Response of cotton to nitrogen and water in a tropical environment. III. Fibre quality

Abstract

SummaryIn two experiments three dates for time of last irrigation were combined factorially with four rates of application of nitrogen fertilizer and two varieties of cotton. Early termination of watering (when the crop had set 70 bolls/m2) combined with heavy application of nitrogen (168and225 kg/ha) decreased fibre strength, micronaire and yarn strength, particularly in 1973. In two other experiments three frequencies of watering were combined factorially with several rates of application of nitrogen. Frequent watering (weekly) combined with heavy application of nitrogen (168 kg/ha) decreased uniformity of fibre length, micronaire and yarn strength and appearance. In both experiments application of nitrogen increased fibre length. The responses of both varieties were similar except for effect of nitrogen on micronaire. Application of nitrogen decreased the micronaire of Deltapine 16 more than that of Acala 1517 BRI.The response of the fibre properties to variation in crop nitrogen and water supplies are interpreted in terms of the effects of these factors on (i) the intrinsic fibre properties of bolls maturing at the same time, (ii) the change in the fibre properties of bolls maturing progressively later in the season, (iii) the proportion of total yield contributed by bolls maturing at different times and (iv) delay in harvest and consequent variation in exposure to weather prior to harvest. Yarn strength did not respond as much as fibre properties to the experimental treatments and in particular did not reflect the influence of weathering on fibre properties to the degree anticipated.