Evaluation of Bitter Vetch (Vicia ervilia) Forage Quality in Intercropping with Spring Barley (Hordeum vulgare)

IntroductionCereal-legume intercropping is a common approach in agricultural systems especially in developing countries. Bitter vetch is a forage legume that belongs to Fabaceae family. This plant can play a role in improving soil fertility by nitrogen fixation, which leads to the benefit of intercropping with forage grasses such as barley. Planting date and density are the determinants of optimal crop yield in intercropping systems. As the planting date changes, meteorological parameters (temperature, sunlight and…) also change, and influencing plant growth and production. The purpose of determining the optimal planting date is to synchronize the growth stages of the plant. On the other hand, plant density varies with factors such as area differences, planting date, climatic conditions and soil type. Vicia ervilia L is a plant of the legume family, which is partly drought tolerant and compatible with most soils. In this research, the forage quality of bitter vetch was evaluated in additive intercropping pattern with barley as well as in different planting dates.Materials and MethodsThe experiment was carried out as a factorial arrangement based on randomized complete block design with 3 replications. The studied factors were included planting dates at three levels (simultaneous planting of bitter vetch and spring barley on March 25, planting of bitter vetch 10 and 20 days after planting of spring barley on April 5 and 16, respectively) and planting densities at four levels (12.5, 25, 50 and 75%) in additive intercropping with spring barley. Bitter vetch and barley pure stands were considered as control treatments. Bitter vetch was harvested for forage at flowering stage. Forage quality indices including organic matter, acid detergent fiber (ADF), neutral detergent fiber (NDF) and mineral nutrients were measured in bitter vetch. Analysis of variance was performed using SAS software and means were compared by Duncan's method at the 1% probability level.Results and DiscussionThe results showed that the highest amount of organic matter, neutral and acid detergent fibers in bitter vetch forage were obtained in simultaneous planting of bitter vetch and spring barley. The lowest values ​​were obtained in sowing bitter vetch 20 days after barley planting, while the highest amount of mineral elements including nitrogen, potassium, sodium and calcium was obtained from sowing bitter vetch simultaneous with barley planting. The delay in bitter vetch sowing makes the plant less likely to grow and increases intensity of its competition with barley for food resources, which reduces the content of forage nutrients contents. The highest phosphorus content was observed at the third planting date (20 days after sowing spring barley) with an average of 52.40 ml.L-1 and was significantly different from other levels of planting date. It seems that the delay in bitter vetch sowing date and the decrease in vegetative growth and its competition with barley for mineral resources of soil did not have a decreasing effect on the phosphorus content and apparently the phosphorus content also increased in the delayed sowing conditions. Increasing bitter vetch density increased nitrogen, potassium and sodium levels of bitter vetch forage but decreased magnesium, phosphorus and calcium contents. Dry matter digestibility was not affected by sowing date, plant density and their interaction. The highest acid detergent fiber (ADF), neutral detergent fiber (NDF) was belonged to 12.5% ​​and the lowest were for 75% bitter vetch density. The planting date of April 6 was preferable to other planting dates in terms of mineral elements and the bitter vetch density of 75% was better due to the reduction of NDF and ADF indices. Results of previous experiments showed that in cereal crops and legume intercropping, the contents of acid detergent fiber (ADF), neutral detergent fiber (NDF) in forage were decreased.ConclusionIn general, the results of this study indicate that the contents of mineral nutrients including calcium, sodium magnesium and phosphorus of forage were higher in intercropping treatments than pure cultivation and the amounts of organic matter and digestible dry matter of bitter vetch forage in simultaneous intercropping with barley were equal to those of pure cultivation. Decreased acid detergent fiber and neutral detergent fiber in forage and production of forage with higher contents of minerals including phosphorus, magnesium and calcium are benefits of intercropped bitter vetch and spring barley compared with soleculture.