Effect of additive and replacement intercropping ratios of forage sorghum (Sorghum bicolor L. Moench) and berseem clover (Trifolium alexandrinum L.) on forage production

To evaluate forage production and land equivalent ratio (LER) in additive and replacement intercropping systems of forage sorghum and berseem clover, a field experiment was conducted using randomized complete block design with eight treatments and three replications at the research field station of Seed and Plant Improvement Institute, Karaj, Iran, in 2016-17 and 2017-18 growing seasons. The experimental treatments consisted of eight intercropping ratios: 75% sorghum + 25% clover (S75C25), 50% sorghum + 50% clover (S50C50), 25% sorghum + 75% clover (S25C75), as replacement intercropping systems and100% sorghum + 50% clover (S100C50), 50% sorghum + 100% clover (S50C100), 100% sorghum + 100% clover (S100C100), as additive intercropping systems, as well as sorghum monoculture (S100C0) and clover monoculture (S0C100). In this experiment, dry forage yield of sorghum and clover, equivalent yield of sorghum and clover, crude protein content, dry matter digestibility, crude protein yield, digestible dry matter yield and LER for dry forage and protein production were evaluated. The results showed that the highest equivalent yield of sorghum, equivalent yield of clover, crude protein, and digestible dry matter yield were obtained from S100C100 treatment with 37598, 17915, 3163, and 17754 kg.ha-1, respectively. S100C50 also ranked in the superior group with 16455 kg.ha-1 of digestible dry matter. The highest land equivalent ratios for dry forage and protein production (1.61 and 1.71, respectively) were calculated for S100C100. S100C50 and S50C100. According to the results of this study, additive intercropping of 100% sorghum + 100% clover can be recommended as the superior intercropping system to meet sustainable agricultural goals in production of these two forage crops.