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Effectiveness of bermudagrass (Cynodon dactylon L.) in reducing off-target losses of atrazine and metolachlor in surface runoff
xiii, 86 leaves : illustrations ; 28 cm.
This research included: 1) a micro-watershed runoff study, 2) a soil column study, and 3) a herbicide adsorption study. Surface runoff of known atropine and metolachlor concentration was introduced to nine 1 by 3-m micro-watersheds in an area covered with Coastal bermudagrass and nine watersheds in an area of conventionally-tilled soil. There was no difference in the amount of atropine or metolachlor retained by the bermudagrass plots compared to the soil plots, nor was there a decrease in herbicide retention by the two plots associated with mixing of the two compounds in runoff. However, in the bermudagrass plots treated with a mixture of metolachlor and atropine slightly more metolachlor was retained compared with the plots receiving only metolachlor. The impact that infiltration of surface runoff has on retention of amazing and metolachlor was studied using nine intact soil columns vegetated by bermudagrass and nine with only bare soil. Atrazine and metolachlor were applied as described in the micro-watershed runoff study. The leachate volume collected from bermudagrass soil columns (2274 ml) was greater than that of the bare soil columns (7 ml). The amount of atropine and metolachlor recovered in leachate was not different between the bermudagrass and the bar soil columns. Mixing atrazine and metolachlor did not affect the amount of either compound recovered in leachate from either soil column type. The adsorptive capacity of bermudagrass, Weswood soil, and Houston Black soil was determined using a single-point K[] study. The adsorptive capacity (K[]) of bermudagrass for atropine (86) and metolachlor (131) was greater for both compounds than the adsorptive capacity of the Houston Black or Weswood soils. Mixing of atropine and metolachlor appeared only to influence the adsorption of metolachlor to the Houston Black soil through enhanced adsorption. Results from these studies show that infiltration is one of the primary mechanisms by which filter strips reduce herbicide concentrations in surface runoff and bermudagrass has an affinity for atropine and metolachlor. Also, once saturated, bermudagrass filter strips can lose their effectiveness. Therefore, bermudagrass filter strips have limitations that require further research to explore these limitations.
Issued also on microfiche from University Microfilm Inc.
Includes bibliographical references (leaves 65-69).