MODELING TEMPERATURE EFFECTS ON MAIN STEM NODE DEVELOPMENT IN COTTON CROPS

Authors: Acock, Basil; PACHEPSKY, YAKOV - DUKE UNIVERSITY

Submitted to: Agricultural Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/2003
Publication Date: N/A
Citation: N/A

Interpretive Summary: Similar to all plants, cotton uses sunlight to turn carbon dioxide into sugar and increase its dry weight. To intercept as much light as possible, farmers try to cover the soil with crop plants quickly. Therefore, knowledge of the rate of stem growth and how it is affected by environment is useful in making management decisions. Rates of node appearance (NAR) and internode elongation (IER) were studied to develop equations describing cotton plant growth. NAR and IER vary with temperature, cultivar, and whether the plants are grown in the field or in controlled-environments. Controlled-environment data were used to determine the equations relating NAR and IER to temperature, and the parameter values for these equations were estimated from field data for individual cultivars. The parameter values for NAR differed between cultivars. At temperatures above 25 degrees C, NAR was up to 40% slower, IER was 40% slower, and the duration of internode expansion was up to 23% longer, in the field than in controlled-environments. Controlled-environment data and field data were both needed to develop the equations. However, it was necessary to choose equations which had a small number of parameters because of the small number of field data available for fitting them. It is not necessary to repeat the controlled-environment experiments for each cultivar because the equations are the same although the parameter values differ.

Technical Abstract: Cotton yields are determined primarily by the amount of sunlight the crop intercepts during the growing season which is determined largely by the rate of vegetative development. For this and other reasons, a knowledge of how crop environment affects the rate of vegetative development is useful in making management decisions. Rates of node appearance (NAR) and internode elongation (IER) were studied to develop equations for a model of cotton crop growth and yield. NAR and IER vary with temperature, cultivar, and whether the plants are grown in the field or in controlled-environments. Therefore, controlled-environment data were used to determine the shapes of the dependencies of NAR and IER on temperature, the shapes were fitted with equations which had few parameters, and these parameter values were estimated from field data for individual cultivars. The parameter values for NAR differed significantly between cultivars. At temperatures above 25 degrees C, NAR was up to 40% slower, IER was 40% slower, and the duration of internode expansion was up to 23% longer, in the field than in controlled-environments. Controlled-environment data and field data were both needed to develop the model. However, it was essential to describe the dependencies with equations which had a number of parameters appropriate to the number of field data available for fitting them. It is not necessary to repeat the controlled-environment experiments for each cultivar.