AMMONIUM SULPHATE ENHANCES CONTROL OF ANNUAL GRASS WEEDS IN CANOLA (Brassica campestris) WITH SETHOXYDIM

Field studies were conducted from 1984 to 1986 to determine the ability of ammonium sulphate to enhance the activity of sethoxydim on green foxtail (Setaria viridis (L.) Beauv.), wild oat (Avena fatua L.), volunteer wheat (Triticum aestivum L.) and volunteer barley (Hardeum vulgare L.) in canola (Brassica campestris L.). Considerable variation in control from year to year was observed. However, green foxtail control was 100% with 0.15 kg ha−1 of sethoxydim alone for the entire study. In 1984 and 1985, control of the other grass species was usually improved with the addition of 4.0 kg ha−1 of ammonium sulphate to 0.15 kg ha−1 of sethoxydim. In 1986, all grasses were completely killed. The high degree of weed control observed in 1986 was attributed to high temperatures at application time followed by more moderate temperatures, adequate relative humidity and rainfall which occurred the day of and the day after application. The lower level of control observed in 1985 was attributed to poor growing conditions including less rainfall and high temperatures in the days following application.