Chapter 2 : Agriculture and Health
Problems of soil and agriculture seldom arouse the interest of urban dwellers. Town and country have become so sharply polarized that the city man and the farmer live in widely separated, contrasting, and often socially antagonistic worlds. The average resident of an American metropolis knows as little about the problems of growing food as the average farmer knows about the problems of mass transportation. The city man, to be sure, does not need to be reminded that good soil is important for successful farming. He recognizes the necessity for conservation and careful management of the land. But his knowledge of food cultivation - its techniques, problems, and prospects - is limited. He leaves the land in trust to the farmer in the belief that modern agricultural methods cannot fail to produce attractive and nourishing food.
In reality, however, modern agronomy is beset with highly controversial problems, many of which deeply concern the welfare of urban man. It has been vehemently argued and as vigorously denied that soil fertility has a profound influence on the quality of food. According to some agronomists, deterioration in the fertility and structure of the soil results in nutritionally inferior crops. Such crops may satisfy the demands of hunger but not necessarily the requirements of human physiology. If a shift from high to low quality crops occurs on a large enough scale, man's health will be adversely affected.
Opponents of this viewpoint contend that soil fertility influences only the size of the crop and that the nutritional quality of a plant is determined primarily by genetic factors, notably the variety of seed that the farmer selects for his crop. If urban man is to exercise any control over the factors that influence his health, it is important that he gain some degree of familiarity with these problems. He need not get involved in technicalities, but he must acquire a general knowledge of soil needs and the relationship between soil fertility and the nutritional quality of crops.
Despite the sentiment and fervor ordinarily evoked by the words "land" and "soil," many people think of soil either as "dirt," a term that is often used synonymously with "filth," or as an inorganic resource, such as copper and iron. These misconceptions have not been completely eliminated by science. The rudiments of a science of soil were established in 1840, when Justus von Liebig published his monumental studies of soil and plant chemistry. Liebig had a profound grasp of his subject. He swept away many alchemistic notions about plant growth and replaced the more doubtful agricultural precepts of his day with new ones based on careful reasoning and scientific research. But Liebig also gave support to a misconception about soil that has yet to be completely removed from the public mind. He fostered the belief that soils are "lifeless storage bins filled with pulverized rocks, which held water and nutrients and which farmers stirred in tillage."
Agronomists generally agree that Liebig's conception of soil is incorrect. Although some soil scientists still hope to manipulate the soil as though it were little more than a reservoir of inorganic nutrients, few, if any, accept Liebig's approach. The soil is a palpitating sheet of life, varying in composition not only from one part of a country to another but from acre to acre. Man can analyze the soil but he cannot manufacture it. The first difficulty he encounters is its highly dynamic character and its remarkable complexity. The soil is a highly differentiated world of living and inanimate things, of vegetable and animal matter in various stages of decomposition, and of rock particles, minerals, water, and air. Soil is always in. the process of formation. It gives up its nutrients to the wind, rain, and plants, and is replenished by the breakdown of rocks, the putrefaction of dead animals and plants, and the neverending activities of microscopic life. The soil is the dramatic arena where life and death complement each other, where decay nourishes regeneration.
The surface soil, where most of the dead matter in soil is concentrated, is not the end product of decay; it is an active stage in the decomposition of organic matter. The decaying process, continually renewed by the addition of dead organisms, is as necessary for the continued existence of the soil as it is for the formation of soil. Hummus, the black or brown organic portion of the soil, is a protoplasmic, jellylike substance made up of cells, leaves, and tissues that have lost their original structure. If hummus were not renewed by the remains of dead organisms, the soil as we know it would disappear. The land surface of the earth would eventually be occupied by mineral particles and rocks, and the land would be inhospitable to advanced forms of plant and animal life.
Soil is made up of not only dead matter but living organisms. The most important of these organisms are either invisible or barely visible to the naked eye. Fungi, which initiate decomposition, and bacteria, which supply plants with usable nitrogen, are as much a part of the soil as hummus and rock particles. These soil microbes supply most of the nitrogen required for plant growth. Their work is supplemented by the activities of countless insects and earthworms, which burrow elaborate galleries through the topsoil. Without the air that these galleries provide, plant nutrition would be inhibited and bacteria would be confined to the top few inches of the soil. Earthworms continually circulate soil nutrients. During a single year they may turn up as much as twenty tons of soil to the acre, burrowing to a depth of as much as six feet below the surface. As organic nutrients pass through their bodies, they leave behind casts that give the soil increased granularity and improve its ability to support plant life.
Soil would be washed or blown away if it were not held together internally. Its connective tissue, indeed its skeleton, is made up of the root systems of the plant life it supports. Roots reach out in all directions, intertwining with one another to form a living grillage beneath the surface of the land. By interlocking and binding soil granules in a network of root branches, they increase the soil's ability to withstand the impact of rain and wind. Above the surface, the forest's canopy of branches and leaves breaks rainfall into a fine spray. The erosive runoff so often encountered in open, sloping land is changed into a gentle flow that makes it possible for much of the water to be absorbed by the subsoil. The soil is spared and the water table is kept high. Finally, when plants die, their remains not only increase the fertility of the soil but also improve its structure. Lignin in roots, stalks, and trunks keeps the soil porous and friable - structural characteristics that favor the penetration of water and air.
