تأثیر کیفیت آب در مخزن سمپاش بر کارایی علف کش های گلیفوسیت و نیکوسولفورون

The influence of water quality on glyphosate and nicosulfuron performance on barnyard-grass and velvetleaf was examined in a greenhouse study as a factorial arrangement of treatments based on a completely randomized design with 6 replications at Ferdowsi University of Mashhad during 2008-9. Factors included were: pH at 8 levels (3, 4, 5, 6, 7, 8, 9, and 10) obtained by using buffer solutions (+3 control pots for each pH level), CaCO3 at 6 levels (0, 100, 200, 300, 400, 500, and 600 ppm (w/v)) in combination with 0 or 3 kg/ha (NH4)2SO4 (AMS), and NaHCO3 at 6 levels (0, 100, 200, 300, 400, 500, and 600 ppm (w/v)) in combination with 0 or 0.5 L/ha NH4NO3 (AMN). The herbicide solutions were applied at the 3-4 leaf stage of the weeds at the ED50 doses estimated in a dose-response preliminary test. Glyphosate at pH of 6 and 7 had the highest effect on barnyard-grass, whereas, the highest activity of nicosulfuron was found at a pH of 8 followed by a pH of 7. Similarly, the best control of velvetleaf was obtained for glyphosate and nicosulfuron at pH of 6 and 8, respectively. The antagonistic effect of CaCO3 and NaHCO3 was higher with glyphosate than with nicosulfuron. Adding AMS and AMN to the spray tank decreased water hardness and alkalinity effects, respectively. In conclusion, the results of these experiments have highlighted the importance of water quality on herbicide performance.