Metolachlor was degraded biologically while atrazine and primisulfuron were degraded biologically and chemically. Half-life values for the herbicides ranted from 3 to 6 days in the filed lysimeters to 14 to 49 days in laboratory flasks. Vertical movement of the three herbicides was inversely correlated with the organic matter content of the soil, while sorption of metolachlor by samples from different soil depths was directly correlated with organic carbon content of the soil. Prediction of tritium movement through the soil using the PRZM model was acceptable but prediction of metolachlor movement was not. Soil column lysimeters proved to be useful in carrying out material balance studies on the movement and dissipation of chemicals in natural cores of Dothan loamy sand in the field.
Further research using other soil types and other pesticides is needed.
The technique is very useful in validating computer models but additional methodology needs to be developed to address volatilization losses of pesticides from the field lysimeter systems. Air, water and soil need to be monitored.