DIRTY BUSINESS - Dirt: The Erosion of Civilizations - David R. Montgomery

Dirt: The Erosion of Civilizations - David R. Montgomery (2007)


A nation that destroys its soils, destroys itself.


SEVERAL YEARS AFTER SEEING THE RAPID PACE of soil destruction in the lower Amazon I found the antithesis while leading an expedition in eastern Tibet. Driving the region's rough dirt roads I saw a thousand-year-old agricultural system along the valley of theTsangpo River. We were there to study an ancient ice-dammed lake that drained in a cataclysmic flood down the Himalayan gorge through which the river slices to join the Ganges. Looking for outcrops of ancient lakebeds we drove through villages full of chickens, yaks, and pigs. All around the towns, low silt walls trapped soil in fields of barley, peas, and yellow flowers with seeds rich in canola oil.

After a few days it became obvious that corralling dirt was only part of the secret behind ten centuries of farming the lakebed. Following an unsupervised daily rhythm, Tibetan livestock head out to the fields during the day, fend for themselves, and come home at night. Driving back through towns at the end of each day's fieldwork, we saw pigs and cattle waiting patiently to reenter family compounds. These self-propelled manure dispensers were prolific; even a brief rain turned fields and roads to flowing brown muck.

The night after finding the remains of the glacial dam that once impounded the lake, we stayed at a cheap hotel in the end-of-the-road town of Pai. Homemade sleeping platforms served as beds in sleeping stalls barely separated by unfinished plank walls. The proprietor advised us on our way in that the backyard would serve as our bathroom. That the pigs clean up the yard bothered me during our pork dinner. Still, I had to appreciate the efficiency of pigs eating waste and fertilizing the soil, and then people eating both crops and pigs.

Overlooking the obvious public health issues, this system sustained soil fertility. Other than the occasional satellite dish protruding from the side of a house, villages along the Tsangpo looked much as they had soon after the lake drained. Controlling soil erosion and letting livestock manure the ground allowed generation after generation to plow the same fields.

But Tibetan agriculture is changing. On the road leading out of Lhasa, immigrant Chinese farmers and enterprising Tibetans are setting up irrigated fields and greenhouse complexes. Throughout history, technological innovation has periodically increased agricultural output since the first farmers began turning the earth with sticks before planting. Plows evolved from harnessing animals to pull bigger sticks. Heavy metal plows allowed farmers to cultivate the subsoil once the topsoil eroded away. This not only allowed growing crops on degraded land, it brought more land under cultivation.

Tilling the soil breaks up the ground for planting, helps control weeds, and promotes crop emergence. Although it helps grow desired plants, plowing also leaves the ground bare and unprotected by vegetation that normally absorbs the impact of rainfall and resists erosion. Plowing allows farmers to grow far more food and support more people-at the cost of slowly depleting the supply of fertile dirt.

Agricultural practices evolved as farming methods improved through trial and error. Key innovations included experience with manure and regionally adapted crop rotations. Before mechanized agriculture, farmers cultivated a variety of crops, often by hand on small farms that recycled stubble, manure, and sometimes even human waste to maintain soil fertility. Once farmers learned to rotate peas, lentils, or beans with their primary crops, agricultural settlements could persist beyond the floodplains where nature regularly delivered fresh dirt.

In the Asian tropics, the first few thousand years of rice cultivation involved dryland farming, much as in the early history of wheat. Then about 2,500 years ago, people began growing rice in artificial wetlands, or paddies. The new practice helped prevent the nitrogen-depletion that had plagued tropical farmers because the sluggish water nurtured nitrogen-fixing algae that functioned as living fertilizer. Rice paddies also provided ideal environments for decomposing and recycling human and animal wastes.

A phenomenally successful adaptation, wetland rice cultivation spread across Asia, catalyzing dramatic population growth in regions ill suited for previous farming practices. Yet even though the new system supported more people, most still lived on the brink of starvation. Greater food production didn't mean that the poor had more to eat. It usually meant more people to feed.

Geographer Walter Mallory found no shortage of ideas for addressing China's famines in the early i92os. Civil engineers proposed controlling rivers to alleviate crop-damaging floods. Agricultural engineers suggested irrigation and land reclamation to increase cultivated acreage. Economists proposed new banking methods to encourage investment of urban capital in rural areas. Others with more overtly political agendas wanted to move people from densely populated regions to the wide-open spaces of Mongolia. Focused on treating symptoms, few addressed the root cause of overaggressive cultivation of marginal land.

In 19206 China it took almost an acre (0.4 hectares) of land to feed a person for a year. A third of all land holdings were less than half an acre-not enough to feed a single person, let alone support a family. More than half of individual land holdings covered less than an acre and a half, a reality that kept the Chinese at perpetual risk of starvation. A bad year-failure of a single crop-brought famine. China was at the limit of its capacity to feed itself.

Obtaining food consumed 70 to 8o percent of an average family income. Even so, the typical diet consisted of two meals of rice, bread, and salt turnips. People survived from harvest to harvest.

Still, Mallory was impressed that peasant farmers maintained soil fertility despite intensive cultivation for more than four thousand years. He contrasted the longevity of Chinese agriculture with the rapid exhaustion of American soils. The key appeared to be intensive organic fertilization by returning human wastes from cities and towns to the fields. Without access to chemical fertilizers Chinese peasants fertilized the land themselves. By Mallory's time, soil nutrients had been recycled through more than forty generations of farmers and their fields.

In the i92os famine-relief administrator Y. S. Djang investigated whether people in provinces with abundant harvests ate more food than they needed. It was considered an issue of national concern that some provinces gorged while their neighbors starved.

One remarkable practice Djang found was prevalent in the province of Shao-hsing (Shaoxing), where crops were reliable and abundant. He re ported that people routinely ate more than twice the rice they could digest, stuffing themselves with as many as three "double-strength" portions of rice a day. So the region's human waste made superb fertilizer-and there was lots of it. Even after abundant harvests the population would not sell to outside buyers. Instead, these practical farmers built and maintained elegant public outhouses that served as rice-recapture facilities. They routinely ate surplus crops, reinvesting in their stock of natural capital by returning the partially digested excess to the soil.

Figure 23. Chinese farmers plowing sand (courtesy of Lu Tongjing).

Today about a third of China's total cultivated area of 130 million hectares is being seriously eroded by water or wind. Erosion rates in the Loess Plateau almost doubled in the twentieth century; the region now loses an average of more than a billion and a half tons of soil a year. Fully half of the hilly area of the Loess Plateau has lost its topsoil, even though labor-intensive terracing during the Cultural Revolution helped halve the sediment load of the Yellow River.

From the 1950s to the 1970s China lost twenty five million acres of cropland to erosion. Between 20 to 40 percent of southern China's soil has lost its A horizon, reducing soil organic matter, nitrogen, and phosphorus by up to 9o percent. Despite growing use of synthetic fertilizers, Chinese crop yields fell by more than io percent from 1999 to 2003. With China starting to run out of farmland, it is unsettling to wonder what might happen were a billion people to start squabbling with their neighbors over food. On a more optimistic note-as we ponder whether agriculture will be able to keep up with the world's population-we might take comfort in the amazing twentieth-century growth in agricultural production.

Until the widespread adoption of chemical fertilizers, growth in agricultural productivity was relatively gradual. Improvements in equipment, crop rotations, and land drainage doubled both European and Chinese crop yields between the thirteenth and nineteenth centuries. Traditional agricultural practices were abandoned as obsolete when discovery of the elements that form soil nutrients set the stage for the rise of industrial agrochemistry.

Major scientific advances fundamental to soil chemistry occurred in the late eighteenth and early nineteenth centuries. Daniel Rutherford and Antoine Lavoisier respectively discovered nitrogen and phosphorus four years before the American Revolution. Humphrey Davy discovered potassium and calcium in i8o8. Twenty years later Friederich Wohler synthesized urea from ammonia and cyanuric acid, showing it was possible to manufacture organic compounds.

Humphrey Davy endorsed the popular theory that manure helped sustain harvests because organic matter was the source of soil fertility. Then in 1840 Justus von Liebig showed that plants can grow without organic compounds. Even so, Liebig recommended building soil organic matter through manure and cultivation of legumes and grasses. But Liebig also argued that other substances with the same essential constituents could replace animal excrement. "It must be admitted as a principle of agriculture, that those substances which have been removed from a soil must be completely restored to it, and whether this restoration be effected by means of excrements, ashes, or bones, is in a great measure a matter of indifference. A time will come when fields will be manured with a solution ... prepared in chemical manufactories. "I This last idea was revolutionary.

Liebig's experiments and theories laid the foundation of modern agrochemistry. He discovered that plant growth was limited by the element in shortest supply relative to the plant's needs. He was convinced that crops could be grown continuously, without fallowing, by adding the right nutrients to the soil. Liebig's discovery opened the door to seeing the soil as a chemical warehouse through which to supply crop growth.

Inspired by Liebig, in 1843 John Bennet Lawes began comparing crop yields from fertilized and unfertilized fields on Rothamsted farm, his family's estate just north of London. An amateur chemist since boyhood, Lawes studied chemistry at Oxford but never finished a degree. Nonethe less, he experimented with agricultural chemistry while running the farm. After investigating the influence of manure and plant nutrients on crop growth, Lawes employed chemist Joseph Henry Gilbert to test whether Liebig's mineral nutrients would keep fields fertile longer than untreated fields. Within a decade it was clear that nitrogen and phosphorus could boost crop yields to match, or even exceed, those from well-manured fields.

