INFLUENCE OF RAINFALL AND TEMPERATURE ON SENSITIVITY OF BARLEY (HORDEUM-VULGARE) TO CHLORSULFURON

Effects of rainfall and temperature on the sensitivity of barley grown in low pH soil to chlorsulfuron applied post-emergence were examined under weed-free conditions. Chlorsulfuron at 15 g a.i. ha-1 applied to barley grown under a rainshelter in the field caused reductions in barley height (16%), leaf area (53%), shoot dry matter (23%) and tiller number (23%) at anthesis if simulated rainfall (5 or 10 mm) occurred within 7 days after treatment (DAT). Chlorsulfuron had little effect on barley when rain did not fall until 14 DAT. No responses of barley to chlorsulfuron were detected at maturity in any treatments, due to a dry end of season which prevented full expression of yield potential of untreated controls. Chlorsulfuron applied to barley growing at temperature regimes of 0/10, 5/15, 10/20 and 15/25-degrees-C (night/day) for 7 DAT caused similar reductions at all temperatures in barley root DM, height, leaf area and tillering in cvv. Schooner and Grimmett grown in growth cabinets. Nodal roots were more sensitive to chlorsulfuron at high than at low temperature. Barley responded similarly to chlorsulfuron when grown at temperatures of 2/11 or 6/16-degrees-C (or combinations of both) for up to 14 DAT. Incidence of rainfall within 7 DAT is critical in causing damage from chlorsulfuron in this environment, although damage may not always result in yield loss at maturity.