Evaluation the Effects of Wheat (Triticum aestivum L.) Cultivars Intercropping Systems on Population, Biomass, Micronutrients Content of Weeds and Crop Yield

Use of chemical herbicides has been very effective for weeds control mainly for reducing yield losses and reduction of weed populations, but the frequently use of herbicides as the only weed management tool is seriously being questioned because of herbicide costs, resistance of weed populations to one or multi herbicides and environmental pollution. Reduce the use of chemical herbicides is one of the sustainable agriculture goals and several alternatives with this purpose have been evaluated, recently. Therefore, diversification of cropping systems by intercropping different species of crops has been proposed as a solution for reducing the use of herbicides in modern agriculture.The main objective of current field experiment was to evaluate the growth and micro nutrients content of weeds and crop yield in wheat cultivar intercropping systems. In order to investigate wheat-weed competition relationships and crop yield under intercropping and sole cropping of wheat cultivars, an experiment was conducted at Darab faculty of Agriculture and Natural Resources, Shiraz University, during the growing seasons 2013-2014. The experiment carried out using randomized complete block design with eight treatments and three replications. Wheat cultivars and genotypes were planted in four row intercropping systems and four sole cropping systems, including I1: intercropping of shirudi + 91-11, I2: intercropping of shirudi + 91-15, I3: intercropping of 91-11 + 91-15, I4: intercropping of shirudi + 91-11 + 91-15, S1: shirudi sole cropping, S2: 91-11 sole cropping, S3: 91-15 sole cropping and S4: F2 sole cropping. Different weed species were recorded in field experiment, but total weed density and total weed dry matter were determined for each experimental plot. Weeds density were determined from each experimental plot by using a quadrat of 1 × 1 m-2 randomly. Then all weeds in each quadrat were harvested and transformed to laboratory for determining their biomass and micronutrients (Fe, Zn, Cu, and Mn) content. At harvest time, all crops harvested in each plot, then crop yield was determined. Results showed that genotype mixtures had a significant effect to reduce the density, biomass and micronutrients content of weeds. The highest and lowest weed density and biomass were observed in sole cropping and intercropping systems, respectively. Intercropping systems of cultivars reduced weed population and their dry matter more than sole cropping systems. Shirudi sole cropping (39.33 plant. m-2) showed the highest weed density and the highest weed dry matter was observed in 91-11 sole cropping (130 g.m-2) and shirudi sole cropping (121.3 g.m-2). The highest and the lowest micronutrients content of weeds including Iron (Fe), Zinc (Zn), Cooper (Cu) and Manganese (Mn) were observed in sole cropping and intercropping systems, respectively. The highest Fe, Zn, Cu and Mn content of weeds were observed in 91-11 and shirud sole cropping (225 and 245.6 mg.kg-1, respectively), shirudi sole cropping (27.5 mg.kg-1), 91-15 sole cropping (21.23 mg.kg-1) and shirudi sole cropping (63.85 mg.kg-1), respectively. The highest and lowest crop yield were observed in shirudi + 91-15 intercropping (5.40 ton.ha-1) and 91-15 sole cropping (2.70 ton.ha-1), respectively. In overall weeds micronutrients content and weed growth in intercropping systems decreased significantly in comparison to sole cropping systems. The results of this experiment showed that row intercropping of wheat cultivars can reduce the weeds ability for use of environmental resources, therefore crop can utilize resources more efficiency and increase its yield. The results showed that wheat cultivars intercropping method limits environmental resources for weeds growth and this have implication for non-chemical management of weeds and increasing crop yield in ecological approach in agro-ecosystems. Thus, wheat cultivar intercropping systems can modify weed infestation in cropping systems. The results of this study suggest that row- intercropping system of wheat cultivars have potential to produce higher yield and less vulnerable to weed infestation than their sole cropping system, because they can provide high genetic diversity.