Effects of Different Tillage Systems on Weed Seedbank Dynamics in Corn-Wheat Rotation

An experiment was conducted to find out effects of different tillage systems on soil weed seedbank density under cornwheat rotation. A split-plot trial based on RCBD with six replications was carried out during two years (2012 and 2013). Main plots included conventional seed bed prepration by moldboard ploughing (CT), minimum tillage (MT) and no-tillage (NT). Each main plot was divided in to two subplots (with herbicide and control). Seed densities were estimated by direct seed extraction in systematic method by an auger with 7cm diameter from 0-20 cm depth from each sampled plot prior to corn planting, just before applying treatments. Sampling was also replicated and continued after corn harvesting, pre and post tillage and finally after wheat harvesting. The seedbank was initially composed of 19 species, mostly annuals. Mean comparison of weed seedbank post wheat harvesting showed Sorghum halepense, Lactuca serriola and Convolvulus arvensis was significantly increased in no till plots, while perennial weed seeds such as Convolvulus arvensis and Malva neglecta were not affected by herbicides. CT, moldboard ploughing increased Avena loduviciana and Hordeum sponteneum seeds significantly by vertical distribution of buried seeds to soil surface.