Fiber quality response of Pima cotton to nitrogen and phosphorus deficiency

Imposing a moderate level of nutrient deficiency may be an effective management strategy to limit vegetative growth and enhance maturity of Pima cotton (Gossypium barbadense L.). Whether such deficiency affects fiber quality of American Pima cotton, however, is not well known. A field study was conducted in 1991 and 1992 to determine the fiber quality responses of Pima cotton to nitrogen and phosphorus fertilization ranging between deficient and excess. Pima cotton cv. "S-7" was treated with nitrogen rates ranging between 0 and 269 kg ha(-1) in a factorial combination with phosphor-us rates ranging between 0 and 44 kg ha(-1). Fiber property measurements included fiber length, strength, fineness, elongation, and color properties. Increasing rate of applied nitrogen significantly (P less than or equal to 0.05) increased fiber length, elongation, micronaire, and color characteristics and reduced fiber uniformity ratio in 1991. Increasing nitrogen rate significantly (P less than or equal to 0.10) increased fiber length, uniformity index, and yellowness in 1992, when the degree of nitrogen deficiency imposed by the lowest nitrogen rate was not as severe as the deficiency imposed by the same treatment in 1991. Phosphorus did not significantly (P less than or equal to 0.10) affect any of the important fiber properties-length, strength, or micronaire-in either cropping season. These results indicate moderate level of nitrogen or phosphorus deficiency does not affect Pima cotton fiber quality. Nitrogen or phosphorus deficiency severe enough to reduce fiber quality and affect marketing of Pima cotton is unlikely to be encountered under normal Pima cotton production practices.