Effect of application time, carrier pH, carrier volume, and rate on Tralkoxydim activity on wild oat (Averza fatua)
Field studies were conducted from 1994 to 1997 at the Agriculture and Agri-Food Canada Research Farm, Scott, Saskatchewan, and Crop Science Dept., University of Saskatchewan, Saskatoon, Saskatchewan. Tralkoxydim was applied to wild oats in hard red spring wheat (Triticum aestivum) at; two application times, 11:00 a.m. and 9:00 p.m.; two carrier pH levels, 8.0 and 4.0; three water volumes, 100, 50 and 30 litres per hectare and four rates, 100, 75, 50 and 25% of recommended (200 g / ha). Wild oat populations were heavy at Saskatoon in 1994 and 1995 and light to moderate in 1996 and 1997 and light to moderate at Scott in all years. At Scott. 9:00 p.m. application compared to 11:00 a.m. reduced wild oat biomass significantly in all years with reductions ranging from 26 to 80%. This suggests that the high intensity of UV light present at midday may reduce the effectiveness of tralkoxydim. Reducing carrier pH from 8.0 to 4.0 produced reductions in wild oat biomass in three of 4 years with reductions ranging from 40 to 76%. The interaction, time X carrier pH was significant for wild oat biomass in all years and wheat yields in one year. Late evening application combined with reduced carrier pH was the most effective. At Saskatoon, time of application and carrier pH had no influence on wild oat biomass or wheat yields although trends toward a reduction in total biomass with reduced carrier pH were noted in all years. Reduced carrier volume decreased efficacy in seven of 8 site years and was particularly evident when carrier volume was reduced to 30 l/ha. Wheat yields declined nine and 14% at Scott and Saskatoon, respectively when tralkoxydim carrier volume was reduced from 100 to 30 l/ha. Reducing the tralkoxydim rate to 75% of recommended had no effect on wild oat biomass in seven of 8 site years. Further reductions to 50 or 25% of recommended resulted in significant increases in wild oat biomass and reductions in wheat yields.
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