Assessing the effects of cultivar and nitrogen application rate on seedling vigor and early‐season canopy growth in cotton

Abstract

AbstractCultivar variation in seed characteristics can affect seedling vigor, and nitrogen (N) availability influences early‐season growth in some instances. However, interactions between cultivar and N application rate for early‐season growth have received limited attention. Thus, the objectives of this research were to quantify the effects of cultivar, N‐application rate, and their interaction on early‐season growth, predict seedling vigor from plant morphology, and identify associations between early‐season crop growth rates (CGR) and other growth indices. To this end, a 2‐year (2018 and 2019) field study was conducted using six cotton cultivars having different seed characteristics and six different N‐application rates. In both years, all single‐plant and whole‐crop growth indices were affected by cultivar but not early‐season N‐application rates. A function was developed that was strongly predictive (R2 = 0.78) of seedling dry weight and utilized only plant height and mainstem node assessments. Leaf area index was a strong and consistent predictor of early‐season CGR, whereas net assimilation rate was only associated with CGR in one of the 2 years. Thus, it is concluded that of the two factors assessed in the current study, cultivar is the dominant driver of seedling vigor up to 35 days after planting. Additionally, leaf area development is a more consistent driver of early‐season CGR than average assimilation rates of the canopy. In contrast, an application of N at planting did not affect seedling vigor or early‐season canopy growth in cotton.