First, it supplies a direct plant food through the nitrogen, phosphorus and potash that it contains, being especially rich in nitrogen.
Next, in decaying it forms compounds that attack the locked-up mineral elements of the soil and sets them free to be absorbed by the plants. Then it absorbs moisture and makes the soil more slow in drying, besides preventing the close packing that comes with puddling in clay soils deficient in humus.
And as important as anything, perhaps most important of all, it puts “life” into the soil. Soils with humus in them are really alive, for the decaying vegetable matter attracts bacteria of many sorts that in their life and death and decay form many compounds that the plants can absorb and thus directly increase fertility and make plants grow.
Good soils are truly “live” soils, filled with legions of microscopic forms of life, most of it beneficial to the higher orders of growing plants useful to men.
Poor soils, deficient in humus, cold, puddled clays, are literally “dead” soils and speak sadly of a dying civilization and decaying people.
Alfalfa, then, revels in a deep, rich, sweet soil. How are we to provide it in the South?
First, there are many river bottoms that are admirably adapted to alfalfa, being made up of rich alluvial loams, pervious to air and moisture, and not holding a surplus of moisture. On these soils alfalfa usually thrives splendidly.
Next, there are new lands freshly cleared where robber crops have not yet had time to take out the fertility. Often these newer soils will respond wonderfully with alfalfa. Some very steep mountain sides are growing alfalfa finely when sown on freshly-cleared surfaces.
Some lands are naturally fertile enough so that they will, with little aid, grow alfalfa very well. Nevertheless, even the best of the old cleared parts need manure before being sown to alfalfa.
We had best admit at the outset that most of the old fields of the South need enrichment to make them produce good alfalfa. And the best way to enrich them is with liberal coatings of stable manures.