Modeling an irrigation management strategy for minimizing the leaching of atrazine

Possible contamination of water resources by applied pesticides (including insecticides and herbicides) is a problem currently confronting irrigated agricultural production. Best management practices have to be adopted to minimize pesticide transport and leaching under irrigated conditions. A field capacity/mixing-cell model (IRRSCHM) and a model that uses Richard’s equation and the convection–dispersion equation to describe water and contaminant dynamics in soils (LEACHP) were used to assess the leaching of atrazine (a herbicide) under corn receiving different levels of early-season irrigation. The early-season irrigation levels were 11.1, 16.8, 23.3, and 28.8 cm out of corresponding seasonal irrigation levels of 31.2, 39.6, 45.5, and 53.1 cm. The objectives were to (a) use a modeling approach to evaluate water management effects on atrazine leaching, and (b) assess the feasibility of using IRRSCHM and LEACHP to guide irrigation for minimizing atrazine leaching.