Effects of Tillage Types on Morpho-Physiological Characteristics and Forage Quality of Vetch (Vicia pannonica) in Rainfed Condition

Introduction Vetches are especially important due to their resistance to cold and water-deficient stresses, and due to the high amount of crude protein and detergent fibers, they have the same nutritional value as alfalfa and clover. Planting vetch can increase soil nitrogen due to the symbiosis of its root nodes with Rhizobium bacteria. No-tillage reserves more moisture in the soil than other tillage systems. No-tillage and reduced tillage significantly increase mycorrhizal fungi in soil compared to conventional tillage. Increased leaf area index (LAI) and dry matter in plants under reduced and no-tillage systems have been observed, too. Also, increases in chlorophyll concentration, decreases in canopy temperature, increases in plant height and improvements in forage quality in plants under a no-tillage system have been reported. This experiment evaluated the effects of different types of tillage on morpho-physiological traits related to yield and quality of vetch forage to protect the soil and select the best tillage system. Materials and Methods This experiment was carried out in Saral Rainfed Agricultural Research Station located 55 km north of Sanandaj county, Kurdistan province, in the west of Iran. The effects of reduce tillage (RT), no-tillage (NT) and conventional tillage (CT) systems were evaluated on rainfed vetch in rotation with wheat during two years (2018-02019). Sowing date was 18 and 9th of October in the two experimental years respectively. All sampling of rhizobium nodules, relative leaf water content, leaf area index, chlorophyll and carotenoids, chlorophyll fluorescence, canopy temperature, enzymes, proline, hydrogen peroxide, malondialdehyde, leaf soluble proteins and carbohydrates, leaf elements took place in early seed filling stage. The combined (2-year data) analysis of variance (ANOVA) was performed using SAS software by the general linear model (GLM). The means value were compared using Duncan’s range test at P ≤ 0.05. Results and Discussion In this study, the yield of dry forage in reduced and no-tillage systems increased by 14 and 24%, respectively, compared to CT. A significant relationship (R = 0.75*) was obtained between the relative leaf water content and dry forage yield. According to the results, vetch in the no-tillage system had the highest percentage of colonization (30.16%), the number of fungal spores (179.8), and rhizobium nodes (12.16) on the roots. The high symbiosis of mycorrhizal fungi in RT and NT compared to CT was probably due to higher water uptake and higher RWC. In the present study, vetches under the NT system probably had higher chlorophyll a and b concentration due to more moisture and higher nitrogen and phosphorus in leaves. The results showed that the tillage treatments had significant effects on the activity of reactive oxygen species (ROS), which was directly related to the amount of plant moisture and antioxidant enzymes. The lowest activity of enzymes was in vetches under a no-tillage system.   Conclusion In this experiment, reduced and no-tillage systems increased yield compared to conventional tillage. Significant increases in relative leaf water content and canopy temperature difference were observed in different types of tillage. Chlorophyll content and carotenoids in plants grown in the conventional tillage were lower than in reduce and no-tillage systems. The percentage of colonization, sporulation of mycorrhizal fungi, and the number of rhizobium nodes were higher in no-tillage system. The levels of antioxidant enzymes, hydrogen peroxide, malondialdehyde, and proline increased in CT compared to RT and NT. Types of tillage in rainfed conditions due to biological and structural changes in the soil cause positive morpho-physiological changes and forage quality in rainfed vetch seem to be effective in increasing yield and improving growth conditions.