In addition to microorganisms, soil fauna, and plants, the fourth major factor in the maintenance and formation of soils is the activity of large terrestrial animals on the surface. Under natural conditions, the land teems with wildlife, which leaves behind organic wastes rich in plant nutrients. Nature, as Sir Albert Howard has emphasized, is a mixed farmer: "Plants are always found with animals; many species of plants and animals live together." Nature seldom cultivates a single crop to the exclusion of all others. Variety and combination, of both plants and animals, constitute the basis for natural equilibrium. Herbivorous animals supply the topsoil with fecal matter, carnivores, in turn, regulate the number of plant eaters and thereby prevent excessive grazing. Normally, predators and their prey live in equilibrium. Rarely does it happen in the natural course of events that either group attains such numbers as to become pests and injure the soil.
Every plot of land should be viewed as a small, highly individuated cosmos. Merely identifying the organisms that promote the welfare of the soil does not adequately describe the dependence of each group on all the others. The performance of bacteria, it has been noted, depends in part on the capillarylike channels opened up by the passage of insects and earthworms through the soil Insects and earthworms, in turn, depend for nutrients on the organic wastes of plants and animals. If the soil is structurally and nutritionally conducive to a balanced, thriving soil fauna, bacteria tend to penetrate further; top soil becomes deeper and richer; plant growth becomes healthier and more luxuriant. When plants are abundant, wildlife is better nourished and more plentiful. If any external element disrupts this cosmos, the soil deteriorates and the living things that occupy the surface are adversely affected.
As long as man is a food gatherer or a hunter, he exercises a minor influence on the soil. He acquires what he needs where he finds it, and generally he has little effect upon the natural world. When he begins to cultivate the land, however, he imposes a new and often largely synthetic environment on his natural one. The soil cosmos is altered drastically. On forest lands, a large part of the indigenous tree cover is removed and the soil is exposed to the direct assaults of rain and wind. With the restriction of animal life, the return of manure to the land becomes fortuitous. Whether the soil is properly fertilized or not depends upon man's foresight, which is usually limited to serving his shortterm economic interests. Lastly, the cultivation of a single plant species on a given tract of land tends to become the prevalent practice, and the checks and balances afforded by a diversity of vegetation are removed. The success of agriculture depends upon the extent to which man preserves the soil cosmos he inherits from nature. If the elements are merely rearranged and adequate compensation is made for necessary changes, the cultivation of food can continue indefinitely without harm to the soil; in fact, virgin soil can be improved immeasurably. But if the soil cosmos is undermined, soil will begin to disappear and the land will be forced to function with, as it were, its vital organs exposed and half its viscera removed.
The results can be disastrous. History supplies us with numerous accounts of civilizations that disappeared solely because of poor agricultural practices. Throughout the Mediterranean world, vast manmade deserts have supplanted rich, fertile lands that once nourished luxuriant crops and supported large populations. In North Africa, for example, a terrible price has been paid for the ancient plantation economy, in which land was cultivated for a few cash crops. The Phoenician merchants who established Carthage found a semiarid but highly fertile soil on the southern shores of the Mediterranean Sea. Almost at the outset, farming assumed a highly commercialized form. A large acreage was irrigated and cultivated by slaves, and crops were planted and harvested primarily for the money they would bring in. "The intensive plantation cultivation which the Carthaginian plantationowner undertook, and which was subsequently imitated by the Roman conquerors of the land, had the longterm effect of letting in the desert," Edward Hyams writes. "Conceivably, the original forest - and grass - soil communities might have acted as a barrier to the advancing sand, might have even pushed slowly southward, carrying a more humid climate with them as trees invaded the grass, and colonized the Sahara. But cultivation which took no account of soil as such, and was concerned with getting the largest possible crops out of the soil, had the opposite effect. The Sahara began its northward march; it has been on the move ever since; it has already invaded Europe, by way of Spain, an old African trick."
It is not difficult to see that the agricultural practices that reduced fertile areas of the Mediterranean world to a desert are being repeated today, especially in many areas of the United States. Both the forms and the effects are often the same. Modern agriculture tends to model itself on industry. Tens of thousands of acres are planted and harvested on a factory schedule, in some cases to meet the daily production requirements of a nearby food processing plant. Every method that will "hurry along'" cultivation and reduce its cost is eagerly seized upon. Food cultivation is rigorously standardized, even "time studied." The division of labor in agriculture is developed to a point where the term "farmer" becomes a most general expression, applicable to pilots who spray insecticides from the air, truck and tractor drivers who merely operate vehicles, mechanics who repair farm implements, foremen who manage workers, and underprivileged migratory laborers, working at piece rates, who view the needs of the land with complete indifference. Husbandry is almost entirely subordinated to mass production. The modern land factory, like the metropolis that it feeds, tries to base the management of living things on a pernicious average. It employs primarily those methods that promote mass manipulation at the lowest cost.
Practices of this sort are as harmful to soil as they are to men. Modern agriculture often demands the largest possible farm machinery to handle its huge crops; heavy tractors move over the same area of land repeatedly - planting, spreading fertilizer, and harvesting crops. Although the use of machines in the performance of arduous tasks is certainly desirable from a human point of view, every mechanical advance should be properly scaled, both in size and form, to the situation at hand. The land is not the concrete floor of a factory; it is a living thing, and it can be mauled and bruised. Injury to the soil, often of a serious nature, inevitably follows the exposure of fields to the weight of extraordinarily heavy machines. The soil becomes compacted, and as a result, proper drainage and the growth of roots are inhibited. Data from Texas indicate that crop yields of compacted soils there have fallen off from 40 to so per cent, and commercial fertilizers have not been able to increase the yields to any great extent. "After 100 years of farmimplement development," observes Howard W. Lull, of the U. S. Forestry Service, "more than half of Germany's cultivated soils are in poor condition - due largely to compaction by tractors. In Great Britain, the rapid increase in the weight of tractors in recent years has led to predictions of serious effects on the soil."
