Where Has All the Soil Gone?
Why topsoil erosion in Illinois is a bad thing
The Ecologist (UK)
No. 5/6, 1984
My introduction to readers in the UK, and my first time in print outside the U.S. The Ecologist was one of the first and long the most respectable of the new generation of environmental-minded magazines. At well more than 4,000 words this was a major piece that ran on the cover. Why I was entrusted with it is a mystery whose solution is buried in my files somewhere.
It is an original piece, not a republication of one of my U.S. pieces on the topic. The facts are the same but the writing is more pointed; Illinois Issues, for example, for whom I’d written extensively about soil loss, was then a journal of fact while The Ecologist was an environmental advocate. Note: I have not changed the British spellings or punctuation of the original.
Intense cropping systems—the struggle to remain profitable—are eroding some of America's best soils. Soil conservation is vital, but few appreciate just how much delay is going to cost.
One need merely review the vocabulary with which six generations of Illinoisans have described the settlement of the state to understand that the European newcomers saw the land as an enemy to be vanquished. The Indians saw the prairie and forests as a benefactor, and they practised a benign tenancy of both. The white man, however, 'tamed' the wilderness, 'improved' the land, 'broke' the prairie. Like the wolf, the mosquito and the Indian, the prairie and forest were regarded as inconveniences to be eradicated.
Illinois still stands along with its neighbour states of Iowa, Indiana, and Missouri in the heart of the Corn-belt. Climate and soils in this stretch of the US Midwest have made it a feed grains factory nearly without equal on the globe. In recent years Illinois has ranked first or second among US states in its harvests of corn and soybeans, accounting for between 15 per cent and 20 per cent of US production of each crop—sales of which accounted for most of the 6 billion dollars or so which Illinois agricultural products earn its farmers in an average year.
The landscape of modern Illinois is as much an artifact of civilisation as a superhighway. Although Illinois still calls itself the Prairie State, the prairie is long gone. Of the 37,000 square miles of prairie that once covered Illinois, only about two square miles remain. Of the estimated 14 million acres of forest that once stood in Illinois, only 3.5 million acres remain. In their place is an Illinois that has been systematically ploughed, drained, paved, dammed, fenced, graded and regraded into more usable shapes.
This artifact was built, however, using the most ancient of materials. The topsoil whose fertility so amazed Europeans was the child of a happy marriage between the glacial till (200 feet thick in places) left behind by the last incursion of Arctic ice 10,000 years ago and the prairie ecosystem that took root on it. The University of Illinois' Cooperative Extension Service has catalogued 425 distinct soil types in Illinois. The best of them (321 in all) fall into one of the three categories of soils designated by the service as 'prime' because of their high grain-crop productivity. According to the US Department of Agriculture statistics, only two states (Kansas and Texas) have more prime farmland than Illinois.
Of Illinois' 36 million acres, 21.4 million (8.7 hectares) are judged to be prime soils, and close to 90 per cent of them are used to grow crops. That means that Illinois has approximately 19 million acres of prime cropland. For those who savour comparisons, this is an area only slightly smaller than Scotland.
When white settlers arrived in Illinois in the early 19th century, the topsoil measured roughly nine inches in thickness over much of the state. By the 1970s those nine inches (described with only slight exaggeration as the distance between Eden and the desert) had shrivelled to six, and in some parts of the state to nothing at all. Erosion, abetted by farming practices, had washed and blown the soil away, mostly into streams from which it worked its way south to the Gulf of Mexico via the Mississippi—a process one writer has dubbed "the great terrain robbery".
History holds a lesson for the Illinois farmer. Spread over an acre, 6.7 tons of soil becomes a paper-thin layer. (One inch of topsoil weighs roughly 150 tons.) This is an insignificant loss—unless continued over significant amounts of time. In the 1820s, corn yields on virgin prairie soils were reported to be as high as 100 bushels. By the 1870s yields were as low as 30 bushels. By the 1930s, soil scientists found that about a third of the state's land was suffering from erosion damage, a heritage of neglect so severe that farms in southern Illinois had to be abandoned because they could no longer grow enough to support the families who worked them.
Pressure to boost yields
A combination of dust-bowl-era soil conservation programmes and government programmes to take marginal land out of row-crop production had caused erosion rates to decline after the 1930s, until by the 1960s topsoil on many Illinois farms was being replaced faster than it was being lost.
