Behaviour of an organomontmorillonite-acetochlor formulation in drained wetland soils of the Hula Valley

Weed control poses a real challenge to agriculture in general, and to agriculture on drained peatlands in particular. An understanding of the interactions between clay minerals and organic molecules has yielded effective preparations of herbicide formulations. In most cases, binding the active ingredient to a suitable organoclay-based platform enhances activity by reducing migration of the herbicide to non-target depths, or by reducing degradation of the active ingredient. In this short communication, a formulation based on an organoclay and the herbicide acetochlor is compared with a commercial formulation. Efficiency was tested in two soils from the Hula Valley: a mineral, clay-based soil (with about 4 % organic matter) and a peat-derived soil with ~20 % organic matter. Although the soils were located only two kilometres apart, completely different herbicidal activity was observed. In the mineral soil, the organoclay formulation improved the behaviour of the herbicide and prevented its leaching; whereas in the peat-derived soil, the organoclay and commercial formulations behaved similarly, and were confined to the upper soil layer. In the latter case, the penetration depth of herbicide added in the organoclay formulation might be too shallow, resulting in poor herbicidal activity. The results of this study demonstrate differences that should be considered in weed control in drained peat soils.