Optimize nicosulfuron efficacy with the addition of nitrogen compounds affected the water quality in spray tank

The influence of water quality on nicosulfuron performance on barnyard-grass (Echinochloa crus-galli L.) and velvetleaf (Abutilon theophrasti Medicus.) were examined in a greenhouse study as a factorial arrangement of treatments based on a completely randomized design with 6 replications ( pots control) at Ferdowsi University of Mashhad in 2011. Prior to the experiment, a dose-response test was carried out to estimate the ED50 doses of nicosulfuron (22 g ai/ha). Water quality tests were included: pH at 7 levels (4, 5, 6, 7, 8, 9, and 10) obtained by using buffer solutions ( control pots for each pH level), water hardness as CaCO3 at 6 levels (0, 100, 200, 300, 400, and 500ppm in deionized water (w/v)), and water alkalinity as NaHCO3 at 6 levels (0, 100, 200, 300, 400, and 500ppm in deionized water (w/v)). Investigation the optimize of nicosulfuron efficacy in water hardness and alkalinity were done with adding nitrogen compounds as 3 kg/ha ammonium solphate (AMS) and 0.5 L/ha ammonium nitrate (AMN), respectively. Results showed the highest activity of nicosulfuron on weeds at pH 8 and 7, respectively. Addition of calcium carbonate in spray tank reduced significantly nicosulfuron performance, and its antagonistic effects on velvetleaf was evident over the barnyardgrass. Adding AMS to the spray tank included calcium carbonate decreased water hardness effects, but was more effective in the control of barnyardgrass. Also, increasing the concentration of sodium bicarbonate in spray tank reduced significantly the nicosulfurim efficacy especially on barnyardgrass, but adding AMN to herbicide soloution overcomed the antagonistic effects of water alkalinity. In conclusion, the results of these experiments have demonstrated the importance of water quality on nicosulfuron performance and the addition of nitrogen compounds in adjustment of water hardness and alkalinity effects.