IMPACT OF ROOTS ON GROUND-WATER QUALITY

Preferential flow is perhaps the major chemical transport process infl uencing the rapid and typically unexpected movement of agricultural ch emicals to ground water. Plant roots are a major contributor to prefer ential flow mechanics as they form spatial voids which can be used as preferential flow pathways. Chemical transport of atrazine, deethylatr azine, and bromide solutions concentrations under tilled and no-tilled corn fields was evaluated below the active root zone. Additionally, t he impact of roots onflow pathways was visualized using a soluble dye (Brilliant Blue FCF). Pictures of the dye-stained pattern were subsequ ently digitized to determine the cross-sectional area used for transpo rt as a function of depth. Bromide transit times through the field soi ls were not influenced by tillage practice, whereas atrazine transport was strongly influenced by tillage practice. Under no-till field cond itions, atrazine was rarely detected but deethylatrazine concentration s were greater than those observed under tilled field conditions. Visu al observation indicated that the dye under no-tillage was more predom inant in the corn row, indicative of transport through void root chann els. No-tillage practices may decrease the likelihood of ground water contamination through leaching due to the formation of stable root cha nnels where an organic carbon source and microbial population are pref erentially located to degrade pesticides.