Effect of Soybean and Wheat as Cover Crops on Corn Yield and Weed Control using Different Fertilizer Sources

Introduction: According to the importance of corn in supplying the human food directly and indirectly, it is one of the most important plants among crops. One of the major problems in corn production systems, is competition with weeds that reduce corn yield significantly. Weeds not only reduce crop yields but also decrease the commercial quality and the feeding palatability of main crops. They enhance the soil seed bank of weeds, which may cause continuous weed infestation of field crops as well. Herbicide application is a reliable and highly effective method for weed control. However, demand for safe food products that have been produced with a minimum application of chemical inputs is increasing. Therefore, farmers interested in weed management have to rely on other control approaches. An alternative weed control method is the use of cover crops, which can suppress the growth of weeds by preventing them from light and by producing allelopathic compounds. Cover crops successfully have been integrated into conservational agriculture systems in many areas of the world. Legumes are used as cover crop because of their rapid growth, in addition their potential to provide further nitrogen,along with high ability to compete with weeds. Materials and Methods: In order to study the effect of cover crops (soybean and wheat) and different fertilizers sources on yield of corn and weed control, a filed experiment was conducted in randomized complete block design with three replications in 2012. Treatments included two cover crop (wheat and soybean) and three fertilizer (no fertilizer, chemical fertilizer and compost)..Fertilizer treatments was used according to soil analysis and requirement of corn (as a main plant). Weed-infestation and weed-free plots were used as controls. Study cultivars of corn, wheat and soybean were NS-640, Milan and Sari, respectively. Planting of corn was in June and cover crop was planted with corn simultaneously and between corn rows. The dominant weed species were velvetleaf (Abutilon theophrasti Medic.), johnson grass (Sorghum halepense (L.) Pers.), wild melon (Cucumis melo var. agrestis) and giant foxtail (Setaria glauca L.) in the field. In order to determine the dry weight and density of weeds, three-stage sampling was performed from the middle rows of corn. Corn yield was also measured by mechanical harvesting in middle rows and adjusting to 14% moisture. A week before the final harvest, ten plants of corn were selected randomly from