THE INFLUENCE OF TEMPERATURE AND SOIL MOISTURE ON THE PHYTOTOXICITY OF DICAMBA, PICLORAM, BROMOXYNIL, AND 2,4-D ESTER
Moisture and temperature differentially affected the phytotoxicity of four herbicides to tartary buckwheat, Fagopyrum tataricum (L.) Gaertn., the test plant. The activity of the systemic herbicides 2,4-D, dicamba, and picloram was greatest when conditions of soil moisture and air temperature tended toward optimum growth of the buckwheat. When moisture limited growth the phytotoxicity of these three herbicides was significantly less. Reducing the temperature from the optimum 24°–13 °C to 18°–7 °C did not significantly reduce the activity of these herbicides. Conversely, the phytotoxicity of the contact herbicide bromoxynil was significantly greater at the low rather than the high temperature program. This activity was accentuated when moisture was also made limiting but its effect was less pronounced. High light intensity tended to result in abnormal buckwheat growth and reduced activity of the herbicides.