The sprayer goes over all the fields before seeding is done. A variety of chemicals are used depending on the weeds and crops that being seeded. I honestly don’t know much more about this. I tend to get lost in the conversations over the 2-way when it comes to how many ounces or quarts or gallons of chemical per tank of water. And which chemical to use. If you are going to seed this then you can’t use this chemical and if you do…you need to wait x days. Then there are the different kinds of nozzles and speeds. Right now I just pick up all the chemical from the elevator.