Effects of the herbicides glyphosate, 2,4,5-trichlorophenoxyacetic acid, and 2,4-dichlorophenoxyacetic acid on forest litter decomposition

Laboratory studies with two leaf litter and one forest floor substrate showed that the herbicides 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), a 50:50 mixture of these, and glyphosate all had toxic thresholds at which they reduced decomposition. However, in all cases, the thresholds were > 50 times higher than residue concentrations that occur in the field after silvicultural herbicide treatments. In a field study at one site, no measurable 1-year postspray effects on litter decomposition were found among treatment plots sprayed at 0.0, 3.4 or 6.7 kg 2,4,5-T/ha.