An enterprising friend aroused Lawes's curiosity and commercial instincts by asking whether he knew of any profitable use for industrial waste consisting of a mix of animal ashes and bone. Turning waste into gold was the perfect challenge for a frustrated chemist. Natural mineral phosphates are virtually insoluble, and therefore have little immediate value as fertilizer-it takes far too long for the phosphorus to weather out and become usable by plants. But treating rock phosphate with sulfuric acid produced water-soluble phosphates immediately accessible to plants. Lawes patented his technique for making superphosphate fertilizer enriched with nitrogen and potassium and set up a factory on the Thames River in 1843. The dramatic effect of Lawes's product on crop yields meant that by the end of the century Britain was producing a million tons of superphosphate a year.

Bankrolled by substantial profits, Lawes split his time between London and Rothamsted, where he used his estate as a grand experiment to investigate how crops drew nutrition from the air, water, and soil. Lawes oversaw systematic field experiments on the effects of different fertilizers and agricultural practices on crop yields. Not only was nitrogen necessary for plant growth, but liberal additions of inorganic nitrogen-based fertilizer greatly increased harvests. He saw his work as fundamental to understanding the basis for scientific agriculture. His peers agreed, electing Lawes a fellow of the Royal Society in 1854, and awarding him a royal medal in 1867. By the end of the century, Rothamsted was the model for government-sponsored research stations spreading a new agrochemical gospel.

Now a farmer just had to mix the right chemicals into the dirt, add seeds, and stand back to watch the crops grow. Faith in the power of chemicals to catalyze plant growth replaced agricultural husbandry and made both crop rotations and the idea of adapting agricultural methods to the land seem quaint. As the agrochemical revolution overturned practices and traditions developed and refined over thousands of years, large-scale agrochemistry became conventional farming, and traditional practices became alternative farming-even as the scientific basis of agrochemistry helped explain traditional practices.

Nineteenth-century experiments showed that grazing animals process only a quarter to a third of the nitrogen in the plants they ingest. So their dung is full of nitrogen. Still, manure does not return all the nitrogen back to the soil. Without fertilizers, periodically cultivating legumes is the only way to retain soil nitrogen and still harvest crops over the long run. Native cultures around the world independently discovered this basic agricultural truth.

In 1838 Jean-Baptiste Boussingault demonstrated that legumes restored nitrogen to the soil, whereas wheat and oats could not. Here at last was the secret behind crop rotations. It took another fifty years to figure out how it worked. In 1888 a pair of German agricultural scientists, Hermann Hellriegel and Hermann Wilfarth, published a study showing that in contrast to grains, which used up the nitrogen in the soil, legumes were symbiotic with soil microbes that incorporated atmospheric nitrogen into organic matter. By the time the pair of Hermanns figured out the microbial basis for the nitrogen restoring properties of beans, peas, and clover, the agrochemical philosophy was already entrenched, spurred on by the discovery of large deposits of guano off the Peruvian coast.

Peruvians had known of the fertilizing effects of guano for centuries before the conquistadors arrived. When scientific explorer Alexander von Humboldt brought a piece collected from the Chincha Islands back to Europe in 1804 the curious white rock attracted the attention of scientists interested in agricultural chemistry. Situated off the arid coast of Peru, the Chincha Islands provided an ideal environment where huge colonies of nesting seabirds left tons of guano in a climate rainless enough to preserve it. And there was a lot-in places the Chincha guano deposits stood two hundred feet thick, a mountain of stuff better than manure. Phosphaterich guano also has up to thirty times more nitrogen than most manures.

Recognition of the fertilizing properties of guano led to a nineteenthcentury gold rush on small islands composed almost entirely of the stuff. The new system worked well-until the guano ran out. By then the widespread adoption of chemical fertilizers had shifted agricultural practices away from husbandry and nutrient cycling in favor of nutrient application.

The first commercial fertilizer imported to the United States inaugurated a new era in American agriculture when John Skinner, the editor of the American Farmer, imported two casks of Peruvian guano to Baltimore in 1824. Within two decades, regular shipments began arriving in New York. The guano business boomed. England and the United States together imported a million tons a year by the 185os. By 1870 more than half a billion dollars' worth of the white gold had been hauled off the Chincha Islands.

Figure 24. Lithograph of mountainous Chincha Islands guano deposit, circa 1868 (American Agriculturist [1868] 27:20).

As much as conservative agricultural societies scoffed at the notion that bird droppings could revive the soil, farmers who tried it swore by the results. Given the cost and difficulty of obtaining the stuff, the steady spread of guano from Maryland to Virginia and the Carolinas attests to its effect on crop yields. Widespread adoption of guano opened the door for the chemical fertilizers that followed by breaking any dependence on manure to sustain soil fertility. This transformed the basis for farming from a reliance on nutrient recycling into a one-way transfer of nutrients to consumers. From then on nothing came back to the farm.

In the end, only so much guano could be mined from South American islands. Peruvian imports peaked in 1856. By 1870 all the high-quality Chincha guano was gone. In 1881 Bolivia-now the only landlocked country with a navy-lost its Pacific coastline to Chile in a war fought over access to guano islands. Within a few years guano taxes financed the Chilean government. Demonstrated to greatly enhance harvests, guano rapidly became a strategic resource.

The government of Peru maintained tight control over its guano monopoly. American farmers frustrated over the rising price of Chincha Islands guano agitated for breaking the Peruvian monopoly. President Millard Fillmore admonished Congress in 1850 that it was the duty of the government to ensure guano traded at a reasonable price. Entrepreneurs scoured whaling records to rediscover unclaimed guano islands where the stuff could be mined freely. After President Franklin Pierce signed the 1856 Guano Island Act, making it legal for any U.S. citizens to claim any unoccupied guano island as their personal property, several dozen small tropical islands became the United States' first overseas possessions. Paving the way for later global engagements, these diminutive territories helped lead to the development of the modern chemical fertilizer industry.

Industrializing European nations that lacked phosphate deposits raced to grab guano islands. Germany annexed phosphate-rich Nauru in 1888, but lost the island after the First World War when the League of Nations placed it under British administration. In 1901 Britain annexed Ocean Island-a pile of phosphate eight and a half miles square. The Britishowned Pacific Islands Company wanted to sell the stuff to Australia and New Zealand, which lacked cheap phosphates. For an annual payment of 150 the company bought the mining rights for the whole island from a local chief with dubious authority. Too lucrative to be inconvenienced by such formalities, the Ocean Island phosphate trade reached one hundred thousand tons a year by 1905.

After the First World War the British Phosphate Commission bought the Pacific Islands Company and increased phosphate mining from Nauru sixfold. In response to the islanders' protests that stripping the island of vegetation and soil was destroying their land, the British government con fiscated the remaining lands that could be mined. Shortly thereafter deep mining operations began throughout the island. After that a million tons of phosphate left for commonwealth farms each year. Although Nauru gained independence in 1968, the phosphate deposits are mostly gone and the government is virtually bankrupt. Once a lush paradise, this island nation-the world's smallest republic-has been completely strip-mined. The few remaining islanders live on the coast surrounding the barren moonscape of the island's mined-out interior.

Ocean Island is no better off. Phosphate deposits were exhausted by i98o, leaving the inhabitants to eke out a living from land made uninhabitable to bolster the fertility of foreign soils. The island now specializes as a haven for tax shelters.

Large phosphate deposits were discovered in South Carolina on the eve of the Civil War. Within two decades South Carolina produced more than a third of a million tons of phosphate a year. Southern farmers began combining German potash with phosphoric acid and ammonia to create nitrogen, phosphorous, and potassium based fertilizer to revive cotton belt soils.

The emancipation of slaves spurred the rapid growth in fertilizer's use because plantation owners could not otherwise afford to cultivate their worn-out land with hired labor. Neither could they afford to have large tracts of taxable land lie idle. So most plantation owners rented out land to freed slaves or poor farmers for a share of the crop or a fixed rent. The South's new tenant farmers faced constant pressure to wrest as much as they could from their fields.

Merchants saw tenant farmers trying to work old fields as a captive market for new commercial fertilizers. They were too poor to own livestock, yet their fields would not produce substantial yields without manure. When merchants began lending small farmers the supplies needed to carry them from planting to harvest, experience quickly showed that paying off high-interest, short-term loans required liberal use of commercial fertilizers. Conveniently, bulk fertilizer could be purchased from the merchants who provided the loans in the first place.

Just before the Civil War, Mississippi's new state geologist Eugene Hilgard spent five years touring the state to inventory its natural resources. His i86o Report on the Geology and Agriculture of the State of Mississippi gave birth to modern soil science by proposing that soil was not just leftover dirt made of crumbled rocks but something shaped by its origin, history, and relationship to its environment.

Seeking out virgin soils, Hilgard soon realized that different soils had different characteristic thickness that corresponded to the depth of plant rooting. He described how soil properties changed with depth, defining topsoil and subsoil (what soil scientists now call the A and B horizons) as distinct features. Most radically, Hilgard conceived of soil as a dynamic body transformed and maintained by interacting chemical and biological processes.

Both geologist and chemist by training, Hilgard argued that the secret to fertile soil lay in retaining soil nutrients. "No land can be permanently fertile, unless we restore to it, regularly, the mineral ingredients which our crops have withdrawn." 2 Hilgard admired the Asian practice of returning human waste to the fields to maintain soil fertility by recycling nutrients. He considered America's sewers conduits draining soil fertility to the ocean. Refusing to contribute to this problem, he personally fertilized his own backyard garden.

