CANOPY PHOTOSYNTHESIS, SPECIFIC LEAF WEIGHT, AND YIELD COMPONENTS OF COTTON UNDER VARYING NITROGEN SUPPLY

Nitrogen (N) nutrition greatly affects the number of nodes above the uppermost white flower (NAWF), an indicator of plant growth and development in cotton (Gossypium hirsutum L). In this study, we examined relationships of NAWF with canopy photosynthesis (CP), specific leaf weight (SLW), and yield components, boll number, and dry weight in cotton under varying N supply. Four pre-plant soil incorporated fertilizer N treatments were imposed on long-term N fertilizer plots (fine-silty, mixed, thermic Typic Fragiudalt); 0, 55, 82, and 110 kg N ha−1. Soil N level had a dramatic effect on NAWF, CP, SLW, and yield components, all of which increased with increasing soil N level. However, CP and NAWF declined as the season progressed under all four soil N levels. Canopy photosynthesis, SLW, and yield components were closely associated with NAWF as the soil N increased from 0 to 110 kg N ha−1. Also, the photosynthetic capacity of the canopy was strongly related to SLW under increasing soil N. These relationships of NAWF with CP, SLW, and yield components suggested that NAWF could be used as an index to predict the yield potential of cotton plants in a given environment.