The calendar says it is the first week in May but the weeds are as big as they normally are May15 to 20. This matters when applying a burn down spray for no-till
Weeds that you should especially watch are knotweed, spreading Atriplex, dandelion, nipplewort, and lambs quarters. Some of these become almost impossible to kill with glyphosate once they get a certain size.
The solution is to spray earlier than other years and keep the rate of glyphosate high. If you are tank mixing a residual herbicide such as Boundary or Conquest with glyphosate you need to increase the glyphosate rate. The clay-based metribuzin that is in Boundary and Conquest ties up some glyphosate. Typically you need 0.25-0.5 L/ac more glyphosate to control perennial weeds if you add Boundary or Conquest.
Spraying on a sunny day with good growing conditions should help control.
BASF has a new product that speeds the burn off of broadleaf weeds. It helps by desiccating these weeds to allow soys a quicker start. It does not kill weeds but desiccates them. It is intended to be used with your normal glyphosate product. It does not speed up the kill of grasses. The grasses will be dead because of the glyphosate but they will not turn brown like the broad leaf weeds will.
If you have a field with particularly big weeds you may have to work it. There are no weeds that are resistant to iron. BF