In an address to the Mississippi Agricultural and Mechanical Fair Association in November 1872, Hilgard spoke of how soil exhaustion shaped the fate of empires. "In an agricultural commonwealth, the fundamental requirement of continued prosperity is ... that the fertility of the soil must be maintained.... The result of the exhaustion of the soil is simply depopulation; the inhabitants seeking in emigration, or in conquest, the means of subsistence and comfort denied them by a sterile soil at home." Hilgard warned that improvident use of the soil would lead America to the same end as Rome.

Armed with better implements of tillage it takes but a short time to "tire" the soil first taken in cultivation.... If we do not use the heritage more rationally, well might the Chickasaws and the Choctaws question the moral right of the act by which their beautiful parklike hunting grounds were turned over to another race, on the plea that they did not put them to the uses for which the Creator intended them.... Under their system these lands would have lasted forever; under ours, as heretofore practiced, in less than a century more the State would be reduced to the condition of the Roman Campagna.3

Hilgard captivated the audience with his conviction and compelling delivery-until he explained that maintaining soil fertility required applying marl to acidic fields and spreading manure year after year. All that sounded like more trouble than it was worth.

Hilgard rightly dismissed the popular idea that the source of soil fertility lay in the organic compounds in the soil. Also rejecting the western European doctrine that soil fertility was based on soil's texture and its ability to absorb water, he believed that clays retained nutrients necessary for plant growth and considered reliance on chemical fertilizers a dangerous addiction that promoted soil exhaustion.

Hilgard recognized that certain plants revealed the nature of the underlying soil. Crab apple, wild plum, and cottonwoods grew well on calciumrich soil. Pines grew well on calcium-poor soil. Hired by the federal government to assess cotton production for the i88o census, he produced two volumes that divided regional soils into distinct classes based on their physical and chemical differences. Hilgard stressed understanding the physical character of a soil, as well as its thickness and the depth to water, before judging its agricultural potential. He thought that phosphorus and potassium in minerals and nitrogen in soil organic matter controlled soil fertility. Hilgard's census report noted that aggressive fertilizer use was starting to revive agriculture in the Carolinas.

He also reported how Mississippi hill country farmers concentrated on plowing valley bottoms where upland dirt had piled up after cotton plantations stripped off the black topsoil. Great gullies surrounded empty manors amidst abandoned upland fields. Hilgard thought that a permanent agriculture required small family farms rather than large commercial plantations or tenant farmers seeking to maximize each year's profits.

With a view of the soil forged in the Deep South, Hilgard moved to Berkeley in his early forties to take a professorship at the new University of California. He arrived just as Californians began shaking off gold rush fever to worry about how to farm the Central Valley's alkali soils-salty ground unlike anything back East. Newspapers were full of accounts of crops that withered mysteriously or produced marginal yields.

The extent of alkali soils increased as irrigation spread across the golden state. Every new irrigated field raised the local groundwater table a little more. Each summer, evaporation pumped more salt up into the soil. Hilgard realized that, like a lamp's wick, clay soils brought the salt closer to the surface. Better drained, sandy soils were less susceptible to salt buildup. Hilgard also realized that alkali soils could make excellent agricultural soils-if you could just get rid of the salt.

Hilgard fought the then popular idea that salty soils resulted from seawater evaporated after Noah's flood. The ancient flood idea simply didn't hold water; the dirt was full of the wrong stuff. California's soils were rich in sodium sulfate and sodium carbonate, whereas seawater was enriched in sodium chloride. The salts in the soil were weathering out of rocks, dissolving in soil water, and then reprecipitating where the water evaporated. He reasoned that drier areas had saltier soil because rain sank into the ground and evaporated in the soil. So just as greater rainfall leached the alkali from the soil, repeated flooding could flush salts from the ground.

Collaborating with farmers eager to improve their land, Hilgard also advocated mulching to reduce evaporation of soil moisture. He experimented with using gypsum to reclaim alkali soils. On New Year's Eve 1893 the San Francisco Examiner trumpeted Hilgard's successful transformation of "alkali plains to fields of waving grain." Later that year, on August 13, the Weekly Colusa Sun went so far as to assert that Hilgard's work was worth "the whole cost of the University."

Whereas Hilgard's Mississippi work showed the importance of geology, topography, and vegetation to soil development, his California work stressed the importance of climate. In 1892 Hilgard published a landmark report that synthesized data from around the country to explain how soils formed. He explained why soils rich in calcium carbonate typical of the West were unusual in the East, and how greater temperature and moisture in the tropics leached out nutrients to produce thoroughly rotten dirt. Hilgard's report laid out the basic idea that the physical and chemical character of soils reflect the interplay of a region's climate and vegetation working to weather the underlying rocks. Soils were a dynamic interfaceliterally the skin of the earth.

Before Hilgard's synthesis, soil science was dominated by perceptions based on the humid climates of Europe and the eastern United States. Differences between soils were thought simply to reflect differences in the stuff left over from the dissolution of different rocks. By showing that climate was as important as geology, Hilgard showed that soil was worthy of study in its own right. He also championed the idea that nitrogen was the key limiting nutrient in soils based on observed variations in their carbon to nitrogen ratio and thought that crop production generally would respond greatly to nitrogen fertilization.

Now recognized as one of the founding fathers of soil science, Hilgard's ideas regarding soil formation and nitrogen hunger were ignored in agricultural colleges back East. In particular, South Carolina professor Milton Whitney championed the view that soil moisture and texture alone controlled soil fertility, maintaining that soil chemistry didn't really matter because any soil had more nutrients than required by crops. What was important was the mix of silt, sand, and clay. Based on bulk chemistry, Whitney had a point. But Hilgard knew that not everything in a soil was available to plants.

In igoi Whitney was appointed chief of the U.S. Department of Agriculture's Bureau of Soils. The new bureau launched a massive national soil and land survey, published detailed soil survey maps for use by farmers, and exuded confidence in the nation's dirt, believing that all soils contained enough inorganic elements to grow any crop. "The soil is the one indestructible, immutable asset that the Nation possesses. It is the one resource that cannot be exhausted; that cannot be used up."4 Outraged, an aging Hilgard complained about the lack of geologic and chemical information in the new bureau's surveys.

Several years before, in 1903, Whitney had published a USDA bulletin arguing that all soils contained strikingly similar nutrient solutions saturated in relatively insoluble minerals. According to Whitney, soil fertility simply depended on cultural methods used to grow food rather than the native ability of the soil to support plant growth. Soil fertility was virtually limitless. An incensed Hilgard devoted his waning years to battling the politically connected Whitney's growing influence.

A year before he published the controversial bulletin, Whitney had hired Franklin King to head a new Division of Soil Management. A graduate of Cornell University, King had been appointed in 1888 by the University of Wisconsin to be the country's first professor of agricultural physics at the age of forty. Considered the father of soil physics in the United States, King had also studied soil fertility.

King's stay in Washington was short. In his new post, King studied relations between bulk soil composition, the levels of plant nutrients in soil solutions, and crop yields. He found that the amount of nutrients in soil solutions differed from amounts suggested by total chemical analysis of soil samples but correlated with crop yields-conclusions at odds with those published by his new boss. Refusing to endorse King's results, Whitney forced him to resign from the bureau and return to academia where he would be less of a nuisance.

While Hilgard and Whitney feuded in academic journals, a new concept evolved of soils as ecological systems influenced by geology, chemistry, meteorology, and biology. In particular, recognition of the biological basis for nitrogen fixation helped lay the foundation for the modern concept of the soil as the frontier between geology and biology. Within a century of their discovery, nitrogen, phosphorus, and potassium were recognized to be the key elements of concern to agriculturalists. How to get enough of them was the issue.

Even though nitrogen makes up most of our atmosphere, plants can't use nitrogen bound up as stable Nz gas. In order to be used by organisms, the inert double nitrogen molecule must first be broken and the halves combined with oxygen, carbon, or hydrogen. The only living organisms capable of doing this are about a hundred genera of bacteria, those associated with the roots of legumes being the most important. Although most crops deplete the supply of nitrogen in the soil, root nodules on clover, alfalfa, peas, and beans house bacteria that make organic compounds from atmospheric nitrogen. This process is as essential to us as it is to plants because we need to eat ten preformed amino acids we can't assemble ourselves. Maintaining high nitrogen levels in agricultural soil requires rotating crops that consume nitrogen with crops that replenish nitrogen-or continually adding nitrogen fertilizers.

Phosphorus is not nearly as abundant as nitrogen, but it too is essential for plant growth. Unlike potassium, which accounts for an average of 2.5 percent of the earth's crust and occurs in rocks almost everywhere in forms readily used as natural fertilizer, phosphorus is a minor constituent of rockforming minerals. In many soils, its inaccessibility limits plant growth. Consequently, phosphorus-based fertilizers greatly enhance a crop's productivity. The only natural sources of phosphorus other than rock weathering are relatively rare deposits of guano or more common but less concentrated calcium-phosphate rock. By 19o8 the United States was the largest single producer of phosphate in the world, mining more than two and a half million tons from deposits in South Carolina, Florida, and Tennessee. Almost half of U.S. phosphate production was exported, most of it to Europe.

By the First World War serious depletion of phosphorus was apparent in American soils.

