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 Circular b44 : University ot Illinois : Uollege ot Agriculture 
 Extension Service in Agriculture and Home Economics
 
 /iliOlS HISTORICAL SL'aVEY 
 
 This circular is based on a critical study by Carl B. Brown, J. B. Stall, and E. E. DeTurk, of 
 the conditions in Lake Decatur and the surrounding watcrshtd (sec The Causes and Effects of 
 Sedimentation in Lake Decatur, Bulletin 37, State of Illinois, Departiiunt of Reeistration and 
 Education, State Water Sur\'ey Division i . 
 
 The stor>- has been told here by E. D. WALKER, Extension Soil Conservationist and Associate 
 Professor in Agronomy Extension, College of Agriculture, University of Illinois. The Decatur 
 Herald-Review, the Decatur Chamber of Commerce, and the Bloomington Daily Pantagraph 
 were kind enough to provide many of the illustrations. I'cu si\iral others, credit is due to 
 W. F. Purnell, Assistant Extension Soil Conservationist. 
 
 Coopfrativc Extension Work in Agricuhurr and Home Economics: L'nivcrsily of Illinois, 
 
 CoUciic of Agricullurc. and ihc United Stales Department of .Agriculture cooperating. 
 
 H. P. Ri.iK. Dirrclm. Acts approved bv Congress May 8 and June 3(1, 1914.
 
 V5 
 
 as 
 
 /4 ^^ne^ (n^cutcf. foe^^foie * . * 
 
 are involved in this sUjry of a small lake in 
 central Illinois. It concerns first the city 
 people who built the lake and live near it, 
 and the farmers whose lands drain down 
 into the lake. But it really is of vital im- 
 portance to all the people of this country 
 
 — everyone, without exception. 
 
 The lessons in this story are crystal clear. 
 Either we as a nation must find a way to 
 hold our fertile soil where it is, or some day 
 we shall be hungry as older nations of this 
 world are now hungry. 
 
 Many of our farmers won't have to wait 
 until they are through with their land to 
 see that it has literally washed out from 
 under their plo\\'s. It is being washed away 
 now — how fast is indicated by the story 
 of this lake. We may be enjoying prosper- 
 ity because of improved varieties of crops 
 
 — hybrid corn, for example — but this 
 prosperity cannot last unless the soil lasts. 
 
 This story, we trust, will convince more 
 farmers to take the steps needed to save 
 their soils, and v\ill stir others to take an 
 interest in the national problem of con- 
 serving our soils — our greatest natural 
 resource, and one we cannot replace.
 
 THE CITY OF DECATUR 
 
 NEEDED A BETTER WATER SUPPLY 
 
 Some years ago the citizens of Decatur, Illinois, faced the problem of getting more 
 water. The population was growing, and so were the man\- processing and manufac- 
 turing plants which were imi)()rtant to the 
 life and prosperity of the city. 70. 
 
 Past the edge of the city Hows a ri\er 
 which seemed to hold an answer to the 
 |)roblem. It was the Sangamon, a stream 
 draining nearly 600,000 acres of the black 
 prairie farm lands abo\-e Decatur. The '"■ 
 people of the city looked at the am|)le flow 
 of the Sangamon, and decided to do what m, 
 seemed easy and logical slorc the water 
 and use it. 
 
 Decaliir's popul.ition, as shown hy the chart, will rlimh 
 to an csliniaird t).i,30fl bv I'.'SO.
 
 so A DAM WAS BUILT AND 
 A BEAUTIFUL LAKE WAS MADE 
 
 The dam was completed in 1922 — more than 25 years 
 ago — at a cost of 2 million dollars. The lake which it 
 formed had an area of 2,800 acres, and extended about 
 8 miles upstream from the city limits. It promised to sup- 
 ply plenty of water for people and industry indefinitely. 
 
 V.
 
 Not only has tho lake meant a fine water 
 supply for the city, but it has a.l'o pio\idi'd 
 a great open area where thousands of 
 people from Decatur and the surrounding 
 country could boat, fish, swim, and enjoy 
 other kinds of healthful, joyous recreation. 
 Homes ha\'e been built arountl the ed^e of 
 the lake. 
 
