Mrs. Humphries has a small garden. She planted tomatoes, zuccinni, onion, garlic and beans (legumes). When summer is over and she harvested her crops, why did Mrs. Humphries pull out all of the plants except the beans? Those she tilled (mixed) back into the soil for next year's crops. Be sure to explain your answer providing a specific reason.

Legumes such as beans are grown basically for their grain seed, as forage for livestock and as soil enhancing green manures. After harvesting other crops, legumes are usually left on the farm lands until the next planting season because of their ability to add nutrients to the soil. In the next planting season, the legumes can be harvested and incorporated into the soil or it can be left as mulch on the farm land surface. Incorporation of legumes into the soil increase the fertility of the soil and bring forth high yield rate of crops. Legumes used as mulch function by retaining soil moisture, regulating soil temperature and suppressing weeds growth.