In the following chapters we deal with the intensive propagation and use of earthworms under controlled environment. As has been stated, the one fact which makes it possible to utilize the earthworm in mass-production of humus-laden topsoil is that the number of earthworms in a given environment is limited only by the amount of available food present.
There are two objectives to be held in mind: The first is the most effective and economical utilization of all possible organic material, such as every form of vegetation, all animal manures, garbage, garden, orchard, and farm waste, and litter of all kinds; in fact, what we have termed the biological end-products of life as opposed to purely chemical end-products and strictly chemical fertilizers. The second objective is to establish the greatest possible earthworm population in the soil, using methods of tillage and organic fertilization that will favor the maintenance of earthworms in the soil, as well as the bacterial population that is concerned in soil-building and maintenance of the highest state of fertility in a permanent agriculture.
In propagating earthworms intensively in special culture beds, we use them very much as we use bacterial cultures, breeding them in high concentrations by furnishing adequate food material to support vast numbers in a limited area. Fertile farm and garden soil, properly handled through organic methods, will easily support from one to two million or more earthworms per acre-foot. Such a population will provide ideal aeration and air capacity for the soil, with good drainage, rapid water penetration and maximum moisture-holding capacity. At the same time, such an earthworm population provides a soil turnover and conditioning of upwards of two hundred tons of material annually, mixed and prepared in the humus mill of the earthworm and delivered to the root-zone of vegetation comprised in the immediate six to eighteen inches of surface soil. In special culture beds, we commonly propagate earthworms in concentrations of upwards of three thousand worms per cubic foot of material, which means, in round numbers, one hundred and thirty million worms per acre-foot.
With the above figures and objectives in mind, it is possible to begin to visualize the possibilities of soil-building, whether it be for a single flower pot, a window box of flowers, a small city yard or garden, or more extensive acreage in large gardens, nurseries, orchards, or farms.
We ordinarily think of earthworms as small, wriggling, insignificant, repugnant creatures. To appreciate properly the possibilities inherent in the intensive propagation and use of worms in soil-building, we should gain a new and different concept, thinking of them in units of hundreds, thousands, or even millions, instead of thinking in terms of separate, tiny, individual worms. For purposes of illustration, suppose we ask, "How many are a million earthworms?" and use our imagination in answering the question.
Mentally, we shall combine one million earthworms into a single, composite animal and place this animal on an acre of ground, with a year's ration of fertile topsoil piled up around it in symmetrical piles for its daily consumption. We shall then have a monster animal, weighing more than 2000 pounds, with 365 piles of soil before it. Each pile will contain approximately one cubic yard of earth, weighing upwards of 2000 pounds. Each pile will represent the daily ration of this fantastic, dirt-eating animal, that will swallow its own weight or more of earth each day of the year. Such will be our composite animal, mentally integrated from one million earthworms. Now let us check with the facts, as they have been established by careful experiment.
We have weighed many of the earthworms which we propagated during our research. On the average, they run about 500 to the pound, or about 31 worms per ounce. The fully mature worm, in good condition, averages four inches in length. Thus we find that one million of them would weigh 2000 pounds. If placed end to end, they would make a continuous line over 6 1/4 miles long. An individual worm, eating its way through the soil, will swallow its own weight of earth daily, in order to absorb from the soil the infinitesimal amount of nutrition required to keep a worm in good condition. When we analyze and carefully study these figures, we begin to gain a concept of the tremendous soil-building force which is at work in the earth when it is populated by one million earthworms per acre. The earthworm is just as truly an air-breathing, manure-producing animal as a horse, cow, or other domestic animal. The difference is that earthworms work unseen and their manure is so thoroughly combined with the soil that it cannot be separated. In fact, as has been pointed out, the manure of the earthworm is finely conditioned soil.
At first thought, when it is stated that an earthworm will ingest its own weight in soil each twenty-four hours, this amount seems almost unbelievable. However, when the eating and excretory activities of the chicken are compared with those of the earthworm, a ration of topsoil equal to the weight of the earthworm each day seems a very reasonable amount. On the average, a mature hen will drop seventy-five pounds of manure each year. Chickens utilize only about ten per cent of the nutritional value of the food they eat, the balance going out in their droppings. Thus they have to gorge many hours each day in order to produce eggs in commercially profitable numbers. Suppose that a laying hen had to swallow enough earth daily to secure the amount of organic food necessary to keep her in good laying condition, instead of feeding on concentrated grains and mashes. To do this, she would have to consume several times her own weight of earth each day, assuming that her digestive organs were similar to those of the earthworm. Yet that is exactly what the earthworm has to do. The earthworm lives on the organic content of the soil, which it swallows with all that is contained therein. The earthworm is so constructed as to be able to digest this material, thus gaining the small amount of food necessary for nutrition. Only because it is perhaps the most perfect digestive organism known to the animal world is the earthworm able to absorb enough food from an amount of earth equal to its own weight to maintain it in a fat and active condition. Thus, the statement that the earthworm swallows its own weight of earth daily appears, on examination, perfectly reasonable and understandable.
We again repeat: Think of earthworms in large units of hundreds, thousands, millions; for in intensive propagation and use of earthworms we must deal with great numbers of them. Otherwise, we cannot expect to attain results worthy of consideration.