Residual effect of 2,4-D on the growth and yield of wheat and barley on alkaline clay soils in southern Queensland

Abstract

Pot and field experiments were conducted to investigate the residual phytotoxicity of 2,4-D to wheat (Triticum aestivum) and barley (Hordeum vulgare) on alkaline clay soils in southern Queensland during winter. Effects of soil moisture, 2,4-D formulation, application rate, crop species and cultivar were investigated. With the exception of a 4% reduction in wheat grain yield in 1 field trial (considered commercially acceptable), grain yields of wheat and barley were not affected when seed was sown within 2 h of field application of 2,4-D dimethylamine or ethyl ester at rates of application up to 1 kg/ha. No significant reduction in phytotoxicity (measured by shoot dry matter reduction of wheat) of 2,4-D dimethylamine occurred when exposed on dry soil for 4 weeks in pots, or of ethyl ester or dimethyl amine exposed for 16 days on dry soil in the field. In moist soil in pots, loss of phytotoxicity to wheat of 2,4-D dimethyl amine was complete within 4 weeks when the herbicide was applied at 2 kg/ha or 2 weeks when applied at 0.5 kg/ha.