 It seems like a pretty i)ieture a bt-auti- 
 ful lake and a prosperou.j city surrounded 
 b\ some of the most fertile farm land in 
 Illinois. 
 
 But that isn't the whole picture, for dis- 
 turbing problems ha\e developed since the 
 ake was formed.
 
 7^ i^^ ^ ie^<MHCK^ ^ cUef 
 
 Through the years since 1922 something 
 iias been happening in the hike itself. 
 Slowly but surely Lake Decatur is dying. 
 It is being smothered and strangled by 
 millions of tons of silt washed in from the 
 farm land in the watershed above the lake. 
 
 In 1946, just 24 years after the lake was 
 built, more than a fourth of its capacity 
 had been filled with precious topsoil. The 
 
 lake can now supply less than three-fourths 
 as much water as it could when it was 
 made, yet the growing city and its indus- 
 tries need more water than e\'er. 
 
 // there had been no siltini^, the lake 
 would have served the city well for 78 years 
 — despite the growth in population and in- 
 dustry. But now, to be safe against possible 
 drouth, more water storage will need to be
 
 1.3% 
 
 
 
 1% of lake's capacity filled each year 
 
 1.2% filled each year ! 
 
 1923 
 
 193; 
 
 1946 
 
 The yearly rale of sediment deposit was onc-lifth more from liKi" to HMti than diirins; llu- first H years of tfie 
 lake's life. Since 1946 soil has found its way into the lake at a still faster rate. 
 
 provided by 1956, when the hike will be 
 only 34 years old. 
 
 The tragic loss of water supply to the 
 city of Decatur is not the only loss to the 
 people of the area. As silt comes in, it spoils 
 recreation spots in and around the lake. 
 Boats stick on mud bars, water is too shal- 
 low for bathing beaches, unsightly weeds 
 mar the landscape. A lot of summertime 
 fun is spoiled for children and adults alike. 
 
 These are the local and the immediate 
 problems. They are of concern to the 
 people of Decatur and others who like to 
 play in and around the lake. At first we 
 might think that they are the only problems 
 and that with some further outlay of skill 
 and money they could be solved without 
 much trouble. 
 
 Rut the fact is that the conditions at 
 
 Lake Decatur point up a much bigger and 
 much more serious situation. 
 
 What is happening here is happening all 
 over our country. Because of uncontrolled 
 erosion we are losing the food-producing 
 layer of our soil. 
 
 That rich topsoil now lying in the bottom 
 of Lake Decatur is, in the words of "Ding" 
 Darling, famous cartoonist and conserva- 
 tionist, "beefsteak and potatoes, roast duck, 
 ham and eggs, and bread and butter with 
 jam on it." 
 
 It is also bright woolen sweaters, Easter 
 hats, mittens, shoes, shirts, coats, and Dad's 
 new tweed suit. 
 
 So we see here a problem that concerns 
 those who own farms and those who live 
 on what our farms produce. And that takes 
 in all of us. 
 
 Ihi l.ikr liulds kvs lliaii llnti-luurllis as much water as uhtn it \\as built in 1'.I22. .\i\ .t\iiai;( 1(; 
 of more than 1 percent a year may not sound serious — until it is multiplied by 2.5! 
 
 in r.ipaiilN
 
 A RICH FARMING AREA SUFFERS 
 
 The Sangamon river watershed above 
 Decatur is in the fine farming area of 
 east-central Ilhnois. Nine-tenths of the 
 land is dark prairie soil, and about one- 
 tenth is light-colored timber soil. Nearly all 
 the land is in farms; most of these farms 
 raise grains — corn, oats, wheat, and, more 
 recently, soybeans. A large part of the area 
 is therefore plowed and cultivated — and 
 so subject to erosion. 
 
