The hay stakes that Jim mentioned are not for farmers, but for construction sites. The stakes are to hold small square bales in place to control runoff. Some companies will use silt fence, or a combination of the two. If there is a large area that they have removed the grass from, there will be large amounts of silt running off of there, so the square bales are needed down close to the edge of the worksite, and they need staked so that the runoff water does not push them around.
Hope that clears it up for you.
Charles