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 upperm ost white flower (NAWF), an indicator of plant growth and development in co tton (Gossypium hirsutum L). In this study, we examined relationships of NA WF with canopy photosynthesis (CP), specific leaf weight (SLW), and yield c omponents, boil number, and dry weight in cotton under varying N supply. Fo ur pre-plant soil incorporated fertilizer N treatments were imposed on long -term N fertilizer plots (fine-silty, mixed thermic Typic Fragiudalt); 0, 5 5, 82, and 110 kg N ha(-1). Soil N level had a dramatic effect on NAWF CP S LW, and yield components, all of which increased with increasing soil N lev el. However, CP and NAWF declined as the season progressed under all four s oil 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). Al so, the photosynthetic capacity of the canopy was strongly related to SLW u nder 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 yi eld potential of cotton plants in a given environment.