UNIVERSITY OF 
 
 ILLINOIS LIBRARY 
 
 AT URBANA-CHAMPAIGN 
 
 ACES 
 
NOTICE: Return or renew all Library Materlalsl The Minimum Fee for 
 each Lost Book is $50.00. 
 
 The person charging this material is responsible for 
 its return to the library from which it was withdrawn 
 on or before the Latest Date stamped below. 
 
 Theft, mutilation, and underlining of books are reasons for discipli- 
 nary action and may result in dismissal from the University. 
 To renew call Telephone Center, 333-8400 
 
 UNIVERSITY OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN 
 
 
 L161— O-1096 
 
 MAR 2 8 2001 
 
 AGRICULTURE LIBRARY 
 
Digitized by the Internet Archive 
 
 in 2011 with funding from 
 
 University of Illinois Urbana-Champaign 
 
 http://www.archive.org/details/estimatingyourso1220walk 
 
. <II=^' • d 
 
 0.(^30.7 , -_1 . /l/- " 
 
 x^^o : ^- . '^Tc , 
 
 
 • p 9 ... 
 
 ,,^' -..^1 - 5 J ..^4- \«%A^ \MW^ 
 
 M . ' * ' ' '^ '.rtn Losses wi* 
 
 J CrtU Erosion i-"^ pv 
 
 =hh« UnWersal sort u ^ , 
 
 i ^ 1 d d 
 
 _z: • ^- ■' ^ ,• 
 
 ^^ ii d 
 
 iP tr Ij 
 
 ^^ -A- JC- -A 
 
 J w M. • - ^ 
 
 ^1 ^- ^^ 
 
 ^^ #_ -4it -1 
 
 1 /•■ I.™,i„ « rf: - „ i „. , - _ , 
 
 ' A] 4i A 
 
 ^ ^^ ^ ^^ _!_# I^ 
 
 1 1 1 ^f a\ W 
 
 ^ ' FT ^ r 
 
 l*".^ ■x-sr*'^ ^— =^ ^ ^ 
 
 ■ ^^Tl^ ^W^ , , il 
 
 i^^JZ^ > ■ V ^^ — .11 Y 4 
 
 ■■■■■■■■■■■■■■a ^5 *^^4S^^I^-f7S^" 
 
 ■■■■■■■■■■■■■■■■■■■•^ ■■■» ^■•^ji # 
 !■■■■■■■■■■■■■■■■■■■ ■■■■^^^^■■■n ■ 
 ■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■a ■ 
 
 !■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■ 
 
 !■■■■ Cooperative Extension Service ■College of Agriculture ■■ Circular 1220 
 ■■■■■ University of Illinois at Urbana-Champaign IBBIBBII 
 
 IBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB 
 
TABLE OF CONTENTS 
 
 Illinois Erosion Control Program 1 
 
 The Universal Soil Loss Equation (USEE) 1 
 
 Rainfall (R) Factor 2 
 
 Soil Erodibility (K) Factor 2 
 
 Slope Length and Steepness (LS) Factor 3 
 
 Cropping and Management (C) Factor 3 
 
 Conservation Practices (P) Factor 5 
 
 Using the USEE 6 
 
 Working through Some Examples 6 
 
 Solving the USEE for C 7 
 
 Getting Help 7 
 
 Tables 8-16 
 
 Appendix: How to Make and Use a Slope Gauge 17 
 
 Table 1. 
 
 Table 2. 
 
 Table 3. 
 
 Table 4. 
 
 Table 5. 
 
 Table 6. 
 
 Table 7. 
 
 Table 8. 
 
 Table 9. 
 
 Table 10 
 
 Tables 
 
 Soil Erodibility (K) and Erosion Tolerance (T) Values 
 
 for Specific Illinois Soils 8 
 
 Soil Erodibility (K) Values for Certain General Soil Types 11 
 
 Slope Length and Steepness (LS) Values for Specific Combinations 
 
 of Length and Steepness 11 
 
 Cropping and Management (C) Values for Northern Illinois 12 
 
 Cropping and Management (C) Values for Central Illinois 13 
 
 Cropping and Management (C) Values for Southern Illinois 14 
 
 C Values for Permanent Pasture, Range, and Idle Land 15 
 
 C Values for Undisturbed Forest Land 15 
 
 Conservation Practices (P) Values for Contour Farming 
 
 and Contour Strip Cropping 16 
 
 Values Used in Determining P Values for Terraces Built on Contour and 
 Used in Combination with Contour Farming and Contour Strip Cropping ... 16 
 
 This circular was prepared by Robert D. Wall<er, Extension natural 
 resources specialist, and Robert A. Pope, former Extension agron- 
 omist, University of Illinois at Urbana-Champaign. The authors 
 would like to thank Steve Probst, Soil Conservation Service, for his 
 careful review and helpful suggestions. 
 
 Information in this circular is based on Agricultural Handbook 537 published by the Science and Education 
 Administration, U.S. Department of Agriculture, and generally corresponds with information contained in the 
 Soil Conservation Service's Illinois Technical Guide. 
 
Excessive soil erosion occurs on 40 percent, or 
 9.6 million acres, of Illinois cropland. Erosion 
 on this land exceeds the soil loss tolerances of 
 one to five tons per acre annually, with a high of 
 over 50 tons per acre and an average of 1 1. 7 tons. 
 In addition, 23 percent, or 700,000 acres, of 
 pastureland and 16 percent, or 600,000 acres, of 
 woodland have excessive soil erosion. 
 
 The loss of valuable topsoil to erosion is 
 compounded by the loss of plant nutrients and 
 organic matter and by more difficulty in tilling 
 since the soil becomes increasingly clayey as 
 more subsoil is brought to the surface. But the 
 problems of erosion are not confined to farm- 
 land. The sediment that leaves fields often has 
 an adverse effect on the water quality and 
 condition of drainage ditches, lakes, reservoirs, 
 and streams. Many types of problems arise: 
 sediment decreases the storage capacity of lakes 
 and reservoirs, clogs streams and drainage 
 channels, causes deterioration of aquatic hab- 
 itats, increases water treatment costs, and car- 
 ries displaced plant nutrients. 
 
 Illinois Erosion Control Program 
 
 In response to the accelerated loss of soil 
 productivity and to the off-the-farm effects of 
 erosion, the state of Illinois has designed an 
 erosion control program. The goal of this pro- 
 gram is to reduce annual soil erosion losses on 
 all agricultural land to one to five tons per acre 
 by the year 2000 depending upon the soil type. 
 This rate of erosion is considered the soil loss 
 tolerance level (the T value). Where erosion 
 exceeds the T value, soil is being lost so fast that 
 the land's natural productivity is being dimin- 
 ished. Table 1 lists the T value for most Illinois 
 soils (all tables are given at the end of the text). 
 
 The erosion control program is divided into 
 intermediate goals, all leading up to the year 
 2000. To begin the program, the 98 soil and 
 water conservation districts in Illinois devel- 
 oped soil erosion standards for all soils in their 
 districts. The districts' standards, which went 
 into effect on January 1, 1983, were required to 
 be at least as stringent as the state's guidelines, 
 although some districts developed standards 
 stricter than the state's guidelines. 
 
 The state's guidelines are as follows: 
 
 • By January 1, 1983, erosion on all farmland 
 could not exceed four times the T value (4 to 
 20 tons per acre annually) established for 
 the soil type. 
 
 • By January 1, 1988, soil loss cannot exceed 
 two times the T value (2 to 10 tons per acre 
 annually). Where conservation tillage would 
 solve the erosion problem and the slope is 
 less than five percent, however, soil loss 
 must not exceed the T value (1 to 5 tons per 
 acre annually). 
 
 • By January 1 , 1 994, erosion on all farmland 
 cannot exceed one and a half times T (V/, to 
 1% tons per acre annually). 
 
 • By January 1 of the year 2000, erosion 
 cannot exceed the T value (1 to 5 tons per 
 acre annually) on any Illinois farmland. 
 
 Although the soil and water conservation dis- 
 tricts are delegated the task of administrating 
 the erosion control program, it is, as of November, 
 1983, still voluntary. There is, however, a clearly 
 defined complaint process. It is always possible 
 that the program will become mandatory if the 
 voluntary approach does not work. 
 
 The Universal Soil Loss 
 Equation (USLE) 
 
 The Universal Soil Loss Equation (USLE) 
 provides a convenient way for you to estimate 
 the rate of soil loss on your land so that you can 
 see how that rate compares with your district's 
 standards. The USLE takes into account the 
 major factors that influence soil erosion by rain- 
 fall: rainfall patterns, soil types, slope steepness, 
 and management and conservation practices. It 
 was developed by the Agricultural Research 
 Service, the state experiment stations, and the 
 Soil Conservation Service (SCS), using research 
 data from many research stations, including 
 work at Dixon Springs, Urbana, and Elwood, 
 Illinois. More than 10,000 plot years of data 
 were analyzed and used to develop the equation 
 in the early 1960s. Additional data, mainly from 
 rainfall simulator plots, have been added to the 
 equation in the latest revision. Most of the 
 recent data covers conservation tillage, reduced 
 tillage, till-plant, and no-till systems. 
 
 The USLE represents the average annual 
 rate of soil loss due to splash, sheet, and rill 
 erosion. It does not estimate soil erosion from 
 gullies or stream banks or the amount of sedi- 
 ment reaching streams. Moreover, the equation 
 only gives the estimated average annual splash, 
 sheet, and rill erosion for the specific field 
 segment for which you have determined the 
 appropriate factors. It will not reflect the aver- 
 age soil erosion rate for the entire field unless 
 
the segment you chose represents the field. In 
 general, however, you should not select a "repre- 
 sentative" field segment, but the field segment 
 where erosion is generally more severe. Taking 
 estimates on several field segments will give 
 you a better idea of the scope of your erosion 
 problems. However, do not take an average of 
 the several estimates because that may mask 
 the severity of erosion on a particular segment. 
 The equation is simple to use. Once you have 
 determined the values for each of the five factors, 
 you multiply them using a pocket calculator or, 
 if you prefer, pencil and paper. The equation is: 
 
 RXKXLSXCXP = A 
 
 where R — rainfall factor 
 
 K = soil erodibility factor 
 LS = length and steepness of slope factor 
 C = cropping and management factor 
 P = conservation practices factor 
 A = the computed average annual soil ero- 
 sion loss in tons per acre 
 
 Once you have determined A, you can com- 
 pare it with the T values in Table 1 and with 
 your Soil and Water Conservation District's 
 standards. You also can use the equation to 
 evaluate the effect that various changes in your 
 farming practices would have on your soil loss 
 rate. Keep in mind, however, that A is only as 
 accurate as the values that you have chosen for 
 the five factors. In general, if you have used 
 reasonable care in selecting the factors, A should 
 be within a range of plus or minus 20 percent of 
 your actual average annual erosion on the field 
 segment. 
 
