ORGANIC AMENDMENTS TO ENHANCE HERBICIDE BIODEGRADATION IN CONTAMINATED SOILS

Authors: Moorman, Thomas; COWAN, JENNIFER - BAKER PETROLITE, TEXAS; ARTHUR, ELLEN - BAYER CORPORATION, KANSAS; COATS, JOEL - IOWA STATE UNIVERSITY

Submitted to: Biology and Fertility of Soils
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Pesticide contamination of soils at agricultural chemical dealership sites and farmsteads is a widespread problem. Bioremediation with low-cost methods would benefit farmers and dealers by reducing potential offsite movement of the chemicals, human exposure, and would be cheaper than disposal of contaminated soil as hazardous waste. We tested the ability of several low cost materials (cornstalks, sawdust, manure, peat, compost and mineral nutrients) to stimulate the degradation of three herbicides present in soil in high concentrations. Each of the three herbicides reacted differently to the soil amendments. Atrazine degradation was enhanced by manure, peat and cornstalks. Metolachlor degradation was enhanced by all amendments at the highest concentration tested. Trifulralin degradation was not stimulated. In addition metolachlor inhibited atrazine degradation when both herbicides were present. Inorganic nutrients had little effect. Our studies show that bioremediation using soil amendments to enhance biodegradation is likely to be a slow process, particularly if the chemicals are present as mixtures. In general, compost, manure, and cornstalks were the materials most effective in stimulating bioremediation. The information obtained in this study could be used in the formulation of guidelines for remediation of these pesticides or as the basis for further research.

Technical Abstract: Pesticide contamination of soil and groundwater at agricultural chemical distribution sites is a widespread problem in the U.S.A. Alternatives to land-farming or solid waste disposal include biostimulation and phytoremediation. This research investigated the ability of compost, corn stalks, corn fermentation byproduct, peat, manure, and sawdust at rates of 0.5 and 5% (w/w) to stimulate biodegradation of atrazine, metolachlor, and trifluralin added as a mixture to soil. Initial concentrations were 175 +/- 42 mg kg**-1 soil of atrazine, 182 +/- 25 of metolachlor, and 165 +/- 23 of trifluralin. After amendment addition, 30% of the atrazine, 33% of the metolachlor, and 44% of the trifluralin was degraded over 245 days, which includes 63 days aging prior to amendment additions. Atrazine degradation was enhanced by 0.5% manure, 5% peat, and 5% cornstalk amendments compared to nonamended soils. Metolachlor degradation was enhanced by all amendments at the 5% level, except for compost and peat. Amendments had no effect on trifluralin degradation. The 5% addition of compost, manure, and cornstalks resulted in significant increases in bacterial populations and dehydrogenase activity. A second experiment compared the persistence of atrazine, metolachlor, and trifluralin applied in a mixture to their persistence in soil individually. A combined average of 123 mg kg**-1 atrazine remained in soil treated with the three herbicide mixture compared to 31 mg kg**-1 atrazine remaining in soil treated with atrazine only. Atrazine mineralization and atrazine-degrading microorganisms were suppressed by high concentrations of metolachlor, but not by trifluralin.