Study of crop rotation and weed management method effects on weed population changes

In order to study of crop rotation and weed management methods effects on weed population، a 5-yr experiment was conducted from 1384 at field research of plant protection research institute، Karaj، Iran. The experimental treatments were crop rotation (including: sugar beet-sugar beet and sugar beet-wheat) and weed management method (including: chemical، chemical+ mechanical and hand weeding) that arranged in factorial experiments based a randomized complete block design with 4 replications. In contrast with sugar beet- wheat treatment، results indicated that annual and perennial weed populations increased in the end of rotational period in mono-culture system. Annual weed population also decreased in integrated weed management plots but it had no effect on perennials. Result suggested that the weed seed community in a sugar beet- wheat rotational system differs in structure and composition from communities associated with continuous sugar beet system، which in the end of 5 years experiment، percentage of bindweed and Johnson grass seeds in soil (in compare with knotweed and amaranth) were fewer in rotational treatments and they distributed in layers deeper than in 0-10 (cm) layer of soil.