 Rainfall (R) Factor 
 
 R represents the erosion potential inherent in 
 the rainfall patterns of a particular area. The 
 factors were developed from U.S. weather data 
 taken at many different locations in the eastern 
 United States over a 22-year period. The erosive 
 potential of rainstorms increases as one moves 
 from northeastern Illinois to extreme southern 
 Illinois. See Figure 1 for the R value in your area. 
 
 Soil Erodibility (K) Factor 
 
 K reflects the fact that various soils erode at 
 different rates because of different physical 
 characteristics such as texture, structure, or- 
 ganic matter content, and soil depth. K values 
 for Illinois range from a low of 0.15 on sandy 
 soils to a high of 0.43 on highly erosive soils. 
 
 If you have a detailed soil map of your farm, 
 find the soil type for the specific field segment or 
 
 segments that you have chosen, and determine 
 the K value from Table 1. Soil maps are avail- 
 able for about one-half of all Illinois counties, 
 and many individual farm soil maps have been 
 prepared for counties without published soil 
 surveys. Check with your SCS district conserva- 
 tionist about any maps for your farm. 
 
 If a detailed soil map is not available, your 
 district conservationist can help you determine 
 the proper K value, or you may use Table 2 until 
 more accurate information is available. Table 2 
 allows you to determine rough K values from 
 your judgment of the soil's color and permeabil- 
 ity. Most Illinois soils with an erosion problem 
 will have K values of 0.28, 0.32, 0.37, or 0.43. 
 
 Area using 
 "R" factor 
 160 
 
 Area using 
 "R" factor 
 180 
 
 Area using 
 "R" factor 
 200 
 
 Area using 
 "R" factor 
 220 
 
 Figure 1. Rainfall (R) values. 
 
Slope Length and Steepness (LS) Factor 
 
 LS represents the erosive potential of a par- 
 ticular combination of slope length and slope 
 steepness. Slope length is not the distance from 
 the highest point in the field to the lowest point. 
 To determine slope length, you must walk the 
 field and determine where water will flow. Dis- 
 regard contour farming channels and concen- 
 trate on natural flow patterns. Once you have 
 identified the natural flow patterns, determine 
 the point on the slope where the flow begins. The 
 slope length is then the distance from this point 
 to the point where (1) the slope gradient de- 
 creases enough that sediment deposition gener- 
 ally occurs, or (2) the runoff water becomes a 
 concentrated flow, or (3) the runoff enters a well- 
 defined channel, for example, part of a natural 
 drainage network or a constructed grass water- 
 way or terrace channel.* There is a tendency to 
 overestimate slope length. Slope lengths will 
 seldom be above 400 feet long on gentle slopes 
 and will usually be shorter on steeper slopes. 
 
 Slope steepness is expressed as a percentage. 
 The percentage of slope is the change in eleva- 
 tion between two points divided by the hori- 
 zontal distance between the two points times 
 100. For example, if the elevation change is 6 
 feet in a horizontal distance of 1 20 feet, the slope 
 has a 5 percent grade (6 ^ 120 X 100 = 5). Per- 
 cent slope can be determined with an engineer's 
 level, a hand level, a line or string level, or a 
 sighting board slope finder like the one on page 
 19 (instructions for using it are on page 17). 
 
 Once you have determined slope length and 
 steepness, you can find the LS value in Table 3. 
 Please note that slope classifications given in 
 detailed soil maps should not be used; they are 
 too general. The slope length and steepness 
 must be determined on the specific segment of 
 the field where you are estimating soil loss, and 
 the LS value must be derived from Table 3. 
 
 Cropping and Management (C) Factor 
 
 C reflects the reduction in soil erosion that 
 will result from growing a crop as compared 
 with leaving the land fallow. The amount of 
 
 *Where terraces are installed, the slope length is 
 usually the distance from the top of the terrace ridge 
 to the center of the next lower terrace channel. If the 
 terraces are built on the contour and used in conjunc- 
 tion with contour farming or contour strip cropping, 
 an additional P factor is used. See pages 5-6 for 
 calculating the P factor for terraces built on contour. 
 
 reduction depends upon the type of crop grown, 
 the cropping system, tillage practices, crop yield, 
 and residue management. Cropping and man- 
 agement practices influence erosion potential 
 by the degree to which their combinations keep 
 the soil surface rough or covered with crop 
 residues or vegetation. C values range from a 
 high of 1.0 for continuous fallow (soil tilled to 
 permit no vegetation to grow) to a low of 0.003 
 for excellent grass cover. By determining R X 
 K X LS for the field segment under examination 
 and multiplying that figure by various C values, 
 you can compare the soil erosion that you could 
 expect from different cropping and manage- 
 ment practices (without the use of soil conserva- 
 tion practices). 
 
 There are many possible cropping and man- 
 agement combinations. For example, almost 
 any crop can be grown continuously or in 
 rotation with other crops, and additional soil 
 protection can be gained by seeding a cover crop 
 in the row crop late in the season. Soils can be 
 left rough with considerable storage capacity, or 
 they can be smoothed by secondary tillage. Crop 
 residues can be removed, left on the soil surface, 
 incorporated near the soil surface, or plowed 
 under. Even if crop residue is left on the surface, 
 it can be chopped or allowed to remain as it was 
 after harvest. 
 
 So that C values would more accurately reflect 
 these and many other possible combinations 
 according to geographical differences in cli- 
 mate, planting dates, and cropping systems, 
 Illinois was divided into three sections. Figure 2 
 shows the three geographical divisions. By lo- 
 cating your county, you can determine which 
 geographically specific table to use to find your 
 C value. If you are in Knox County, for example. 
 Figure 2 tells you to see Table 4. 
 
 Northern Illinois C values can be found in 
 Table 4, those for central Illinois in Table 5, and 
 those for southern Illinois in Table 6. If you wish 
 to make soil erosion estimates for permanent 
 pasture and grazed or burned woodland, use 
 Table 7 for the appropriate value. Table 8 can be 
 used to find C values for undisturbed forest. 
 
 Once you have identified the table to use, 
 identify in column 1 of the table the cropping 
 sequence being used on the field segment being 
 evaluated. (Note that C values for double-crop- 
 ping sequences also are listed in the central and 
 southern Illinois tables.) If the rotation includes 
 soybeans, locate the row width in column 2. 
 
 The C value can now be found in the subse- 
 quent columns depending upon the type of 
 
Northern 
 Illinois Area 
 Use Table 4 
 
 Central 
 Illinois Area 
 Use Table 5 
 
 Southern 
 Illinois Area 
 Use Table 6 
 
 Figure 2. Cropping and management (C) factor map. 
 
 tillage that is used — conventional, reduced, or 
 no-till. (Each table also lists C values for some 
 more common combinations of these tillage 
 systems. See your SCS district conservationist 
 if you are using other combinations.) Conven- 
 tional tillage includes moldboard plowing, disk- 
 ing, planting, and cultivating. Reduced tillage 
 includes either a chisel plow or a disk as the 
 primary tillage tool, followed by a field culti- 
 vator or other secondary tillage tools that leave 
 a portion of the crop residue on the soil surface 
 after planting. No-till involves leaving the soil 
 surface nearly undisturbed and all crop residue 
 on the soil surface, thus providing maximum 
 soil erosion protection all season. 
 
 If you are using conventional tillage, you can 
 look under either the "fall plow" or "spring 
 plow" column to determine your C value. If you 
 are using a reduced tillage or no-till system, 
 however, you will first need to determine the 
 percentage of residue cover after planting before 
 finding your C value. 
 
 Residue soil surface cover after planting is 
 important because it provides soil protection 
 when the soil would otherwise be most vulner- 
 able to erosion: from seedbed preparation until 
 new crop growth provides soil cover. This time 
 period, when the ground is exposed to the ele- 
 ments, is also when the most intensive rains 
 usually occur. 
 
 There is a difference in the amount of residue 
 cover left on the soil surface by different crops 
 and how well this cover holds up under planting 
 operations. For example, a good field of corn 
 with a yield of over 100 bushels per acre will 
 leave about 90 to 95 percent of the soil surface 
 covered after harvest, while a good field of 
 soybeans with a yield of 40 to 45 bushels per acre 
 will leave about 80 to 85 percent. Because soy- 
 bean residue is more fragile, additional tillage 
 or travel over the field after harvest and during 
 planting will cover much more of the soybean 
 residue than the corn residue. 
 
 To estimate the percentage of soil surface still 
 covered by residue after planting, you can use 
 the point and line method. You can make your 
 own line, use any line, rope, or measuring tape 
 that has 100 evenly spaced points, or buy a 
 commercially made line. To make your own line, 
 take a piece of 1/8- or 3/16-inch nylon rope, 
 about 70 feet long, and tie 100 knots, 6 inches 
 apart. After the knots are tied, the rope should 
 shorten to just about 50 feet long. 
 
 Next, make a short loop at each end of the 
 rope and tie the ends to stakes. Then stretch the 
 line across the crop rows at approximately 45 
 degrees. The angle or position of the rope should 
 be adjusted so that both stakes are placed on a 
 row (see Figure 3, insert). 
 
 Standing over the rope and looking straight 
 down at the knots, count the knots that intersect 
 a piece of crop residue (Figure 3). Ignore small 
 pieces of residue that will decay quickly or that 
 are too small to intersect a raindrop. Even 
 though stones will intersect raindrops, do not 
 count them. The number of knots that intersect 
 a piece of crop residue equals the percentage of 
 soil surface covered. For example, if 75 knots 
 intersect residue, then the surface cover is 75 
 percent. Make a count on three other randomly 
 
selected areas in the field segment, and take an 
 average of the four areas. 
 
 Once you have determined the percentage of 
 soil surface covered, you can directly find the 
 appropriate C value in the table if you are 
 planting continuous corn or soybeans. Round 
 percentages to the nearest number of the col- 
 umn. If you are rotating crops, you will need to 
 estimate the average percentage of soil cover to 
 determine which column to use. For example, if 
 residue covered 20 percent of the soil surface 
 after corn was planted under a reduced tillage 
 system and 40 percent after soybeans were 
 planted, you would find your C value in the 30 
 percent column (20 + 40 ^ 2 = 30). 
 
