Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/1998
Publication Date: N/A
Interpretive Summary: The pollution of surface and ground waters by agricultural chemicals is one of today's foremost environmental concerns. Herbicides and other agricultural chemistry are vital tools for maintaining and improving the world's food production. Many approaches, both technical and cultural have been undertaken to reduce the environmental impact of agricultural chemicals while maintaining efficacy and overall production output. This work was undertaken to more fully understand the role and potential of pesticide formulation and chemical adjuvants in modifying the environmental impact of herbicides. The study utilized herbicides encapsulated in cornstarch or polyurea polymers as well as commercial formulations alone and mixed with polymeric adjuvants. All of the formulations that were tested gave acceptable weed control in the corn crop. Encapsulated formulations and commercial formulations with added polymeric adjuvants reduced the leaching and off-site movement of the herbicides, compared to the standard conventional tillage practices. The effectiveness of the formulations varied with tillage and environmental conditions. No single formulation or adjuvant was superior to all others under all conditions. Addition of polymeric adjuvants or the adoption of encapsulated formulation of widely used herbicides has the potential to substantially reduce the environmental impact of these products. Shifts to no-tillage production practices will require increased levels of management to reduce herbicide leaching. The adoption of encapsulation and polymer adjuvant technologies in formulating agriculture chemistry could greatly contribute to the goal of reduced environmental impact with improved production.
Technical Abstract: Controlling herbicide levels and mass transported in drainage from cropland while maintaining efficacy, are critical requisites of agronomic management. The objective of this research was to compare root zone leaching losses of atrazine and metolachlor, preemergence applied, as standard commercial formulations with and without a tank-mixed polymeric adjuvant, and as microencapsulated or starch-encapsulated formulations in different tillage systems. Herbicides were applied in combination at 2 rates to 2 replicated tillage systems established on Hagerstown silt loam. Atrazine leached more than metolachlor to pan lysimeters, installed 1.2m deep, and leaching losses were greater from untilled than tilled soil. Starch-encapsulated atrazine and microencapsulated- metolachlor were effective in reducing herbicide translocation in this soil. Likewise, reductions in transport of these chemicals were achieved by tank-mixing a polymeric adjuvant with standard commercial formulations. In a season when atrazine was more leachate-available, the starch-encapsulated formulation demonstrated a greater capacity to reduce both early season and yearly losses of this compound in untilled soil compared with the adjuvant-amended formulation. A melamine ethylene polymer-encapsulated atrazine was not effective in reducing atrazine losses in a single season characterized by low rainfall and leaching potential. Therefore, the use of encapsulated formulations and polymeric adjuvant-amended spray mixtures offers a means of mitigating herbicide losses through the vadose zone and to ground water.