Microbial Degradation of Five Substituted Urea Herbicides

Abstract

Phytotoxicity of five substituted urea herbicides 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), 3-(p-chlorophenyl)-1,1-dimethylurea (monuron), 3-phenyl-1,1-dimethylurea (fenuron), 3-hexahydro-4,7-methanoindan-5-yl) −1,1-dimethylurea (norea), and 3-(m-trifluoromethylphenyl)-1,1-dimethylurea (fluometuron) at 0, 10, 100, and 1000 ppm were determined in factorial combination at four urea nitrogen levels of 0, 45, 450, and 900 ppm with three Aspergilli: A. niger, A. sydowi, and A. tamarii. Response interactions were apparent, with all three fungi most tolerant for fenuron and least for diuron. Apparent tolerance order of the three intermediates were: A. niger, norea > fluometuron > monuron; A. sydowi, fluometuron > monuron > norea; and A. tamarii, fluometuron > norea > monuron. Oat (Avena sativa L.) bioassay for residual herbicide toxicity indicated significant differences in herbicide degradation rates between these three fungi at 5, 10, and 20 ppm in Eufaula sand. Diuron was more rapidly degraded than monuron at these levels with fluometuron and norea somewhat intermediate. A. niger was most effective in degradation of these herbicides with A. tamarii greater than A. sydowi. High nitrogen levels in soil organic matter amendment generally favored increased rates of urea herbicide degradation.

Adsorption, Mobility, and Degradation of Cyanazine and Diuron in Soils

“…On the average, diuron breakdown was in the order of 35 C >20C = 50C>5C while the cyanazine degradation series was 20 C = 35 C = 50 C> 5 C. That 35 C appears to be the optimum temperature for dissipation corroborates research in- dicating that degradation of this compound is microbially dependent (8,14,15). Loss of cyanazine phytotoxicity in soil appears to be more related to non-biological degradation, or to a combination of biological and non-biological degradation.…”

“…), sugarcane (Saccanim officinarum L.), and cotton. The adsorption (9,13), leaching in columns (8,9), leaching in the field (4,8), and degradation (4,8,14,15) of diuron have been recorded, but these studies usually have been conducted on dissimilar soils. The purpose of this research was to compare the leaching of diuron and cyanazine under laboratory and field conditions and evaluate the adsorption, mobility and degradation prop erties of these compounds on two different soil types.…”

Adsorption of the Herbicides Diuron, Terbacil, and Simazine to Blueberry Mulches

“…Amending soil with organic matter high in N accelerated diuron decomposition (Murray et al, 1969). Other evidence shows chemical degradation to be of minor importance (McCormick and Hiltbold, 1966;Murray et al, 1969). Diuron phytotoxicity was found to be inversely correlated with soil organic matter and cation exchange capacity (Upchurch, 1958).…”

“…More herbicide was inactivated per unit of metabolized soil carbon in a loamy sand than in a clay loam. Amending soil with organic matter high in N accelerated diuron decomposition (Murray et al, 1969). Other evidence shows chemical degradation to be of minor importance (McCormick and Hiltbold, 1966;Murray et al, 1969).…”

“…The adsorption (Rhodes et al, 1970), leaching (Murray et al, 1969), and degradation (McCormick and Hiltbold, 1966) of diuron in soils have been recorded. The importance of microbial decomposition and soil organic matter content in diuron persistence was demonstrated by the work of Mc-Cormick and Hiltbold (1966).…”