 Please note that certain assumptions have 
 been made about the level of management, the 
 rotation sequence, and the tillage methods in 
 order to determine C values. These assumptions 
 are detailed in the footnotes to each table. 
 Therefore, you should take special care to read 
 the footnotes to make sure your practices and 
 the table's assumptions are the same. Each 
 footnote will give you instructions about what to 
 do if your practices are not the same as the 
 assumptions. Usually the footnote will instruct 
 you to multiply the value in the table by another 
 number to arrive at a C value that reflects your 
 individual practices. For example, as the gen- 
 eral note to Tables 4, 5, and 6 explains, all C 
 values in the tables assume that the field seg- 
 ment being evaluated is under a high level of 
 management with corn yields exceeding 100 
 
 bushels per acre; soybeans, 40 bushels; wheat, 
 45 bushels; oats, 60 bushels; and hay, 3 tons per 
 acre. The note instructs you to multiply the C 
 value in the table by 1.2 if the section is under a 
 medium level of management with lower yields. 
 Also please note that it is impossible to 
 predict all the individual variations in cropping 
 and management practices. If you cannot find 
 your exact practices in the appropriate table, 
 consult with your SCS district conservationist 
 or county Extension adviser about how you 
 might arrive at a reasonable value. 
 
 Conservation Practices (P) Factor 
 
 P represents the reduction in soil erosion 
 resulting from the use of conservation practices 
 that change the flow of runoff water, such as 
 contour farming, contour strip cropping, and 
 terracing. RxKXLSXCX Pthus equals the 
 soil erosion for a field segment with conserva- 
 tion practices applied. 
 
 The P factors for contour farming and contour 
 strip cropping are shown in Table 9. Because 
 contouring loses its effectiveness as slope length 
 increases, the table also gives the maximum 
 slope length on which contour farming is effec- 
 tive. Remember that contouring benefits are 
 obtained only when the field is relatively free 
 from gullies and depressions other than grassed 
 waterways. 
 
 When terraces are built on the contour and 
 used in combination with contour farming or 
 
 Figure 3. Overview (insert) and closeup of the point-and-line method of determining percentage of surface residue covering. 
 
contour strip cropping, you must use Tables 9 
 and 10 in conjunction to determine your P value. 
 (P values are not used when terraces are not 
 built on the contour. Parallel terrace systems 
 may not meet the contour criteria.) After choos- 
 ing values from both tables, you multiply these 
 values to arrive at the correct P value. 
 
 For example, assume that you have installed 
 level ridge tile outlet terraces on the contour, 120 
 feet apart, on a 5 percent slope, and contour 
 farmed. From Table 9 you would determine that 
 the contour factor is 0.5, while from Table 10 
 you would determine that the terrace factor is 
 0.6. You would then multiply the two factors to 
 arrive at a conservation practices (P) value of 
 0.3 (0.5 X 0.6 = 0.3). This is the value that you 
 would insert into the USLE to determine the 
 annual soil erosion rate. 
 
 Research has shown that trapped sediment 
 accumulates in the terrace channel and ridge 
 area to such an extent that this portion of the 
 land does not deteriorate significantly. The P 
 factor is proportioned to give credit where the 
 soil resource is maintained, that is, the factor 
 gets larger as the terrace interval gets wider, 
 thus giving less credit. Tile outlet terraces are 
 more effective in trapping sediment than open 
 outlets, and trapping efficiency goes down as 
 terrace grade increases. 
 
 Using the USLE 
 
 Working through Some Examples 
 
 How the land's physical features, the climate, 
 your crops, and your soil conservation practices 
 affect soil losses has been briefly discussed. The 
 USLE enables you to estimate your average 
 annual soil erosion losses for a cropping and 
 management system by multiplying all the 
 values assigned to factors that affect erosion. 
 Two examples of how to use the equation follow. 
 
 Example 1. Our first example assumes a farm 
 in Pike County, Illinois, with Fayette silt-loam 
 soil. The field segment is on a 5 percent slope 
 that is 300 feet long. The R value for Pike County 
 is 200 (Figure 1); the K value for Fayette silt- 
 loam is 0.37 (Table 1); the LS value is 0.93 (Table 
 3). The amount of soil lost annually under fallow 
 would thus be: 
 
 R K LS A 
 
 200 X 0.37 X 0.93 = 68.8 tons 
 
 Figure 2 indicates that the C values for Pike 
 County can be found in Table 5. The crop 
 
 rotation used is corn, soybeans, wheat, and a 
 clover catch crop. The field is conventionally 
 tilled and spring plowed. Residues are left on the 
 soil surface, and soybeans are drilled in 10-inch 
 rows. The field segment is under a high level of 
 management. According to Table 5, therefore, 
 the C factor is 0.22. (Note that footnote / indi- 
 cates to use the same C factor with or without 
 legume seeding.) We can now determine the 
 annual soil erosion loss that would occur if the 
 farm did not use conservation practices (P value): 
 
 C A 
 
 R X K X LS = 68.8 X 0.22 = 15 tons 
 
 If the field is contour farmed, a P factor of 0.5 
 (Table 9) would be multiplied by the above value 
 to determine A. As a result, the amount of soil 
 lost annually would be: 
 
 P A 
 
 R X K X LS X C = 15 X 0.5 = 7.6 tons 
 
 Because the soil loss tolerance level is 5 tons 
 per acre for a Fayette silt-loam soil that has 
 more than three inches of topsoil (Table 1), 7.6 
 tons per acre is well above the limit. 
 
 If the tillage system were changed to a reduced 
 tillage system that used primary tillage and two 
 secondary operations prior to planting, A would 
 be significantly lower. Let us assume that this 
 reduced tillage system resulted in an average 
 percentage of soil cover of 40 percent (the aver- 
 age of the percent residue cover after corn was 
 planted and after soybeans were planted). The C 
 value, according to Table 5, would change to 
 0.12. As a result, A would reduce to: 
 
 R K LS C P A 
 
 200 X 0.37 X 0.93 X 0.12 X 0.5 = 4.1 tons 
 
 Thus, this particular cropping and manage- 
 ment system would bring the average annual 
 soil erosion below the 5-ton soil erosion limit. 
 Other conservation options include terracing 
 the field, changing the crop rotation, using zero 
 till, or using a combination of practices. 
 
 Example 2, As a second example, let us assume 
 a farm in Perry County with a field segment of 
 Ava silt loam soil and a 5 percent slope that is 
 200 feet long. The R value for Perry County is 
 220 (Figure 1); the K value for silt loam is 0.43 
 (Table 1); the LS value is 0.76 (Table 3). The T 
 value for this soil is 4 tons per acre (Table 1). The 
 calculation below gives the annual soil loss 
 under fallow: 
 
 R K LS 
 
 220 X 0.43 X 0.76 
 
 A 
 71.9 tons 
 
Figure 2 indicates that the C value for Perry 
 County can be found in Table 6. On this seg- 
 ment, a corn and soybean rotation is grown 
 conventionally tilled and spring plowed. Both 
 crops are planted in 30-inch rows. The field 
 segment is under a medium level of manage- 
 ment with corn yields of 75 bushels per acre and 
 soybean yields of 33 bushels per acre. 
 
 According to the spring plow column in Table 
 6, therefore, the C value is 0.31. However, the 
 general note to the entire table indicates that the 
 value in the table must be multiplied by 1.2 
 when the field is under a medium level of 
 management. The C value for the field segment 
 in this example is thus actually 0.37 (0.31 X 1.2). 
 As a result, 26.6 tons of soil would be lost 
 annually without any conservation practices: 
 
 C A 
 
 R X K X LS = 71.9 X 0.37 = 26.6 tons 
 
 If the field is contour plowed, a P factor of 0.5 
 (Table 9) would be multiplied by the above value 
 to determine A under conservation practices: 
 
 P A 
 
 26.6 X 0.5 = 13.3 tons 
 
 This value is substantially above the T value of 
 4. The farmer would thus probably have to 
 change several practices to lower the value. 
 
 Perhaps the operator would consider chang- 
 ing to a no-till system. But would such a change 
 lower the soil loss to the established T value? A 
 quick answer can be obtained by looking at the 
 C value for a no-till corn-soybean rotation. 
 Assuming that such a no-till rotation would 
 achieve an average of 50 percent soil cover after 
 planting, the C value would be 0.11. However, if 
 the operator still plans a medium level of man- 
 agement, the C value actually would be 0.13 
 (0.11 X 1.2). As the calculation below indicates, 
 a no-till system would substantially reduce the 
 field's annual soil loss, nearly meeting the T 
 value and long-term state goals: 
 
 R K LS C P A 
 
 220 X 0.43 X 0.76 X 0.13 X 0.5 = 4.6 tons 
 
 Increasing the crop yield to meet the high level 
 of management would lower the soil loss to 
 below the T value: 
 
 R K LS C P A 
 
 220 X 0.43 X 0.76 X 0.11 X 0.5 = 3.95 tons 
 
 Of course, other options exist. The operator 
 could change the rotation (corn and double-crop, 
 no-till wheat and soybeans, for example, would 
 result in a C value of 0.08), use a combination 
 
 tillage system, terrace on the contour, or plant 
 narrow-row soybeans, to name a few. 
 
 As both these examples suggest, the use of the 
 USLE is not just limited to determining the 
 nearness of your soil loss to the T value. The 
 USLE also can be used to evaluate the effects of 
 your management decisions on the soil erosion 
 on your farm. 
 
 Solving the USLE for C 
 
 Let us assume that you have determined your 
 annual rate of soil loss using the USLE and 
 found that the rate is above the T value for your 
 soil type. If you do not have the option of 
 changing or adding conservation practices (P 
 value), you will want to know what particular 
 cropping and management practices (C value) 
 would lower your annual rate to or below the T 
 value. To solve the USLE for C, use the follow- 
 ing formula: 
 
 R X K X LS X P 
 
 Using the information from Example 1, we 
 could solve for an acceptable C factor: 
 
 5 5 
 
 200 X 0.37 X 0.93 X 0.5 
 
 34.4 
 
 = 0.14 
 
 After solving this equation, we would know 
 that any crop rotation and tillage system in 
 Table 5 with a Cfactorof 0.14 or less would help 
 us meet the annual soil erosion goal in that 
 example of 5 tons per acre. 
 
