Assessment of the Drilosphere of a. Trapezoides or L. Terrestris in the Activity of Clopyralid in Palouse Soils.

Name: Ayobami Olatunji Adegbite, Jodi Johnson-Maynard, Ian Leslie, Matthew Morra, Timothy Prather

Topic: Assessment of the drilosphere of A. trapezoides or L. terrestris in the activity of Clopyralid in Palouse soils

Abstract

Through chemical, physical and biological alteration of soil, earthworms can influence the degradation, leaching and adsorption of herbicides. These interactions may reduce the efficacy of herbicides and potentially impact ground water quality. The drilosphere created by earthworms is characterized by high nutrient availability and microbial activity which suggests that the drilosphere might be playing important role in the degradation of herbicides such as clopyralid. Clopyralid is generally soluble in water and has a high mobility in soils. Leaching of clopyralid is associated with preferential flow through the macropore (Shang and Arshad 1998). This study will use mesocosms with either Aporrectodea trapezoides or Lumbricus terrestris to assess the impacts of earthworm activity on clopyralid in a bioassay type study conducted in the greenhouse.  Replicate mesocosms with A. trapezoides L. terrestris or no earthworms will be sprayed with clopyralid at normal rates.  Pea (Pisum sativum) will be seeded into each mesocosm using a fixed grid.  Germination will be recorded at each point in the grid daily for a two-week period. Differences in germination rates and any spatial pattering of germination rates between controls and earthworm treatments will be used to assess the impact of earthworm activity on clopyralid activity. Results will contribute to our understanding of how soil organisms influence degradation, adsorption and leaching of clopyralid in earthworm worked soil.