Ominously, soil loss rates rose 10 per cent between 1970 and 1977. Midwestern grain farming had entered a new era in the 1970s. Other nations had a series of poor harvests, the US government ended its surplus-dampening acreage 'set-aside' programmes of the 50s and 60s. Consequently US export trade expanded. The need to absorb chronic US grain surpluses and the calamitous rise in oil prices led to pressures to harvest more and more bushels through the more intensive use of land, machinery and fertilisers. In a process repeated across the Cornbelt, more Illinois land was put into the cultivation of profitable row crops, including former set-aside land plus other marginal acreage such as pasture and woods that had never been farmed. Although the total land farmed in Illinois dropped by some 700,000 acres between 1970 and 1979, the number of acres planted in corn or soybeans jumped from 17.1 million to 19.5 million. (Because beans leave behind a thinner residue, soybean fields tend to be especially erosive; soybean acreage in Illinois increased from 1970 to 1979 from roughly 6.4 million acres to 9.8 million.)
The pressure to farm more land pushed up farmland prices to record levels; at a time when Illinois topsoil had never been worth so much money, its owners were treating it as if it were dirt. Farmers to whom a few bushels per acre meant a difference between a profit or a loss began fall-ploughing to save precious workdays in the spring. Bigger machines often are unable to follow the contour of the land, and terraces and grassed drainage ditches installed during the Depression were simply ploughed over. The result: soil erosion.
The effects of erosion became vividly evident off the farm in the '70s. The Illinois Environmental Protection Agency labelled dirt as the state's single biggest water pollution problem. Sediment is itself 190 both a pollutant and a polluter. Farm pesticides am herbicides are carried piggyback into water supplies via soil particles. So are fertilisers, which feed the ruinous growth of algae in lakes and streams.
On the farm, erosion's effects are slower to make themselves felt. Modern mechanised grain farming is a triumph of technology over bad management. The lavish application of synthetic fertilisers (especially nitrogen) enabled farmers to compensate for losses in soil productivity caused by erosion. The Illinois EPA has estimated that past erosion has reduced the productivity of all state soil by 2.2 per cent in the last hundred years (which in turn reduced the dollar yield of that land by roughly 100 million dollars a year). Furthermore, this erosion of productivity continues to increase inexorably at an average rate of .022 per cent per year. But, in the last five years alone, average yields of Illinois corn have gone down about 2 per cent per year, not per century.
The Illinois EPA has further estimated that the statewide average corn yield per acre in 2010 will be 164 bushels if present erosion trends continue; while if farmland erosion is halted and, the so-called, 'best management practices' are adopted, the yield by 2010 could be 185.1 bushels, or 11 per cent higher. At the same time, if the amount of land planted in corn were to remain at the 1979 level, the difference would amount to nearly a quarter-billion bushels, which at 1981 prices would be worth about 2.6 billion dollars.
Technology has enabled us to believe that soil erosion and farmland conversion do not matter, that it might indeed be possible someday (as two Illinois agricultural economists have phrased it) "to feed the world from a single window box". But the curve that traces the postwar increased national output per acre is beginning to flatten out. Fertiliser use on corn, for instance, may be bumping into both a biological and economic ceiling, with the result that heavier applications return less and less yield increase per dollar invested. There remains the hope that new technologies, or even new plants, will keep the productivity curve on its upward arc, or that land now in desert or forest may be reclaimed for farming. For the moment, they remain only hopes.
It is not strictly accurate to call topsoil irreplaceable. The processes of plant growth, decay and regeneration which converted glacial dirt into soil continues in modern cornfields. With good land management, annual soil losses of between two and five tons per acre are considered tolerable on most Illinois soils because that much new topsoil per acre is created each year. It is at this point, when topsoil gains equal or exceed topsoil losses, that it becomes possible to talk of a 'permanent' or 'sustainable' agriculture. Soil scientists refer to this loss level as the 'T' level. As already noted, current average soil losses in Illinois are running from two-and-a-half to six times this 'T' level, largely as a result of intensive farming practices.