The deterioration of soil is carried further when large areas of land are used to cultivate a single crop. The land factory separates not only animal from plant, but plant from plant. Precisely where plant and animal wastes are most needed to help the soil withstand the weight of heavy machinery, a strong emphasis is placed on onecrop agriculture and industrial methods. The structure of the soil breaks down and the layer of hummus begins to disappear. In many areas of the United States, the land has been turned into a nearly lifeless, inorganic medium that must be nursed along like an invalid at the threshold of death.
The term "inorganic medium" can be taken literally. Modern agriculture may be distinguished from earlier forms of cultivation by its reliance on chemistry for soil nutrients and the control of insect infestations. With the removal of many natural checks and balances, we are compelled to use many synthetic materials to grow and protect our foods. These chemical agents enable us to produce large crops on indifferent and even poor soils. The ultimate is reached with hydroponics, which uses no soil at all. An open box is filled with pebbles and a solution of inorganic nutrients. Then seeds or roots are placed directly in the medium, or sometimes seeds are supported in the solution by a wire screen until they germinate and sink their roots into the pebbles. With adequate light, proper temperature, and the appropriate renewal of inorganic nutrients, the plants mature rapidly and become an edible crop.
In an age of demonstrable scientific achievement, it is hardly necessary to emphasize the agricultural importance of chemistry. Chemical analysis has advanced our knowledge of the soil cosmos and plant nutrition enormously, and there is no a priori reason why manmade chemical agents cannot be used to considerable advantage in increasing the fertility of the soil. Soil is fertilized to increase the quantity and quality of food crops. Wherever man acquires the knowledge and the chemical agents to achieve these ends, he enjoys a decisive advantage over lessdeveloped agricultural communities. Natural processes can be rendered more efficient and some of the life lines that determine the abundance and quality of plants can be shortened, both to the advantage of man and the organisms on whose wellbeing he depends. If rational standards were applied to agriculture, it would be possible for farmers to systematically meet various needs of the land that would probably have remained unsatisfied if the solution of soil problems had been left to natural processes alone.
But there is a danger that the techniques of modern chemistry will be abused. This danger is especially pronounced in an age of scientific achievement, in which a limited amount of knowledge tends to create the illusion that our command of the agricultural situation is complete and our standards of agricultural success are rational. Modern society places a strong emphasis on the merits of mass production. We tend to confuse quantity with quality. The thoughtless use of chemical agents in the production of food may well make it possible to grow crops of great abundance but of low quality on soil that is basically in poor condition. "High yields are not... synonymous with a high content of nutrient elements," observes A. G. Norman, of the University of Michigan "Crops from well fertilized plots may have a lower content of some essential elements than those from poorly yielding plots, the addition of a fertilizer may cause a reduction in content of some of the other nutrient elements, or, if the supply of the major elements is such that the content of each in the plant falls in the poverty adjustment zone [where a partial deficiency of nutrients exists], moderate addition of one of them may have rather little effect on content."
Without making a fetish of nature, a number of responsible agronomists and conservationists doubt strongly whether a basically poor soil is capable of meeting all the nutritional requirements of plants, animals, and man with the support of a few chemical fertilizers. "In the long run life cannot be supported, so far as our present knowledge goes, by artificial processes," observes Fairfield Osborn, a noted American conservationist. "The deterioration of the lifegiving elements of the earth, that is proceeding at a constantly accelerating velocity, may be checked but cannot be cured by manapplied chemistry." Osborn sees two basic reasons why "artificial processes, unless they are recognized as complements to natural processes, will fail to provide the solution" to current soil and health problems. "The first is concerned with the actual nature of productive soils," by which is meant the complexity of the soil cosmos. "The second reason is a practical one and hinges upon the difficulty, if not impossibility, of instructing great numbers of people who work on the land regarding the extremely complicated techniques that need to be applied to produce even a reasonable degree of fertility by artificial methods."
Whatever one may think of Osborn's conclusions, the issue is obviously of great importance in any discussion of environmental health, and it raises the additional question of one's approach to our synthetic environment. Knowledge is never absolute. What we "know" about anything, be it soil or nutrition, generally consists of the facts that are selected for our purpose. If our objectives are comprehensive, so too will be the data they command. If they are limited, the data adduced in their support may entail a suppression, conscious or unconscious, of facts that support broader objectives. The physician who is burdened with a schematic conception of disease is inclined to ignore subtle functions of the body whose impairment contributes to the incidence of chronic and degenerative illnesses. Similarly, the agriculturist who is guided primarily by such quantitative criteria as the size of the crops is inclined to ignore ecological processes whose impairment may lower the nutritional quality of food. The evidence that both adduce in support of their views, such as man's greater longevity and larger crops, does not prove that man's longer life span is the result of better health or that the abundant crop is greater in food value.
The tendency to place the soil on a limited ration of chemical fertilizers becomes stronger with each passing year. Nearly a decade ago, George L. McNew, of the Boyce Thompson Institute for Plant Research, observed that the quantity of inorganic fertilizers used in agriculture had increased over 200 per cent between the prewar years and 1948. "Less barnyard manure is being added to the soil each year. Not enough green manure from cover crops is being plowed under to maintain the organic matter content in soils on most of our farms." The implications of this change in agricultural methods call for sober consideration. We must closely examine the way in which current fertilization practices are likely to affect the nutritional quality of food, especially in circumstances where economic incentives are likely to make misuses of chemicals the rule rather than the exception.
