Effects of tillage on biomass, roots, N-accumulation of vetch (Vicia sativa L.) on a clay loam soil in semi-arid conditions

The experiment was conducted during the cropping period of 2001–2004, to evaluate the effects of three tillage systems: conventional tillage with mouldboard plough (CT), shallow tillage with rototiller (ST) and double disc tillage (DD) on growth (biomass and roots), concentration of organic C and N, grain yield and yield components of common vetch (Vicia sativa L.). Based on the 3-year results, at the time just before green forage harvesting, the nitrogen content in biomass was higher in the CT followed by DD and ST, and corresponding values for grain and soil nitrogen were higher in the DD followed by CT and ST. Nitrogen content in roots was higher in the ST compared with that of the DD and ST treatments. Organic carbon in soil increased after DD, ST and CT with 21.3, 18.0 and 12.5 Mg kg−1, respectively; as compared to the amount at the beginning of the study at a depth of 0–20 cm. Organic carbon improvement in the DD treatment was also associated with a significant increase in grain yield compared to the other treatments. DD resulted in a reduced number of seed per pod and 1000-seed weight compared with CT. However, dry weight of biomass at the early podding stage was slightly higher under CT, although the main stem and plant height were lower than ST, which produced higher root weight.