A good food plant for many caterpillars.

A good green manure plant, it is fairly deep rooted, has good resistance to 'Clover rot' but it is not very fast growing. It can be undersown with cereals, succeeding even in a wet season.

Pre-soak the seed for 12 hours in warm water and then sow in spring in situ. The seed can also be sown in situ in autumn. Green manure crops can be sown in situ from early spring until early autumn. (the later sowings are for an over-wintering crop).

Dislikes shade.

This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby.

Edible uses:

Leaves - cooked. Used as a potherb. 

Seed - cooked. Parched and eaten or ground into a powder. The seed is said to contain trypsin inhibitors. These can interfere with certain enzymes that help in the digestion of proteins, but are normally destroyed if the seed is sprouted first.

http://practicalplants.org/wiki/Medicago_lupulina