Before we can understand the role that soil fertility plays in environmental health, an important question must be answered. Do we have a complete knowledge of the nutritive constituents of common foods and do we fully understand the function that all the known nutrients have in the human body? Many researchers in the field of nutrition and in related sciences agree that the answer is no. "There is no known laboratory method or group of methods by which all the nutritive constituents in a food can be measured and evaluated in terms of the nutrition of man or animals," observes Kenneth C. Beeson, formerly director of the Department of Agriculture's Plant, Soil, and Nutrition Laboratory. "... All of the constituents contributing to nutritive quality have probably not been recognized and there are no adequate methods for quantitative measure in many constituents that we do recognize."
The same problem is stated very clearly by Bruce Bliven in a popular discussion of hydroponics. "We do not know whether we have yet enumerated the entire list of chemicals and other substances necessary for the maintenance of health and vigor. The 'trace minerals' that occur in minute quantities in our food, including cobalt, copper, phosphorus, manganese, iodine, and others, are known to be of enormous importance to health, though we are not yet sure just how many of them are required, or in what quantities. We do not even know how many vitamins there are, or which are essential. Theoretically, it should be possible to produce fruits and vegetables from soil that is lacking in some of the substances necessary for the health of animals and man; these fruits and vegetables would look all right, and yet prove to be harmful if they were a principal part of the diet."
The possibility of producing plants that 'look all right" but vary widely in nutritional values is more than theoretical; such cultivation is eminently practical and very common. Identical varieties of vegetables, fruit, and grain may differ appreciably in mineral, protein, and vitamin content. These variations are caused by many factors, a number of which are not within man's control. For example, the vitaminC content of fruit and leafy vegetables seems to depend primarily upon the amount of sunshine to which the plants are exposed. Variations in temperature influence the production of thiamine and carotene in different plant species. The longer the growing season, the greater will be the amount of vitamin C in beans, spinach, and lettuce. Aside from these climatic and seasonal factors, however, a decisive role in plant nutrition is played by soil fertility. Despite sharp differences of opinion that have developed around the issue of soil and nutrition, a large amount of evidence supports the conclusion that the nutritional quality of plants is influenced profoundly by the fertility of the soil.
This influence may be beneficial or undesirable, depending upon the type and quantity of fertilizer used in any given agricultural situation. In general, nitrogen fertilizer tends to increase the proportion of crude protein in grain. This relationship has been established in several experiments. During the late 1940's, research by R. L. Lovern and M. F. Miller at the University of Missouri showed that the percentage of crude protein in one variety of wheat could be raised from a minimum of 8.9 to a maximum of 17 by successive applications of soluble nitrogen to the soil. Three years of experimental work by A. S. Hunter and his coworkers on 133 farms in the Columbia Basin counties of Oregon indicated that applications of nitrogen fertilizer usually increase the amount of protein in pastrytype wheats. Results of a similar nature have also been achieved with corn. H. E. Sauberlich and his colleagues at the Alabama Agricultural Experiment Station cultivated two grades of corn - a 'low protein" grain (6.8 to 9.1 per cent) and a "high protein" grain (9.5 to 13.6 per cent). The "high protein" corn was produced by increasing the application of nitrogen fertilizer to the soil.
When agronomists turn their attention from the protein to the mineral constituents of plants, they find that soil fertility exercises a more subtle influence on nutritive quality. The addition of calcium, phosphorus, potassium, and other nutrients to depleted soils often increases the mineral content of plants; but the experiments do not yield consistent results. In many cases an increase does not take place. In fact, if the soil is not deficient in common minerals, attempts to increase yields by adding high concentrations of commercial fertilizers to the soil may actually reduce the nutritive quality of plants. The soil may become "overfertilized," and the quantity of important nutrients in the crop will diminish.
How are these contradictory results to be explained? A partial answer is provided by the findings of soil chemistry and plant physiology. Many factors may inhibit a plant's uptake and utilization of a nutrient. Research workers have discovered that an excessive quantity of one nutrient in the soil may prevent the absorption and utilization of another. "Too much nitrogen, for example, in proportion to the phosphorus available to plants, may encourage undesirable physiological conditions. Also too much calcium may interfere with phosphorus and boron nutrition or may encourage chlorosis [lack of chlorophyll] due to a reduction in the availability of the soil iron, zinc, or manganese." Several key nutrients have been paired together on the basis of such interactions, notably calcium and magnesium, iron and manganese, and cobalt and manganese. Moreover, it would be incorrect to assume that a simple onetoone relationship exists between available soil nitrogen and the protein content of plants. Proteins differ markedly in nutritional value. By applying excessive quantities of commercial nitrogen fertilizer to the soil, a farmer may well produce a lush crop that contains less highquality and more lowquality proteins than crops cultivated on properly fertilized soils. An objective review of the evidence at hand not only justifies the conclusion that soil fertility influences the nutritive quality of food; it also leads us to believe that this influence is more complex and more subtle than was formerly suspected. A balanced array of nutrients, modified where necessary to satisfy the needs of a specific soil, is indispensable to the cultivation of highly nutritious crops.
