Extinction coefficient and radiation use efficiency of cotton varieties for different planting densities in Gorgan

Knowledge of management factors effect on plants and consumption the maximum capacity of environment can increase crop yield. Application of crops growth simulation models is a valuable approach to identify the impact of various management factors on yield. If the necessary information of each crop in each region is accessed, it is possible to use crop growth models. The aim of this study was to evaluate effect of planting density (250000 and 62500 plants per hectare) and cotton varieties (Golestan, Sepid and Armaghan) on extinction coefficient and radiation use efficiency. The experiment was carried out as split plot design based on randomized complete block design whit three replications in 2011. The plant density was as main plot factor while cotton varieties were considered as sub-plot factor. The results showed that effect of variety on the extinction coefficient and radiation use efficiency was not significant. Extinction coefficient decreased significantly from 0.87 to 0.61 when plant density was increased. However, the radiation use efficiency was 1.35 and 3.17 g.MJ-1 respectively for 62500 and 250,000 plants per hectare density. Higher plant density increased leaf area index and canopy closure at higher temperatures which caused to increase the radiation use efficiency in 250,000 plants density.