Maturity and Lint Yield of Nitrogen‐ and Phosphorus‐Deficient Pima Cotton

Abstract

The Pima cotton (Gossypium barbadense L.) plant is inherently late maturing and unsuitable for production in areas where highly probable late‐season rainfall coincides with boll opening. A field study was conducted between 1990 and 1992 to determine if the maturity of Pima cotton can be enhanced with applied N and P without reducing lint yield. Five preplant‐applied N rates up to 180 kg ha−1 in 1990 and up to 269 kg ha−1 in 1991 and 1992 were tested. Four P rates from 0 to 45 kg ha−1 in a factorial combination with N were tested in 1991 and 1992. Nitrogen did not affect yield, days to first flower, or estimated percent open bolls in 1990. Nitrogen deficiency significantly enhanced maturity in 1991 and 1992. In 1991, >70% of the total bolls opened by 153 days after planting (DAP) where no N was applied, compared with 178 DAP where 202 or 269 kg N ha−1 was applied. In 1992, 68% of the bolls in the 0 kg N ha−1 treatment opened by 142 DAP, compared with <55% for all other treatments. The 0 kg N ha−1 treatment also significantly increased the ratio of reproductive to total plant dry weight earlier during the boll development period; however, the maturity‐enhancing effect of N deficiency occurred at the expense of lint yield. Relative to the 67 kg N ha−1 treatment, zero N reduced lint yield by 277 kg ha−1 (26%) in 1991 and 214 kg ha−1 (18%) in 1992. Phosphorus deficiency reduced lint yield in 1991, but did not affect percent open bolls or reproductive efficiency in 1991 and 1992. Earliness of Pima cotton may, therefore, be managed more effectively by minimizing applied N rates than by manipulating P fertilization.

Fiber Quality Response of Pima Cotton to Nitrogen and Phosphorus Deficiency

“…[1,4,5,8,18] Applied phosphorus did not affect fiber length (2.5 or 50% span length), strength, or micronaire (Table 1) despite its yield and growth reducing effects. [13,14] But phosphorus significantly affected elongation, reflectance, individual seed weight, and lint turnout (Tables 1 and 2). Fiber elongation decreased with increasing applied phosphorus.…”

“…The lint yield reducing effect of Fiber Quality Response of Pima Cottonnitrogen deficiency therefore may not be the result of its direct effect on lint growth but a result of its effect on seed growth in addition to its effect on boll size and number of bolls per plant. [13] Hearn [18] stated that nitrogen rate affected weight and number of seeds more than weight of lint per seed in Upland cotton. In our study with Pima cotton, the number of seeds per boll was not affected even by the most severe nitrogen deficiency (Table 2).…”

“…Moderate nitrogen deficiency equivalent to that of the 67 kg N ha À1 treatment may not affect fiber quality that results in discounts. Imposing a moderate level of nitrogen deficiency as a management strategy to selectively suppress excessive vegetative growth and enhance maturity as discussed by Tewolde et al [13] may therefore be a plausible practice without affecting the quality of the fiber produced.…”

“…An earlier report showed that imposing a moderate level of nitrogen deficiency may be an effective management strategy to selectively limit vegetative growth and enhance maturity of Pima cotton. [13,14] Because the value of Pima cotton depends on producing high quality fiber, whether such deficiency of nitrogen or phosphorus nutrition affects its fiber properties needs to be established. The objective of this study was to determine the fiber quality responses of Pima cotton to nitrogen and phosphorus fertilization ranging from deficient to excess.…”

Response of the enzymes to nitrogen applications in cotton fiber (Gossypium hirsutum L.) and their relationships with fiber strength

“…As nitrogen (N) is one of the most important factors influencing fiber yield and quality, research concerning N effect on fiber quality are crucial. It was reported that either excessive or deficient N caused reduction in fiber strength [3] , while optimal N application increased fiber quality [4] . However, most related research was concerned with the final fiber quality, with relatively limited investigation of the mechanisms of how N influences fiber quality development.…”