A crop monitored on our farm showed a yield of 4300 pounds per acre of dry matter in the top growth and 800 pounds in the roots. This is translocated into the clover plant and returned to the soil surface. The roots also open up the soil, enhancing water retention and root development of future crops. A second essential is crop rotation. We have found about 5 years to be the limit of our rotation, after this we need a green manure crop to boost the fertility again.
Livestock play an important role in the overall plan to maintain soil fertility.
These grass-legume mixtures improve soil fertility and structure. We practice mostly a three or four year rotation - underseed with a companion crop, harvest and or graze for three or four years, then back to cereal production. Our cattle operation allows us to manure about 40 acres per year. Nitrogen release from a green manure crop is a slow release - over three years or so.