassium deficiency reduced the lint yield and fiber length of PD 5286 and PD 5358 but not that of PD 5472. Besides yield and fiber length, fiber perimeter was the only parameter reduced by K deficiency. Late planting caused reduced yield in only I of the 3 yr, and for only two of the three genotypes. In general, cotton planted in late May had higher yarn strength, elongation, and fiber length, but lower micronaire and fiber maturity than cotton planted in late April. No interactions that included both K and planting date were significant for lint yield, yarn strength, or any of the fiber properties. This indicates that additional attention to K fertility is not needed in production systems where the boll maturation period is delayed.