Effects of summer crops on weeds densities and biomass and wheat (Triticumaestivum L.) yield in Khuzestan province

To investigate the effects of summer cultivation of crops on weeds densities and biomass as well as yield and performance of following planted wheat, field studies were carried out in Shavoor Research Station (Ahvaz, Khuzestan) over 3 years (2013-2016) using 5 treatments in a randomized complete block design. Treatments included rice-wheat, corn-wheat, sesame-wheat, mung bean-wheat and fallow-wheat rotations. The crops and weed densities and types had been observed during the year before the experiment, and no herbicides were used in all experiments to understand the pure effects of treatments. The main crop (wheat) was planted after autumn harvesting of above-mentioned crops. Densities and types of weeds were recorded 15 and 30 days after wheat primary tillering stage, and weed dry weights and grain yield were measured at the end of experiment. Results of this study indicated that considering the indices of weeds number and biomass (55-90%) as well as wheat yield (80-220%), wheat might not require to any herbicides after rice cultivation. Moreover, in the grain or forage corn planted fields, herbicide application is declined significantly, due to several and irrigations and frequent tillage. The whole three-years outcome of the experiments demonstrated that summer cultivation of crops might lead to sharp decline in the seed banks of important weeds such as wild oat (Avena ludoviciana), wild barley (Hordeum spantaneum) and some main broad leaf weed.