Effects of Different Densities of Cotton (Gossypium Hirsutum) and Common Lambsquarter (Chenopodium Album) on Some Cotton Growth Characteristics in Birjand Condition

Abstract

Abstract Weeds are problematic plants in agroecosystems as a competitor for crops. In order to evaluate effects of cotton (Gossypium hirsutum) and common lambsquarter (Chenopodium album) densities on some crop growth indices, a study was conducted during 2006 in Experimental Station of Faculty of Agriculture, The University of Birjand as factorial experiment based on complete randomized block design with four replications. Three densities of cotton (6, 9 and 12 Pl.m-2) and four weed densities (0, 6, 9 and 12 Pl.m-2) were used to provide different weed interference levels. Indeed, three plots in each replication were intended to cultivation of lambsquarter alone at 6, 9 or 12 Pl.m-2. Results showed that crop growth rate (CGR) of cotton was influenced by weed density, and its relative growth rate (RGR) and net assimilation rate (NAR) indicated a declining trend as weed density increased. Dry matter accumulation of cotton also was affected negatively by weed densities, as interference of lambsquarter at 6, 9 and 12 Pl.m-2 resulted to 35, 42 and 48 percent dry matter reduction, respectively, than weed-free treatment. Increasing of cotton density could partly compensate for negative impact of weed attendance on cotton growth. Thus, it seems higher plant densities can be used as a managing tool against weeds in cotton fields to avoid reduction of yield. Keywords: Cotton, Density, Weed, competition, Growth analysis