Response of cotton to water and nitrogen in a tropical environment: II. Date of last watering and rate of application of nitrogen fertilizer

Publisher Website
Google Scholar
Abstract
Four rates of nitrogen fertilizer, three dates for the last application of water, and two varieties were combined factorially in two experiments in successive years. Leaf water potential was measured. There were large yield responses to water and nitrogen; in both cases the response in number of bolls was relatively twice as great as that in boll weight. Because one effect of nitrogen was to prolong the setting of bolls, which required continued watering for its full expression, there was an interaction between the nitrogen and water treatments which affected number of bolls, and thus yield. Deltapine 16 yielded more than Acala 1517BRI and responded more to nitrogen than did Acala 1517BRI. Heavy nitrogen rates decreased the initial rates of boll setting of Acala. Weekly picks of open bolls showed that, with early cessation of water and with the lightest rate of nitrogen, the boll weight decreased in the fourth and subsequent picks. This effect of nitrogen was more marked in Acala. These responses were analysed into the components of boll weight and are discussed in relation to the timing of the development of the bolls in order to explore the physiological implications. Nitrogen and water delayed harvest by prolonging effective flowering, by increasing boll maturation period, and by increasing the number of defoliant sprays required.