Alfalfa (lucerne) hay or pea straw make great nutritious mulches

Both are legumes, high in nitrogen, trace minerals and offer minerals, trace elements, and other valuable nutrients stored in the plants, returning to the soil. Keep to a depth of 4 inches thick. This settles down to about 2 inches. Is still effective for both moisture retention and seed suppression. Needs to be reapplied. Avoid using in very windy areas.