This section is from "The Horticulturist, And Journal Of Rural Art And Rural Taste", by P. Barry, A. J. Downing, J. Jay Smith, Peter B. Mead, F. W. Woodward, Henry T. Williams. Also available from Amazon: Horticulturist and Journal of Rural Art and Rural Taste.
This term (occasionally met with in agricultural writings) has been applied to a kind of manuring adopted by a Mr. Gurney, in England. The operation consists in covering grass land with straw, coarse hay, or other fibrous matter, under which the grass springs up with astonishing rapidity. A similar practice has for some time been commented upon here as " fall manuring." It has been long observed, that where soil has been covered for a time, it has enriched itself. This has been explained on the supposition that the water of the subsoil, in its upward passage, by capillary attraction, to supply surface evaporation, having in solution various mineral salts, is arrested in its upward progress by a colder substance, where it is condensed, and the mineral ingredients are retained in the surface soil, in a condition immediately available for future vegetation. It would seem, therefore, that the beneficial effects of spreading manure on the surface, and leaving it uncovered, do not proceed so much from the enriching qualities of the manure as from its effects as a simple covering. This is, no doubt, the true solution of the question, for it cannot be doubted that much of the essential properties of manure must be lost by exposure and evaporation.
While, therefore, it does not by any means prove that the best method of applying manure is to spread it on the surface, and leave it exposed for months, it is an additional proof of the great utility of mulching; and the principle is a valuable one to gardeners and fruit cultivators, since it is inexpedient to disturb the soil, and incorporate manure with many of their crops. We learn, further, that when we cover strawberry plants over, the roots of raspberries, fruit-trees, etc, we not only protect from cold, but enhance the productive capacity of the soil, whether the covering be shavings, saw-dust, tan bark, charcoal dust, straw, or farm-yard manure.