The Hawaiian Forester and Agriculturist 12(10): 261-264 (1915)
CHARCOAL AND SOILS
GEO. A. RETAN
Mount Alto Pennsylvania Nursery

Every farmer, gardener and nurseryman should be familiar with the results of experiments carried on for a period of three years, which have demonstrated that charcoal can be made of great use in improving the structure and properties of the soil.

It improves the water and air content of the soil, loosens and intensifies the sub-soil, apart from the chemical materials it may carry, and from its uses with manure. These are not theoretical, but practical conclusions drawn from the use of charcoal in one of the largest nurseries in the State of Pennsylvania, under the management of the writer.

Two general classes of material are available for purposes of fertilization. In the first class are commercial fertilizers. In the second class are those indirect fertilizers which do not furnish plant food directly, but by their action upon the soil may so affect it as to make plant food available by setting it free, through the altering of the physical condition of the soil. The principal fertilizer in this class is lime. Lime is really a stimulant instead of a plant food, and its continued use may be harmful or exhausting to the soil. Air, water and heat are more necessary for plant growth than mineral food. Production depends upon the proper aeration of the soil, the maintenance of a proper water content and through these two, the raising of the temperature of the soil. These conditions add plant food in that they render available the material that is stored away in soil compounds. The control of moisture in the soil lies in the physical state of the soil. If it is loose, porous, small grained, it will raise moisture freely from the sub-soil and hold it where it will be available for the plants and retard evaporation. The soil may be kept in such condition by proper tillage and by the addition of such materials as will effect a loosening and breaking up of the soil particles.

Green manure is valuable and barnyard manure and charcoal, with constant tillage, are among the best known agents. In using barnyard manure the best part of the manure is often lost. A large part of the mineral content is washed out if the pile is exposed and the liquid portions leak out or escape in gases. Many different substances have been tried for the purpose of preventing this loss. One of the very best materials which can be used for this purpose is charcoal. This is true because of its exceptional power of absorption, it possessing the capacity of absorbing many times its own weight in moisture and also because its physical effect upon the soil and the sub-soil has been conclusively demonstrated. Charcoal is already extensively used as a deodorizer or disinfectant, and the fact should not be lost sight of that the ammonia gas, which is quite lost in the manure heap, would be absorbed by the charcoal and made available for plant use.

For many years the attempt to raise coniferous seedlings in this nursery was a comparative failure because of the hard clay soil, which greatly increased the loss from unfavorable moisture and surface conditions. Among the agents tried for the relief of this condition were green manures, fertilizers and charcoal, and of these only the last has proved successful, as may be observed by the size and weight of seedlings developed from clay beds, fertilizer beds or charcoal beds. The seedlings are much larger and heavier and of better color on the charcoal beds than on any other. Some fertilizer beds show good seedling development, but the beds were not as densely covered with little trees as on the charcoal beds, notwithstanding that the charcoal beds were in the worst section of the nursery, while the fertilizer beds which show the best weights were in sections cultivated for a longer period. The charcoal seedlings averaged a weight of 250 grams for a bundle of 100 trees, as against 127 grams for a check bed in the same grade of soil. These trees were two years old. At one year the differences are not so striking, but are strongly marked. One hundred seedlings from a clay bed weighed 22 grams, while the same number from a charcoal bed weighed 40 grams. These beds contained a relatively large quantity of charcoal, such as could only be used in hotbeds, gardens, or other intensive work. But the same tendency is shown in the use of smaller quantities. Furthermore, the soil conditions are exceptionally bad in this nursery.

From constant observation and experiment, the action of char coal that makes it so valuable in the nursery seems to be entirely in the improved conditions of moisture and warmth. It might be thought that charcoal would loosen the soil to the extent that it would dry easily if used in large quantities, but the opposite condition occurs. In dry periods the power of the soil to retain water is increased, and in wet seasons the soil drains quickly with a consequent prevention of fungus that always follows a wet season in a coniferous nursery. The clay beds, by reason of their caking habit in dry weather, and poor drainage in wet weather, exerted the opposite effects and the loss was much more marked. In some cases it was complete. Again, charcoal beds are much warmer, because of the darker color imparted to the soil. This is of the greatest importance in the spring, when the ground has a tendency to be cold. Germination is almost entirely dependent on the warmth present and is consequently greatly helped by the darker color of the soil. Since the darker colored soil does not radiate any more rapidly at night, this heating effect is carried forward into the night and lessens the liability of damage from frost. In gardens and hotbeds, this is of considerable importance. This increased heat is of value in another direction. The aeration of the soil depends upon the heating, and it will be greater in the soil which becomes warmer during the day.

Thus we find that the action of charcoal in the soil is exerted along the lines where the most can be accomplished. The physical conditions of the soil are so improved that the air, heat and moisture coming to the crop is regulated in the most advantageous manner, and mechanical analyses of the sub-soil have shown that the charcoal exerts a beneficial action at a considerable depth, twelve to eighteen inches below the surface. The sub-soil beneath charcoal beds is of a better color and better physical structure than soil from the surface of untreated beds. This means an increase in the water-holding power, and a breaking up of unavailable compounds into available plant food.

To the farmer especially, the use of charcoal extends a wide range of advantages. He can add to the value of his manure, can improve the sanitary condition of the barnyard, poultry house, hog pen, etc.; and at the same time improve the physical condition of his land. When used in larger quantities in gardens, nursery beds, and in intensive cultivation, it offers the best physical condition for the growing crop with a decrease of loss from fungal attacks. The action of charcoal is comparatively permanent as compared with the other agents, which are used for the same purposes. Experiments carried on over three growing seasons have shown no lessening of the effects under the most unfavorable conditions. The agriculturists of the future must look forward to the conservation of the resources of the land. This is accomplished best by proper control of physical conditions with the subsequent fullest utilization of the natural forces of sunshine, air and moisture. Any man who will look forward to such a careful utilization of his land will surely increase his wealth materially.—North Woods (Minnesota Forestry Association).