SHOOT ZONE UPTAKE OF SOIL‐APPLIED HERBICIDES*

Abstract

Summary. Studies were conducted to determine the effects of herbicide placement at different zones of maize ( Zea mays L.) and pea ( Pisum sativwm L.) shoots below the soil surface after emergence. Soil was removed from around the shoots and replaced with herbicide‐treated soil. A wax barrier ensured separate exposure of the zones to treated soil. EPTC, chlorpropham, propham and sulfallate did not affect pea shoot growth, but in maize the shoot zone adjacent to the crown root node was extremely sensitive. Treatment in this area markedly reduced growth and severely inhibited the crown roots. The difference in susceptibility between these species may he due to the location of the growing point relative to the treated soil. Shoots of maize and pea were sensitive to diuron. In maize the shoot adjacent to the crown root node and the tissue of the first internode were the most susceptible. In pea the‐ uppermost shoot (beneath the soil surface) was the most sensitive. Trifluralin did not affect growth of maize and pea when placed in the shoot zone after emergence, although the crown roots of maize were severely inhibited. Naptalam, dalapon and 2,4‐D did not affect growth of maize under similar conditions, and of these only 2,4‐D reduced growth of pea. Zone d'abiorption des tiges pour les herbicides appliqués sur h sol