For extensive areas in the South and East the phosphorus is so deficient that there is scarcely any attempt to raise a crop without the use of phosphate compounds as fertilizers.... Western New York and Ohio, which not more than fifty or sixty years ago were regarded as the very center of the fertility of the country, are very seriously depleted in this element; and into them there is continuous importation of phosphate fertilizer.5

Early twentieth-century estimates of the amount of phosphorus lost in typical agricultural settings predicted that a century of continuous crop ping would exhaust the natural supply in midwestern soils. As phosphate became a strategic resource, calls for nationalizing phosphate deposits and prohibiting exports began to circulate in Washington.

On March 12, i9oi, the United States Industrial Commission invited Bureau of Soils chief Milton Whitney to testify about abandoned farmland in New England and the South. Whitney attributed New England's abandoned farms to the falling price of crops pouring out of the Midwest on the nation's new railroads. In his opinion, New England's farmers just could not compete with cheap wheat and cattle from out West.

Whitney told the committee that growing crops poorly suited to a region's soil or climate led to abandoned farms. He described how farms established twenty years earlier in semiarid parts of Kansas, Nebraska, and Colorado had experienced boom times for a few years, and then failed after a run of dry years. Whitney was certain that it would happen again given the region's unpredictable rainfall.

Whitney also thought that social conditions affected farm productivity. Prime farmland in southern Maryland sold for about ten dollars an acre. Similar land in Lancaster County, Pennsylvania, sold for more than ten times as much. Since Whitney believed that all soils were capable of similar productivity, he invoked social factors to explain differences in land values. Pennsylvanian farmers owned their farms and grew a diverse array of crops, including most of their own food. They sold their surplus locally. In contrast, hired overseers or tenant farmers worked Maryland's farms growing tobacco, wheat, and corn for distant markets. Whitney considered export-oriented, cash-crop monoculture responsible for impoverishing Maryland, Virginia, and the southern states in general.

Whitney saw that fertilizers could greatly increase crop yields. He considered natural fertility to be sustained by rock weathering that produced soil. Fertilizers added extra productivity. "We can unquestionably force the fertility far beyond the natural limit and far beyond the ordinary limits of crop production.... In this sense the effect of fertilization is a simple addition of plant food to the soil in such form that the crops can immediately use it."6 Whitney thought fertilizers sped the breakdown of soil minerals, accelerating soil production. Pumped up on fertilizers, the whole system could run faster.

In effect, Whitney conceived of the soil as a machine that required tuning in order to sustain high crop yields. He thought that American farmers' destructive habit of ignoring the particular type of soil in their fields reflected the fact that they didn't stay on their land very long. In i9ro more than half of America's farmers had been on their land for less than five years, not long enough to get to know their dirt.

Here was where soil scientists could help. "The soil scientist has the same relation to the partnership between the man and the soil that ... the chemist has to the steel or dye manufacturer." Whitney literally considered soil a crop factory. "Each soil type is a distinct, organized entity-a factory, a machine-in which the parts must be kept fairly adjusted to do efficient work." 7 However, he was unimpressed with how American farmers ran the nation's dirt factories. In Whitney's view, new technologies and more intensive agrochemistry would define America's future. The Bureau of Soils chief did not realize that it would be a British idea implemented with German technology.

In 1898 the president of the British Association, Sir William Crookes, addressed the association's annual meeting, choosing to focus on what he called the wheat problem-how to feed the world. Crookes foresaw the need to radically restructure fertilizer production because society could not indefinitely mine guano and phosphate deposits. He realized that higher wheat yields would require greater fertilizer inputs and that nitrogen was the key limiting nutrient. The obvious long-term solution would be to use the virtually unlimited supply of nitrogen in the atmosphere. Feeding the growing world population in the new century would require finding a way to efficiently transform atmospheric nitrogen into a form plants could use. Crookes believed that science would figure out how to bypass legumes. "England and all civilised nations stand in deadly peril of not having enough to eat.... Our wheat-producing soil is totally unequal to the strain put upon it.... It is the chemist who must come to rescue.... It is through the laboratory that starvation may ultimately be turned into plenty."8 Ironically, solving the nitrogen problem did not eliminate world hunger. Instead the human population swelled to the point where there are more hungry people alive today than ever before.

In addition to being natural fertilizers, nitrates are essential for making explosives. By the early twentieth century, industrial nations were becoming increasingly dependent on nitrates to feed their people and weapons. Britain and Germany in particular were aggressively seeking reliable sources of nitrates. Both countries had little additional cultivatable land and already imported large amounts of grain, despite relatively high crop yields from their own fields.

Vulnerable to naval blockades that could disrupt nitrate supplies, Germany devoted substantial effort toward developing new methods to capture atmospheric nitrogen. On July 2, i9o9, after years of attempting to synthesize ammonia, Fritz Haber succeeded in sustaining production of liquid ammonia for five hours in his Karlsruhe laboratory. Crookes's challenge had been met in just over a decade. Less than a century later, half the nitrogen in the world's people comes from the process that Haber pioneered.

Badische Anilin- and Sodafabrik (BASF) chemist Carl Bosch commercialized Haber's experimental process, now known as the Haber-Bosch process, with amazing rapidity. A prototype plant was operating a year later, construction of the first commercial plant began in 1912, and the first commercial ammonia flowed in September the following year. By the start of the First World War, the plant was capturing twenty metric tons of atmospheric nitrogen a day.

As feared by the German high command, the British naval blockade cut off Germany's supply of Chilean nitrates in the opening days of the war. It soon became clear that the unprecedented amounts of explosives used in the new style of trench warfare would exhaust German munitions in less than a year. The blockade also cut off BASF from its primary markets and revenue sources. Within months of the outbreak of hostilities the company's new ammonia plant was converted from producing fertilizer to nitrates for Germany's ammunition factories. By the war's end, all of BASF's production was used for munitions and together with the German war ministry the company was building a major plant deep inside Germany, safe from French air raids. In the end, however, the German military did not so much run out of ammunition as it ran out of food.

After the war, other countries adopted Germany's remarkable new way of producing nitrates. The Allies immediately recognized the strategic value of the Haber-Bosch process; theTreaty of Versailles compelled BASF to license an ammonia plant in France. In the United States, the National Defense Act provided for damming the Tennessee River at Mussel Shoals to generate cheap electricity for synthetic nitrogen plants that could manufacture either fertilizers or munitions, depending on which was in greater demand.

In the 192os German chemists modified the Haber-Bosch process to use methane as the feedstock for producing ammonia. Because Germany lacked natural gas fields, the more efficient process was not commercialized until 1929 when Shell Chemical Company opened a plant at Pittsburg, California to convert cheap natural gas into cheap fertilizer. The technology for making ammonia synthesis the dominant means of fixing atmospheric nitrogen arrived just in time for the industrial stagnation of the Depression.

Ammonia plant construction began again in earnest in the run-up to the Second World War. The Tennessee Valley Authority's (TVA) dams provided ideal sites for additional ammonia plants built to manufacture explosives. One plant was operating when Japan bombed Pearl Harbor; ten were operating by the time Berlin fell.

After the war, governments around the world sought and fostered markets for ammonia from suddenly obsolete munitions factories. Fertilizer use in the TVA region shot up rapidly thanks to abundant supplies of cheap nitrates. American fertilizer production exploded in the 1950s when new natural gas feedstock plants in Texas, Louisiana, and Oklahoma were connected to pipelines to carry liquid ammonia north to the corn belt. Europe's bombed-out plants were rebuilt and converted to fertilizer production. Expansion of Russian ammonia production was based on central Asian and Siberian natural gas fields. Global production of ammonia more than doubled in the i96os and doubled again in the 197os. By 1998 the world's chemical industry produced more than 150 million metric tons of ammonia a year; the Haber-Bosch process supplied more than 99 percent of production. Natural gas remains the principal feedstock for about 8o percent of global ammonia production.

The agricultural output of industrialized countries roughly doubled in the second half of the twentieth century. Much of this newfound productivity came from increasing reliance on manufactured fertilizers. Global use of nitrogen fertilizers tripled between the Second World War and 1960, tripled again by 1970, and then doubled once more by 1980. The ready availability of cheap nitrogen led farmers to abandon traditional crop rotations and periodic fallowing in favor of continuous cultivation of row crops. For the period from 1961 to 2000, there is an almost perfect correlation between global fertilizer use and global grain production.

Soil productivity became divorced from the condition of the land as industrialized agrochemistry ramped up crop yields. The shift to largescale monoculture and increasing reliance on fertilizer segregated animal husbandry from growing crops. Armed with fertilizers, manure was no longer needed to maintain soil fertility.

Much of the increased demand for nitrogen fertilizer reflects the adoption of new high-yield strains of wheat and rice developed to feed the world's growing population. In his 1970 Nobel Peace Prize acceptance speech, Norman Borlaug, pioneering developer of the green revolution's high-yield rice, credited synthetic fertilizer production for the dramatic increases in crop production. "If the high-yielding dwarf wheat and rice varieties are the catalysts that have ignited the Green Revolution, then chemical fertilizer is the fuel that has powered its forward thrust."9 In 1950 high-income countries in the developed world accounted for more than 90 percent of nitrogen fertilizer consumption; by the end of the century, lowincome developing countries accounted for 66 percent.

In developing nations, colonial appropriation of the best land for export crops meant that increasingly intensive cultivation of marginal land was necessary to feed growing populations. New high-yield crop varieties increased wheat and rice yields dramatically in the i96os, but the greater yields required more intensive use of fertilizers and pesticides. Between 1961 and 1984 fertilizer use increased more than tenfold in developing countries. Well-to-do farmers prospered while many peasants could not afford to join the revolution.

