Weeds are typically the worst enemy of any wildlife food plot. Controlling weeds in your field is something to consider weeks or even months before you get the seed in the ground.
With this in mind, it is always easiest and least expensive to start with a weed free seedbed utilizing glyphosate. (RoundUp)
A good rule of thumb before planting is “Kill It & Till It, then Kill It & Till It again”. Each time you till your plot you bring new seeds to the surface. By spraying vegetation more than once you have a much better chance of eliminating weeds that can lay in your hunting plot for years just waiting for the opportunity to grow. This is especially true with broadleaves. (thistle, milkweed, pigweed, etc) Once the thick grasses that have prevented them from growing are eliminated, weed seeds that have lain dormant in the soil for years can now grow and take over your field.
Grasses in your clover plots are always a problem, even when you use RoundUp prior to planting. We have been using a product called Arrow 2EC with very good success killing off the grasses in plots that are over a year old. Arrow is available at many Feed & Farm locations or online at www.keystonepestsolutions.com. With an application rate of 16oz/acre a one gallon jug will do 8 acres for less than $100, not too bad and if you can get a few extra years from your clover plot it is well worth it.