By: SR Walker, VA Osten, DW Lack and L Broom
The residual phytotoxicity of 2,4-D mine and dicamba to sorghum (Sorghum
bicolor L.) and sunflowers (Helianthus annuus L.) was investigated under central
Queensland conditions of variable rainfall and high temperatures. Effects of
soil water content, sowing depth, and leaching in clay soils were determined.
Phytotoxicity, as measured by decreases in shoot dry matter in pots, increased
with herbicide rate and decreased rapidly in moist soil (34% w/w) but was
maintained for at least 14 days in dry soil (114% w/w). 2,4-D and dicamba
were phytotoxic when leached into the soil but not when they remained on the
soil surface. Seedling growth and yield were not affected by 2 kg 2,4-Dha
applied at 7 or more days pre-sowing, or by 0.5 kg 2,4-D/ha and 0.14 kg dicamba/ha applied at 1 day pre-sowing, in 5 field
environments. When either herbicide was applied at higher rates 1 day
pre-sowing, seedling growth was reduced if 25 mm of irrigation was received
within 4 days of sowing, and yields were reduced in the field environment that
received 144 mm of rainfall within 14 days of sowing.Yangzhou pioneer chemical CO.,LTD
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