Effect of concentration on the decomposition rates in soil of atrazine, linuron and picloram

The decomposition of atrazine, linuron and picloram when incubated with two soils at four levels of application was measured for periods of 3 or 4 months. The applicability of zero‐order, half‐order, first‐order and Michaelis‐Menten kinetics was considered. None of the equations described the breakdown rates adequately in spite of the apparent theoretical advantage for using an expression of the Michaelis‐Menten type. In each case the rate of decomposition increased as the initial herbicide concentration decreased.