The effects of herbicides, applied atone and in sequence, on the control of wild-oats (Avena fatua) and broad-leaved weeds, and on yield of winter wheat

Experiments were done to examine the effects of controlling wild-oats and autumn-germinating broad-leaved weeds in winter wheat, early in winter or late in spring. The herbicides used were barban (winter), chlortoluron or isoproturon (winter), and benzoylprop-ethyl, at the recommended doses and at half doses. Sequential treatments of two herbicides at half doses were also examined. All treatments were given a routine broad-leaved herbicide treatment in spring. Yields of wheat were influenced more by the time of weed removal than by the degree of control achieved. Grain yields at three sites with dense autumn broad-leaved weed populations were greatest following the use of chlortoluron or isoproturon. At three other sites with moderate to dense wild-oat populations (60 to 240 plants/m¹), the use of barban at the crop three-leaf stage gave larger yields than benzoylprop-ethyl in late spring at the early stem elongation stage of the crop. Seed formation from surviving A. fatua was similar with both wild-oat herbicides. The treatment which reduced seed production of A. fatua and maintained crop yield most consistently was barban followed by benzoylprop-ethyl, each at half the normal recommended dose.