Earthworms have historically been absent from agricultural fields in eastern Colorado.  Recently there have been a growing number of earthworms seen in no-till fields, and as a result there is a growing interest in the effect of earthworms to alter soil nutrient availability and physical properties.   The objective of the study was to determine the effect of Aporrectodea trapezoides on solute leaching on soil from eastern Colorado (Adena, Ustic Paleargid) that is amended with biosolids.   To help understand A. trapezoides’s effect, a laboratory column study was established to investigate the impacts of the earthworms on the breakthrough curves (BTC) of column sections with and without earthworms.  After 16 weeks of worm interactions with the soil, the columns were divided into 3 sections.  Saturated and unsaturated BTC were developed on each section using a non-absorbing dye.   The BTC data was analyzed using Hydrus 1-D to determine the solute dispersivity of the dye for each column section.  Model simulations for field scale will be presented to predict the earthworm effect on nitrate leaching.