Nature's Short Supply. The total area of lime-deficient soil is large, comprising certainly much more than half of all the land east of the semi-arid belt of the United States. No small part of this area was not deficient at one time, as the nature of the original timber indicates, and it is well within the knowledge of practical men that land which once produced the walnut and ash and shellbark hickory can be brought back to productivity with reasonable ease after very hard usage. It has a good inheritance. It is a disconcerting fact in our American agriculture that, fertile as our country is as a whole, very great areas were so deficient in lime before they came under man's control that the chestnut, pine, and the oaks of mean growth were fully at home. The gradation from low lime content to high, and its relation to soil type, give us all sorts of mixtures of lime-loving and acid-resistant varieties of trees in original forests, but our agriculture is hampered by the high percentage of land for which nature made no great provision of lime, and on this land farming lags.
Effect of Irrational Farming. Interest in liming might well have been due to the amendment of all this soil, but the rational use of lime that has been the subject of much study in the last quarter of a century concerns chiefly great areas that probably could have been kept in alkaline condition and friendly to the clovers for a long time despite a short natural supply as compared with the content of our limestone lands. The success of individual farmers in areas now admittedly acid as a whole is convincing on this point. Nature tries constantly to cure the ills of her soil through the addition of vegetable matter. An excess of water or a deficiency is atoned for in a degree by the leaves and rotted wood of her forests. Aeration is kept possible. The lime in the product of the soil goes back to it. A system of farming that involves the application of manure, thorough tillage, drainage where needed, and the free use of sods in some way, has kept portions of these non-calcareous soils out of the distinctly acid class. Clover grows satisfactorily, grass sods are heavy, and there is no acute lime problem. Such farms are relatively few in the great stretches of land now classed as acid soil, and probably the most of the lime that is being applied goes only on ground that once was sufficiently alkaline to grow the clovers. The loss of organic matter through failure to use the best methods of farming is responsible for no small part of the widespread need of lime today. This subtracts nothing from the urgency of its use to restore a condition favoring clover and grass sods, but it does teach a lesson of the highest value. The day of destructive soil acidity can be retarded by good farming, but in the long run the inevitable losses of lime from most soils must be met by applications.
Limestone Soils. The old-time practice of making heavy applications of fresh burned lime to stiff limestone soils to make them friable, and to make their plant food available, led to disuse of all lime in some sections on account of the exhaustion that followed dependence upon these large amounts as a manure. Queerly enough, these original limestone soils have latterly been going into the acid class through loss of their distinctive elements, and they, too, have become dependent upon means for the correction of acidity.
CHAPTER III
SOUR SOILS
Loss of Lime. Nature made the value of land as a producer of food utterly dependent upon the activity of lime, and at the same time gave it some power to shirk its work. In a normal soil is a percentage of lime that came from the disintegration of rock of the region or was transported by action of water on a huge scale. Possibly rarely would it be in insufficient amount to keep a soil in a condition friendly to plant life, and to feed the plant, if it stayed where nature placed it and kept in form available for the needs it was intended to meet. There is land that always was notably deficient in this material, and there is land that was known in the early history of the world's agriculture to be "sour," but the troubles of our present day in the case of the farming country in the humid region of the United States is less due to any natural absolute shortage than to combination that destroys value and to escape by action of water.
Clover and Timothy Unfertilized at the Pennsylvania Experiment Station Yielded 2460 Pounds per Acre