The green revolution simultaneously created a lucrative global market for the chemicals on which modern agriculture depended and practically ensured that a country embarked on this path of dependency could not realistically change course. In individuals, psychologists call such behavior addiction.

Nonetheless, green revolution crops now account for more than threequarters of the rice grown in Asia. Almost half of third-world farmers use green revolution seeds, which doubled the yield per unit of nitrogen fertilizer. In combination with an expansion of the area under cultivation, the green revolution increased third-world agricultural output by more than a third by the mid-1970s. Once again, increased agricultural yields did not end hunger because population growth kept pace-this time growing well beyond what could be maintained by the natural fertility of the soil.

Between 195o and the early 1970s global grain production nearly doubled, yet per capita cereal production increased by just a third. Gains slowed after the 1970s when per capita grain production fell by more than 1o percent in Africa. By the early 198os population growth consumed grain surpluses from expanded agricultural production. In 1980 world grain reserves dropped to a forty-day supply. With less than a year's supply of grain on hand, the world still lives harvest to harvest. In developed nations, modern food distribution networks typically have little more than a few days' supply in the pipeline at any one time.

From 1970 to 1990 the total number of hungry people fell by 16 percent, a decrease typically credited to the green revolution. However, the largest drop occurred in communist China, beyond the reach of the green revolu tion. The number of hungry Chinese fell by more than 50 percent, from more than 400 million to under zoo million. Excluding China, the number of hungry people increased by more than io percent. The effectiveness of the land redistribution of the Chinese Revolution at reducing hunger shows the importance of economic and cultural factors in fighting hunger. However we view Malthusian ideas, population growth remains criticaloutside of China, increased population more than compensated for the tremendous growth in agricultural production during the green revolution.

Another key reason why the green revolution did not end world hunger is that increased crop yields depended on intensive fertilizer applications that the poorest farmers could not afford. Higher yields can be more profitable to farmers who can afford the new methods, but only if crop prices cover increased costs for fertilizers, pesticides, and machinery. In third world countries the price of outlays for fertilizers and pesticides increased faster than green revolution crop yields. If the poor can't afford to buy food, increased harvests won't feed them.

More ominously, the green revolution's new seeds increased third-world dependence on fertilizers and petroleum. In India agricultural output per ton of fertilizer fell by two-thirds while fertilizer use increased sixfold. In West Java a two-thirds jump in outlays for fertilizer and pesticides swallowed up profits from the resulting one-quarter increase in crop yields in the i98os. Across Asia fertilizer use grew three to forty times faster than rice yields. Since the i98os falling Asian crop yields are thought to reflect soil degradation from increasingly intensive irrigation and fertilizer use.

Without cheap fertilizers-and the cheap oil used to make them-this productivity can't be sustained. As oil prices continue climbing this century, this cycle may stall with disastrous consequences. We burned more than a trillion barrels of oil over the past two decades. That's eighty million barrels a day-enough to stack to the moon and back two thousand times. Making oil requires a specific series of geologic accidents over inconceivable amounts of time. First, organic-rich sediment needs to be buried faster than it can decay. Then the stuff needs to get pushed miles down into the earth's crust to be cooked slowly. Buried too deep or cooked too fast and the organic molecules burn off; trapped too shallow or not for long enough and the muck never turns into oil. Finally, an impermeable layer needs to seal the oil in a porous layer of rock from which it can be recovered. Then somebody has to find it and get it out of the ground. It takes millions of years to produce a barrel of oil; we use millions of barrels a day. There is no question that we will run out of oil-the only question is when.

Estimates for when petroleum production will peak range from before 2020 to about 2040. Since such estimates do not include political or environmental constraints, some experts believe that the peak in world oil production is already at hand. Indeed, world demand just rose above world supply for the first time. Exactly when we run out will depend on the political evolution of the Middle East, but regardless of the details oil production is projected to drop to less than io percent of current production by the end of the century. At present, agriculture consumes 30 percent of our oil use. As supplies dwindle, oil and natural gas will become too valuable to use for fertilizer production. Petroleum-based industrial agriculture will end sometime later this century.

Not surprisingly, agribusiness portrays pesticide and fertilizer intensive agriculture as necessary to feed the world's poor. Even though almost a billion people go hungry each day, industrial agriculture may not be the answer. Over the past five thousand years population kept pace with the ability to feed people. Simply increasing food production has not worked so far, and it won't if population growth keeps up. The UN Food and Agriculture Organization reports that farmers already grow enough to provide 3,500 calories a day to every person on the planet. Per capita food production since the i96os has increased faster than the world's population. World hunger persists because of unequal access to food, a social problem of distribution and economics rather than inadequate agricultural capacity.

One reason for the extent of world hunger is that industrialized agriculture displaced rural farmers, forcing them to join the urban poor who cannot afford an adequate diet. In many countries, much of the traditional farmland was converted from subsistence farms to plantations growing high-value export crops. Without access to land to grow their own food, the urban poor all too often lack the money to buy enough food even if it is available.

The USDA estimates that about half the fertilizer used each year in the United States simply replaces soil nutrients lost by topsoil erosion. This puts us in the odd position of consuming fossil fuels-geologically one of the rarest and most useful resources ever discovered-to provide a substitute for dirt-the cheapest and most widely available agricultural input imaginable.

Traditional rotations of grass, clover, or alfalfa were used to replace soil organic matter lost to continuous cultivation. In temperate regions, half the soil organic matter commonly disappears after a few decades of plowing. In tropical soils, such losses can occur in under a decade. By contrast, experiments at Rothamsted from 1843 to 1975 showed that plots treated with farmyard manure for more than a hundred years nearly tripled in soil nitrogen content whereas nearly all the nitrogen added in chemical fertilizers was lost from the soil-either exported in crops or dissolved in runoff.

More recently, a fifteen-year study of the productivity of maize and soybean agriculture conducted at the Rodale Institute in Kutztown, Pennsylvania showed no significant differences in crop yields where legumes or manure were used instead of synthetic fertilizers and pesticides. The soil carbon content for manured plots and those with a legume rotation respectively increased to three to five times that of conventional plots. Organic and conventional cropping systems produced similar profits, but industrial farming depleted soil fertility. The ancient practice of including legumes in crop rotations helped retain soil fertility. Manuring actually increased soil fertility.

This is really not so mysterious. Most gardeners know that healthy soil means healthy plants that, in turn, help maintain healthy soil. I've watched this process in our own yard as my wife doused our lot with soil soup brewed in our garage and secondhand coffee grounds liberated from behind our neighborhood coffee shop. I marvel at how we are using organic material imported from the tropics, where there are too few nutrients in the soil in the first place, to help rebuild the soil on a lot that once had a thick forest soil. Now, five years into this experiment, the soil in our yard has a surface layer of rich organic matter, stays moist long after it rains, and is full of coffee-colored worms.

Our caffeinated worms have been busy since we hired a guy with a small bulldozer to rip out the ragged, eighty-two-year-old turf lawn our house came with and reseed the yard with a mix of four different kinds of plants, two grasses and two forbs-one with little white flowers and the other with little red flowers. The flowers are a nice upgrade from our old lawn and we don't have to water it. Better still, the combination of four plants that grow and bloom at different times keeps out weeds.

Our eco-lawn may be advertised as low maintenance, but we still have to mow it. So we just cut the grass and leave it to rot where it falls. Within a week all the cuttings are gone-dragged down into worm burrows. Now I can dig a hole in the lawn and find big fat worms where there used to be nothing but dry dirt. After just a few years, the ground around the edges of the lawn stands a quarter of an inch higher than the patio surface built at the same time we seeded the eco-lawn. The worms are pumping up the yard-plowing it, churning it, and pushing carbon down into the ground-turning our dirt into soil. Recycling organic matter literally put life back in our yard. Adjusted for scale, the same principles could work for farms.

About the same time that mechanization transformed conventional agriculture, the modern organic farming movement began to coalesce around the ideas of Sir Albert Howard and Edward Faulkner. These two gentlemen with very different backgrounds came to the same conclusion: retaining soil organic matter was the key to sustaining high intensity farming. Howard developed a method to compost at the scale of large agricultural plantations, whereas Faulkner devised methods to plant without plowing to preserve a surface layer of organic matter.

At the close of the 193os Howard began to preach the benefits of maintaining soil organic matter as crucial for sustaining agricultural productivity. He feared that increasing reliance on mineral fertilizers was replacing soil husbandry and destroying soil health. Based on decades of experience on plantations in India, Howard advocated incorporating large-scale composting into industrial agriculture to restore and maintain soil fertility.

In Howard's view, farming should emulate nature, the supreme farmer. Natural systems provide a blueprint for preserving the soil-the first condition of any permanent system of agriculture. "Mother earth never attempts to farm without live stock; she always raises mixed crops; great pains are taken to preserve the soil and to prevent erosion; the mixed vegetable and animal wastes are converted into humus; there is no waste; the processes of growth and the processes of decay balance one another."10 Constant cycling of organic matter through the soil coupled with weathering of the subsoil could sustain soil fertility. Preservation of humus was the key to sustaining agriculture.

