EFFECTS OF METHYLAMMONIUM AND UREA AMMONIUM-NITRATE ON FOLIAR UPTAKE OF THIFENSULFURON IN VELVETLEAF (ABUTILON-THEOPHRASTI)

Effects of ammonium and methylammonium on foliar uptake of C-14-thifensulfuron, in the presence of 0.2% nonionic surfactant by vol, into velvetleaf were investigated. Total C-14 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 total C-14 uptake to 31, 38, or 59%, respectively. Total C-14 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 in C-14 uptake was followed by an increase in total C-14 translocated, the relative amount of C-14 translocated (expressed as a percentage of total C-14 uptake) was not affected by nitrogen additives. Enhancement of uptake of C-14-thifensulfuron by CH3NH2.HCl was partially reversed by addition of 0.16 M CaCl2 to the application solution.