CONCEPT FOR MONITORING THE GROWTH AND DEVELOPMENT OF COTTON PLANTS USING MAIN-STEM NODE COUNTS

Management efficiency in cotton (Gossypium hirsutum L.) can be improved by implementing strategies that may be adjusted in response to expected or realized changes in plant growth and development. We propose that successive counts of main-stem nodes bearing sympodia with a preflower fruiting structure in the first position are practical, dynamic measurements of plant development. A technique of monitoring number of main-stem nodes above the sympodial branch bearing a white flower in the first position from the main axis (NAWF) was investigated. The physiological basis of NAWF was established by relating NAWF to other measurements of crop growth and yield. A critical value of NAWF was determined by retention, size, and number of seed associated with first-position bolls. In separate tests, influences of cultivars, plant densities, irrigation, and two insect pests on NAWF were evaluated. The number of NAWF was closely related to variation in canopy photosynthesis indicating that growth activity of the crop can be monitored by NAWF. Based on individual boll measurements, potential economic value of flowers declined rapidly as NAWF approached 5.0. From regression equations of NAWF by days from planting, the number of days to NAWF of 5.0 (representing the last effective flower population) were calculated and used to distinguish effects of the management factors on plant development. Increased precision and confidence in end-of-season management decisions will likely be the first major benefit of this monitoring technique. As effects of additional management factors on NAWF are established, manipulation of the effective fruiting period and developmental pace of the crop should be possible by various combinations of factors, thereby providing a useful management tool.