Loess Is More
How prairie plants turned dirt into soil
See Illinois (unpublished)
Soil is to the old Grand Prairie of east central Illinois what crude oil is to OPEC. The uncountable tons of pulverized Canada imported by the glaciers is the glaciers’ legacy to Illinois farmers. But while the glaciers made dirt, it was grass that turned it into soil. Plants added remnants rich in organic carbon and nitrogen to the topmost layers of soil, plus microbes that facilitate the cycle of growth and decay by which nutrients are put into forms usable by plants.
The following is taken from the draft of my never-published guide to Illinois history and culture. (See Publications for more about that project.)
In all but a few corners of the Grand Prairie, rubble left behind the glaciers was subsequently buried by loess (“luss”). Loess is a German word that is rendered more picturesque (and pronounceable) as “rock flour.” A mixture of clays and fine particles of quartz, feldspar, mica and other minerals known as Peoria Silt, this loess was laid down beginning about 22,000 years ago by meltwater. Great piles of it accumulated along the floodplains of the Illinois River valley to the west. As fine as talcum powder, the mineral-rich silts were as vulnerable to winds as a farmer is to a tornado. Easterly winds picked up the dust and blew it downwind.
Where the winds weakened, the silt fell from the air, a farmer's idea of manna from heaven. Most of Champaign County is blanketed with 24 to 60 inches of loess; farther from the rivers, in the northern and eastern reaches of the Grand Prairie, it is less than 20 inches thick on average. The difference partly explains why grain yields on Ford County farms tend to be lower than Champaign County’s.
The plants that grew upon glacial deposits aerated upper soil layers with their roots and held soil particles firm against marauding raindrops. Grasses also added organic matter to the mineral-rich loess left by the glaciers. The plants’ top growth died each year and was recycled, and more organic matter was added by the plants’ massive root systems, whose decay enriched the soil to depths measured in feet.
Trees are not such efficient soil-builders, as they store their organic matter more permanently in the form of wood, above the soil surface. John Madson, an able biographer of the tallgrass prairie, reported in Where the Sky Began that a forest soil may include 20 to 50 tons of humus per acre while a prairie soil next door may have 250 tons. As a result, soils that developed under grasses are generally more fertile than those that developed under trees. Darker too—the lighter color of the soils is a clue by which modern scientists deduce the extent of long-vanished forests.
An acre of good prairie soil may contain six to 30 tons of assorted mineral nutrients but also will hold the same amount of nitrogen in various forms, plus 60 to 300 tons of organic carbon. The resulting soils are among the richest in the world in terms of their ability to retain moisture, their store of trace minerals, and their benign pH.
As for microbes, the root zone of a tallgrass prairie hosts a microscopic world that rivals the Amazon rain forest in complexity. One gram of prairie loam is estimated to contain as many as two million protozoans and another 58 million bacteria. Some of these creatures break down chemicals into forms usable by plants; one such miracle-worker is the Bradyrhizobium bacteria that takes nitrogen from the air and “fixes” it in forms available to host soybean plants through nodules it forms on the latter’s roots.
The process has not been going for very long, and could be said to be ongoing, as grasses (in the form of corn, which is a grass) are growing on these soils still). Their relative freshness is another reason why the silts laid down by the Wisconsin ice made such good parents to the Grand Prairie’s best soils. Weather has had only about 12,000 years to worry the surface here. That is not long enough for leaching and exposure to leach away mineral fertility as happened in much of western and southern Illinois, where soils have lain exposed for much longer. Brownstown, near Vandalia in Fayette County, lies about 100 miles and about 60,000 years from Champaign County. A soybean field on older glacial soils there will struggle to yield 35 bushels while one is most parts of Champaign County will produce 50.
Illinois at its founding was the Prairie State in nature as well as name, and no region in Illinois was more festooned with prairie than its east-central counties. Save for a few scatterings of upland groves and trees that lined the stream bottoms, tall grasses and kindred flowering plants dominated the living landscape across all or parts of two dozen counties of this part of Illinois. The region was dubbed the Grand Prairie, and if Texas, Nebraska, and Arkansas also boasted Grand Prairies, none was quite as grand as Illinois’s. The first Euro-Americans who saw it often likened it to Eden. The judgment proved to be uninformed, but if Western humans were not yet adapted to life on the prairie, others were—more than 300 species of plants, 60 of mammals, 300 species of birds, and well over 1,000 kinds of insects buzzing over an expanse bigger than Belgium.
Geology and biology thus created here the nearly perfect place for the factory-style production of row-crops like corn or soybeans. True, the Grand Prairie is hardly the only place in Illinois suited to corn. Corn is raised in every county; even Chicago’s Cook County, which most Downstaters assume harvests more crooks than corn, harvests a million bushels a year. But in no other region of Illinois is corn grown as widely and as well as in the old Grand Prairie. Champaign and Ford counties in recent decades have led the state that leads the world in corn and bean yields—well above one hundred and fifty bushels per acre for corn and approximately forty-five bushels per acre for soybeans. It was not whimsy that left the athletes of Hoopeston Area High School known as the Cornjerkers or the team mascot dressed up like a stalk of corn. Cornjerking is the act of snapping an ear of corn off its stalk.
What Grand Prairie farmers owe to the glaciers is made clear by a drive south through southern Illinois. Between, say, Champaign and Shelbyville the farmland is richer and flatter than farther south, but it stands no comparison to the best land in east-central Illinois, mainly because the older soils outside its river bottoms are weather-beaten, having been exposed to leaching more than 40 times as long as that to the north. In the days before cheap artificial fertilizers, such soil was quickly exhausted by even subsistence farming. Burl Ives grew up nearby, and in his autobiography, Wayfaring Stranger, he recalled, “The yellow-clay land of Jasper County was not very productive. Those farmers who farmed on the share, as our family was doing then, moved frequently. ‘We are moving in March.’ I heard a hundred times, ‘We are moving in March.’”
