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Published online by Cambridge University Press: 12 June 2017
Dicamba (dimethylamine salt of 2-methoxy-3,6-dichlorobenzoic acid) followed slightly behind the forward penetration of added water in both loam and sandy loam soils. Dicamba persisted longer than 2,4-D butyl ester in autoclaved and not-autoclaved loam and sandy loam soils. Tartary buckwheat, Fagopyrum tataricum (L.) Gaertn. planted at intervals in the autoclaved soils showed no injury from the 2,4-D at 16 oz/A after 4 weeks but was completely killed by dicamba at 8 oz/A after 12 weeks of incubation. In the not-autoclaved soils there was no visible effect on the buckwheat plants from 2,4-D after 2 weeks but nearly all of the plants were killed by dicamba after 12 weeks of incubation. Oxygen consumption in the loam soil was greatly reduced by dicamba at concentrations of 10,000 ppm or higher. Similar concentrations of 2,4-D butyl ester had only a slight and sometimes no effect on oxygen uptake. These concentrations are well in excess of those suggested for selective weed control in grain crops.