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

Abstract

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 lb K 2 O/acre. Soil K in the upper 6‐in. was 95 lb/acre at the initition 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 lb K 2 O/acre treatment than in the 0 lb 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 1 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. Research Question Production systems with late plantings, like double‐cropping cotton with small grain, causes cotton boll growth and development to occur later in the season and lower temperatures during this time can influence yield and fiber properties. Potassium deficiency also reduces yield ahd affects fiber properties. Should production systems that delay boll development be adopted on K‐deficient soils, the yield and fiber quality may be compromised beyond the individual effects of low temperature stress and K deficiency. This study was conducted to compare the effects of K deficiency on yield, fiber properties, and yarn strength on early‐and late‐planted cotton. Literature Summary Both low temperature stress during boll development and K deficiency affect the yield and fiber properties of cotton. Studies have been conducted to determine the optimum planting time for highest yield with acceptable fiber properties. As planting is delayed beyond the optimum date, yield and micronaire generally decline while elongation, fiber strength, and yarn strength increase. Recently, K deficiency was reported to be widespread throughout the cotton growing region of the USA. Potassium deficiency reduces micronaire, elongation, fiber length, fiber uniformity, and fiber maturity. There are conflicting reports about the role of cultivar selection in reducing the effect of K deficiency. Study Description A 3‐yr (1991–1993) study was conducted at Clemson University's Pee Dee Research and Education Center near Florence, SC, on a Homsville loamy sand soil. Initial soil K rating at the beginning of the experiment was medium (95 lb K/acre), indicating a yield response to K fertilizer 50% of the time. Treatments: a) Seeding dates of late April and late May. b) K levels of 0 and 100 lb K 2 O/acre applied annually. c) Three cotton germplasm lines (PD 5286, PD 5358, and PD 5472) chosen because of their differential yield response to early and late production systems in previous studies. Applied Questions How did planting date and K fertilization affect cotton yield and fiber properties? Cotton in both planting dates had similar responses to K deficiency in this study. Averaged over all 3 yr, lint yield was increased for two of the three genotypes by applying 100 lb K 2 O/acre. Fiber length was slightly higher with added K for those two genotypes that responded with higher yield to the K fertilizer. Other fiber properties and yarn strength were not substantially affected by K, regardless of genotype or planting date. Late planting reduced yield in only I of the 3 yr, and then only 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. The dala from this study indicate that K fertility strategies developed for full‐season cotton production systems do not have to be modified for short‐season systems.

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