Persistence of Atrazine and Oxyfluorfen in Soil Added with Tithonia Diversifolia and Chromolena Odorata Organic Matter

The components of humic and fulvic acid of organic matter determine the effectiveness of herbicide adsorption in soil. The persistence of atrazine and oxyfluorfen in soils added with invasive weeds organic matter (Tithonia diversifolia and Chromolena odorata) was determined. The soils were treated with no organic matter (P0), Chromolena odorata compost (P1), Chromolena odorata compost (P2), Chromolena odorata green manure (P3) and Tithonia diversifolia green manure. All kinds of organic matter were added at a rate of 10 t ha-1. Herbicide containing Atrazine (D1) and Oxyfluorfen (D2) were also applied to the soils. Highest persistence as shown by DT50 value of 46.20 d was found in the soil added with Tithonia diversifolia green manure. The persistence of atrazine and oxyfluorfen in the soils added with Tithonia diversifolia green manure were higher with DT50 value of 46 d and 37.46 d, respectively, than when added with Chromolena odorata green manure with DT50 values of 27.07 d and 17.20 d, respectively. These are related to the differences in fulvic and humic acids contained in both types organic matters. Tithonia diversifolia weed fiber contained higher fulvic and humic acids (28,24% and 8.28%, respectively) while Chromolena odorata were only 19.32% and 7.67%, respectively.