Effects of replacement series on qualitative and quantitative yield and land equivalent ratio in maize-soybean cultivars intercropping

Intercropping, growing two or more crop types or cultivars on one field, is considered as one of the most important agricultural operations that can improve the utilization of environmental resources through increased plant growth and yield. Diversity and stability of fields, reduction in chemical fertilizers application and nutrient availability such as biological nitrogen fixation, are considered as some of the benefits of intercropping. Hence, selection of legume cultivars in intercrops is important and should be taken into account. This experiment was laid out in order to study of yield, yield components and land equivalent ratio in maize and soybean mixed cropping. The experiment was laid out as split-plot arrangement based on a randomized complete block design with four replications in research farm, agriculture collage, Ferdowsi University of Mashhad, Iran, during 2013-2014. Experimental treatments were combined of Wiliams and Sahar soybean varieties with Ns640 and Ossk713 maize varieties and both maize and soybean ratio in 0, 25, 50, 75 and 100%. Sowing ratio and cultivars composition were designed based on the replacement series: 100 % maize - 0 % soybean, 75 % maize - 25 % soybean, 50 % maize - 50 % soybean, 25 % maize - 75 % soybean, and 0 % maize - 100 % soybean. Results showed that cultivars combined and ratio treatments in mixed cropping had significant effect on yield, yield components and land equivalent ratio in mixed cropping of maize and soybean. During 2013 and 2014 growing sesaons, increasing the soybean ratio in intercrops lead to a significant increase in 1000-seed weight of this plant. The maximum grain and biological yield of maize and soybean were obtained in pure cropping and decreased by reducing the ratio of maize and soybean. The maize cv. Ossk713 and soybean cv. Sahar had the higher grain and biological yield because of longer growing season. Between soybean cultivars, Wiliams has higher nitrogen, protein and crude fiber as compared to Sahar cultivar. Maize and Soybean harvest index in pure cropping was more than mixed cropping treatments. Also, during both growing sesasons, the highest protein content was obtained in 50 % maize - 50 % soybean treatment. From the results, the highest total land equivalent ratio (maize + soybean) equal to 1.68 units was computed in 25% maize cv. Ns640 + 75% soybean cv. Sahar. The results of current experiment can emphasize the positive aspects of maize-soybean intercropping in terms of increasing the utilization of environmental resources per cultivated area.