One should quickly point out that these are statewide averages. Much of the soil loss in Illinois, as in the rest of the Cornbelt, is occuring from a relatively few, steeply sloped acres. The most productive Illinois farmland is flat or only gently sloped—indeed, is productive because it is flat or gently sloped—and thus protected by topography. It is this combination of gentle terrain and deep soils which make erosion seem best a long-term threat on most Illinois soils. Indeed, even assuming that no new soil was being formed, a field with a topsoil layer nine inches deep could lose that soil at a rate of five tons per acre per year and not exhaust itself for 270 years. To farmers who tend to define the future in terms of the next four-year federal farm programme, that seems forever.
However, tomorrow may get here more quickly than that. For one thing, losses in soil productivity may be expected to show themselves well before topsoil layers are completely exhausted. For another, the processes of soil formation remain little understood. The five ton per acre per year T level set for most Illinois soils, for instance, may be optimistic. Critics point out that such rapid soil formation is only to be expected under ideal crop management conditions.
Then, too, soil formation rates vary considerably according to soil type, how considerably is not known with much precision. For example, erosion tends to be more severe on topsoils found atop impermeable clay subsoils than on topsoils with more water-absorbing subsoils. In the former condition rainwater does not sink into the ground but drains away from near the surface, taking topsoil with it. What is bad for topsoil is worse for plants; as topsoil layers are reduced, plants must increasingly root in a medium through which the movement of water, nutrients, and oxygen is constricted.
Subsoils clearly play a vital role in crop production. Those subsoil layers typically are replenished much more slowly than soils in the busy few inches near the surface, where plough action and the decomposition of plant remains constantly add organic matter. While intensive cultivation of coarser soils can add as much as one inch of new soil every 30 years, subsoil formation proceeds at a slug's pace—as slowly as one inch every 300 years. T levels adequate to maintain topsoil levels, in short, would not be sufficient to keep overall soil depth from shrinking over time.
In the shorter term, it is water quality, not agricultural productivity, which suffers most from soil erosion. T levels believed sufficient to protect productivity are generally thought too lenient to protect nearby streams and lakes. (Not all the soil washed into the Midwest's muddy waters comes from farm fields; stream banks are thought to be a major source, since much eroded soil does not leave the farm at all, or if it does, takes years to hitchhike, one storm at a time, to the nearest drainage ditch or streamlet.) However, since no firm relationship has yet been established between soil loss upstream and sedimentation rates downstream, it is hard to say how much too lenient those T levels might be.
As noted, mud is to the rural Midwest what smog is to Los Angeles. The effect of displaced soils on aquatic life is pronounced. When it settles, sediment obliterates natural underwater topography, covering a variegated habitat with a featureless blanket of ooze. Sediment covers sand and gravel beds vital to fish spawning cycles and provides a root medium too unstable to support aquatic plants. As plant growth slows, the amount of dissolved oxygen in the water drops. In extreme cases, the final inheritor of such a lake are the anaerobic or nonoxygen-using bacteria which feed on decaying organic matter, emiting putrid hydrogen sulphide gas as proof of their presence.
But sediment must be condemned not only for the damage it causes but for the damage it brings. When soil washes away from a farm field (or to a lesser extent, from an urban building site or a suburban lawn), it carries with it an assortment of chemicals-weed killers, fertilisers, pesticides—which have been applied to the soil and which become dissolved in runoff water or attached (adsorbed) to the soil particles themselves.
These chemical hitchhikers worry state environmental officials as much as the sediment itself, particularly as the amounts of such chemicals in use (especially on farms) continue to increase. Their concern explains the otherwise anomalous fact that the IEPA, in carrying out its part of the federally mandated water quality planning process, took the lead in farm erosion-control planning in Illinois in the late 1970s, rather than the state's department of agriculture. When the IEPA surveyed 353 Illinois lakes in 1978 it found that all of them were eutrophic (the word means literally 'rich in food'). An excess of basic plant nutrients such as nitrogen and phosphorus prompts excessive growth of aquatic plants, including algae. This process is a part of any lake's natural history, but humans can speed it up materially. Ironically, the high turbidity of many Illinois lakes is a saving fault in that it blocks light which would feed even more vigorous plant growth.
