The silt and the sand as minerals in the absence of the clay offer so little active surface, and are so insoluble that the root in direct contact with them can get very little from their slow chemical breakdown. The sand, in particular, that has survived weathering forces to remain in particles of larger size, is naturally harder and more insoluble as this resistance to disintegration and decomposition testifies. Then, too, its main mineral constituent is quartz. This mineral carries no element of nutritive value. The silt, however, that is softer and is therefore more readily ground to smaller size by weathering agencies, is richer in nutrient minerals and is more readily broken down chemically. It is, therefore, the soil’s main reserve supply of nourishing elements in the rocks and minerals that by their slow decomposition keep these passing to the clay in adsorbed form for plant nutrient service.

Clay as the Jobber Handles Acidity as Well as Nutrients

Fig. 1. Plant nutrients, like calcium, held on the colloidal clay or humus, are exchanged to the plant root for the hydrogen or acidity it gives off. As the nutrient supplies on the colloid become exhausted the excessive hydrogen substituted for them serves to break down the mineral reserves to pass their stock of nutrients to the colloid and to the root.

Soil Rest to Restock the Clay with Plant Nutrients

Humus, Too, May Be a Nutrient Jobber

In our virgin soils that have had myriads of generations of plants to come and go and to pass on their dead tops and incorporated roots as decayed organic matter to form colloidal humus, there was this stock of prefabricated soil fertility for our crops. As we plowed these virgin soils to fan the microbial fires of humus destruction, and to use this additional organic colloidal exchanger of nutrients taking hydrogen from the plant roots and breaking down the mineral silt fraction, we were running, at high speed, this humus assembly line that made for high crop yield. We had little thought of soil depletion. We worried little about impending deficiencies in the crops as animal feeds or as human foods. It was this destruction of natural humus in the soil that made such good crops on land freshly cleared of forest. It was this destruction that spelled early American prosperity and pushed high the unearned increments of our lands. It is this destruction that calls for soil conservation and soil fertility restoration today.

This high production of crops occurred on land that, without the drop of forest leaves as natural “forest manure” and as returning fertility to go into trees again, could scarcely produce even the wood crop by which few animals or higher life forms can be nourished. It is this waning humus supply in the soil that has been pushing nutritious vegetation westward except as the soil is bolstered up through lime and other fertilizers with the nutrients that make crops more than merely woody bulk of value only as fuel.

Differences in the Stage of the Soil’s Development Give Differences in the Plant’s Chemical Composition

Soil may be said to be a temporary rest stop of the rocks enroute to solution and to the sea. When the trip has just been started, the soil is not yet significantly developed. As the rock nears solution, or represents those remaining minerals of high resistance to weathering, the soil is overdeveloped. Thus, we may have soils in construction and in destruction in a geological sense. Soils at their best, however, are those with the rock broken down sufficiently to provide a fair amount of clay, and to have the adsorptive, or exchange, capacity of this soil separate fairly well saturated with the nutrient elements like calcium, magnesium, potassium, and others of positive electrical charges, and commonly called the bases. The better soils have not been weathered far enough to remove completely the softer rocks and minerals carrying the essential nutrients as reserves to be weathered out later. The silt separate still carries a supply of nourishing mineral reserves to be mobilized to the clay as it gives up its adsorbed nutrient supply to plants. Nor has the weathering gone far enough to load much of the clay’s exchange capacity with acid, the non-nutrient hydrogen. Better soils are midway between construction and destruction, both of which, as processes, contribute to the productive capacity of our soils.

Under still higher rainfalls to leach soils more toward their destruction, the acid dominance and fertility deficiency encourage a carbonaceous vegetation rather than a proteinaceous one. Humus made from this material has a wide carbon-nitrogen ratio. Consequently, nitrogen is hoarded near the soil surface by microbial competition for it. This magnifies the differences in color and makes more prominent the surface and subsoil horizons in the profile. While the leaching forces are pulling nutrient elements downward, plant roots and struggles by surviving vegetation are pulling them upward to magnify the contrasting darker color and higher fertility in the surface layer against the fertility deficiency in the lighter colored subsoil. This second soil horizon becomes a kind of a “No man’s land” over which both forces have fought for the nutrient elements, leaving little of fertility value for crop production after the surface soil is eroded. Humus, by its prominence and scarcity in different degrees; its distribution in the profile in different extents; its different carbon-nitrogen ratio; and its differing speeds of nitrogen mobilization during the growing season, is associated with the mobilized soil fertility and the crop-producing power of high value as nutrition to higher forms of life.

