This depends on your needs. Plowing is only used for large areas of land such as that found in farms and is different from tilling. Plowing is used to break up weeds and dig deep into the soil, turning it over to bury old crop residues. Whereas tilling is used to cultivate and prepare the ground for planting. If you have a large plot of land such as a farm then it is generally thought that you should plow during the fall and till during the spring for the best quality soil. If you have a small garden then plowing is unnecessary.