I just broadcast some 2, 4d amine weed killer and was planning to aerate and overseed in the near future.
How long after applying the 2,4d amine weed killer is it advisable to overseed?
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This reference claims that
The degradation of 2,4-D is rapid (half life of 6.2 days) in aerobic mineral soils
This reference claims
Most of the time, 2,4-D breaks down in soil so that half of the original amount is gone in 1-14 days.
If you follow the references it is very difficult to find a clear statement of how long it lingers. Note the reference to aerobic mineral soils which also imply a reasonable level of organic matter and consequent microbial activity. In other words it will break down faster in a healthy soil than a dry impoverished soil.
Also keep in mind that 2,4 D is rarely sold without other chemicals added to the mixture and even the ingredients that are considered "inert" which can be 85% of the mixture can change how long it remains active.
When I was a landscaper and my money was on the line I would not over seed for at least four weeks. Grass seed is not as cheap as it was and customers have little tolerance for seed failing to germinate.
This fact sheet makes for thoughtful reading.