Metamitron seems most likely to be applied at drilling or shortly afterwards. The results show that even under abnormally dry conditions, no more than 20% of the initial activity remained in the top 7 cm of soil at the time red beet were harvested. Some activity was detectable at a depth of 7.5–10 cm, but more than half of that still present was in the surface 2.5 cm. The tests under controlled conditions showed that both temperature and soil moisture content affect the rate of degradation of metamitron, but it appears that in comparison with other herbicides the loss of phytotoxicity from soil applications of metamitron is relatively rapid.