Investigating the Quantitative and Qualitative Yield of Bitter Vetch (Vicia ervilia) and Grass Pea (Lathyrus sativus) in Intercropping with Wheat (Triticum aestivum) under Different Tillage Systems

To investigate the quantitative and qualitative traits of bitter vetch, grass pea, and wheat intercropped under different tillage systems, a split-plot field experiment was conducted based on a randomized complete block design with three replications. The field trials were performed at the research farm of Ilam University in the 2019 and 2020 growing seasons. The tillage systems (no-tillage, minimum tillage, and conventional tillage) were assigned to main plots and the planting pattern at six levels (monoculture of wheat with weeds, monoculture of wheat without weeds, intercropping of 100% wheat+ 50% bitter vetch, 100% wheat+ 50% grass pea and monoculture of bitter vetch and grass pea) were assigned to sub-plots. The results showed that the highest wheat grain yield was obtained in wheat monoculture without weeds under minimum tillage (8.78 t ha-1) and the highest forage yield of bitter vetch (7.80 t ha-1) was observed in monoculture of bitter vetch under minimum tillage condition. The highest forage yield (4.08 and 3.98 t ha-1) of grass pea was observed in both minimum tillage and conventional tillage systems, respectively. Intercropping patterns increased wheat grain protein concentration by 9.12%. Monoculture of legumes, compared to intercropping, led to improvement in forage quality by increasing protein, phosphorus, and calcium concentrations, and decreasing of neutral detergent fiber and acid detergent fiber. The land equality ratio was more than one in all intercropping patterns of wheat and legumes indicating the advantage of intercropping patterns over monoculture for land use and increased crop yield. In conclusion, the intercropping of wheat with bitter vetch under a minimum tillage system can be considered an appropriate environmentally-friendly approach for crop yield improvement.