 Getting Help 
 
 The Soil Conservation Service (SCS) district 
 conservationist located in each of the soil and 
 water conservation district offices has for many 
 years used this method of estimating soil ero- 
 sion losses. Therefore, you may wish to have an 
 SCS representative assist you in determining 
 the appropriate factors to insert into the USLE. 
 The district conservationist can also help you 
 by recommending alternative soil erosion con- 
 trol practices. In addition, the SCS conserva- 
 tionist can supply you with C values for com- 
 binations of tillage systems for a rotation. 
 
8 
 
 Table 1. Soil Erodlbllity (K) and Tolerance (T) Values for Specific Illinois Soils 
 
 
 K 
 
 T 
 
 
 K 
 
 T 
 
 
 K 
 
 T 
 
 Soil type 
 
 factor 
 
 factor* 
 
 Soil type 
 
 factor 
 
 factor* 
 
 Soil type 
 
 factor 
 
 factor* 
 
 Ade98 
 
 0.17 
 
 5-5 
 
 Brooklyn 136 
 
 0.37 
 
 4 
 
 Drummer 152 
 
 0.28 
 
 5 
 
 Alford 308 
 
 .37 
 
 5-4 
 
 Bryce 235 
 
 .28 
 
 3 
 
 Drury 75 
 
 .37 
 
 5 
 
 Allison 306 
 
 .28 
 
 5 
 
 Burkhardt 961 
 
 .20 
 
 3-2 
 
 Dubuque 29 
 
 .37 
 
 4-3 
 
 Alvin 131 
 
 .24 
 
 5-4 
 
 Burnside 427 
 
 .37 
 
 4 
 
 Dunbarton 505 
 
 .37 
 
 2-1 
 
 Ambraw 302 
 
 .28 
 
 5 
 
 Cairo 590 
 
 .28 
 
 4 
 
 Du Page 321 
 
 .28 
 
 5 
 
 Andres 293 
 
 .28 
 
 5-4 
 
 Calamine 746 
 
 .28 
 
 5 
 
 Dupo 180 
 
 .37 
 
 5 
 
 Aptakisic 365 
 
 .37 
 
 5-4 
 
 Calco 400 
 
 .28 
 
 5 
 
 Durand 416 
 
 .32 
 
 5-4 
 
 Arenzville 78 
 
 .37 
 
 5 
 
 Camden 134 
 
 .37 
 
 5-4 
 
 Ebbert 48 
 
 .37 
 
 5 
 
 Argyle 227 
 
 .32 
 
 4-3 
 
 Canisteo 347 
 
 .28 
 
 5 
 
 Edgington 272 
 
 .32 
 
 5 
 
 Armiesburg 597 
 
 .28 
 
 5 
 
 Cape 422 
 
 .32 
 
 3 
 
 Edinburg 249 
 
 .37 
 
 4 
 
 Ashdale411 
 
 .32 
 
 5-4 
 
 Carmi 286 
 
 .20 
 
 4-3 
 
 Edmund 769 
 
 .32 
 
 2-1 
 
 Ashkum 232 
 
 .28 
 
 5 
 
 Casco 323 
 
 .32 
 
 3-2 
 
 Elburn 198 
 
 .28 
 
 5 
 
 Assumption 259 
 
 .32 
 
 4-3 
 
 Catlin 171 
 
 .32 
 
 5-4 
 
 Elcoll9 
 
 .37 
 
 4-3 
 
 Atkinson 661 
 
 .28 
 
 4-3 
 
 Channahon 315 
 
 .37 
 
 2-1 
 
 El Dara 264 
 
 .24 
 
 5-4 
 
 Atlas 7 
 
 .43 
 
 3-2 
 
 Chats worth 241 
 
 .43 
 
 3-2 
 
 Eleroy 547 
 
 .37 
 
 4-3 
 
 Atterberry 61 
 
 .32 
 
 5-4 
 
 Chauncey 287 
 
 .37 
 
 3 
 
 Elkhart 567 
 
 .32 
 
 5-4 
 
 Ava 14 
 
 .43 
 
 4-3 
 
 Chelsea 779 
 
 .17 
 
 5 
 
 ElHott 146 
 
 .28 
 
 4-3 
 
 Backbone 768 
 
 .24 
 
 4-3 
 
 Chute 282 
 
 .15 
 
 5 
 
 ElHson 137 
 
 .37 
 
 4-3 
 
 Banlic 787 
 
 .43 
 
 4 
 
 Cisne 2 
 
 .37 
 
 3 
 
 Elsah 475 
 
 .37 
 
 3 
 
 Harrington 443 
 
 .32 
 
 5-4 
 
 Clarence 147 
 
 .37 
 
 3-2 
 
 Emma 469 
 
 .37 
 
 5-4 
 
 Batavia 105 
 
 .32 
 
 5-4 
 
 Clarksdale 257 
 
 .37 
 
 5-4 
 
 Faxon 516 
 
 .28 
 
 4 
 
 Baxter 599 
 
 .32 
 
 4-3 
 
 Clarksville 471 
 
 .24 
 
 2-1 
 
 Fayette 280 
 
 .37 
 
 5-4 
 
 Baylis 472 
 
 .37 
 
 4-3 
 
 CHnton 18 
 
 .37 
 
 5-4 
 
 Fieldon 380 
 
 .28 
 
 5 
 
 Beardstown 188 
 
 .32 
 
 5-4 
 
 Coatsburg 660 
 
 .37 
 
 3-2 
 
 Fincastle 496 
 
 .37 
 
 5-4 
 
 Beasley 691 
 
 .43 
 
 3 
 
 Coffeen 428 
 
 .32 
 
 5 
 
 Fishhook 6 
 
 .43 
 
 3-2 
 
 Beaucoup 70 
 
 .32 
 
 5 
 
 Colo 402 
 
 .28 
 
 5 
 
 Flagg 419 
 
 .37 
 
 5-4 
 
 Bedford 598 
 
 .43 
 
 4-3 
 
 Colp 122 
 
 .43 
 
 3-2 
 
 Flagler 783 
 
 .20 
 
 4-3 
 
 Beecher 298 
 
 .37 
 
 3 
 
 Comfrey 776 
 
 .28 
 
 5 
 
 Flanagan 154 
 
 .28 
 
 5 
 
 Belknap 382 
 
 .37 
 
 5 
 
 Corwin 495 
 
 .32 
 
 5 
 
 Fox 327 
 
 .37 
 
 4-3 
 
 Berks 955 & 986" 
 
 .28 
 
 3-2 
 
 Cowden 112 
 
 .37 
 
 3 
 
 Frankfort 320 
 
 .37 
 
 3-2 
 
 Billett 332 
 
 .20 
 
 5-4 
 
 Coyne 764 
 
 .20 
 
 5-4 
 
 Friesland 781 
 
 .20 
 
 5-4 
 
 Birds 334 
 
 .43 
 
 5 
 
 Creal 337 
 
 .37 
 
 5-4 
 
 Frondorf 786 
 
 .32 
 
 3-2 
 
 Birkbeck 233 
 
 .37 
 
 5-4 
 
 Dakota 379 
 
 .28 
 
 4-3 
 
 Gale 413 
 
 .37 
 
 4-3 
 
 Blackoar 603 
 
 .28 
 
 5 
 
 Dana 56 
 
 .32 
 
 5-4 
 
 Genesee 431 
 
 .37 
 
 5 
 
 Blair 5 
 
 .43 
 
 3-2 
 
 Darmstadt 620 
 
 .43 
 
 3 
 
 Gilford 201 
 
 .20 
 
 5 
 
 Bloomfield 53 
 
 .15 
 
 5 
 
 Darroch 740 
 
 .28 
 
 5 
 
 Ginat 460 
 
 .43 
 
 4 
 
 Blount 23 
 
 .43 
 
 3-2 
 
 Darwin 71 
 
 .28 
 
 3 
 
 Gorham 162 
 
 .32 
 
 5 
 
 Bluford 13 
 
 .43 
 
 3-2 
 
 Del Rey 192 
 
 .43 
 
 3-2 
 
 Gosport 551 
 
 .43 
 
 3-2 
 
 Bodine 471 
 
 .24 
 
 2-1 
 
 Denny 45 
 
 .37 
 
 3 
 
 Goss 606 
 
 .24 
 
 2-1 
 
 Bold 35 
 
 .43 
 
 5-4 
 
 Denrock 262 
 
 .37 
 
 3-2 
 
 Granby 513 
 
 .17 
 
 5 
 
 Bonfield 493 
 
 .24 
 
 3 
 
 Derinda 417 
 
 .43 
 
 3-2 
 
 Grantsburg 301 
 
 .43 
 
 4-3 
 
 Bonnie 108 
 
 .43 
 
 5 
 
 Dickinson 87 
 
 .20 
 
 4-3 
 
 Grays 698 
 
 .32 
 
 5-4 
 
 Booker 457 
 
 .37 
 
 5 
 
 Disco 266 
 
 .20 
 
 4 
 
 Grellton 780 
 
 .24 
 
 5-4 
 
 Boone 397 
 
 .15 
 
 4 
 
 Dodge 24 
 
 .37 
 
 4-3 
 
 Griswold 363 
 
 .32 
 
 5-4 
 
 Bowdre 589 
 
 .28 
 
 4 
 
 Dodgeville 40 
 
 .32 
 
 4-3 
 
 Hamburg 30 
 
 .43 
 
 5 
 
 Bowes 792 
 
 .32 
 
 5-4 
 
 Dorchester 239 
 
 .37 
 
 5 
 
 Harco 484 
 
 .32 
 
 5 
 
 Boyer 706 
 
 .17 
 
 4-3 
 
 Douglas 128 
 
 .32 
 
 5-4 
 
 Harpster 67 
 
 .28 
 
 5 
 
 Brandon 956" 
 
 .37 
 
 3-2 
 
 Dowagiac 346 
 
 .28 
 
 4-3 
 
 Harrison 127 
 
 .32 
 
 5-4 
 
 Brenton 149 
 
 .28 
 
 5 
 
 Downs 386 
 
 .32 
 
 5-4 
 
 Hartsburg 244 
 
 .28 
 
 5 
 
 Broadwell 684 
 
 0.32 
 
 5-4 
 
 Dresden 325 
 
 0.28 
 
 4-3 
 
 Harvard 344 
 
 0.32 
 
 5-4 
 
 Source: Illinois Technical Guide, Section 2, Soil Conservation Service, Champaign, Illinois. 
 
