MANIPULATION OF LEY PASTURES WITH HERBICIDES TO CONTROL TAKE-ALL

The effect of grass-selective and broad-spectrum herbicides in pasture : wheat rotation experiments were studied from 1981 to 1986 at Esperan ce, W.A. The quantity of pasture and the proportion of grass present i n the pasture phases were determined. Pastures were grazed by sheep. I ncidence and severity of take-all and grain yield were measured in the wheat phases. The rotations studied were either a 2 year pasture:1 ye ar crop or 1 year pasture:1 year crop. Herbicide treatments greatly de creased the grass content of pastures in the year of application, and this effect carried over to the second year in the 2 year pasture: 1 y ear crop rotation. Herbicide reduced total pasture yield in the year o f application, but not in the year following. Herbicide treatment of p astures decreased the incidence and severity of take-all in the follow ing wheat crop. Crop yields were increased following treated pastures and to a greater extent than could be explained by decreased take-all alone. Incidence of take-all depended primarily upon the quantity of g rass in the previous pasture (5.4% incidence of take-all per 100 kg ha -1 grass dry matter in the previous pasture). Incidence of take-all wa s also related to the incidence of take-all in previous wheat crops an d the quantity of grass in the pasture in the preceding two years.