Howard felt that soil was an ecological system in which microbes provided a living bridge between soil humus and living plants. Maintaining humus was essential for breaking down organic and mineral matter needed to feed plants; soil-dwelling microorganisms that decompose organic matter lack chlorophyll and draw their energy from soil humus. Soil organic matter was essential for the back half of the cycle of life in which the breakdown of expired life fueled the growth of new life.

In the i92os at the Institute of Plant Industry in Indore, India, Howard developed a system to incorporate composting into plantation agriculture. His process mixed plant and animal wastes to favor the growth of microorganisms, which he considered tiny livestock that enriched the soil by breaking organic matter into its constituent elements. Field trials of Howard's methods in the tropics were extremely successful. As word of his increased crop yields and soil-building methods spread, plantations in India, Africa, and Central America began adopting his approach.

Howard saw intensive organic farming as how to undo the damage industrial farming inflicted on the world's soils. He thought that many plant and animal diseases arose from reliance on artificial fertilizers that disrupted the complex biology of native soils. Reestablishing organic-rich topsoil through intensive composting would reduce, if not eliminate, the need for pesticides and fertilizers while increasing the health and resilience of crops.

After the First World War, Howard saw munitions factories begin manufacturing cheap fertilizers advertised as containing everything various crops needed. He worried that adopting fertilizers as standard practice on factory farms would emphasize maximizing profits at the expense of soil health. "The restoration and maintenance of soil fertility has become a universal problem.... The slow poisoning of the life of the soil by artificial manures is one of the greatest calamities which has befallen agriculture and mankind."li The Second World War derailed adoption of Howard's ideas. After the war the companies that supplied the world's armies turned to pumping out fertilizer, this time cheap enough to eclipse soil husbandry.

In the middle of the Second World War, Edward Faulkner published Plowman's Folly in which he argued that plowing-long considered the most basic act of farming-was counterproductive. Enrolled in courses on soil management and farm machinery decades earlier at the University of Kentucky, Faulkner had annoyed his professors by asking what was the point of tearing apart the soil for planting instead of incorporating crops into the organic layer at the ground surface where plants naturally germinate. Despite the usual reasons offered for plowing-preparing the seedbed, incorporating crop residues and manure or fertilizers into the soil, and allowing the soil to dry out and warm up in spring-his instructors sheepishly admitted that they knew of no clear scientific reasons for why the first step in the agricultural process was actually necessary. After twenty-five years working as a county agricultural agent in Kentucky and Ohio, Faulkner eventually concluded that plowing created more problems than it solved.

Challenging agronomists to reconsider the necessity of plowing, he argued that the key to growing abundant crops was maintaining an adequate surface layer of organic material to prevent erosive runoff and maintain soil nutrients. This was heresy. "We have equipped our farmers with a greater tonnage of machinery per man than any other nation. Our agricultural population has proceeded to use that machinery to the end of destroying the soil in less time than any other people has been known to do in recorded history." 12 Faulkner also considered reliance on mineral fertilizers unnecessary and unsustainable.

Like most heretics', Faulkner's unconventional beliefs were grounded in experience. He inadvertently discovered in his backyard garden that he could greatly increase crop yields by not tilling when he began growing corn in soil he considered better suited for making bricks. From 1930 to 1937 he introduced organic matter into his backyard plot by digging a trench with a shovel and mixing in leaves at the bottom of the trench to emulate the standard practice of plowing under last year's crop stubble. Like conventional plowing, this buried the organic-rich surface material to a depth of six or eight inches. In the fall of 1937 he tried something different. He mixed the leaves into the surface of the soil.

The next year his soil was transformed. Previously he had been able to grow only parsnips in the stiff clay soil; now the soil texture was granular. It could be raked like sand. In addition to parsnips, he harvested fine crops of carrots, lettuce, and peas-without fertilizer and with minimal watering. All he did was keep the weeds down.

When the Soil Conservation Service staff were unimpressed with his backyard experiment, Faulkner took up the challenge and leased a field for a full-scale demonstration. Instead of plowing before planting, he disked the standing plants into the surface of the soil, leaving the ground littered with chopped-up weeds. Skeptical neighbors forecast a poor harvest for the careless amateur. Surprised and impressed when Faulkner's crop exceeded their own, they were unsure what to think about his mysterious success without plowing, fertilizers, or pesticides.

After several years of repeated success on his leased field, Faulkner began to advocate rebuilding surface layers of organic material. He was confident that with the right approach and machinery, farmers could recreate good soil wherever it had existed naturally. "Men have come to feel ... that centuries are necessary for the development of a productive soil. The satisfying truth is that a man with a team or a tractor and a good disk harrow can mix into the soil, in a matter of hours, sufficient organic material to accomplish results equal to what is accomplished by nature in decades." What farmers needed to do was stop tilling the soil and begin incorporating organic matter back into the ground. "Everywhere about us is evidence that the undisturbed surface of the earth produces a healthier growth than that portion now being farmed.... The net effect of fertilizing the land, then, is not to increase the possible crop yield, but to decrease the devastating effects of plowing."13 Like Howard, Faulkner believed that reestablishing healthy soil would reduce, if not eliminate, crop pests and diseases.

Soil organic matter is essential for sustaining soil fertility not so much as a direct source of nutrients but by supporting soil ecosystems that help promote the release and uptake of nutrients. Organic matter helps retain moisture, improves soil structure, helps liberate nutrients from clays, and is itself a source of plant nutrients. Loss of soil organic matter reduces crop yields by lowering the activity of soil biota, thereby slowing nutrient recycling.

Different soils in different climates can sustain agriculture without supplemental fertilization for different periods of time. Organic-rich soil of the Canadian Great Plains can be cultivated for more than fifty years before losing half its soil carbon, whereas Amazon rainforest soils can lose all agricultural potential in under five years. A twenty-four-year fertilization experiment in northwestern China found that soil fertility declined under chemical fertilizers unless coupled to addition of straw and manure.

Nowhere is the debate over the appropriate application of technology more polarized than in the field of biotechnology. Downplaying notions of population control and land reform, industry advocates push the idea that genetic engineering will solve world hunger. Despite altruistic rhetoric, genetic engineering companies design sterile crops to ensure that farmerslarge agribusinesses and subsistence farmers alike-must keep on buying their proprietary seeds. There was a time when prudent farmers kept their best seed stock for next year's crop. Now they get sued for doing so.

Despite the dramatically increased yields promised by industry, a study by the former director of the National Academy of Sciences' Board on Agriculture found that genetically modified soybean seeds produced smaller harvests than natural seeds when he analyzed more than eight thousand field trials. A USDA study found no overall reduction in pesticide use associated with genetically engineered crops, even though increased pest resistance is touted as a major advantage of crop engineering. Whereas the promise of greatly increased crop yields from genetic engineering has proven elusive, some fear that genetically modified genes that convey sterility could cross to nonproprietary crops, with catastrophic results.

Given the significant real and potential drawbacks of bioengineering and agrochemistry, alternative approaches deserve a closer look. Over the long run, intensive organic farming and other nonconventional methods may prove our best hope for maintaining food production in the face of population growth and continuing loss of agricultural land. In principle, intensive organic methods could even replace fertilizer-intensive agriculture once cheap fossil fuels are history.

Here is the crux of Wes Jackson's argument that tilling the soil has been an ecological catastrophe. A genetics professor before he resigned to become president of the Land Institute in Salina, Kansas, Jackson says he is not advocating a return to the bow and arrow. He just questions the view that plowing the soil is irrefutably wholesome, pointedly suggesting that the plow destroyed more options for future generations than did the sword and that-with rare exceptions-plow-based agriculture hasn't proven sustainable. He estimates that in the next two decades severe soil erosion will destroy 20 percent of the natural agricultural potential of our planet to grow crops without fertilizer or irrigation.

Yet Jackson is neither doomsayer nor Luddite. In person he sounds more like a farmer than an environmental extremist. Instead of despair, he calls for agricultural methods based on emulating natural systems rather than controlling, or replacing them. In promoting natural systems agriculture, Jackson is the latest prophet for Xenophon's philosophy of adapting agriculture to the land rather than vice versa.

Drawing on experience in the American farm belt, Jackson seeks to develop an agricultural system based on imitating native prairie ecosystems. Unlike annual crops raised on bare, plowed ground, the roots of native perennials hold the soil together through drenching rainstorms. Native prairies contain both warm-season and cold-season grasses, as well as legumes and composites. Some of the plants do better in wet years, some thrive in dry years. The combination helps keep out weeds and invasive species because plants cover the ground all year-just like our eco-lawn.

As ecologists know, diversity conveys resilience-and resilience, Jackson says, can help keep agriculture sustainable. Hence he advocates growing a combination of crops year-round to shield the ground from the rain's erosive impact. Monocultures generally leave the ground bare in the spring, exposing vulnerable soil to erosion for months before crops get big enough to block incoming rain. Storms hitting before crops leaf out cause two to ten times the erosion of storms later in the year when the ground lies shielded beneath crops. Under monoculture, one good storm at the wrong time can send erosion racing decades ahead of soil production.

The beneficial effects of Jackson's system are evident at the Land Institute. Research there has shown that a perennial polyculture can manage pests, provide all its own nitrogen, and produce a greater per-acre crop yield than monocultures. Although the specifics of Jackson's approach were designed for the prairies, his methods could be adapted to other regions by using species mixtures appropriate to the local environment. Understandably, pesticide, fertilizer, and biotechnology companies are not very excited about Jackson's low-tech approach. But Jackson is not a lone voice in the wilderness; over the past few decades many farmers have adopted methods like those advocated by Faulkner and Howard.