 ^The first number in the column applies to soils with no erosion to moderate erosion; the second number, where it appears, applies to 
 
 seriously eroded land with three inches or less topsoil remaining. 
 
 ''In complexes with other soils. 
 
Table 1. Continued 
 
 
 K 
 
 T 
 
 
 K 
 
 T 
 
 
 K 
 
 T 
 
 Soil type 
 
 factor 
 
 factor^ 
 
 Soil type 
 
 factor 
 
 factor' 
 
 Soil type 
 
 factor 
 
 factor' 
 
 Hayfield 771 
 
 0.32 
 
 5 
 
 Lorenzo 318 
 
 0.28 
 
 3-2 
 
 Ockley 387 
 
 0.37 
 
 5-4 
 
 Haymond 331 
 
 .37 
 
 5 
 
 Lukin 167 
 
 .37 
 
 4-3 
 
 Oconee 113 
 
 .37 
 
 3-2 
 
 Hennepin 25 
 
 .32 
 
 5-4 
 
 Marissa 176 
 
 .37 
 
 4 
 
 Octagon 656 
 
 .32 
 
 5-4 
 
 Herbert 62 
 
 .32 
 
 5 
 
 Markham 531 
 
 .37 
 
 3-2 
 
 Odell 490 
 
 .32 
 
 5-4 
 
 Herrick 46 
 
 .28 
 
 5 
 
 Markland 467 
 
 .43 
 
 3-2 
 
 Ogle 412 
 
 .28 
 
 5-4 
 
 Hesch 390 
 
 .20 
 
 4-3 
 
 Marseilles 549 
 
 .37 
 
 4-3 
 
 Okaw 84 
 
 .43 
 
 3-2 
 
 Hickory 8 
 
 .37 
 
 5-4 
 
 Marshan 772 
 
 .28 
 
 4 
 
 Onarga 150 
 
 .20 
 
 4-3 
 
 High Gap 556 
 
 .37 
 
 4-3 
 
 Martinsville 570 
 
 .37 
 
 5-4 
 
 Oneco 752 
 
 .32 
 
 5-4 
 
 Hitt 506 
 
 .32 
 
 5-4 
 
 Martinton 189 
 
 .32 
 
 4-3 
 
 Orio 200 
 
 .28 
 
 4 
 
 Homer 326 
 
 .37 
 
 4 
 
 Massbach 753 
 
 .32 
 
 4-3 
 
 Orion 415 
 
 .28 
 
 5 
 
 Hononegah 354 
 
 .15 
 
 4 
 
 Matherton 342 
 
 .20 
 
 4-3 
 
 Otter 76 
 
 .28 
 
 5 
 
 Hoopeston 172 
 
 .20 
 
 4 
 
 Maumee 89 
 
 .17 
 
 5 
 
 Palsgrove 429 
 
 .32 
 
 4-3 
 
 Hosmer 214 
 
 .43 
 
 4-3 
 
 McFain 248 
 
 .28 
 
 4 
 
 Pana 256 
 
 .32 
 
 4-3 
 
 Hoyleton 3 
 
 .37 
 
 3-2 
 
 McGary 173 
 
 .43 
 
 3-2 
 
 Papineau 42 
 
 .20 
 
 4 
 
 Huey 120 
 
 .43 
 
 2 
 
 McHenry 310 
 
 .37 
 
 5-4 
 
 Parkville 619 
 
 .28 
 
 5 
 
 Huntington 600 
 
 .28 
 
 5 
 
 Medway 682 
 
 .32 
 
 5 
 
 Parr 221 
 
 .32 
 
 5-4 
 
 Huntsville 77 
 
 .28 
 
 5 
 
 Metea 205 
 
 .17 
 
 5-4 
 
 Patton 142 
 
 .28 
 
 5 
 
 Hurst 338 
 
 .43 
 
 3-2 
 
 Miami 27 
 
 .37 
 
 5-4 
 
 Pecatonica 21 
 
 .37 
 
 5-4 
 
 lona 307 
 
 .37 
 
 5-4 
 
 Middletown 685 
 
 .37 
 
 5-4 
 
 Pella 153 
 
 .28 
 
 5 
 
 Ipava 43 
 
 .28 
 
 5 
 
 Milford 69 
 
 .28 
 
 5 
 
 Peotone 330 
 
 .28 
 
 5 
 
 Iva 454 
 
 .43 
 
 4-3 
 
 Millbrook 219 
 
 .32 
 
 5-4 
 
 Petrolia 288 
 
 .32 
 
 4 
 
 Jacob 85 
 
 .28 
 
 3 
 
 Millington 82 
 
 .28 
 
 5 
 
 Piasa 474 
 
 .37 
 
 3 
 
 Jasper 440 
 
 .28 
 
 5 
 
 Millsdale317 
 
 .32 
 
 4 
 
 Pike 583 
 
 .37 
 
 5-4 
 
 Joliet 314 
 
 .28 
 
 3 
 
 Milroy 187 
 
 .24 
 
 4 
 
 Pillot 159 
 
 .32 
 
 4-3 
 
 Joslin 763 
 
 .32 
 
 5-4 
 
 Mokena 295 
 
 .28 
 
 4-3 
 
 Piopolis 420 
 
 .43 
 
 4 
 
 Joy 275 
 
 .28 
 
 5-4 
 
 Mona 448 
 
 .28 
 
 4-3 
 
 Plainfield 54 
 
 .17 
 
 5 
 
 Jules 28 
 
 .37 
 
 5 
 
 Monee 229 
 
 .37 
 
 3-2 
 
 Piano 199 
 
 .32 
 
 5-4 
 
 Juneau 782 
 
 .37 
 
 5 
 
 Montgomery 465 
 
 .37 
 
 5 
 
 Plattville 240 
 
 .32 
 
 5-4 
 
 Kane 343 
 
 .28 
 
 4 
 
 Montmorenci 57 
 
 .32 
 
 5-4 
 
 Port Byron 277 
 
 .32 
 
 5-4 
 
 Kankakee 494 
 
 .20 
 
 4 
 
 Morley 194 
 
 .43 
 
 3-2 
 
 Proctor 148 
 
 .32 
 
 5-4 
 
 Karnak 426 
 
 .32 
 
 3 
 
 Morocco 501 
 
 .17 
 
 5 
 
 Racoon 109 
 
 .43 
 
 3 
 
 Keller 470 
 
 .37 
 
 3-2 
 
 Mt. Carroll 268 
 
 .32 
 
 5-4 
 
 Raddle 430 
 
 .32 
 
 5-4 
 
 Keltner 546 
 
 .32 
 
 4-3 
 
 Mundelein 442 
 
 .28 
 
 5-4 
 
 Radford 74 
 
 .28 
 
 5 
 
 Kendall 242 
 
 .37 
 
 5-4 
 
 Muren 453 
 
 .37 
 
 5-4 
 
 Rantoul 238 
 
 .28 
 
 3 
 
 Keomah 17 
 
 .37 
 
 5 
 
 Muscatine 41 
 
 .28 
 
 5 
 
 Raub 481 
 
 .28 
 
 5 
 
 Kernan 554 
 
 .37 
 
 4-3 
 
 Muskingum 425 
 
 .28 
 
 3-2 
 
 Reddick 594 
 
 .28 
 
 5 
 
 Kidder 361 
 
 .32 
 
 5-4 
 
 Myrtle 414 
 
 .32 
 
 5-4 
 
 Reesville 723 
 
 .37 
 
 5 
 
 Knight 191 
 
 .32 
 
 4 
 
 Nappanee 228 
 
 .43 
 
 3-2 
 
 Richview 4 
 
 .32 
 
 5-4 
 
 La Hogue 102 
 
 .28 
 
 5 
 
 Nasset 731 
 
 .32 
 
 4-3 
 
 Ridgeville 151 
 
 .20 
 
 4 
 
 Lamont 175 
 
 .24 
 
 5-4 
 
 Negley 585 
 
 .32 
 
 3-2 
 
 Ridott 743 
 
 .32 
 
 4-3 
 
 Landes 304 
 
 .20 
 
 5 
 
 Neotoma 976 & 977" 
 
 .20 
 
 3-2 
 
 Riley 452 
 
 .28 
 
 4 
 
 La Rose 60 
 
 .32 
 
 5-4 
 
 Newberry 217 
 
 .37 
 
 3 
 
 Ringwood 297 
 
 .28 
 
 5-4 
 
 Lawler 647 
 
 .28 
 
 4 
 
 New Glarus 928 & 
 
 
 
 Ripon 324 
 
 .32 
 
 4-3 
 
 Lawndale 683 
 
 .32 
 
 5 
 
 561" 
 
 .37 
 
 4-3 
 
 Ritchey 311 
 
 .37 
 
 2-1 
 
 Lawson 451 
 Lax 628 
 
 .28 
 .43 
 
 5 
 4-3 
 
 Niota 261 
 Oakville 741 
 
 .37 
 0.15 
 
 3 
 5 
 
 Robbs 335 
 Roby 184 
 
 .43 
 .24 
 
 4-3 
 4 
 
 Lisbon 59 
 
 .28 
 
 5-4 
 
 
 
 
 Rockton 503 
 
 .28 
 
 4-3 
 
 Littleton 81 
 
 .28 
 
 5 
 
 
 
 
 Rodman 93 
 
 .20 
 
 3-2 
 
 Lomax 265 
 
 .28 
 
 5 
 
 
 
 
 Romeo 316 
 
 0.37 
 
 1 
 
 Loran 572 
 
 0.28 
 
 4-3 
 
 
 
 
 
 
 
 ""The first number in the column applies to soils with no erosion to moderate erosion; the second number, where it appears, applies to 
 seriously eroded land with three inches or less topsoil remaining. 
 ''In complexes with other soils. 
 
