Farmers try to select varieties which will produce the highest yields. Most farmers plant certified seed. This is seed that has been tested and is guaranteed to have a high germination rate, few weed seed, and be free of plant diseases. Before a farmer plants his crop he must decide how and when to till his fields. Tilling or tillage means to prepare the soil and make a good seed bed in which to plant the seed.
Tillage normally begins after the last crop is harvested.
The farmer uses a disc that he pulls behind his tractor. The disc mixes the stubble left over from the last crop with the soil. As this stubble rots over the winter it provides nutrients, or plant food for the next crop. In the late winter, the farmer again plows his fields. This time he is destroying any weeds or grass that might have grown during the winter.