At a time when many farmers are trying to cultivate large crops by supplying the soil with a few highly concentrated inorganic fertilizers, it would be appropriate to emphasize the important role that organic matter plays in plant nutrition as well as in the reconstruction of soil. Organic matter is extremely complex and highly varied in nutritional content. Manure, for example, will not only supply soil with adequate quantities of nitrogen released by microbes in close accord with the plant's needs; it will also add most of the nutrients that plants require for growth and wellbeing. No one seriously claims that manure alone meets all the needs of a crop, but its array of nutrients is probably unequaled by the commercial fertilizer preparations that are normally used today.
The use of organic fertilizers has often made the difference between successful food cultivation and outright crop failures. Until well into the 1920's, many American agronomists were convinced that soil merely required heavy dosages of nitrogen, phosphorus, and potassium - the wellknown NPK formula - to produce flourishing crops. These elements, it was supposed, were all that organic fertilizers contributed to plant nutrition. When inexpensive commercially prepared fertilizers became available, nitrogen, phosphorus, and potassium compounds replaced manures, bone meal, and plant residues. Serious crop failures often followed the changeover. In Florida, for example, nutritional deficiencies appeared in citrus and tuna trees; they were corrected by a return to the use of organic matter. Intensive research disclosed that bone meal supplied citrus trees with sorely needed magnesium in quantities that were not provided by the inorganic compounds in use at the time. Fortunately, the deficiency appeared in an acute form; it was easily discovered and later corrected by new chemical agents. But success in correcting acute nutritional deficiencies is likely to lower our guard against insidious deficiencies that may not manifest themselves as clearcut plant disorders. Many plants may require nutrients in amounts that are not supplied by commonly used inorganic preparations.
The majority of commercial fertilizers in use today are relatively simple chemical preparations. The farmer deliberately replaces complex, bulky. slowacting organic materials with a few soluble, purified, inexpensive, and easily handled salts. The regulation of soil fertility now falls for the most part to man. "The agronomist and the farmer are ordinarily preoccupied with yield," Norman writes. "They are rarely concerned with mineral composition. The varieties selected, the cultural practices followed, the fertilizers applied, all are decided on the basis of yield expectation." The manipulation of soil fertility in accordance with this criterion may produce very curious results. For example, in studies conducted at the Missouri Agricultural Experiment Station, it was found that by changing the ratio of calcium to potassium, it was possible to increase the vegetative bulk of soybeans by one fourth. "Such increased tonnage would warrant agronomic applause," observes William A. Albrecht, of the University of Missouri. "But this increase in vegetative mass represented a reduction in the concentration of protein by one fourth, a reduction in the concentration of phosphorus by one half and a reduction in the concentration of calcium by two thirds over that in the smaller tonnage yield" produced by a different ratio of calcium to potassium.
Although heavy applications of NPK fertilizer to the soil often produce lush, abundant forage, the crop may be very deficient in key nutrients. Beeson presents a summary of an interesting experiment by H. A. Keener and E. J. Thacker at the New Hampshire Agricultural Experiment Station that clearly illustrates this point. "Excellent yields of bromeladino or timothy hay produced in New Hampshire with high level applications of fertilizer have failed to provide an adequate forage for calves. Deficiency symptoms observed in calves are poor growth, rough coats, anemia, sagging of the spinal column behind the shoulders, an ataxia [lack of coordination] of the hind legs (timothyfed calves only), loss of tips of ears, and broken bones." Supplements of copper and iron did not remove any of these symptoms. When similar hay was fed to rabbits, the same deficiency symptoms appeared.
A chemical analysis of samples from the crop would not have disclosed the complete extent of the deficiency. At first Keener and Thacker suspected that the "timothy hay was deficient in iodine and one or more organic factors," but later studies by Thacker showed that the "deficiency in the hay was related to its mineral composition." Similar experiments have led many agronomists to conclude that the nutritional value of a crop must be judged primarily by the response of the organism that consumes it, not merely by chemical analyzes of the soil and the plant.
If the adequacy of our agricultural methods is judged by the health of our livestock, then American agriculture must be regarded as a failure. The health of our domestic animals has been deteriorating noticeably for years. Veterinary medicine has been able to reduce the incidence of infectious diseases in livestock and poultry primarily because of new antibiotic preparations, but the resistance of the animals is very low. The number of cattle with cancers of the lymph and bloodforming organs that are being condemned at federally inspected packing plants has increased from 9.2 per 100,000 in 1950 to 18.2 in 1959, nearly 100 per cent in nine years; during the same period the number of swine condemned for similar cancers rose 97 per cent. Sterility in animals is arousing deep concern. "The most important problem in the beef industry is poor reproductive performance, as evidenced by low percentage calf crops," note a group of investigators at the Beltsville Experiment Station in Maryland. (The experimental work reported by these investigators shows that diet is a prime factor in the reproductive performance of animals. By increasing, decreasing, or changing the composition of the ration, the Beltsville researchers found that beef cows respond with remarkable variations in fertility, sexual activity, and the ability to deliver offspring. A moderate but balanced ration of carbohydrates and proteins yielded the highest reproductive rates.) The ubiquitous environmental changes of our time seem to have affected animal life as profoundly as they have affected man.
