A short series on Seedbed quality and its affect on residual herbicides and the control of Black grass.
Part 1. Seedbeds
The winter wheat seedbed has to perform many functions. Those illustrated in the diagram indicate a few of the key ones for successful crop establishment.
What is missing from this diagram is the reality in field relating to grass weed control.
When you consider different soil types and cultivation regimes your end result varies considerably. This variation in seedbed quality affects firstly the number of blackgrass plants that establish and secondly the likelihood of killing them.
The safest approach to killing blackgrass is to use a pre emergence herbicide (there are many factors and reasons for this statement.) Pre em herbicides work most efficiently in the top 25 mm of soil. This is where 99% of your blackgrass seed needs to germinate. In reality it does not and consequently your blackgrass pre em herbicide fails to provide the level of control you would like (what ever the colour of the bottle or how much you paid for it.)
This series of photographs shows the variation in seedbed found on farm and how each presents the likelihood of wide variation in the performance of herbicides.