Farm fields are presumed to be a major source of such nutrients, and eroded soil particles often are the means by which they migrate. For example, phosphorus is not very soluble in water. (Some tests have shown that less than one per cent of phosphorus applied as fertiliser leaves a field in runoff water.) But it does attach itself to fine soil particles; indeed, because most eroded soils tend to be made up of these easily transportable particles, the amount of phosphorus found in sediment can be as much as three to four times higher than that in the farm soil from which it came. In fact, there is some concern that improved erosion control might actually increase phosphorus contamination in some watersheds. There would be less soil washed away, but it would carry a higher proportion of adsorbed phosphorus, especially if farmers were to switch to certain reduced tillage methods which require that fertilisers be applied to the surface rather than incorporated into the soil.
Pesticides tend to be less easily transported than fertilisers, but they too have been showing up in Illinois lakes. (Of the 23 pesticides in common use in Illinois, 17 move via adsorption to soil particles.) In the past, wide use of long-lived organochlorine compounds such as DDT led to much contamination. In 1977 the fish in 14 lakes and rivers were found to harbour concentrations of organochlorines (mainly Dieldrin) that were higher than the minimums considered safe by the US Food and Drug Administration, even though sales of Dieldrin had been halted several years earlier.
Most of the pesticides in use by Illinois farmers today are the relatively short-lived organophosphate type which break down chemically in water within a week or two. Still, they remain potent killers in concentrated doses. In 1980, 13 of the recorded 23 fish kills in Illinois were traced to farm chemicals, usually pesticides washed into adjacent water supplies by a heavy rain; prior to 1976 most fish kills in the state were traceable to industrial rather than agricultural sources.
Ironically, some of the same economic forces which led to what state farm officials have called the 'mining' of the state's topsoil may force them to stop it. With fuel costs a major item in farmers' budgets, trips across fields in tractors are becoming more and more expensive. In an attempt to save energy costs, Illinois farmers are turning to one of the varieties of so-called 'reduced tillage' methods of cultivation, which typically use a chisel plough instead of mouldboard plough and rely on chemical herbicides instead of fall ploughing and mechanical cultivation to control weeds. (In the 'zero-till' systems, the field is not ploughed at all; seeds are planted right in the sod left from the previous year's crop.) The result is fewer field trips, lower fuel bills—and less soil erosion. Erosion 192 from corn fields, for instance, can be cut by up to per cent.
Dismissed as quackery a few years ago, reduced tillage is now used on an estimated 4.5 million of Illinois' farm acres and may be the next revolution in Illinois farming, equal in its impact to that of the tractor or artificial fertilisers. Conservation tillage promises to be to the 1980s what contour ploughing was in the '30s, the central tenet of a new conservation orthodoxy. It is catching on because it offers a relatively low-cost way to cut soil losses without sacrifices in productivity. Robert Walker of the Cooperative Extension Service estimates that perhaps half the cropland in Illinois that is losing soil could be adequately treated by some form of conservation tillage without significant loss in farm income.
But will saving the soil put Midwest waters at risk? Weeds are controlled mechanically using conventional tillage systems. With reduced tillage systems, however, weeds are controlled chemically, so as to preserve the protective blanket of crop residue. The result is higher herbicide use.
This is inherently inefficient, even extravagant. Some herbicide is inevitably lost to the atmosphere; much more is washed off the surface of the crop rubble with the first big rain. Indeed, while reduced tillage cuts soil erosion dramatically, the concentrations of chemicals in runoff can actually increase compared to conventionally managed fields, partly because the actual volume of rain runoff from a field is reduced, partly because those chemicals are exposed to the erosive effects of precipitation on the soil surface.
To date the US has published so-called 'concentration criteria'—maximum safe levels of chemical contamination in water supplies and aquatic habitats—for only two herbicides. (They are 2,4-D and 2,4,5-T.) No criteria have been set for the dozens of other weed killers in farm use. While lab tests show that most of these substances are no more toxic to test animals than aspirin, the potential effects of chronic, long-term exposure on animals or humans is not at all well understood. Losses of herbicides to adjacent watersheds are especially large during heavy rains immediately following application. William A. Hayes, for 31 years an agronomist with the US Soil Conservation Service, told the Journal of Soil and Water Conservation recently that such episodes "could have disastrous consequences for surface and subsurface waters".
The anxiety of observers such as Mr Hayes is not yet shared by most state environmental officials in the Midwest. For example, Illinois' water quality monitoring programmes do not include tests for herbicides. (Persistent insecticides such as chlordane are tested for.) But the new generation of farm herbicides are officially assumed not to be persistent in the environment, so environmental agencies do not look for them.