Every problem, to be sure, should be placed in its proper setting. The use of highly concentrated chemical fertilizers and massproduction techniques increases agricultural output at relatively small cost and with little effort. If the purpose of growing food is to prevent famine and acute nutritional disorders, these methods produce immediate results. They satisfy the dire need for food, and they remove the more obvious diseases produced by an inadequate diet. But if we enlarge our view of modern agriculture to include such problems as the quality of food and the health of plants, livestock, and human beings, the success that is ordinarily claimed for current agricultural techniques requires qualification. Man does not practice agriculture in a vacuum. His activities as a cultivator of food are influenced more by his forms of social organization than by his solicitude for the needs of the soil. The majority of American farmers, large and small, cultivate food as a business enterprise. They try to produce large crops at a minimum cost. As it may well be difficult to increase the output of the soil without lowering the quality of crops, the farmer who places quality above quantity can scarcely hope to survive the competitive demands of American agriculture. Accordingly, we can expect any technique that promotes large crops to be carried to the point of abuse. Economic competition leaves the farmer little choice but to replace low standards of food cultivation with even lower ones.
It is highly probable that exploitation of the soil has already produced a deterioration in the nutritive quality of crops in many parts of the United States. William A. Albrecht, one of America's most perceptive and creative agronomists, suggests that more carbohydrates and fewer highquality proteins tend to appear in our food staples with the passage of time. The extent of this shift in nutritive quality is difficult to determine. Commercial foods are generally graded according to appearance, and very little attention is given to nutritive quality. The information that is available, however, is not encouraging. Albrecht has pointed out that between 1940 and 1949 the concentration of protein in Kansasgrown corn declined from 9.5 to 8.5 per cent, although the decade was marked by substantial increases in corn yields. "It is interesting to note the reduction in the protein content of corn as reported in successive editions of a standard handbook of feeds and feeding. In the Eleventh Edition, published 40 years ago, the only figure quoted for crude protein of dent corn was 10.3 per cent. In the TwentyFirst edition, 1950, five grades of corn were cited, for which the protein figures ranged from 8.8 to 7.9, with a mean of nearly 8.4 per cent. During the interval of 40 years between the two editions, crude protein in corn dropped from 10.3 to 8.4, a reduction of 22 per cent."
There also seems to be evidence of an overall decline in the protein content of Kansasgrown wheat. "A survey of the percentage protein of Kansas wheat grain made in 1940 showed a range of 10 to almost 19 per cent," Albrecht notes. "In a similar survey ten years later, in 1949, protein concentration was found to range from 9 to less than 15 per cent."
We can ill afford such losses. At a time when many individuals are consuming substantially more food than they require for the work they do, an increase in carbohydrates at the expense of proteins is obviously undesirable, particularly for middleaged people. Great importance should be attached to the quality of the food we consume. We are continually being reminded that there is a close connection between obesity and chronic diseases. An overweight individual has a greater chance of acquiring cancer, diabetes, and cardiovascular disorders than one who maintains his proper weight. Any shift in the quality of foods that results in an increase of carbohydrates can be expected to contribute to the erosion of public health.
Viewing nutritional problems in a broader perspective, it is difficult to believe that human fitness can be maintained while the soil is gradually deteriorating. Albrecht observes: "Man has become aware of increased needs for health preservation, interpreted as a technical need for more hospitals, drugs, and doctors, when it may simply be a matter of failing to recognize the basic truth in the old adage which reminded us that 'to be well fed is to be healthy.' Unfortunately, we have not seen the changes man has wrought in his soil community in terms of food quality for health, as economics and technologies have emphasized its quantity. Man is exploiting the earth that feeds him much as a parasite multiplies until it kills its host. Slowly the reserves in the soil for the support of man's nutrition are being exhausted. All too few of us have yet seen the soil community as the foundation in terms of nutrition of the entire biotic pyramid of which, man, at the top, occupies the most hazardous place."
There is a close relationship between modern concepts of progress and man's attempt to control the forces of nature. From the time of the Renaissance, man has tended to evaluate nearly all the advances of society and science in terms of the amount of power over the natural world which they gave him. The word "power," however, has many shades of meaning. To the men of the Renaissance and the Enlightenment, it would have seemed preposterous that power over nature meant more than living in harmony with the natural world. Like the animals around him, man was a product of natural forces and depended upon nature for his survival and wellbeing. What made him unique in the animal kingdom was his ability to reason. This faculty gave him the power to remove fortuity from his relationship to nature, to bring a certain degree of guidance to natural processes. He could try to mitigate the harshness of the natural world and make the interplay of natural forces relatively benign. Power over nature was regarded as the ability of man to enter into conscious symbiosis with the biotic world.
With the Industrial Revolution, the concept of power over nature underwent a radical change. The word "nature" was replaced by the phrase "natural resources." The new captains of industry regarded land, forests, and wildlife as materials for wanton exploitation. The progress of man was identified with the pillage of nature. The needs of commerce and industry produced a new ideology: There are no dictates of nature that are beyond human transgression. Technology, it was claimed, is capable of giving man complete mastery over the natural world. If these notions seem naive today, it is because the needless, often senseless, conflict between man and nature is yielding unexpected consequences. We are now learning that the more man works against nature, the more deeply entangled he becomes in the very forces he seeks to master.
The problems created by our conflict with nature are dramatically exemplified by our chemical war against the insect world. During the past two decades, a large number of insecticides have been developed for general use on farms and in the home. The bestknown and most widely used preparations are the chlorinated hydrocarbons, such as DDT methoxychlor, dieldrin, and chlordane. The chlorinated hydrocarbons are sprayed over vast acres of forest land, range land, crop land, and even semiurban land on which there are heavy infestations of insects. It is doubtful whether any part of the United States with some kind of vegetation useful to man has not been treated at least once in the past ten years. Most of our fields and orchards are sprayed recurrently during the growing season. Aside from the hazards that insecticides create for public health, many conservationists claim that extensive use of the new insecticides is impairing the ability of wildlife and beneficial insects to exercise control over pests. They point out that the insecticides are taking a heavy toll of life among fish, birds, small mammals, and useful insects. There is a great deal of evidence that the new chemicals are selfdefeating. Not only have they failed to eradicate most of the pests against which they are employed; in some cases, new pests and greater infestations have been created as a result of the damage inflicted on predators of species formerly under control.