Climatic Geography Locates Mainly Carbonaceous or Proteinaceous Crops According to the Requisite Soil Fertility

Differences in climate are basic to differences in the degree of soil development and therefore to differences in the degree to which the soil provides the elements of plant nutrition. Too readily have we accepted the belief that the chemical composition of plants is controlled by the differences in rainfall rather than by the differences in soil fertility brought about by those differences in precipitation. Too readily have we accepted the belief that a single variety of plant is always of the same composition and that it delivers seeds or fruits of constant nutritive value. So-called “hard” wheat is grown in regions of lower annual rainfall. Its higher protein content, which is responsible for the “hardness” and better properties for so-called “light” bread, originates, however, only on soils still well supplied with calcium, and hence with other fertilizer elements, whereby a good supply of nitrogen is properly mobilized to make the protein production possible. Similarly “soft” wheat is ascribed to higher rainfall areas. Yet by providing the proper soil fertility, the wheat in the so-called “soft” wheat areas can be made as “hard” as any ever grown in the drier, hard wheat regions.

Fig. 2. Rainfall is the natural force weathering rock to soil. Exclusive of the western coast of the United States there is an increasing amount of rainfall from west to east and southeast to serve in soil construction in the western half and in soil destruction in the eastern half (upper figure).

When rainfall is divided by evaporation from free water surface (both as inches/acre/year times 100, or as percentage) the high evaporation in the Cornbelt to lessen the leaching effect of the rain, it is readily understandable why the Cornbelt was “prairie” soils (middle figure).

The weathering agencies as climatic forces of the United States serve clearly to give us the soil areas as they were mapped, with soils “in construction” in the western half, and soils “in destruction” in the eastern half, and the properties of the soils as they minister for or against particular crop production (lower figure).

The production of protein within the plant, or of the many other essentials for body construction and bone-building in humans and animals, is, however, more than a matter of weather. This process represents the mobilization of the soil fertility through the plant factory. The output in the form of these compounds as bulk is not so large. The amounts of these essentials within the crop are not so readily represented by the bulk of vegetative mass. Rather, their elaboration within the plant during the entire growing season may result in only the small amount finally delivered as the seed crop. It is these complex elaborations, however, that have high value as foods in terms of body building rather than in terms of provisioning it with fuels. They come only from the soil fertility. In consequence, they are apt to be deficient in the plant’s crop delivery because of our failing soils.

Proteinaceousness of the crop is connected with soils that are less leached of their calcium and other elements of soil fertility. Only the more fertile soils can therefore give us, in abundance, the feeds and foods so essential for growing young animals with good bone and good brawn. Soils in regions of lower rainfall, then, provide the soil fertility to serve this function. On the other hand, the carbonaceous crops are readily produced on soils more highly leached and of lower content in soil fertility. Such soils still supply the potassium requisite for carbohydrates synthesis but they are deficient in the calcium, the phosphorus, the nitrogen, and other requisites by which these carbonaceous compounds of energy values can be converted through biosynthesis into proteins, vitamins, and other complexes serving in body construction rather than as energy for keeping it going or maintaining its temperature.

Fig. 3. The native vegetation of Kansas increases in tonnage production per acre from west to east as the rainfall increases from 17 to 37 inches. Its chemical composition is related to the fertility of the soil, as indicated by the bison’s choice of buffalo grass because of its nutritive value more than its tonnage yield per acre.

The climatic geography of the United States and its crop distribution serve very effectively to illustrate this general principle of soil fertility depletion as basic to the natural incidence, or to the success on their introduction, of carbonaceous or woody crops in contrast to the more fertile and less leached soils as natural areas for proteinaceous products. In the rainfall of the United States (exclusive of the western coast) the lowest annual precipitation is in the West with less than ten inches. As one goes eastward, there are longitudinal zones of increasing amounts until one reaches the belt of 30 to 40 inches of rainfall. This amount runs north and south in the southern half as a longitudinal belt but more like a blanket over the northern portion of the eastern half of our country. In the southeastern states the annual rainfall figures are not so zonally arranged as they climb to the serious soil-leaching amounts of 50 to 60 inches per annum.