10 
 
 Table 1. Continued 
 
 
 K 
 
 T 
 
 
 K 
 
 T 
 
 
 K 
 
 T 
 
 Soil type 
 
 factor 
 
 factor" 
 
 Soil type 
 
 factor 
 
 factor' 
 
 Soil type 
 
 factor 
 
 factor" 
 
 Ross 73 
 
 0.32 
 
 5 
 
 Strawn 224 
 
 0.37 
 
 4-3 
 
 Washtenaw 296 
 
 0.37 
 
 5 
 
 Rowe 230 
 
 .28 
 
 5 
 
 Streator 435 
 
 .28 
 
 3 
 
 Watseka 49 
 
 .17 
 
 2 
 
 Rozetta 279 
 
 .37 
 
 5-4 
 
 Stronghurst 278 
 
 .37 
 
 5-4 
 
 Wauconda 697 
 
 .32 
 
 4-3 
 
 Ruark 178 
 
 .24 
 
 4 
 
 Sunbury 234 
 
 .32 
 
 5-4 
 
 Waukee 727 
 
 .24 
 
 4-3 
 
 Rush 791 
 
 .37 
 
 5-4 
 
 Swygert 91 
 
 .43 
 
 3-2 
 
 Waukegan 564 
 
 .32 
 
 4-3 
 
 Rushville 16 
 
 .43 
 
 3 
 
 Sylvan 19 
 
 .37 
 
 5-4 
 
 Waupecan 369 
 
 .32 
 
 4-3 
 
 Russell 322 
 
 .37 
 
 5-4 
 
 Symerton 294 
 
 .32 
 
 5-4 
 
 Wea 398 
 
 .32 
 
 5-4 
 
 Rutland 375 
 
 .32 
 
 5-4 
 
 Tallula 34 
 
 .32 
 
 5-4 
 
 Weinbach 461 
 
 .43 
 
 4-3 
 
 Sabina 236 
 
 .37 
 
 5-4 
 
 Tama 36 
 
 .32 
 
 5-4 
 
 Weir 165 
 
 .43 
 
 4 
 
 Sable 68 
 
 .28 
 
 5 
 
 Tamalco 581 
 
 .43 
 
 3-2 
 
 Wellston 339 
 
 .37 
 
 4-3 
 
 Saffell 956" 
 
 .20 
 
 4 
 
 Tell 565 
 
 .37 
 
 4-3 
 
 Wenona 388 
 
 .32 
 
 4-3 
 
 Sarpy 92 
 
 .15 
 
 5 
 
 Terril 587 
 
 .24 
 
 5 
 
 Wesley 141 
 
 .24 
 
 3-2 
 
 Saude 774 
 
 .28 
 
 4-3 
 
 Thebes 212 
 
 .37 
 
 4-3 
 
 Westland 300 
 
 .28 
 
 5 
 
 Sawmill 107 
 
 .28 
 
 5 
 
 Thorp 206 
 
 .37 
 
 4 
 
 Westmore 940" 
 
 .37 
 
 4 
 
 Saybrook 145 
 
 .32 
 
 5-4 
 
 Tice 284 
 
 .32 
 
 4 
 
 Westville 22 
 
 .37 
 
 5-4 
 
 Saylesville 370 
 
 .37 
 
 3-2 
 
 Timula 271 
 
 .37 
 
 5-4 
 
 Whalan 509 
 
 .32 
 
 4-3 
 
 Schapville 418 
 
 .32 
 
 3-2 
 
 Titus 404 
 
 .32 
 
 4 
 
 WheeHng 463 
 
 .32 
 
 4-3 
 
 Sciotoville 462 
 
 .37 
 
 4-3 
 
 Toronto 353 
 
 .32 
 
 5-4 
 
 Whitson 116 
 
 .43 
 
 4 
 
 Seaton 274 
 
 .37 
 
 5-4 
 
 Traer 633 
 
 .37 
 
 5 
 
 Will 329 
 
 .28 
 
 4 
 
 Selma 125 
 
 .28 
 
 5 
 
 Trempealeau 765 
 
 .28 
 
 3 
 
 Wingate 348 
 
 .32 
 
 5-4 
 
 Sexton 208 
 
 .43 
 
 4 
 
 Troxel 197 
 
 .28 
 
 5 
 
 Winnebago 728 
 
 .32 
 
 5-4 
 
 Shadeland 555 
 
 .37 
 
 4 
 
 Uniontown 482 
 
 .37 
 
 4-3 
 
 Woodbine 410 
 
 .37 
 
 4-3 
 
 Sharon 72 
 
 .37 
 
 5 
 
 Ursa 605 
 
 .37 
 
 4-3 
 
 Worthen 37 
 
 .32 
 
 5-4 
 
 Shiloh 138 
 
 .28 
 
 3 
 
 Varna 223 
 
 .32 
 
 4-3 
 
 Wynoose 12 
 
 .43 
 
 3 
 
 Shoals 424 
 
 .37 
 
 5 
 
 Velma 250 
 
 .32 
 
 4-3 
 
 Xenia 291 
 
 .37 
 
 5-4 
 
 Shullsburg 745 
 
 .32 
 
 4-3 
 
 Virden 50 
 
 .28 
 
 5 
 
 Zanesville 340 
 
 .43 
 
 3-2 
 
 Sidell 55 
 
 .32 
 
 5-4 
 
 Virgil 104 
 
 .32 
 
 5-4 
 
 Zipp 524 
 
 .28 
 
 5 
 
 Sogn 504 
 
 .28 
 
 1 
 
 Wabash 83 
 
 .28 
 
 5 
 
 Zurich 696 
 
 .37 
 
 5-4 
 
 Sparta 88 
 
 .17 
 
 5 
 
 Wagner 26 
 
 .28 
 
 3 
 
 Zwingle 576 
 
 0.43 
 
 3-2 
 
 St. Charles 243 
 
 .37 
 
 5-4 
 
 Wakeland 333 
 
 .37 
 
 5 
 
 
 
 
 St. Clair 560 
 
 .37 
 
 3-2 
 
 Walshville 584 
 
 .43 
 
 3-2 
 
 
 
 
 Starks 132 
 
 .37 
 
 5 
 
 Ware 456 
 
 .32 
 
 4 
 
 
 
 
 Stockland 155 
 
 .20 
 
 2-1 
 
 Warsaw 290 
 
 .28 
 
 4-3 
 
 
 
 
 Stonelick 665 
 
 .24 
 
 5 
 
 Wartrace 215 
 
 0.37 
 
 5-4 
 
 
 
 
 Stoy 164 
 
 0.43 
 
 4-3 
 
 
 
 
 
 
 
 "The first number in the column applies to soils with no erosion to moderate erosion; the second number, where it appears, applies to 
 seriously eroded land with three inches or less topsoil remaining. 
 In complexes with other soils. 
 
Table 2. Soil Erodlbility (K) Values for Certain General Soil Types 
 
 11 
 
 Soil type 
 
 K Soil loss tolerance" 
 
 value (tons/acre/year) 
 
 Dark and moderately dark soil somewhat wet and with good perme- 
 ability (for example, Muscatine, Ipava, Flanagan, and Herrick) 0.28 5 
 
 Dark and moderately dark prairie soil with good permeability (for 
 
 example, Catlin, Harrison, Proctor, Saybrook, and Tama) .32 5-4 
 
 Dark and light prairie soil with restricted permeability (for example, 
 
 Cisne, Cowden, and Clarence) .37 3-2 
 
 Dark prairie soil with very restricted permeability (for example, 
 
 Swygert) .43 3-2 
 
 Light-colored forest soil with good permeability (for example, Alford, 
 
 Birkbeck, Clinton, and Fayette) .37 5-4 
 
 Light-colored forest soil with restricted permeability (for example, Ava, 
 
 Blount, Grantsburg, Hosmer, and Wynoose) .43 4-3 
 
 Sandy loam soil (for example, Dickinson, Onarga, and Ridgeville) .... .20 4-3 
 
 Loose sand (for example, Ade, Plainfield, and Sparta) 0.17 5 
 
 Note: See Table 1 for a more complete listing of K values for specific soils. 
 
 "The first number represents the soil loss tolerance for soils with less than severe soil erosion. The second number, 
 where it appears, represents the soil loss tolerance for soils with severe soil erosion and strong evidence of subsoil 
 mixing with the topsoil. 
 
 Table 3. Slope Length and Steepness (LS) 
 
 Values 
 
 for Specific Combinations of Length and Steepness 
 
 Slope 
 steepness 
 
 
 
 
 
 Slope length (feet) 
 
 
 
 
 
 (percent) 
 
 25 
 
 50 
 
 75 
 
 100 
 
 150 200 
 
 300 
 
 400 
 
 500 
 
 600 
 
 1 0.01 0.11 0.12 0.13 0.15 0.16 0.18 0.19 0.20 0.21 
 
 2 0.13 0.16 0.19 0.20 0.23 0.25 0.28 0.31 0.33 0.34 
 
 3 0.19 0.23 0.26 0.29 0.33 0.35 0.40 0.44 0.47 0.49 
 
 4 0.23 0.30 0.36 0.40 0.47 0.53 0.62 0.70 0.76 0.82 
 
 5 0.27 0.38 0.46 0.54 0.66 0.76 0.93 1.07 1.20 1.31 
 
 6 0.34 0.48 0.58 0.67 0.82 0.95 1.17 1.35 1.50 1.65 
 
 8 0.50 0.70 0.86 0.99 1.21 1.41 1.72 1.98 2.22 2.43 
 
 10 0.69 0.97 1.19 1.37 1.68 1.94 2.37 2.74 3.06 3.36 
 
 12 0.90 1.28 1.56 1.80 2.21 2.55 3.13 3.61 4.04 4.42 
 
 14 1.15 1.62 1.99 2.30 2.81 3.25 3.98 4.59 5.13 5.62 
 
 16 1.42 2.01 2.46 2.84 3.48 4.01 4.92 5.68 6.35 6.95 
 
 18 1.72 2.43 2.97 3.43 4.21 4.86 5.95 6.87 7.68 8.41 
 
 20 2.04 2.88 3.53 4.08 5.00 5.77 7.07 8.16 9.12 10.0 
 
12 
 
 Table 4. Cropping and Management (C) Values 
 
 for Northern 
 
 Illinois 
 
 
 
 
 
 
 
 
 Soybean 
 
 row 
 width" 
 
 Conventional 
 tillage*^ 
 
 Chisel, disk 
 
 20% 30% 
 
 or ridge**® 
 
 40% 50% 
 
 All corn 
 
 and 
 
 soybeans planted no-till* 
 
 
 Crop 
 sequence* 
 
 Fall 
 plow 
 
 Spring 
 plow 
 
 
 20% 30% 
 
 40% 
 
 50% 
 
 60% 
 
 70% 
 
 80% 
 
 90% 
 
 Continuous 
 soybeans 
 
 wide 
 narrow 
 
 .44 
 .36 
 
 .39 
 .32 
 
 .36 
 .31 
 
 .32 
 .29 
 
 
 
 .25 .20 
 .21 .18 
 
 .16 
 .15 
 
 
 
 
 
 
 Continuous 
 corn 
 
 
 .34 
 
 .29 
 
 .21 
 
 .18 
 
 .15 
 
 .12 
 
 
 