To understand this problem clearly, it is necessary to examine the conditions that promote infestations of pests. A species becomes a pest when it invades a new area that is not inhabited by its natural enemies or when environmental changes occur that provide more favorable conditions for its growth. Under natural conditions, infestations are episodic and rare. An increase in the pest species creates propitious conditions for those predators that live on the pest. The proliferation of the pest encourages the proliferation of its predators and attracts additional enemies from nearby regions. Whichever way the problem is solved, the remarkable diversity and adaptability of life under natural conditions seldom permit the pest to get completely out of hand.
Insect infestations become persistent and serious, however, when natural variety is diminished by man. Agriculture, especially when limited to one crop, tends to simplify a natural region. "The first person to harvest and store natural cereal grain for later sowing started the simplification of agriculture," observes Robert L. Rudd, of the University of California. "Until the mechanization and later chemicalization of agriculture, there was little substantial departure from the methods of the first agriculturalists. Acreages were small, landscapes diverse." The simplification of ecological systems "was relatively slight and was in any event local. Hedgerows, trees, weed patches, seasonal cropping and multipurpose farming combined to form a diversified base for a diversified fauna. Mechanized and chemicalized crop production has resulted in large expanses of single crop species - the destruction of diversity in the landscape."
Simplification of the landscape, followed by a diminution in the variety of fauna, creates highly favorable conditions for an infestation. A potential pest is left with a large food supply and a small number of predators. The job of eradicating the pest, like that of fertilizing the soil, falls primarily to man, and thus far the methods employed and the results achieved have been very unsatisfactory. Man can usually eradicate a pest - but only for a while. In the process, he often eradicates nearly every other form of life in the area aside from the crop. When the pest returns, as it often does, the ecological system may have been so simplified by the pesticidal treatment that the new conditions are more favorable for infestation than the old. "Initial chemical control, therefore, creates the later need for more chemicals," Rudd adds. "Once begun, there is no stopping if the crop is not to be lost."
Many responsible conservationists regard the nonselective spraying of open land and forests as an ecological "boomerang." In a number of cases, the damage inflicted on beneficial insects outweighs the damage inflicted on the pest. Pesticidal treatments have started infestations that would have been very mild, if not averted entirely, had the treatment not been used. In one region, for example, the treatment of a stand of timber with a fivepoundperacre dosage of DDT in early summer resulted in a general infestation of at least fourteen species of aphids. The aphids, clinging to the undersurface of the leaves, survived the spray, but their predators were decimated and failed to reestablish themselves rapidly enough to check the infestation. In still other cases, controlled insects have been transformed into serious pests by the destruction of their predators through spraying programs aimed at an entirely different species of pest. For example, until fairly recently the redbanded leaf roller caused very little damage in apple orchards, although widely distributed, the insect was strictly controlled by parasites and predators. "Rare indeed was the orchardist who knowingly had to contend with it," writes Howard Baker, of the Bureau of Entomology. "Now it is a problem pest throughout the Midwest and East, where in 1947 and 1948 particularly it caused severe damage in many orchards." The insect became a pest after its parasites had been destroyed by DDT. To control the leaf roller, orchardists are now compelled to supplement DDT treatments with TDE and parathion. "Never before... have so many pests with such a wide range of habits and characteristics increased to injurious levels following application of any one material as has occurred following the use of DDT in apple spray programs."
Nonselective spraying programs are taking a heavy toll of life among birds and rodents - animals that play a major role in limiting infestations of harmful insects. Although rodents are generally regarded as little more than pests themselves, forest rodents are voracious consumers of insects. On an average, insects constitute 20 per cent of the diet of forest mice, chipmunks, and flying squirrels. The importance of birds in insect control scarcely requires emphasis. Suffice it to say that naturalists who have made careful counts of insects in the stomachs of birds have found, for example, 5,000 ants in a flicker, 500 mosquitoes in a night hawk, and 250 tent caterpillars in a yellowbilled cuckoo. A brown thrasher will eat more than 6,000 insects in a single day; a swallow, about 1,000 leaf hoppers. Spraying commonly destroys an appreciable number of these creatures, even when the program is fairly limited in scope. To cite a case in point: In 1956 the Cranbrook Institute of Science, in Michigan, undertook a limited survey of the decline in bird life produced by DDT spraying programs to control the Dutch elm disease. Residents of the immediate area were asked to turn in or report to the Institute any birds suspected of having been poisoned by DDT. "During April, May and June of that year, but mostly in May, more than 200 dead and dying birds were turned in to the Institute... By 1959 the number of specimens received had mounted to about 400, with an estimated 600 calls or reports regarding birds not turned in." A survey of the bird life on the Cranbrook campus showed that the breeding population declined from 250 pairs to 25 or less. Most of the dead and dying birds were robins that were probably poisoned by eating worms impregnated with DDT.