In terms of this picture of the precipitation one can see that the rainfall increase up to about 30 inches is an ascending force in soil construction. Beyond this figure, and particularly as one goes southeastward to higher temperature, one can see the increased rainfall as a force in soil destruction. Fortunately for the area known as “the cornbelt”, its location so far from seashore and within the center of a large land mass conferring the properties collectively known as “continentality”, gives it a higher summer evaporation which reduces the leaching of the nutrients by its higher rainfall. Its soils have therefore retained significant amounts of those mineral reserves representing the plant nutrients in the original rocks. The low ratios of the annual rainfall to annual evaporation from a free water surface as they can be delineated on the map serve to show that the fertility of the cornbelt is similar to that of the grassy prairie areas farther west. It was the fertility of the soil that presented the cornbelt pioneers with the highly productive plains of the prairies. It was not the prairie grasses that made the fertile soils, as one might erroneously be led to believe. Conversely, the fertile soils made the nutritious grass.

Fig. 4. Protein production demands more than air and water. The elaboration of this food complex depends on soil fertility. As the soils are less leached by lower rainfall the wheat grain is higher in protein. Using the lower tier of counties in Kansas going from the East (37 inches rainfall) to the West (17 inches rainfall), the protein content of the wheat in 1940 went from 10 to 17 percent.

The Soil Fertility Pattern of the United States Is Replicated in Other Centers of Civilization in the World

Here is a pattern of soil conditions, as determined by climatic forces, by which we can locate areas of similar soil productivity on the globe. Within the temperate zone these areas with annual rainfalls approaching the 30-inch figure, represent the combination of conditions that gave us soils which provision life with its food essentials. It was in this narrow belt of soils running north and south across the United States that the pioneer found the buffalo roaming in thundering herds. It is on these same soils that the cattle production is centered today with possible shipment eastward to higher rainfall areas for fattening purposes. It is on this belt that wheat as the staff of life can be produced. But even this food grain demonstrates its high protein content of eighteen percent in the 17-inch rainfall area of western Kansas in contrast to the ten percent of protein in wheat grown in eastern Kansas with its 37 inches of annual rainfall. It is this fortunate combination of climatic forces operating on a fortunate combination of mineral resources originally left to the climate for construction of soil that makes the midlands of the United States the well-laden breadbasket and meat basket that it is.

It is on similar soil patterns that other parts of the world are supporting corresponding populations and have established civilizations of similar accomplishments. That hard wheat has been the staff of life so universally the world over is not wholly due to inborn powers in the crop. Rather it is the soil fertility by which this crop can be both a protein-producer of growth values and a starch-former of energy values that locates civilizations on the higher rainfall sides of the hard wheat belts of the world. It is this soil fertility condition that is closely linked with all civilizations, not only in the United States but in other parts of the globe. A close scrutiny of the world for similar climatic soil combinations demonstrates that wherever civilizations of higher accomplishments have been established they are built on such soils of similar fertility levels serving as their basic resource. Europe with its hard wheat belt in Russia and higher rainfalls to the west is the picture of the United States with its East and West reversed. Similar soil and climatic combinations prevail in the Argentine, South Africa, Australia, New Zealand and to a similar degree in northeastern China. Studied in terms of the world wars, the basic food resources at the disposal of the warring nations loom as factors in the combat as well as any military or political maneuverings.

Fig. 5. The settlements of peoples in different parts of the world suggest the higher concentrations of them according as the climatic forces have made soils of such fertility levels that guarantee survival and permit development of their civilizations. (Map according to Griffith Taylor.)

Plant Ecology Indicates the Vegetations Changing in Chemical Composition with the Declining Soil Fertility

Forests abound where quite the opposite fertility condition prevails, or where potassium is in relative dominance to calcium. This is the situation in rocky regions not yet developed into soils, also on highly weathered soils from the clay of which sufficient potassium is still delivered to the deeply penetrating tree roots to support this plant’s activities that are predominantly photosynthetic as it builds its body mainly of wood. Even this carbonaceous construction mainly by means of air, water, and sunshine — all supra-soil in origin and action — can proceed only as the annual drop of fertility elements in the leaves keeps going back to maintain this annual cycle of self-fertilization. The plant pattern is as the soil permits and not as the plant wills.

The processes of soil development and soil depletion then give us the ecological pattern of plant composition and therefore the pattern also of the possibilities of feeding wild animal life, domestic animal life, and human life as well. They point the warning finger to the waning of human health, too, when cropping depletes the soil and when the same crop, that once was a life-sustaining food with body-building powers, has shifted its chemical output to products that are neither proteinaceous nor mineral-rich as they once were, but have become carbonaceous or woody materials of fuel value only. Our depletion of the soil or our failure to restore the removed nutrients is therefore an insidious under-miner of health in its many ramifications. As our soils are becoming deficient through our exhaustion of them, or as they had serious natural deficiencies originally, our foods have been or are becoming deficient and our health and growth along with them. And, unfortunately, the popular demand is for cures for these troubles, not for prevention by way of more fertility put back to give us restored soils.

