Effects of Methylammonium and Urea Ammonium Nitrate on Foliar Uptake of Thifensulfuron in Velvetleaf (Abutilon theophrasti)

Effects of ammonium and methylammonium on foliar uptake of14C-thifensulfuron, in the presence of 0.2% nonionic surfactant by vol, into velvetleaf were investigated. Total14C uptake into velvetleaf 24 h after treatment was only 15% without addition of nitrogen, but addition of 0.32 M NH4Cl, urea ammonium nitrate, or CH3NH2·HCl increased total14C uptake to 31, 38, or 59%, respectively. Total14C uptake 24 h after treatment was increased 3- and 4-fold by addition of 0.08 and 0.16 M CH3NH2·HCl, respectively, but was not increased further by greater CH3NH2·HCl concentrations. Although the increase in14C uptake was followed by an increase in total14C translocated, the relative amount of14C translocated (expressed as a percentage of total14C uptake) was not affected by nitrogen additives. Enhancement of uptake of14C-thifensulfuron by CH3NH2·HCl was partially reversed by addition of 0.16 M CaCl2to the application solution.