A more extensive survey was made during the widely publicized fireant campaign that the Department of Agriculture initiated in November 1957. The data, compiled by the National Audubon Society, deal with many animals, including more than a hundred head of cattle killed in an area near Climax, Georgia. We shall confine ourselves, however, to losses among birds. "The drastic effect of applying insecticide during the birdnesting season was dramatically shown in Texas. In a 60acre clover field bird numbers declined alarmingly: 38 of 41 nests with eggs were abandoned or destroyed. Lay's Texas report summarizes the devastating results tersely as follows: 'Bird populations along ranch roads in the treated areas were reduced 9297 per cent in two weeks. Bird populations within acre plots studied were reduced 85 per cent in two weeks. Nesting success of birds in the area was reduced 89 per cent (compared with a nontreated area).' Lay adds, 'Large scale abandonment of nests with eggs could be explained only by the mortality of the adults. The missing birds did not appear in adjacent areas.' "
To aggravate the damage, insecticides are carried by surface and ground water into streams and lakes, where they kill large numbers of aquatic animals. For example, one pound of dieldrin per acre, applied to a large tract of land in St. Lucie County, Florida, destroyed twenty to thirty tons of fish. During 1958, a DDT campaign against the spruce budworm in northern Maine killed thousands of trout and other game fish; as long as three months after spraying, trout were found whose bodies contained DDT concentrations of from 2.9 to 198 parts per million. The sprayers were not entirely unaware of what the consequences of the program would be. Two years earlier a campaign of much the same kind produced heavy losses of young salmon in the nearby Miramichi River system of New Brunswick, Canada. "As expected, an alarmingly reduced adult Atlantic salmon run was noted in 1960 when the 1956 hatch returned to spawn in the Miramichi River system."
The discovery of DDT led to a widespread belief that insect pests could be eradicated by relying exclusively on the use of chemical agents. This belief was severely shaken when it was found that a number of harmful species were producing strains that were resistant to existing insecticides, and now many entomologists suspect that the appearance of such strains in nearly all major species of pests is merely a matter of time. As long as present methods of control are employed, new insecticides will be required every few years just to hold the line in man's chemical war against the insect world. The appearance of resistant strains among man's most formidable insect enemies has profound biological implications. In addition to all the harm man has inflicted on the land and the biosphere, he is now becoming a selfdamaging selective force in the insect world. Insecticides do not make "the susceptible more resistant," A. W. A. Brown observes, "for they are dead. Rather, the chemical had discovered the favored few that had a certain margin of resistance and selected them to survive and breed. Normally they would be eliminated by parasites and predators, to whom this kind of resistance means nothing. But if the chemical treatment has removed the biological control species, the more resistant individuals of the pest species can survive to breed... It is ironic that the economic entomologist has thus been able to speed up evolution to man's own disadvantage."
Brown's conclusion is an indictment of our methods of dealing with the natural world. Biological evolution has been governed not only by the survival of the fittest but also by the ability of living things to assume an inexhaustible variety of forms. The world of life has met every change in climate and landscape with a more diversified and interdependent biosphere. Each stage of organic evolution has been marked by a greater degree of specialization, complexity, and interrelatedness than the preceding one. Almost every species that has been "selected" for survival exhibits a higher order of specialization and depends for its continued existence upon a more complex environment than its predecessors.
Modern man is undoing the work of organic evolution, replacing a complex environment with a simpler one. He is disassembling the biotic pyramid that has supported human life for countless millennia. Almost all the manifold relationships on which man's food plants and domestic animals depend for health are being replaced by more elementary relationships, and the biosphere is slowly being restored to a stage in which it will be able to support only a simpler form of life. It is not within the realm of fantasy to suggest that if the breakdown of the soil cosmos continues unabated, if plant and animal health continue to deteriorate, if insect infestations multiply, and if chemical controls become increasingly lethal, many of the preconditions for advanced life will be irreparably damaged and the earth will prove to be incapable of supporting a viable, healthy human species.
The simplification of man's environment has evoked deep concern among ecologists, particularly in connection with the insect problem. Only in the "conscious pitting of one living thing against another - biological control - can we directly control pests without the hazards accompanying repetitive chemical applications," Rudd writes. "... European entomologists now speak of managing the entire plantinsect community. It is called manipulation of the biocenose. The biocenetic environment is varied, complex and dynamic. Although numbers of individuals will constantly change, no one species will normally reach pest proportions. The special conditions which allow high populations of a single species in a complex ecosystem [a pattern of life] are rare events. Management of the biocenose or ecosystem should become our goal, challenging as it is."
Needless to say, the soil is no less an ecosystem than the complexes established by plants, insects, and animals. When an agronomist emphasizes that organic matter is vital to the fertility of the soil, his emphasis derives from an appreciation of the manifold requirements of the soil cosmos and plant nutrition. Although organic matter is not a panacea for the ills of agriculture and human health, it provides good crops and it supplies plants with nutrients in a manner that has met the requirements of plant life over long ages of botanical evolution. The role played by chemical fertilizers in agriculture may be very important, especially in circumstances where animal and plant wastes are in short supply or where man's need for food is pressing. But the value of chemical fertilizers lies in their ability to complement the nutritional diversity of organic matter, not to supplant animal and plant wastes entirely.
An ecological point of view that emphasizes the use of organic materials and the practice of biocenetic control admittedly restricts man. It requires him to reconstruct the agricultural situation along more natural lines, to defer to the dictates of ecology rather than those of economics. To borrow the words of Charles Elton, this point of view is not intended "to promote any idea of complete laissez faire in the management of the ecosystems of the world... The world's future has to be managed, but this management would not be just like a game of chess - more like steering a boat. We need to learn how to manipulate more wisely the tremendous potential forces of population growth in plants and animals, how to allow sufficient freedom for some of these forces to work among themselves, and how to grow environments... that will maintain a permanent balance in each community."
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