Effect of Nettle-leaf goosefoot (Chenopodium murale) on bulb Onion (Allium cepa) yield

In order to study the competitive ability of onion against Nettle-leaf goosefoot (Chenopodium murale), an experiment was conducted at the research center of Iranshahr during 2003 and 2004. The experimental design was split-plot based on Randomized Complete Block Design (RCBD) with 4 replications. Main plots were Planting systems  (direct-seeded and transplanted) and sub plots were five density patterns (0, 0.33, 1, 3 and 6 plant/m2) at fix density of onion. The relationships between onion yield and Nettle-leaf density for each year were described using a rectangular hyperbolic function suggested by Cousens. The initial slop of the hyperbola (parameter I), representing the percentage yield reduction per unit density for very low Nettle-leaf infestations, was estimated 66.86 and 23.89% for direct-seeded onion and transplanted onion in 2003 while 48.09 and 42.86% in 2004. Maximum yield loss (parameter A), was estimated 92.92% in first year and 80.95 in second year for transplanted onion. In direct-seeded that have less competitive ability than tranplanted onion, A, was 100% in two year. Generally, the results from experiments data and regression model showed that nettle-leaf is more competitive than onion