 
 .08 
 
 .06 
 
 .04 
 
 .03 
 
 C-Sb 
 
 wide 
 
 .38 
 
 .33 
 
 .28 
 
 .24 
 
 .20 
 
 .19 
 
 
 .18 
 
 .14 
 
 .10 
 
 .09 
 
 
 
 
 narrow 
 
 .34 
 
 .30 
 
 .27 
 
 .23 
 
 .19 
 
 .18 
 
 
 .17 
 
 .14 
 
 .10 
 
 .09 
 
 
 
 C-C-Sb 
 
 wide 
 
 .36 
 
 .32 
 
 .26 
 
 .22 
 
 .18 
 
 .17 
 
 
 
 .14 
 
 .11 
 
 .08 
 
 .07 
 
 
 
 narrow 
 
 .34 
 
 .30 
 
 .25 
 
 .21 
 
 .17 
 
 .16 
 
 
 
 .14 
 
 .11 
 
 .08 
 
 .07 
 
 
 C-Sb-G' 
 
 wide 
 
 .27 
 
 .25 
 
 .18 
 
 .16 
 
 .13 
 
 .12 
 
 
 .10 
 
 .07 
 
 .05 
 
 .04 
 
 
 
 
 narrow 
 
 .25 
 
 .23 
 
 .17 
 
 .15 
 
 .12 
 
 .11 
 
 
 .09 
 
 .07 
 
 .05 
 
 .04 
 
 
 
 C-C-G-M^*^ 
 
 
 .14 
 
 .12 
 
 .10 
 
 .09 
 
 .08 
 
 .07 
 
 
 
 
 .04 
 
 .03 
 
 .02 
 
 .02 
 
 C-Sb-G-M9'' 
 
 wide 
 
 .15 
 
 .13 
 
 .10 
 
 .09 
 
 .08 
 
 .08 
 
 
 .05 
 
 .04 
 
 .03 
 
 .03 
 
 
 
 
 narrow 
 
 .13 
 
 .12 
 
 .10 
 
 .09 
 
 .08 
 
 .07 
 
 
 .05 
 
 .04 
 
 .03 
 
 .03 
 
 
 
 C-Sb-M-Mfl-»' 
 
 wide 
 
 .12 
 
 .10 
 
 .08 
 
 .07 
 
 .06 
 
 .06 
 
 
 .03 
 
 .02 
 
 .02 
 
 .01 
 
 
 
 
 narrow 
 
 .11 
 
 .08 
 
 .07 
 
 .07 
 
 .06 
 
 .06 
 
 
 .03 
 
 .02 
 
 .02 
 
 .01 
 
 
 
 C-G-M9*' 
 
 
 .09 
 
 .07 
 
 .07 
 
 .07 
 
 .06 
 
 .06 
 
 
 
 
 .03 
 
 .02 
 
 .02 
 
 .01 
 
 C-M-M-Mfl*^ 
 
 
 .05 
 
 .04 
 
 
 
 
 
 
 
 
 .01 
 
 .008 
 
 .006 
 
 .006 
 
 Combination Tillage Systems 
 
 Crop 
 sequence' 
 
 C-Sb 
 
 Tillage systems used for sequence 
 
 Corn after soybeans, no-till; soybeans after corn, 
 fall chisel, spring secondary tillage 
 
 Soybean row 
 width*' 
 
 wide 
 narrow 
 
 Percent soil cover after 
 planting each crop 
 
 20% 
 
 .23 
 
 .21 
 
 30% 
 
 .19 
 
 .18 
 
 40% 
 
 .15 
 .14 
 
 Source: C values for this table were calculated from the Soil Conservation Service's Illinois Technical Guide, Section I-C (EI Curve 14). 
 NOTE: Values in this table are based on high level management with yields equal to or exceeding the following: corn, 100 
 bushels per acre; soybeans, 40 bushels per acre; wheat, 45 bushels per acre; oats, 60 bushels per acre; meadow, 3 tons per 
 acre. For medium level management, multiply values by 1.2. 
 
 *In this column, C = corn, Sb = soybeans, G ~ small grain, M = meadow, and W = wheat. 
 
 "Use the wide-row values for soybean rows wider than 20 inches. Use the narrow-row values for soybean rows planted 20 
 inches or less, including drilled. 
 
 ''Where corn residue is removed for silage or other purposes, multiply the C value by 1.2 for intensive rotations such as 
 corn and soybeans or corn, corn, and soybeans. Do not multiply the C value by any number for the less intensive 
 rotations, including meadow crops, where crop residue is removed. 
 
 "Values for chisel and disk systems are for aSi primary tillage and two secondary tillage operations prior to planting. For 
 primary tillage in the spring or ridge planting up and down hill, multiply the appropriate C values by 0.9 in northern 
 Illinois, by 0.8 in central Illinois, and by 0.7 in southern Illinois. For ridge planting on the contour, multiply the 
 appropriate C value by 0.7 in northern Illinois, by 0.6 in central Illinois, and by 0.5 in southern Illinois. Ridge planting is 
 applicable only for row crops following row crops. 
 
 ®The percent figures represent the percentage of the soil surface covered after planting. The percent figure for a rotation is 
 equal to the average cover for the crop sequence. For example, if, in a corn-soybean rotation, residue covered 20 percent of 
 the soil surface after corn was planted and 60 percent after soybeans were planted, the average cover would be 40 percent, 
 and you would find your C value in the 40 percent column. 
 
 The same C values are applicable for small grain both with and without a catch crop. 
 
 ^Chisel and disk C values are calculated for spring-plow, conventional tillage when corn follows meadow. 
 
 ''Values are based on a sod or grass legume mixture consisting of at least 50 percent grass and established at least one full 
 growing season. If meadow is primarily legume, multiply the appropriate C value by 1.2. 
 
13 
 
 Table 5. Cropping and Management (C) Values for Central Illinois 
 
 Crop 
 sequence" 
 
 Soybean 
 
 row 
 width" 
 
 Conventional 
 tillage*^ 
 
 Fall Spring 
 plow plow 
 
 Chisel, disk, or ridge**'* 
 
 20% 30% 40% 50% 
 
 All corn and soybeans planted no-till' 
 
 20% 30% 40% 50% 60% 70% 80% 90% 
 
 Continuous 
 
 soybeans wide .48 .41 
 
 narrow .40 .30 
 
 Continuous 
 
 corn .36 .29 
 
 C-Sb wide .41 .35 
 
 narrow .36 .31 
 
 C-C-Sb wide .39 .33 
 
 narrow .36 .30 
 
 C-C-Sb-G' wide .32 .26 
 
 narrow .29 .24 
 
 C-Sb-G' wide .30 .25 
 
 narrow .27 .22 
 
 C-Sb-G-Mfl'*' wide .17 .13 
 
 narrow .14 .12 
 
 C-Sb-Mfl-*' wide .19 .15 
 
 narrow .16 .13 
 
 C-C-C-M-M-Ms-*^ .10 .08 
 
 C-M-M-Ma-"^ .05 .04 
 
 .37 
 .31 
 
 .21 
 
 .28 
 .27 
 
 .26 
 .25 
 
 .19 
 
 .18 
 
 .18 
 .17 
 
 .10 
 .10 
 
 .11 
 .10 
 
 .06 
 
 .35 
 .30 
 
 .18 
 
 .24 
 .23 
 
 .22 
 .21 
 
 .16 
 .16 
 
 .15 
 .15 
 
 .09 
 .09 
 
 .10 
 .09 
 
 .05 
 
 15 
 
 20 
 19 
 
 18 
 18 
 
 13 
 13 
 
 13 
 12 
 
 08 
 08 
 
 09 
 09 
 
 .12 
 
 .19 
 .18 
 
 .16 
 .16 
 
 .11 
 .11 
 
 .11 
 .10 
 
 .08 
 .08 
 
 .08 
 .08 
 
 05 .05 
 
 26 
 20 
 
 20 
 16 
 
 .16 
 .13 
 
 .18 
 
 .17 
 
 .09 .06 .05 
 
 03 
 
 .09 
 .09 
 
 .05 
 .05 
 
 .04 
 .03 
 
 .13 
 .13 
 
 .15 
 .14 
 
 .09 
 .09 
 
 .07 
 .06 
 
 .04 
 .04 
 
 .03 
 .03 
 
 .01 
 
 .10 
 .09 
 
 .11 
 .10 
 
 .07 
 .06 
 
 .05 
 .05 
 
 .03 
 .03 
 
 .02 
 .02 
 
 .09 
 .09 
 
 .08 
 .08 
 
 .05 
 .05 
 
 .04 
 .03 
 
 .02 
 .02 
 
 .02 
 .02 
 
 .07 
 .07 
 
 .04 
 .04 
 
 .01 .01 
 .008 .008 
 
 .005 .005 
 
 Combination Tillage Systems 
 
 Crop 
 sequence^ 
 
 C-Sb 
 
 C-C-Sb 
 
 Tillage systems used for sequence 
 
 Corn after soybeans, no-till; soybeans after corn, 
 fall chisel, spring secondary tillage 
 
 Corn after soybeans, no-till; corn after corn, fall 
 chisel, spring secondary tillage; soybeans after 
 corn, fall chisel, spring secondary tillage 
 
 Soybean row 
 
 Percent soil cover after 
 planting each crop 
 
 width" 
 
 20% 
 
 30% 
 
 40%) 
 
 wide 
 narrow 
 
 .22 
 
 .21 
 
 .18 
 .17 
 
 .14 
 
 .14 
 
 wide 
 narrow 
 
 .22 
 
 .21 
 
 .18 
 .17 
 
 .14 
 .14 
 
 Double-Cropping Systems 
 
 Crop 
 sequence' Tillage systems used for double-cropping sequence 
 
 C-W/Sb Corn, conventional tillage, fall plow; disk for wheat 
 
 and soybeans 
 
 C-W/Sb Corn, fall chisel, spring secondary tillage, 30 percent 
 soil cover after planting; disk for wheat and 
 soybeans 
 
 C-W/Sb Same as above except no-till for soybeans 
 
 C-W/Sb Corn, no-till; wheat, disk; soybeans, no-till 
 
 C-W/Sb No-till for corn, wheat, and soybeans 
 
 C value 
 .26 
 
 .20 
 .19 
 .11 
 .09 
 
 Source: C values for this table were calculated from the Soil Conservation Service's Illinois Technical Guide, Section I-C (EI Curve 16). 
 
