Investigation of Weed Control on Assimilate Remobilization, Yield and Yield Components in Mix Cropping of Wheat Cultivars

Wheat is the most important crop on the land, which has always been of particular importance since its domestication and has the highest cultivated area among crops. Among the factors that reduce wheat production in the country, weeds are of particular importance and according to the studies; the average weed damage in wheat fields is 23% in Iran. This study was carried out to investigate the effect of weed control on remobilization, yield and yield components in mixed cropping of wheat cultivars and compare it with monoculture.

In order to investigate the effect of weed control on remobilization, yield and yield components in mix cropping of wheat cultivars, a randomized complete block design with three replications was conducted in research field of Agriculture College and Natural Resources of Darab, Shiraz University during 2018-2019 growing season. Experimental treatments included six levels of weed control at tillering, stem elongation, booting, ear emergence, weed-free and weedy check which in each stage, all weeds controlled manually, and cropping system treatments including of Sirvan monoculture, Setereh monocultures and mix cropping of Sirvan and Setereh, which were in a ratio of one to one.

Simple effects of weed control and cropping system on assimilate remobilization, percentage of assimilate contribution, weed biomass, plant height, 1000-grain weight, number of spike per square meter and grain yield was significant. Also, assimilate remobilization, remobilization efficiency and contribution of assimilate in treatment of weed control at tillering stage increased by 37.7%, 57.2% and 5.8%, respectively, compared to weed-free control which these traits in mixed cropping of Sirvan and Setereh increased by 29.7%, 6.6% and 18.2%, compared to monoculture of Sirvan, respectively. Results showed that weed biomass in mix cropping treatment compared to monoculture of Setareh and Sirvan decreased 29.6% and 21.25%, respectively. Also, the highest grain yield was obtained in mix cropping, which was 22.8 and 11.2% more than Setareh and Sirvan monoculture, respectively Weed control at tillering reduced grain yield as 11.9%, which had the lowest yield reduction compared to the other weed control treatments, so it may be the best time to weed control in mix cropping system.

The results showed that the mix cropping of wheat cultivars could be successful in weed control and competing, so that the weed biomass in the mix cropping had more reduction and this may be due to more canopy shading on weeds in mix cropping of two wheat cultivars. The results of assimilate remobilization showed that the dwarf cultivar of Setareh had a more efficient in assimilate remobilization and tall cultivar of sirvan by suppress the weeds at flowering has less demand for assimilate remobilization in grain filling stage. Also, the highest grain yield was obtained in mix cropping compared to monoculture and mix cropping can be used as an appropriate strategy for optimizing the use of environmental factors to increase production stability.