 But in 1922 the threat of erosion aroused 
 no concern. No thought was given to the 
 need for managing the land in such a way 
 as to protect both the land and the lake. 
 Hadn't the farms been operated for years 
 with little damage? Couldn't things stay as 
 
 they had been? If we had looked at the 
 lake and the land closely enough and early 
 enough, we would have found the answer. 
 And the answer would have been No. 
 
 The first sign of trouble appeared in the 
 small bays and inlets. They began to fill 
 with silt. Men making a partial survey in 
 1930 found deposits of silt 1 to 4 feet deep 
 in various spots. A complete survey made in 
 1936 showed that in the 14 years since the 
 lake was built sediment had been filling it 
 at the rate of 1 percent of its capacity each 
 year. This survey was made jointly by the 
 U. S. Soil Conservation Service, State 
 Water Survey, Illinois Agricultural Experi- 
 ment Station, and the city of Decatur. 
 
 This is topsoil from a soybean field on its way into the lake — lost to food production and a costly nuisance in 
 the lake. Since 1922 fertile topsoil equal to that from some 7,500 acres has been buried in Lake Decatur. 
 
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 J-' A
 
 70- 
 
 60- 
 
 50- 
 
 ■}()- 
 
 Percentage of Farm Land 
 in Corn and Soybeans 
 
 1922 
 
 1929 
 
 1934 
 
 1939 
 
 1944 '4G '47 
 
 The inirt-ased acreage of corn and soybeans in Macon, Piatt, De Witt, Champaign, Ford, and McLean counties 
 parallels the increase in the rate of sediment deposit. The Lake Decatur watershed lies in these six counties. 
 
 As yt-ars went along, moir sit;ns of 
 troublr appeared. Bays and inlets con- 
 tinued to fill — some completely. Mud bars 
 showed in th(> upper i)ail of the lake and 
 became conckcI wilii willows, cattails, and 
 grasses. Boats ran aground on the mud bars 
 and had trouble reaching their docks. By 
 1941 there was so much concern that the 
 city set up the Upper Sangamon Valley 
 Conservation Scr\ice and employed two soil 
 conservationists to help with the problem. 
 
 In 1946 a second survey, made by the 
 same agencies as in 1936, showed startling 
 changes. By that time silt deposits had 
 filled in the lake until its area was 201 
 acres less than in 1922, and its capacity 
 was 26 percent less. In the 10 years from 
 1936 to 1946 good soil ccjual to the top 7 
 inches from 3,400 acres of land — more 
 than half a section a year — had been torn 
 away and carried into the lake. 
 
 With this .soil went a\ailable nitrogen 
 worth $92,000 and a\ailable phosphorus 
 worth $35,000. During the entire 24 years 
 the losses of these materials alone totaled 
 a third of a million dollars. Had thev been 
 
 left on the cropland, the\ were all ready to 
 be changed into corn and wheat and soy- 
 beans. The displaced soil also contained 
 millions of pounds of reserve nitrogen and 
 phosphorus that would h<i\<' later become 
 a\ ailable to crops. 
 
 Why has tin rate of ( rusion increased 20 
 percent since the larly days of Lake De- 
 catur? The answer lies in the marked 
 change in the use of the land. Back in 1922, 
 the intertilled, erosion-producing crops, 
 corn and soybeans, were grown on 41 per- 
 cent of the farm land in the six counties 
 from which water Hows into the lake. The 
 other 59 percent was used for small grains, 
 hay, and other crops that hold the soil 
 better than tilled crops. 
 
 By 1945 the corn acreage had decrea.sed 
 slightly, but the soybean acreage had ex- 
 panded until these two crops occu])ied 6(1 
 percent of the farm area. Total acreage of 
 these crops has since declined slightly. In 
 some areas, however, HO percent of the 
 land is still in corn and .soybeans. 
 
 This leaves little room for the close- 
 growing crops which help to hold the soil.
 