A.G. Taylor is the assistant for agricultural programmes of the Illinois EPA. He admits that the environmental implications of rising herbicide use have triggered 'increasing concern' among his colleagues around the Cornbelt. But Taylor notes that expanding routine water quality monitoring programmes to include tests for the three dozen or so herbicides in use in Illinois would be very expensive. Besides, says Taylor, "The benefits of minimising soil erosion (through the use of reduced tillage methods) may exceed the hazards we may expect from the increasing volumes of pesticides used."
Chemical industry spokesmen remain sanguine that solutions to the problems of chemical runoff, will be found, either through improved chemicals, improved equipment, or improved farming techniques. But the fact remains that the distance between the lab and the farm field is measured in dollars rather than miles. Farmers tend to over apply both fertilisers and pesticides, inadvertently or in anticipation of weather reverses. Even if machines capable of meeting the peculiar demands of chemical application in the new cultivation systems are marketed, farmers may find it cheaper to continue to over apply chemicals rather than invest in equipment needed to do it more efficiently. In the meantime, the poisoning of watersheds with farm chemicals will proceed apace, with unknown economic and ecological costs.
The fact that solving one environment problem caused by modern farm methods may be aggravating another is the kind of irony Midwest environmental officials have grown accustomed to. Stricter controls on farm practice might help. But US farmers, like farmers around the world, are notoriously jealous of their independence, and the administrative structures of farm programmes of every kind have been built to accommodate their clientele's affection for local control and their abhorrence of regulation. The voluntary nature of erosion programmes make participation a function of economics rather than ecology. To farmers pushed onto the thinnest of profit margins by increased costs for fuel, fertilisers, equipment and loans, erosion control was simply unaffordable. Specialists from the SCS and other agencies had co-plained for years about the wastage of Illinois topsoil, but their warnings were lost in a clatter of combines rushing to harvest enough corn to meet the next bank payment.
Jim Frank ran Illinois' erosion control programme in the 1970s. In a speech Frank once observed, "It remains to be seen whether a programme of voluntary education and incentives can motivate farmers to do what they know they should be doing but can't afford to do." Nearly all the proposed remedies cost farmers money in either cash outlays or lost production. Recognising this, and recognising that a voluntary programme without penalties, federal and state erosion programmes alike stipulate that cost-sharing money be made available to farmers.
Alas, federal funds are themselves something of an eroding resource in the US under Reagan's rule. The most recent estimate puts the cost of bringing soil losses on all Illinois farmland down to T levels or below by the turn of the century at nearly one billion dollars—61 million dollars a year for the next 16 years. The average annual federal cost sharing budget for Illinois during the last few years has been 6.5 million dollars.
Expanded use of reduced tillage systems has already carried Illinois a good distance toward 'T\ More expensive remedies for its more sloping fields, such as terraces, await further funding. But nearly one million acres of the state's most erosive land simply cannot be farmed for row crops without acceptable soil losses.
The only sure cure for these vulnerable lands is to take them out of row crop production. The trouble is that there are few attractive economic alternatives to row crop production. Wheat earns less than corn or soybeans, there is little cash market for hay, and few farmers keep cattle that might feed on forage crops because the beef market is depressed. One plan suggests the public purchase of 'cropping rights' to incurably eroding land.
Under such a plan owners would be forbidden to plant crops but instead would plant pasture, forage or forest crops in return for cash payments in lieu of income thus lost. But money for such a scheme is not likely to be available soon. It has even been suggested that Illinois may someday levy a severance tax on farm products similar to the taxes levied by energy exporting states, to pay for repairs to the land damaged by the mining of topsoil for grain production.
To a large extent, of course, erosion is a function of a farming system that requires the intensive cultivation of maximum amounts of land; with profit margins so thin, it is produce or perish. Beginning with the Nixon administration, farmers were urged to all-out production to meet global demand for grain. Little heed was paid to the impact which the subsequent frenzy of planting had on the land, so that during the 1970s erosion and food exports rose together. It was as if the president had urged motorists to drive more during the OPEC oil embargo.
Ultimately, it is the US public which will pay for the failure to control soil erosion, in higher food prices, clogged reservoirs and the vitiation of rural economies. Pay now in cost-sharing, farmers say in effect, or pay later. But there is yet no strong constituency for soil conservation. The general public simply does not understand the costs. □