Whatever we call it, today's organic farming combines conservationminded methods with technology but does not use synthetic pesticides and fertilizers. Instead, organic farming relies on enhancing and building soil fertility by growing diversified crops, adding animal manure and green compost, and using natural pest control and crop rotation. Still, for a farm to survive in a market economy it must be profitable.

Long-term studies show that organic farming increases both energy efficiency and economic returns. Increasingly, the question appears not to be whether we can afford to go organic. Over the long run, we simply can't afford not to, despite what agribusiness interests will argue. We can greatly improve conventional farming practices from both environmental and economic perspectives by adopting elements of organic technologies. Oddly, our government subsidizes conventional farming practices, whereas the market places a premium on organic produce. A number of recent studies report that organic farming methods not only retain soil fertility in the long term, but can prove cost effective in the short term.

In 1974, under the leadership of ecologist Barry Commoner, the Center for the Biology of Natural Systems at Washington University in St. Louis began comparing the performance of organic and conventional farms in the Midwest. Pairing fourteen organic farms with conventional farms of similar size, operated with a similar crop-livestock system on similar soils, the two-year study found that organic farms produced about the same income per acre as did conventional farms. Although the study's preliminary results surprised skeptical agricultural experts, many subsequent studies confirmed that substantially lower production costs more than offset slightly smaller harvests from organic farms. Industrial agrochemistry is a societal convention and not an economic imperative.

Subsequent studies also showed that crop yields are not substantially lower under organic agricultural systems. Just as important is the demonstration that modern agriculture need not deplete the soil. Rothamsted, the estate where John Lawes proved the fertilizing effects of chemical fer tilizers, hosts the longest ongoing comparison of organic and conventional agriculture-a century and a half-placing manure-based organic farming and chemical fertilizer-based farming side by side. Wheat yields from conventionally fertilized and organic plots were within 2 percent of each other, but the soil quality measured in terms of carbon and nitrogen levels improved over time in the organic plots.

A twenty-two-year study by the Rodale Institute on a Pennsylvania farm compared the inputs and production from conventional and organic plots. Average crop yields were comparable under normal rainfall, but the average corn yields in the organic plots were about a third higher during the driest five years. Energy inputs were about a third lower, and labor costs about a third higher in the organic plots. Overall, organic plots were more profitable than the conventional plots because total costs were about 15 percent lower, and organic produce sold at a premium. Over the twodecade-long experiment, soil carbon and nitrogen contents increased in the organic plots.

In the mid-i98os, researchers led by Washington State University's John Reganold compared the state of the soil, erosion rates, and wheat yields from two farms near Spokane in eastern Washington. One farm had been managed without the use of commercial fertilizers since first plowed in i9o9. The adjoining farm was first plowed in 1908 and commercial fertilizer was regularly applied after 1948.

Surprisingly, there was little difference in the net harvest between the farms. From 1982 to 1986 wheat yields from the organic farm were about the average for two neighboring conventional farms. Net output from the organic farm was less than that of the conventional farm only because the organic farmer left his field fallow every third year to grow a crop of green manure (usually alfalfa). Lower expenses for fertilizer and pesticides compensated him for the lower net yield. More important, the productivity of his farm did not decline over time.

Reganold's team found that the topsoil on the organic farm was about six inches thicker than the soil of the conventional farm. The organic farm's soil had greater moisture-holding capacity and more biologically available nitrogen and potassium. Soil on the organic farm also contained many more microbes than the conventional farm's soil. Topsoil on the organic farm had more than half again as much organic matter as topsoil on the conventional farm.

The organic fields not only eroded slower than the soil replacement rates estimated by the Soil Conservation Service, the organic farm was building soil. In contrast, the conventionally farmed field shed more than six inches of topsoil between 1948 and 1985. Direct measurements of sediment yield confirmed a fourfold difference in soil loss between the two farms.

The bottom line was simple. The organic farm retained its fertility despite intensive agriculture. Soil on the conventional farm-and by implication most neighboring farms-gradually lost productive capacity as the soil thinned. With fifty more years of conventional farming, the region's topsoil will be gone. Harvests from the region are projected to drop by half once topsoil erosion leaves conventional farmers plowing the clayey subsoil. To sustain crop production, technologically driven increases in crop yields will have to double just to stay even.

European researchers also report that organic farms are more efficient and less detrimental to soil fertility. A twenty-one-year comparison of crop yields and soil fertility showed that organic plots yielded about zo percent less than plots cultivated using pesticide-and-fertilizer-intensive methods. However, the organic plots used a third to half the input of fertilizer and energy and virtually no pesticides. In addition, the organic plots harbored far more pest-eating organisms and supported greater overall biological activity. In the organic plots, the biomass of earthworms was up to three times higher and the total length of plant roots colonized by beneficial soil mycorrhizae was 40 percent greater. Organic farming methods not only increased soil fertility, profits from organic farms were comparable to those of conventional farms. Commercially viable, organic farming need not remain an alternative philosophy.

Other recent studies support this view. A comparison of neighboring farms using organic and conventional methods on identical soils in New Zealand found the organic farms had better soil quality, higher soil organic matter, and more earthworms-and were as financially viable per hectare. A comparison of apple orchards in Washington State found similar crop yields between conventional and organic farming systems. The five-year study found that organic methods not only used less energy, maintained higher soil quality, and produced sweeter apples, they proved more profitable than conventional methods. An orchard grown under conventional methods that became profitable in about fifteen years would show profits within a decade under organic methods.

While the organic sector is the fastest-growing segment of the U.S. food market, many currently profitable conventional farming methods would become uneconomical if their true costs were incorporated into market pricing. Direct financial subsidies, and failure to include costs of depleting soil fertility and exporting pollutants, continue to encourage practices that degrade the land. In particular, the economics and practicalities of largescale farming often foster topsoil loss and compensate with fertilizers and soil amendments. Organic farming uses fewer chemicals and-for that very reason-receives fewer research dollars per acre of production. At this point, individuals seeking healthier food contribute more to agricultural reform than do governments responsible for maintaining long-term agricultural capacity.

Over the past decade American farm subsidies averaged more than $io billion annually. Although subsidy programs were originally intended to support struggling family farms and ensure a stable food supply, by the i96os farm subsidies actively encouraged larger farms and more intensive methods of crop production focused on growing single crops. U.S. commodity programs that favor wheat, corn, and cotton create incentives for farmers to buy up more land and plant only those crops. In the 197os and i98os, subsidies represented almost a third of U.S. farm income. A tenth of the agricultural producers (coincidentally, the largest farms) now receive two-thirds of the subsidies. Critics of the subsidy program, including Nebraska Republican senator Chuck Hagel, maintain that it favors large corporate farms and does little for family farms. Good public policy would use public funds to encourage soil stewardship-and family farms, they argue-instead of encouraging large-scale monoculture.

Organic agriculture is starting to lose its status as a fringe movement as farmers relearn that maintaining soil health is essential for sustaining high crop yields. A growing shift away from agrochemical methods coincides with the renewed popularity of methods to improve the soil. Today, a middle ground is evolving in which nitrogen-fixing crops grow between row crops and as cover in the off-season, and nitrate fertilizer and pesticide are used at far lower levels than on conventional farms.

The challenge facing modern agriculture is how to merge traditional agricultural knowledge with modern understanding of soil ecology to promote and sustain the intensive agriculture needed to feed the world-how to maintain an industrial society without industrial agriculture. While the use of synthetic fertilizers is not likely to be abandoned any time soon, maintaining the increased crop yields achieved over the past half century will require widespread adoption of agricultural practices that do not further diminish soil organic matter and biological activity, as well as the soil itself.

Soil conservation methods can help prevent land degradation and improve crop yields. Simple steps to retain soil productivity include straw mulching, which can triple the mass of soil biota, and application of manure, which can increase the abundance of earthworms and soil microorganisms fivefold. Depending on the particular crop and circumstances, a dollar invested in soil conservation can produce as much as three dollars' worth of increased crop yields. In addition, every dollar invested in soil and water conservation can save five to ten times that amount in costs associated with dredging rivers, building levees, and flood control in downstream areas. Although it is hard to rally and sustain political support for treating dirt like gold, American farmers are rapidly becoming world leaders in soil conservation. Because it is prohibitively expensive to put soil back on the fields once it leaves, the best, and most cost-effective strategy lies in keeping soil on the fields in the first place.

For centuries the plow defined the universal symbol of agriculture. But farmers are increasingly abandoning the plow in favor of long-shunned notill methods and less aggressive conservation tillage-a catchall term for practices that leave at least 30 percent of the soil surface covered with crop residue. Changes in farming practices over the past several decades are revolutionizing modern agriculture, much as mechanization did a century ago-only this time, the new way of doing things conserves soil.

The idea of no-till farming is to capture the benefits of plowing without leaving soils bare and vulnerable to erosion. Instead of using a plow to turn the soil and open the ground, today's no-till farmers use disks to mix organic debris into the soil surface and chisel plows to push seeds into the ground through the organic matter leftover from prior crops, minimizing direct disturbance of the soil. Crop residue left at the ground surface acts as mulch, helping to retain moisture and retard erosion, mimicking the natural conditions under which productive soils formed in the first place.