 'C*^ ^ .-**^.-.. .-Mil*-*-, 
 
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 AND A NATION GROWS POORER 
 
 Decatur can, and doubtless will, make 
 some shift to solve its problems of water 
 supply and recreation. But nobody will or 
 can put back the soil and plant food which 
 have been washed oflF the good farm land 
 of the upper Sangamon valley. That is for- 
 ever lost. As a result, the nation is poorer, 
 and so are you and I. 
 
 Lake Decatur serves merely as a mirror 
 to reflect our wasteful methods of land 
 management. Much the same story can be 
 told of other lakes in the state, particularly 
 those where a large part of the watershed is 
 in cultivation. Spring Lake, at Macomb, is 
 approximately half full of sediment. Lake 
 Calhoun, near Galva, built as a recreation 
 center, is so nearly full that it has lost much 
 of its value. The acreages of corn and soy- 
 beans run high in both watersheds. On one 
 section of land above Lake Calhoun, 520 of 
 the 640 acres were in corn in 1947 and t he- 
 corn was planted up and down the slope. 
 
 Even though there is not always a lake to 
 catch the runaway soil, we know that the 
 same serious problem of soil loss exists in 
 all parts of our state, and in all parts of our 
 country. When the Mississippi river is at 
 Hood stage, the ecjuivalent of the topsoil 
 from a 40-acre farm is carried past Vicks- 
 burg, Mississippi, every minute, according 
 to careful estimates of engineers. Much of 
 that topsoil comes from Illinois farms. E\i- 
 dence of this fact lies in the eroded fields, 
 and e\en abandoned land, in all parts of 
 the state. 
 
 Best available estimates show that about 
 9 percent of Illinois land is subject to de- 
 stiurtix'c erosion, 9 percent to serious ero- 
 sion, and 59 percent to harmful erosion. 
 This means that ()\er three-fourths of the 
 land in the state is threatened with erosion, 
 and that its fertility will continue to be de- 
 pleted unless correct farming methods are 
 more widely adopted.
 
 A wise coiiibinalioii of crops on (he IcNcl land, Iri-t's on Iht- slo|)f 
 
 BUT OUR LAND CAN BE SAVED 
 
 Those of us who are farmers have a 
 hea\y responsibility to do all we can to 
 keep the good topsoil on our lands — laiuls 
 v\e hold in trust for future generations. 
 
 The general pattern of good soil man- 
 agement is clear. To begin with, we should 
 put into crop production only land that can 
 be safely used for that purpose and lea\e 
 the rest for hay, pasture, and timber. 
 
 The next great need is better rotations on 
 the land set aside for crop production. No 
 more than luilf of e\en the best land should 
 be planted to intertilled crops such as corn 
 and soybeans in an\ one \(ar; this leaves 
 a fourth of the land for small grains and 
 a fourth for meadow mixtures of legumes 
 and grasses. On land of low fertility or in 
 greater danger of erosion, the proportion 
 
 Steep, erodini; Nlop<s like thi' 
 in trees. 
 
 should be 
 
 Legumes and grasses hold the soil, and 
 provide feed for sloek. 
 
 A good grass waterway stops gullies 
 before they start. 
 
 ■r^^* 
 
 "^;'-4,
 
 Curved rows, cutting across the slope on the level, save soil and water — and the crops yield more. 
 
 planted to intertilled crops should be cut 
 down to a third, a fourth, or even a fifth, 
 and the acreage of small grain crops 
 and meadow should be correspondingly 
 increased. 
 
 High yields of the soil-building legumes 
 and grasses are necessary to make rotations 
 most eflfective. To get high yields of these 
 crops, soil treatment is essential; limestone, 
 phosphate, and potash are most likely to be 
 needed. Tests that show the actual needs of 
 
 the soil should be the basis for supplying 
 fertilizer. To be completely successful, a 
 fertility program must include permanent 
 pasture, as well as cropland. 
 
 Other measures may be needed on many 
 farms. Sloping land may need grass water- 
 ways, contouring, strip' cropping, and ter- 
 racing, and the Hatter land may ha\e to be 
 drained. Reforestation, farm woodlot man- 
 agement, and wildlife protection will also 
 come in for attention. 
 
