LABORATORY STUDY OF ZONAL MANAGEMENT EFFECTS ON PREFERENTIAL SOLUTE MOVEMENT IN SOIL

Water quality in agricultural areas is often influenced by chemicals u sed in crop production. The application methods of agricultural chemic als can affect how these solutes move through soil. Precision manageme nt of zones within each crop row is often achieved via tillage (e,g,, mechanical weed control in a standing crop), but few methods for speci fic management to reduce transport of chemicals from treated sons have been suggested. Management of separate soil zones during chemical app lication was investigated using solute breakthrough studies with undis turbed soil cores (fine-loamy, mixed Aquic Hapludoll), Treatments were the application of 13.8 g/m(2) chloride (Cl-) using three strategies: (i) ponded application of the solute; (ii) unsaturated solute infiltr ation; and (iii) a zonal management technique, in which a small zone ( volume) of soil was disturbed and mixed with solute before leaching. C olumn effluent was analyzed for Cl-. Columns were leached with Cl--fre e solution before another treatment was applied. Each column received each treatment in succession. The solute breakthrough patterns during the first 2.5-cm drainage were influenced by both solute application m ethod and soil column macroporosity, These results suggest that compar ed with broadcast applications, solutes restricted to soil management zones had slower transport through soil that, overall, had an abundanc e of macropores.