Animal Instincts Offer Helpful Suggestions

The deer has demonstrated by its choice of browse in the forest that even trees give different chemical compositions in their growing buds and different feeds to wild animals. Sheep have selected the early growing rye where manure from alfalfa was applied, and in the same field where the soil was enriched by lime. Cattle have chosen pastures fertilized with 200 pounds of fertilizer in preference to that with only 100 pounds of this soil treatment. Hogs have taken the grain from the part of the field first where the soil was once fertilized to grow alfalfa. They have taken the corn at different rates from different compartments of the self-feeder according to the treatments of the soil where the grain was grown. The choices of the rats in cutting the bags of the same stored grains corresponded with the choice by the hogs. The rats failed to cut the bags of the corn that was disregarded by the hogs.

These animal choices are in accord with the demonstrations by Dr. Curt Richter using experimental rats to demonstrate their appetite as an attempt to maintain their physiological condition at the proper level for their best nourishment and survival. We are just beginning to appreciate the fine discrimination exercised by animals with reference to the chemical composition of their feeds as these feed qualities are dependent on the fertility of the soils producing them.

Diseases of domestic animals suggest that in their confinement by fences and barns to feeds provided for them, the animals are merely making manifest our failure to nourish them properly. Rickets, “loin disease”, “creeps”, acetonemia, pregnancy disease, and other ailments forcefully suggest that we need to look to the quality “grown into” the feed rather than antidotes or remedies “thrown into” it and into the animals.

Fig. 6. Hogs put into this field to “hog down” the corn selected this area of the forty acres where this Missouri farmer had treated the soil and grown alfalfa some years previously. It was Prof. Evvard, the inventor of the self-feeder, who said, “If you will give the pig a chance it will make a hog of itself in less time than you will.”

Fig. 7. Three lots of lambs were fed for nine weeks on equal amounts of grains and of hays from adjoining plots given the different soil treatments. Those fed with hay from the plots given lime and phosphate gained twice as much as those fed from the hays grown without soil treatment.

Experiments using the animals to assay the value of the soil treatment in producing better feed quality have demonstrated the validity of the belief that we can feed our animals by treating the soil. The use of equal amounts of supplements and of hay per head per day with the hay coming from three plots with different soil treatments demonstrated clearly that the animals’ meat-making machine can run no more efficiently than is made possible by the raw materials supplied as feed.

Fig. 8. Fertilizer treatments of the soil register their beneficial effects in the plant, but more noticeably in the physiology of the animal, as indicated by better weight, wool, fur, bones, or other body products and functions. On the left, the rabbit and bones record the lack of soil treatment, in contrast to the effect of treatment measured by similar gauges on the right.

Rabbits selected for uniformity in sexes and weights as litter mates, were fed the lespedeza hay grown on the five different soil types of the experiment fields in five different parts of Missouri both with and without soil treatment, only to find that the animals on hays from untreated soils in final appearances suggested five distinctly different kinds of rabbits. Those fed the hay from treated soils were similar. Studies of their various body parts, as glands, bones, and others, revealed the extensive variations as the result of the differences, not in initial animal, not in kind of plant, but in the quality of the same feed originating in the differences in the fertility of the soil growing it. Differences in the soils made differences when the animals were originally alike in age, size, pedigree and other properties of controlled uniformity at the outset. They were eventually different because the soils supporting them were different and therefore the qualities of their forage feeds were different.

Fig. 9. Human, as well as plant and animal health, declines as the fertility of our soils is leached or washed away.

Declining soil fertility, then, as it provokes the plant’s failing synthesis of growth essentials may be the fundamental cause in the declining food quality. These qualities cannot be adequately bolstered by mineral additions to the ration. If these are the facts, then, we may well look to the treatment of our soils with those fertilizer essentials that contribute to plant composition in terms of the elaborated compounds that give food its life sustaining values of the highest service in terms of good health. In this respect all of us, and our children need to appreciate the great fact, that food quality for all life is no higher than the fertility of the soil producing it. If our declining soil fertility is not to sweep us down with it, our efforts in soil conservation must be to push the fertility of the soil back up by a proper treatment of the land. Our future health as well as our wealth depends on the restoration of our soils.