Also, since the ice last visited far southern Illinois, weather has had time to erode it severely. As a result, much of the terrain, at least in the extreme south, is ill suited to cultivation by machine. The thin topsoils are underlain across much of the region with hard clay, and water runs off as if off a shingled roof, taking soil with it. That mattered less in the days when farmers grew their own “tractor” fuel in the form of grass-like hay and pasturage that protected topsoil from eroding rains. The switch in the 1920s to petroleum-powered tractors, however, freed up these fields to be planted in cash-earning row crops like corn that exposed soils to damage from erosion just as they exposed farmers to damage from a cash economy.
Climate and terrain were abetted in the theft of soil in Egypt by many of its farmers. Often more desperate than their counterparts in more fertile parts of the state, southern Illinois farmers also have been less informed, less provident, less expert. Many forested hillsides—land that was never suited to crops but was cheap because of it—had been cleared for farming. Hill farming was something the many Southern settlers had learned back home in Kentucky and Tennessee; sadly, they never learned to do it well. Among hill farmers the solution to soil wastage was to move to a place with new soil. (Norma Jacke Tucker in her memoir refers ruefully to her ancestors who had stopped for a while in Virginia or Tennessee or Kentucky, “ruining a little land” before moving on to Illinois to do the same.) “Fruitgrower,” a pseudonymous correspondent to the Jonesboro Gazette in the 1860s, chastised his neighbors “Hezekiah Slovenly” and “Jim Careless” for their improvidence, to no particular effect.
In short, soil is among the mineral wealth that has been mined to exhaustion in southern Illinois. By end of the 1930s many southern Illinois farm fields looked as though they had been strip-mined, which, in a way, they had. The Shawnee National Forest was justified as a setting for recreation and timber production, but these were means to its larger end, which (as revealed in the official report that led to its establishment) was erosion control. Tucker recalls playing in the gullies that scarred her family farm and rued the day forest rangers came and planted soil-holding pine trees. “The government had it in for gullies,” she wrote. “They gummed up, totally ruined the best playground in the whole wide world.”
The poor quality of Egypt’s soils has always been reflected in land prices. In 1930 corn and bean land in McLean and Champaign counties sold for around $190 an acre; in Hardin and Pope counties, such land brought barely $20 per acre. While such soils can be made productive, they needed capital that southern Illinois farmers found hard to raise. It is his land that a farmer borrows against for capital to improve his operation; the less valuable the land, the smaller the loan.
Also, farmers in most of the rest of Illinois equipped themselves for commercial agriculture after the Civil War, but farms in the southern counties were so small or so hilly that investing in machines made no sense. Some soils that are ill-suited to grains are good for fruits and vegetables, but their cultivation demands a lot of hand labor. The result was that farmers in the region were trapped in old-fashioned labor-intensive styles of farming for decades after farmers in the rest of Illinois moved on.
In the 1920s and ‘30s, many former farmers who had lost town jobs returned to the land in hopes of at least feeding themselves and families. They farmed any land they had, with terrible results. Erosion from the region’s sloping land at first merely made fields less productive; extreme erosion that led to gullying made many of them unfarmable. Exposed subsoils wash away too, and when they settled atop fertile fields below them, two fields ended up being wasted. Eroded soil filled drainage ditches too, and drainage districts passed on to farmers the costs of keeping them unclogged, which contributed to tax delinquencies before and during the Depression.
Southern Illinois got much attention from the federal government in that era. One of the aims of the Resettlement Administration, the rural version of the WPA, was to take people off land that was too poor to sustain them and resettle them elsewhere. after which submarginal farms could be turned into productive forests, recreation areas, and public reserves. Two Resettlement Administration projects were located in the southern part of the state—Crab Orchard, a 20,000-acre development centered on an 8,000-acre lake in Williamson County, and Dixon Springs, a demonstration forest in Pope County.
Marion Pedersen Teal’s The Earth Is Ours, published in 1948, is part memoir, part polemic on behalf of soil-saving farming methods—a sort of agronomic Uncle Tom’s Cabin. Unhappily for the region, the lessons of the 1920s and ‘30s were lost on many later farmers. In the 1950s, Washington tried a new tack—“land banking,” in which the government paid farmers to not plant vulnerable land. It worked for a while, but in the 1970s, a run of high grain prices tempted the owners of these set-aside lands to convert them to row-crop production. Profits jumped; so, predictably, did erosion. Average soil losses in parts of the region in the mid-1980s were more than twice what is considered sustainable, spurring Washington to again pay farmers to take land out of production via an old program that was given a new name, the Conservation Reserve Program.
Any prediction that the region’s profligate ways worth soil have changed for good would be rash, but soil-wasting in southern Illinois has at least slowed. By the late 1990s the careless farmer has been pretty much forced out of business, as has the uneducated one. Soil-saving tillage methods of some kind was being used on a much higher proportion of the region’s land than in the state as a whole, as much as four acres in five in some areas. In some of the hillier parts of the region only half the land is in agricultural use, and much of the land that is cultivated grows pasture—grazing cattle and hogs can navigate steep slopes easier than can tractors—or grass-like crops such as small grains. This is especially true in areas that have even more hills than nature provided because of strip mining; thousands of acres of reclaimed mined land in the region have been converted into pasture. The net result is that soil losses from farm fields have dramatically lessened since the 1930s. ●