Sounds like you got everything needed. If you have tall grass, I would bushhog it first to help the soil turn better when you plow. Burning is another way to reduce the chances of having the plow clog up with a bunch of debris. If it is not allot on the surface then I would just plow and let that decay for awhile. If the ground is hard/compacted I would disk it first. The main thing when it comes to plowing is to try to keep an even depth and keep you furrows straight as possible. When done right you should not be able to tell one pass from the next. I've seen guys wreck a field by creating ridges and holes that take allot to fix. Once it is plowed I would disc enough to get a firm seedbed, preferrably disk one last time right before you plant. Most corn planters use a different size planter-plate for the size kernal you purchase. Say you have a bag of MR=medium round kernal you will need the correct size plate to get the desired population per acre, which will be critical if you are going to try to go with no chemical. The better the stand of corn the more it will shade the ground, suppressing weed growth. I personally would not attempt to grow corn without chemicals due to the types weeds in my area: pigweed,crabgrass,lambsquarter,velvetleaf etc. One thing additional you will need is a cultivator to keep the weeds from over taking your corn after it comes up, you will need to make a pass through the corn about every 2 weeks untill it gets to tall to make a pass over.