i 





SoilE 



rosion 



By John E. Nelson, E. C. W, Engineer 



A GLANCE at the soil erosion map 

 of Illinois will disclose that most 

 of the erosion lies along the Mis- 

 sissippi and Illinois rivers. This is partly 

 due to the fact that most of this area is 

 rolling or hilly, but other hilly areas in 

 the State are not subject to much erosion. 

 Why does this condition exist? 



Let us turn back a few million years 

 for the answer. The last ice sheet is re- 

 ceding from the Great Lakes, region and 

 rivers are carrying a full load of glacial 

 silt. Much of this is deposited in mud 

 banks, which dry and are blown eastward 

 as dust, by the prevailing west winds. 

 By the time a timber growth has be- 

 come large enough to hold most of the 

 soil in place, a blanket of this "loess" 

 covers most of what is later to become 

 Illinois. This blankfet varies in thickness 

 from thirty feet near the Mississippi, to 

 a mere trace as far east as Champaign. 

 Another long period of time elapses dur- 

 ing which topsoil is gradually built up by 

 vegetation. Then the white man invades, 

 clears off the timber, and plows up the 

 sod. Rains begin to wash, the loosened 

 topsoil from the hills. This continues, 

 until today the loess is again near the 

 surface, and in many spots is actually 

 exposed. 



The process of surface washing is 

 known as sheet erosion, and while not so 

 apparent as gully erosion, is much more 

 detrimental. University of Illinois Col- 

 lege of Agriculture figures show that on 

 rolling farm lands, the fertility lost 

 through sheet erosion is 21 times that 

 used by crops. Too much stress cannot 

 be laid on the fact that erosion is occur- 

 ring on all farmed land with a slope 

 greater than 3%. even though no gullies 

 are visible. Aside from reforestation 

 ther» are two general methods of check- 

 ing sheet erosion. One is by seeding 

 down, strip cropping, or contour farm- 

 ing. The other is a mechanical means 

 of preventing erosion, known as terrac- 

 ing. Terraces have been used for nearly 

 fifty years in the Carolinas, Kentucky, 

 and Virginia. At first they were merely 

 ridges thrown up across the face of the 

 hillside to check the runoff during rains. 

 Gradually they were improved, however, 

 until today terraces are built to meet the 

 particular soil, slope, and cropping re- 

 quirements of any locality. 



The terrace recommended by the state 

 University is a. shallow channel 25 t« 30 

 feet wide, and from 15 to 20 inches deep. 

 Its slope is about 4 inches in 100 feet, 

 just enough so that the water will slow- 

 ly flow toward the edge of the field and 



not break over the ter- 

 race. The vertical dis- 

 tance between succes- 

 sive terraces should be 

 from three to six feet. 

 Thus, on a 4% slope 

 the terraces would be 

 about 100 feet apart. 

 An adequate outlet is 

 very important since all 

 of the water from the 

 field is concentrated at 

 the lower ends of the 

 terraces. For this purpose a permanent 

 channel with check structures below each 

 terrace is recommended. 



In Illinois, broad base terraces are be- 

 ing used on only about 16,000 acres of 

 farm land. In view of the fact that more 

 than 12 million acres of Illinois land are 

 subject to sheet and gully erosion, it is 

 apparent that further interest in terrac- 

 ing is necessary. Withiff the past few 

 years the moisture conservation value of 

 terraces has been realized. In a dry year 

 the College of Agriculture has obtained 

 15 bushels more corn per acre on a 

 terraced slope than on a similar slope 

 which had no terraces. Thus, the idea 

 that terraces are particularly beneficial 

 during a rainy season, is supplemented 

 by the fact that during dry years a ter- 

 race acts as a moisture saver. 



This next spring the Illinois Emer- 

 gency Conservation Work program will 

 undertake a cooperative terracing proj- 

 ect with the farm owners of Illinois. Such 

 plans have been in operation on a large 

 scale in Texas. Kansas, Oklahoma, and 

 other states for a year or more. There 

 are 19 CCC camps in this State which 

 are doing soil erosion work on farm 

 lands. In the past CCC labor has been 

 available only for gully control work in 

 Illinois. Since sheet erosion is so preva- 

 lent and terracing so necessary, how- 

 ever, these 19 camps, if authorized for 

 continuation by Congress, will aid in ter- 

 racing farm lands as well as doing gully 

 work. The plan will be for the farmer 

 to construct the terraces according to a 

 survey made by an E. C. W. engfineer. 

 CCC labor will then be used to build the 

 necessary permanent outlet structures for 

 each terrace system. For a limited time. 

 E. C. W. funds will be used to purchase 

 material for these structures. 



In order to facilitate the terrace build- 

 ing, "terracing clubs" are being formed 

 by the farm owners in the counties which 

 are to have the benefit of CCC labor for 

 this work. The object of these clubs is 

 to purchase or rent machinery for build- 



GULLY DAM BtJIIT BY THE CIVILIAN CONSrHVATION C0HP6 

 near Elmwood. Peoria i.uuaty. IJlmoig. 



ing terraces. A terracing grader and a 

 caterpillar tractor are best for this work. 

 Thus, a farm owner wishing to terrace a 

 field will sign an agreement with his 

 local terracing club to have the work 

 done. He will then sign a cooperative 

 agreement with the State to have the 

 outlet structures built by CCC labor. His 

 only expense will be cost of operating 

 the terracing equipment. Figures from 

 other states show that this will vary 

 from $1.50 to $2.50 an acre. This figure 

 includes retiring the cost of new equip- 

 ment or rental charges for rented equip- 

 ment. Incidentally, the cost to the State 

 for materials for the concrete check 

 structures in the outlet channel will Tar> 

 from $7.00 to $10.00, exclusive of labor 

 Certainly no Illinois farmer can afford 

 to lose this opportunity for expert a4vic« 

 and E. C. W. aid in terracing his rolling 

 land. 



First Prize Essay 



(Continued from page 24) 

 loves one another and who has learned 

 cooperation through the home and 

 through these organizations that support 

 the home, cannot help but live happily 

 and successfully. 



Karl Brandt writing in Social Research 

 for February declares: "Inventors, •ngi- 

 neers, chemists, biologists, physicists, ar^ 

 straining their brains to substitute indus- 

 trial products for farm products. Lard, 

 tallow, and rapeseed oil have been re- 

 placed by mineral oil as fuel for lamps; 

 wood and peat fiave been replaced by 

 coal, leather and hides by rubber. But 

 there are new and more far-reaching at- 

 tacks pending. Sulphitspirit, rayon and 

 woodsugar are examples. Sulphitspirit 

 replaces alcohol which is distilled from 

 potatoes or grain, rayon replaces silk, 

 and woodsugar is converted cellulose to 

 be used instead of feed grain or other 

 carbohydrates for hogs or any other ani- 

 mals to be fattened. 



APRIL. 1935 