In the r96os almost all U.S. cropland was plowed, but over the past thirty years adoption of no-till methods has grown rapidly among North American farmers. Conservation tillage and no-till techniques were used on 33 percent of Canadian farms in r99i, and on 6o percent of Canadian croplands by 2ooi. Over the same period conservation tillage grew from about 25 percent to more than 33 percent of U.S. cropland, with i8 percent managed with no-till methods. By 2004, conservation tillage was practiced on about 41 percent of U.S. farmland, and no-till methods were used on 23 percent. If this rate continues, no-till methods would be adopted on the majority of American farms in little more than a decade. Still, only about 5 percent of the world's farmland is worked with no-till methods. What happens on the rest may well shape the course of civilization.

No-till farming is very effective at reducing soil erosion; leaving the ground covered with organic debris can bring soil erosion rates down close to soil production rates-with little to no loss in crop yields. In the late 1970s, one of the first tests of the effect of no-till methods in Indiana reported a more than 75 percent reduction in soil erosion from cornfields. More recently, researchers at the University of Tennessee found that no-till farming reduced soil erosion by more than 9o percent over conventional tobacco cultivation. Comparison of soil loss from cotton fields in northern Alabama found that no-till plots averaged two to nine times less soil loss than conventional-till plots. One study in Kentucky reported that no-till methods decreased soil erosion by an astounding 98 percent. While the effect on erosion rates depends on a number of local factors, such as the type of soil and the crop, in general a io percent increase in ground surface cover reduces erosion by 20 percent, such that leaving 30 percent of the ground covered reduces erosion by more than 50 percent.

Lower erosion rates alone do not explain the rapid rise in no-till agriculture's popularity. No-till methods have been adopted primarily because of economic benefits to farmers. The Food Security Acts of 1985 and 199o required farmers to adopt soil conservation plans based on conservation tillage for highly erodible land as a condition for participating in popular USDA programs (like farm subsidies). But conservation tillage has proven to be so cost-effective that it also is being widely adopted on less erodible fields. Not plowing can cut fuel use by half, enough to more than offset income lost to reduced crop yields, translating into higher profits. It also increases soil quality, organic matter, and biota; even earthworm populations are higher under no-till methods. Although adopting no-till practices can initially result in increased herbicide and pesticide use, the need declines as soil biota rebound. Growing experience in combining no-till methods with the use of cover crops, green manures, and biological pest management suggests that these so-called alternative methods offer practical complements to no-till methods. Farmers are adopting no-till methods because they can both save money and invest in their future, as increasing soil organic matter means more fertile fields-and eventually lower outlays for fertilizer. The lower cost of low-till methods is fueling growing interest even among large farming operations.

No-till agriculture has another advantage; it could provide one of the few relatively rapid responses to help hold off global warming. When soil is plowed and exposed to the air, oxidation of organic matter releases carbon dioxide gas. No-till agriculture has the potential to increase the organic matter content of the top few inches of soil by about i percent a decade. This may sound like a small number, but over twenty to thirty years that can add up to io tons of carbon per acre. As agriculture mechanized over the past century and a half, U.S. soils are estimated to have lost about 4 billion metric tons of carbon into the atmosphere. Worldwide, about 78 billion metric tons of carbon once held as soil organic matter have been lost to the atmosphere. A third of the total carbon dioxide buildup in the atmosphere since the industrial revolution has come not from fossil fuels but from degradation of soil organic matter.

Improvement of agricultural soils presents an opportunity to sequester large amounts of carbon dioxide to slow global warming-and help feed a growing population. If every farmer in the United States were to adopt notill practices and plant cover crops, American agriculture could squirrel away as much as 300 million tons of carbon in the soil each year, turning farms into net carbon sinks, rather than sources of greenhouse gases. While this would not solve the problem of global warming-the soil can hold only so much carbon-increasing soil carbon would help buy time to deal with the root of the problem. Adoption of no-till practices on the world's 1.5 billion hectares of cultivated land has been estimated to be capable of absorbing more than 9o percent of global carbon emissions for the several decades it would take to rebuild soil organic matter. A more realistic scenario estimates the total carbon sequestration potential for the world's cropland as roughly 25 percent of current carbon emissions. Moreover, more carbon in the soil would help reduce demand for fertilizers and would lead to less erosion, and therefore further slow carbon emissions, all while increasing soil fertility.

The attraction of no-till methods is immense, but obstacles remain to their universal adoption. And they don't work well everywhere. No-till methods work best in well-drained sandy and silty soils; they do not work well in poorly drained heavy clay soils that can become compacted unless tilled. Slow-to-change attitudes and perceptions among farmers are primary factors limiting their wider adoption in the United States; the lag in adoption of no-till methods in Africa and Asia additionally reflects lack of financial resources and governmental support. In particular, small-scale farmers often lack access to specialized seed drills to plant through crop residues. Many subsistence farmers use the residue from the previous year's crops as fuel or animal fodder. These challenges are substantial, but they are well worth tackling. Reinvesting in nature's capital by rebuilding organic-rich soils may well hold the key to humanity's future.

It is no secret that if agriculture doesn't become sustainable nothing else will; even so, some still treat our soil like dirt-and sometimes worse. The eastern Washington town of Quincy is an unlikely place to uncover one of our nation's dirtiest secrets. But in the early 199os the town's mayor clued Seattle Times reporter Duff Wilson in to how toxic waste was being recycled into fertilizer and sprayed on croplands. Patty Martin was an unusual candidate for a whistle blower, a conservative housewife and former pro basketball player who won a virtually uncontested race for mayor of her small farming community. When Martin's constituents began complaining about mysteriously withered crops and crop dusters spraying fertilizer out on the open prairie for no apparent reason, she learned that Cenex, a fertilizer-specialty division of the Land O'Lakes Company (yes, the butter people), was shipping toxic waste to her town, mixing it with other chemicals in a big concrete pond near the train station, and then selling the concoction as cheap, low-grade fertilizer.

It was a great scheme. Industrial polluters needing to dispose of toxic waste avoided the high cost of legitimate dumps. (Anyone who puts something into a registered toxic waste dump owns it forever.) But mixing the same stuff into cheap fertilizer and spreading it on vacant land-or selling it to farmers-makes the problem, and the liability, disappear. So trains pulled in and out of Quincy in the middle of the night and the pond went up and down with no records of what went in or out of it. Sometimes Cenex sold the new-fangled fertilizer to unsuspecting farmers. Sometimes the company paid farmers to use it just to get rid of the stuff.

Martin discovered that state officials allowed recycling waste rich in heavy metals into fertilizer without telling farmers about all those extra "nutrients." Whether or not something was considered hazardous depended not so much on what the stuff was as on what one intended to do with it. Approached about the practice of selling toxic waste as fertilizer, staff at the state department of agriculture admitted they thought it was a good idea, kind of like recycling.

Curiously enough, the toxic fertilizer began killing crops. Unless they are eroded away, heavy metals stick around in the soil for thousands of years. And if they build up enough in the soil, they are taken up by plants-like crops.

Why would a company like Cenex be mixing up a toxic brew and selling it as low-grade fertilizer? Try the oldest reason around-money. Company memos reveal that they saved $170,ooo a year by calling their rinse pond waste a product and spraying it on farmer's fields. The legal case ended in 1995 when the company agreed to plead guilty to using pesticide for an unapproved purpose and pay a $io,ooo fine. Now I don't particularly like to gamble, but even I'd take my savings to Vegas anytime with a guaranteed 17 to I payout.

After the Cenex case, other farmers in the area began to wonder whether bad fertilizer had been the cause of their failing crops. One told Martin's friend Dennis DeYoung about a fertilizer tank that Cenex delivered to his farm and forgot about years earlier. Dennis scooped out some of the dried residue from the abandoned tank and sent it off to a soil-testing lab in Idaho. The lab found lots of arsenic, lead, titanium, and chromium-not exactly premium plant food. The lab also reported high lead and arsenic concentrations in peas, beans, and potatoes DeYoung sent in from crops fertilized by Cenex products. Samples of potatoes another friend of DeYoung's sent in were found to have ten times the allowable concentration of lead.

Washington wasn't the only place where toxic waste was being reclassified as fertilizer. Between 1984 and 1992, an Oregon subsidiary of ALCOA (the Aluminum Company of America) recycled more than two hundred thousand tons of smelter waste into fertilizer. ALCOA saved two million dollars a year turning waste into a product marketed as a road de-icer during the winter and plant food in the summer. Companies all across America were saving millions of dollars a year selling industrial waste instead of paying to send it to toxic waste dumps. By the late 199os, eight major U.S. companies converted 120 million pounds of hazardous waste into fertilizer each year.

Strangely, nobody involved seemed too anxious to talk about the toxic waste-into-fertilizer industry. They didn't have to worry. No rules prevented mixing hazardous waste into fertilizer, and then into the soil. No one appeared too concerned about such blatant disregard of the importance of healthy soil. Never mind that, as seems obvious, farms are about the last place we should use as a dumping ground for heavy metals.

The way we treat our agricultural soils, whether as locally adapted ecosystems, chemical warehouses, or toxic dumps, will shape humanity's options in the next century. Europe broke free from the ancient struggle to provide enough food to keep up with a growing population by coming to control a disproportionate share of the world's resources. The United States escaped the same cycle by expanding westward. Now with a shrinking base of arable land, and facing the end of cheap oil, the world needs new models for how to feed everybody. Island societies provide one place to look; some consumed their future and descended into brutal competition for arable land, others managed to sustain peaceful communities. The key difference appears to be how social systems adapted to the reality of sustaining agricultural productivity without access to fresh land-in other words, how people treated their soil.