Thorough plowing and disking of a food plot before planting will kill many of the existing weeds, and any grasses appearing later in the plot can be controlled by applying a grass-specific herbicide such as Poast, Whitetail Institute's Arrest, or BioLogic's Weed Reaper . However, the surest way to control weeds right from the start is by applying a non-selective herbicide such as Roundup about 2 weeks prior to plowing and disking.
Roundup is absorbed through the leaves and green stems of actively growing weeds and grasses. Once absorbed, it moves throughout the weed, including the roots. Roundup stops the weed from producing food so it can't survive. The dead weed won't grow back, and it enriches the soil as it decomposes.
Before using Roundup, keep the following guidelines in mind:
*Weeds are most vulnerable during the early stages of their growth. If weeds are more than 5 feet tall, it's best to mow them, wait 2 weeks and then spray Roundup on the re-growth.
*Roundup works more effectively on vigorously growing weeds, so plan your spraying when a few days of warm temperatures (60 degrees or above) are forecasted.
*Don't spray when weeds are wet or when rain is expected within 2 hours (Roundup becomes rain-proof after 2 hours).
*For effective coverage, don't spray when it's windy.
*Treated weeds will wilt and turn yellow within hours; complete kill usually takes 1 to 2 weeks.
Because I generally wait until approximately August 1 to plant brassicas and other annuals on my Wisconsin and South Dakota food plots, I'll spray Roundup on these plots in mid July. Then, to conserve soil moisture as much as possible, I'll plow, disk and plant on the same day. And then pray for rain!