Research at OSU has shown that the use of an organic mulch (cover crop) in processing tomato production can help reduce early weed establishment. The presence of the mulch on the surface of the tomato bed acts much like a plastic mulch in inhibiting weed establishment. For tomatoes, a weed-free period of 5 weeks after transplanting is critical for plant establishment. Fewer weeds during this period will result in improved tomato plant growth. In the foreground of the picture are conventional (unmulched) raised tomato beds. As you can see, a few weeks after transplanting weeds are already established. In the background are chemically killed cover crop beds which are weed-free. Two of the benefits of using a herbicide application to desiccate the cover crop are that any weeds present will be killed during the process and the desiccated mulch will tend to lay more uniform across the beds which will help prevent weed establishment later in the season.