Leaf area relationships to plant vegetative characteristics in cotton (Gossypium hirsutum L.) grown in a temperate sub-humid environment

Measurement or estimation of leaf area is essential for understanding crop responses to experimental treatments. The objective of this study was to develop regression models for estimating leaf area of field-grown cotton (Gossypium hirsutum L.) from measurements of leaf dry weight (LDW), vegetative components (stems and leaves) dry weight (VDW) and plant height (PH). Three cotton cultivars (Deltapine 25, Sahel and Siokra 324) with different leaf morphologies were grown under varying growth conditions created by four different planting dates in a temperate sub-humid environment (Gorgan, Iran). Leaf area, LDW, VDW and PH were measured at one month after emergence, squaring, flowering, bolling, boll opening and second harvest. Data set for validation was collected during growing season of 2003 in different experiments. Measured leaf area ranged from 170 to 8167 cm2 plant -1. Different regression models were examined for describing leaf area relationships to LDW, VDW and PH. It was found that the power function gives the best fit in terms of R2 and root mean square of error (RMSE). Cultivar differences were not significant and a general equation was adequate for all the three cultivars. LDW and VDW provided good estimation of leaf area. However, PH was not a good predictor of leaf area. It was concluded that cotton leaf area can be estimated or simulated as a function of LDW or VDW with reasonable accuracy.