Effects of Tillage and Fertility on Weed Communities over 48 Years in Southern Illinois.

Effective soil management programs may improve soil conservation efforts and limit erosion through reduced disturbance. We hypothesize that these management actions will also impact the weed community composition over time. Our objective was to quantify the differences in weed community composition across a combination of four tillage regimes (moldboard plow, chisel plow, alternate-till (2-1-2), and no-till) and three fertility treatments (no fertilizer, nitrogen only, and nitrogen-phosphorus-potassium) following 46 years of study implementation. Aboveground community composition as well as seedbank composition will be assessed. In all previous years throughout the 46-year study period, weed-free conditions have been maintained with normal practices. This season, in order to quantify weed community differences, soil residual herbicides will not be applied to half of the 6m wide plots in order to identify weed species which emerge. After weed emergence, the populations will be controlled to prevent buildup of the seedbank. To assess seedbank composition, 70 20cm soil cores will be taken per plot. Each soil core will be separated by depth into 5cm sections, creating 4 5cm sections. A subset of these 5cm sections will be evaluated for soil fertility measures, and the remainder will be grown out in order to see weed emergence in each layer.