PESTICIDE LEACHING SENSITIVITY TO IRRIGATION, SALINITY AND N APPLICATION: MODEL SIMULATIONS

Publisher Website
Google Scholar
Abstract
Pesticides in groundwater are of concern because much of the population depends on groundwater for drinking. Pesticides can be transported to aquifers by water that percolates below the crop root zone. Therefore, agricultural management factors that affect the amount of deep percolation also affect the potential for groundwater degradation by pesticides. Evapotranspiration (ET) is a function of plant growth as well as of climatic conditions. Therefore, agricultural practices that affect plant growth-such as fertilizers, water amount, water salinity-also affect ET and, consequently, affect deep percolation for a given amount of water. The objectives of this paper were to simulate the effects of salinity, irrigation, and nitrogen application on leaching of dicamba and atrazine using the ENVIRO-GRO model. Dicamba has a Kd approximately 7% of atrazine and a half-life approximately 20% of atrazine. Corn (Zea mays) was the simulated crop. The simulated variables were N applications of 0, 90, 180, and 360 kg N ha−1, growing season irrigation of 52, 66, and 80 cm of water, and water salinity of 0.2 and 4 dS m−1. Leaching of dicamba was approximately three time higher than atrazine. Increasing water amount, increasing water salinity, and decreasing N application contributed to increased simulated pesticide leaching. Those management variables that resulted in less crop yield and, therefore, more deep percolation contributed to more pesticide leaching. A policy to protect groundwater quality by regulating the application of agrichemicals may have limited benefit and may be counter productive if plant growth is reduced causing increased deep percolation.