Evaluation of seed yield and competition indices for intercropped barley (Hordeum vulgare) and annual medic (Medicago scutellata)

Annual medic is an annual crop which performs well in various forage cropping systems. However availability of medic seeds is a major challenge for livestock producers in Iran. This study was conducted to determine if intercropping annual medic with barley can produce supplement medic seeds while barley grain yield as the main crop is not compromised. Two experiments were carried out at the experimental farm of University of Tehran. In experiment I (2007), a randomized complete block design with eight cropping ratios comprising of 1B:1M (one row of barley: one row of annual medic), 2B:2M, 4B:4M, 6B:6M, 6B:2M, 4B:2M, 2B:4M, and 2B:6M along with sole culture of barley and annual medic was studied. In experiment II (2009 and 2010), four new treatments were added to the intercropping ratios used in experiment I and also weeds were controlled. The overall results as indicated by competition indices including LER, RCC, and MAI revealed that regardless of ratios, the grain yield of barley when intercropped with medic was lowered. The total seed yield of both crops however, was improved in some of the intercropping ratios when compared to the monoculture of either crop. In 2007 where weeds were not controlled, the LER of the cropping ratio of 2H:2M was 1.32 which is an indication of 32 percent yield advantage over the sole cropping of the two crops. When weeds were controlled (2009 and 2010) the intercropping ratio of 6B:2M was the highest and had a LER of 1.29. The yield advantage of intercropping of medic and barley over their monoculture was also confirmed by RCC and MAI indices. The results of this study indicated that although intercropping of annual medic with barley, using 6B:2M replacement series yielded 259 kg ha-1 less grain compared to barley sole cropping but it produced a 365 kg ha-1 annual medic seed which has significantly higher market value than barley.