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ARS Home » Research » Publications at this Location » Publication #154020
Title: EFFECT OF ROUNDUP ULTRA ON ATRAZINE DEGRADATION IN SOIL

Author
item KRUTZ, L - TEXAS A&M UNIVERSITY
item SENSEMAN, S - TEXAS A&M UNIVERSITY
item Haney, Richard

Submitted to: Biology and Fertility of Soils
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2003
Publication Date: 7/15/2003
Citation: Krutz, L.J., Senseman, S.A., Haney, R.L. 2003. Effect of Roundup Ultra on atrazine degradation in soil. Biology and Fertility of Soils. 38:115-118.

Interpretive Summary: Farmers sometimes mix herbicides together before spraying on their cropland. This eliminates an extra trip through the field. Since soil microorganisms are largely responsible for removing harmful chemicals from the field, we wanted to determine the effect on these soil microorganisms from mixing two widely used herbicides (Roundup and atrazine). We found that microbial activity was actually stimulated in the presence of Roundup and atrazine. Therefore, we foresee no harmful side effects in tank-mixing these two chemicals together for controlling weeds.

Technical Abstract: Tank mixing pesticides and the use of pre-packaged mixtures have become common agricultural practices. However, pesticide degradation in multi-pesticide systems is rarely evaluated. The objective of this laboratory study was to determine the effect of Roundup Ultra on atrazine degradation in soil. Based on a 2-mm glyphosate-soil interaction depth, the isopropylamine salt of glyphosate was added to Aatrex-amended and non-amended soil at rates of 0, 1 (43 mg ai kg**-1), 2, 3, 4, and 52. Treatments were incubated for 4, 8, 12, 16, 20, 24, 28, and 32 days. Atrazine degradation was significantly different among treatments in 8 days. In the 02 treatment (Aatrex only), 87% of the atrazine was degraded. During the same 8-day period, atrazine degradation in the 1, 2, 3, 4, and 52 treatments was 77%, 69%, 60%, 61%, and 52%, respectively. Atrazine degradation approached 97% for all treatments after 12 days and statistical differences were no longer observed. Atrazine degradation was inversely correlated with Roundup Ultra rate and microbial activity at 8 ®*82 = 0.97) and 12 days ®**2 = 0.92). These results indicate that Roundup Ultra stimulated microbial activity while simultaneously inhibiting atrazine degradation.