 A concrete dam keeps tile and waterway from washing out. A farm pond can he used to heal a gully and save water for 
 Note how crops are contoured. livestock and family recreation.
 
 /■ 
 
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 ,iu«k. 
 
 Some land must be drained before it can 
 do the best job of producing crops. The top 
 picture shows a machine layini; till- to drain 
 excess water oil a central Illinois farm. Open- 
 ditch drainage is also commonly used, (irow- 
 ing plenty of legumes and grasses in the ro- 
 tation is needed to keep soil open and in 
 condition to drain properly. 
 
 Before these soil-building legumes and 
 grasses will make good growth, lime and 
 other plant food must be added to much of 
 our land. In the center picture a farmer is 
 liming his field according to the need shown 
 by a careful soil test. .Seventy-two soil-testing 
 laboratories in Illinois are guiding farmers in 
 the application of record tonnages of lime, 
 phosphate, and other fertilizers. 
 
 In the bottom photograph, something is 
 happening which should never happen. We 
 would not deliberately burn up dollar bills. 
 \N e do worse when we burn cornstalks and 
 other crop residues. U hen plowed into the 
 soil such residues decay and form organic 
 matter or hiinuis. Ibis huuuis helps soil to 
 hold more water, impro\es its texture and 
 makes it easier to work, and enables it to 
 produce more crops.
 
 DOES CONSERVATION FARMING PAY? 
 
 The answer to this question is an em- 
 phatic Yes. Costs and benefits of soil and 
 water conservation ha\e been studied on 
 farms in several parts of Illinois. Figures 
 derived from the studies show that con- 
 servation farming does pay. 
 
 All the farms studied showed a better net 
 income after a good conserxation program 
 had been put into efi"ect. Among a group of 
 
 central Illinois farms, those where the best 
 conser\ation practices were followed re- 
 turned, as a five-year average, $6.65 an 
 acre more than similar farms where good 
 soil management was not applied. On a 
 160-acre farm this extra income would 
 total more than $1,000 a year. Farms in 
 other parts of the state showed similar 
 gains from soil conservation practices. 
 
 STARTING A CONSERVATION PROGRAM 
 
 The first step in getting a conservation 
 program underway on a farm is to outline 
 carefully the soil situation on that particu- 
 lar farm. When this is done, the next step 
 is to write out a detailed plan showing what 
 cropping system and conservation prac- 
 tices will be used, where they will be used, 
 and when. In this way it is possible to make 
 sure that all soil problems will be given the 
 attention they need, and that the conser\a- 
 tion measures will be correctly related to 
 one another. On rented farms a good plan 
 can be of further value by becoming the 
 
 basis for better understanding between the 
 tenant and the landlord. 
 
 Those who want help in planning a 
 program of good land management can 
 obtain it from sexeral sources. The Uni- 
 versity OF Illinois College of Agricul- 
 ture, the U. S. Soil Conservation 
 Service, the farm adviser in each county in 
 the state, and the soil conservation districts, 
 which now include 90 percent or more of 
 the counties in Illinois, all stand ready to 
 help actively in any farmer's program to 
 save his soil. 
 
 EVERYONE'S INTEREST IS NEEDED 
 
 One of our big national concerns is to 
 have our farm lands used in the best pos- 
 sible way. This is a problem that can be 
 solved only by millions of people demon- 
 strating willingness to do the right thing. 
 
 Those of us who ovxn or operate farm 
 land have an obligation to so handle it that 
 we shall keep the precious top inches of 
 fertile soil where they belong. This means 
 farming the "conservation wav. " Those of 
 
 us who are not landowners or operators 
 have an obligation too. Wc can help build 
 public sentiment favoring good soil man- 
 agement and can give our support to pub- 
 lic and private movements that will achieve 
 this important goal. 
 
 If we take to heart the .story told so 
 clearly by this lake in central Illinois, per- 
 haps the damage done here will have been 
 worth what it has cost. 
 
 25M— 6-49 — 40641
 
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