One way is mechanical treatment. Turning over the ground using some type of disc harrow or tiller will aerate the soil and kill some of the existing plant matter. There are both tillers and disc harrows available for use with ATVs. Tillers can be more aggressive; but are also more expensive. Harrows provide a more economical option, and may be a better choice for cutting new ground.
Mechanical treatment will kill some of the existing unwanted weedy competition. However, it won’t knock down everything. And many of the more aggressive species will quickly recover and repopulate. This usually occurs just about the time your newly-planted seed crop is germinating. Because they’re native (or naturalized), more aggressive and already established, weeds usually out-compete food plot species.
Chemical treatment is a much more effective means for eliminating competition. Because it’s specific, it will kill undesirable species but won’t harm your crop. The most common type are glycophosphates like Round-Up and its generic substitutes. They are systemic, which means plants take them up through their vascular system; so they kill the entire plant. Not just the above-ground growth.
Your best option is to apply both treatments. Start with a chemical application; then allow two weeks for it to take effect. Then, turn over the soil. This will destroy any residual vegetation, as well as turning dead organic matter back into the soil to increase the nutrient base. Now you can apply your minerals, sew your seeds and pray for rain.