 NOTE: The footnotes for Table 5 are the same as for Table 4. Please be sure to read all footnotes because values in this 
 table are based upon assumptions detailed in the footnotes and your practices could be different from these assumptions. 
 NOTE: Values in this table are based on high level management with yields equal to or exceeding the following: corn, 100 
 bushels per acre; soybeans, 40 bushels per acre; wheat, 45 bushels per acre; oats, 60 bushels per acre; meadow, 3 tons per 
 acre. For medium level management, multiply values by 1.2. 
 
14 
 
 Table 6. Cropping and Management (C) Values for Southern Illinois 
 
 
 Soybean 
 
 row 
 width" 
 
 Conventional 
 tillage*^ 
 
 Chise 
 
 20% 
 
 I, disk 
 30% 
 
 or ri 
 
 40% 
 
 dge"*-' 
 
 50% 
 
 
 All onvn nnH s 
 
 soybeans planted n 
 
 o-till* 
 
 
 Crop 
 sequence* 
 
 Fall Spring 
 plow plow 
 
 * *** w-.-.-. *^M.m.-»^ m. 
 
 
 20% 30% 40% 
 
 50% 
 
 60% 
 
 70% 
 
 80% 90% 
 
 Continuous 
 corn 
 
 
 .38 .25 
 
 .20 
 
 .18 
 
 .15 
 
 .13 
 
 
 
 .07 
 
 .05 
 
 .04 .03 
 
 Continuous 
 soybeans 
 
 wide 
 narrow 
 
 .48 .37 
 .42 .29 
 
 .37 
 .34 
 
 .36 
 .33 
 
 
 
 .22 .17 .13 
 .19 .14 .10 
 
 
 
 
 
 
 C-Sb 
 
 wide 
 
 .42 .31 
 
 .27 
 
 .24 
 
 .21 
 
 .20 
 
 
 . .14 
 
 .11 
 
 .08 
 
 
 
 
 
 narrow 
 
 .39 .28 
 
 .26 
 
 .24 
 
 .20 
 
 .19 
 
 
 
 .. .14 
 
 .11 
 
 .08 
 
 
 
 
 C-Sb-G' 
 
 wide 
 
 .32 .24 
 
 .18 
 
 .15 
 
 .14 
 
 
 
 
 .. .08 
 
 .07 
 
 .05 
 
 
 
 
 
 narrow 
 
 .30 .22 
 
 .17 
 
 .15 
 
 .14 
 
 
 
 
 .. .08 
 
 .07 
 
 .05 
 
 
 
 
 C-Sb-G-M''** 
 
 wide 
 
 .17 .13 
 
 .10 
 
 .09 
 
 .09 
 
 .08 
 
 
 
 ... 
 
 .05 
 
 .04 
 
 .03 
 
 .03 
 
 
 
 narrow 
 
 .16 .12 
 
 .10 
 
 .09 
 
 .09 
 
 .08 
 
 
 
 
 
 .05 
 
 .04 
 
 .03 
 
 .03 
 
 
 C-C-Sb 
 
 wide 
 
 .40 .29 
 
 .26 
 
 .23 
 
 .20 
 
 .19 
 
 
 
 .. .12 
 
 .09 
 
 .07 
 
 .06 
 
 ... 
 
 
 
 narrow 
 
 .38 .27 
 
 .25 
 
 .22 
 
 .19 
 
 .19 
 
 
 
 .. .12 
 
 .09 
 
 .07 
 
 .06 
 
 
 
 C-C-Mo" 
 
 
 .17 .11 
 
 .10 
 
 .09 
 
 .08 
 
 .08 
 
 
 
 ... 
 
 .03 
 
 .02 
 
 .02 
 
 .01 
 
 
 C-C-M-M-M8 
 
 h 
 
 .10 .06 
 
 .06 
 
 .06 
 
 .05 
 
 .05 
 
 
 
 ... 
 
 .02 
 
 .02 
 
 .01 
 
 .01 
 
 
 C-M-M-Mo-" 
 
 
 .04 .03 
 
 
 
 
 
 
 
 
 .01 
 
 .007 
 
 .005 
 
 .005 . 
 
 
 Combination Tillage Systems 
 
 Crop 
 sequence' 
 
 C-Sb 
 
 C-C-Sb 
 
 Tillage systems used for sequence 
 
 Corn after soybeans, no-till; soybeans after corn, 
 fall chisel, spring secondary tillage 
 
 Corn after soybeans, no-till; corn after corn, fall 
 chisel, spring secondary tillage; soybeans after 
 corn, fall chisel, spring secondary tillage 
 
 Soybean row 
 
 Percent soil cover after 
 planting each crop 
 
 width" 
 
 20% 
 
 30% 
 
 40% 
 
 wide 
 
 .20 
 
 .16 
 
 .13 
 
 narrow 
 
 .18 
 
 .15 
 
 .13 
 
 wide 
 
 .20 
 
 .17 
 
 .14 
 
 narrow 
 
 .19 
 
 .16 
 
 .13 
 
 Double-Cropping Systems 
 
 Crop 
 sequence' Tillage systems used for double-cropping sequence 
 
 C-W/Sb Corn, conventional tillage, spring plow; disk for wheat and soybeans 
 
 C-W/Sb Same as above except no-till for soybeans 
 
 C-W/Sb Corn, no-till, 40 percent soil cover after planting; disk for wheat; 
 
 no-till soyl)eans 
 
 C-W/Sb Same as above except no-till wheat 
 
 C-Sb-W/Sb Com, conventional tillage, spring plow; soybeans, wide-row, con- 
 ventional tillage, spring plow; disk for wheat and soybeans 
 
 C-Sb-W/Sb Corn, no-till, 30 percent soil cover after planting; soybeans, wide- 
 row, conventional tillage, spring plow; disk for wheat; no-till 
 soybeans 
 
 C-Sb-W/Sb Corn, no-till, 40 percent soil cover after planting; soybeans, wide- 
 row, no-till, 80 percent soil cover after planting; disk for wheat; 
 no-till soybeans 
 
 C value 
 .21 
 .19 
 
 .10 
 .08 
 
 .24 
 .18 
 
 .08 
 
 Source: C values for this table were calculated from the Soil Conservation Service's Illinois Technical Guide, Section I-C (EI Curve 19). 
 NOTE: The footnotes for Table 6 are the same as for Table 4. Please be sure to read all footnotes because values in this table 
 are based upon assumptions detailed in the footnotes and your practices could be different from these assumptions. 
 NOTE: Values in this table are based on high level management with yields equal to or exceeding the following: corn, 100 
 bushels per acre; soybeans, 40 bushels per acre; wheat, 45 bushels per acre; oats, 60 bushels per acre; meadow, 3 tons per 
 acre. For medium level management, multiply values by 1.2. 
 
15 
 
 Table 7. C Values for Permanent Pasture, Range, and Idle Land 
 
 Vegetative 
 
 canopy 
 
 
 
 Ground 
 
 cover that contacts the soil surface 
 
 
 Type 
 
 Height" 
 
 Percent 
 cover" 
 
 Type' 
 
 0% 
 
 20% 
 
 40% 
 
 60% 
 
 80% 
 
 95+% 
 
 No appreciable canopy 
 
 
 
 G 
 
 0.45 
 
 0.20 
 
 0.10 
 
 0.042 
 
 0.013 
 
 0.003 
 
 
 
 
 W 
 
 .45 
 
 .24 
 
 .15 
 
 .091 
 
 .043 
 
 .011 
 
 Tall weeds or short 
 brush 
 
 20 in. 
 
 25 
 
 G 
 
 .36 
 
 .17 
 
 .09 
 
 .038 
 
 .013 
 
 .003 
 
 
 
 
 W 
 
 .36 
 
 .20 
 
 .13 
 
 .083 
 
 .041 
 
 .011 
 
 
 20 
 
 50 
 
 G 
 
 .26 
 
 .13 
 
 .07 
 
 .035 
 
 .012 
 
 .003 
 
 
 
 
 W 
 
 .26 
 
 .16 
 
 .11 
 
 .076 
 
 .039 
 
 .011 
 
 
 20 
 
 75 
 
 G 
 
 .17 
 
 .10 
 
 .06 
 
 .032 
 
 .011 
 
 .003 
 
 
 
 
 W 
 
 .17 
 
 .12 
 
 .09 
 
 .068 
 
 .038 
 
 .011 
 
 Appreciable brush 
 or bushes 
 
 6.5 ft. 
 
 25 
 
 G 
 
 .40 
 
 .18 
 
 .09 
 
 .040 
 
 .013 
 
 .003 
 
 
 
 
 W 
 
 .40 
 
 .22 
 
 .14 
 
 .087 
 
 .042 
 
 .011 
 
 
 6.5 
 
 50 
 
 G 
 
 .34 
 
 .16 
 
 .08 
 
 .038 
 
 .012 
 
 .003 
 
 
 
 
 W 
 
 .34 
 
 .19 
 
 .13 
 
 .082 
 
 .041 
 
 .011 
 
 
 6.5 
 
 75 
 
 G 
 
 .28 
 
 .14 
 
 .08 
 
 .036 
 
 .012 
 
 .003 
 
 
 
 
 W 
 
 .28 
 
 .17 
 
 .12 
 
 .078 
 
 .040 
 
 .011 
 
 Trees but no appreci- 
 able low brush 
 
 13 ft. 
 
 25 
 
 G 
 
 .42 
 
 .19 
 
 .10 
 
 .041 
 
 .013 
 
 .003 
 
 
 
 
 W 
 
 .42 
 
 .23 
 
 .14 
 
 .089 
 
 .042 
 
 .011 
 
 
 13 
 
 50 
 
 G 
 
 .39 
 
 .18 
 
 .09 
 
 .040 
 
 .013 
 
 .003 
 
 
 
 
 W 
 
 .39 
 
 .21 
 
 .14 
 
 .087 
 
 .042 
 
 .011 
 
 
 13 
 
 75 
 
 G 
 
 .36 
 
 .17 
 
 .09 
 
 .039 
 
 .012 
 
 .003 
 
 
 
 
 W 
 
 0.36 
 
 0.20 
 
 0.13 
 
 0.084 
 
 0.041 
 
 0.011 
 
 Note: The listed C values assume that the vegetation and mulch are randomly distributed over the entire area. 
 
 ■In this table, height is not the actual height of the weeds, bushes, brush, or trees. It is the drop fall height, which is the 
 average distance between the lowest twig, branch, or leaf and the ground (the average distance that a drop of water 
 would fall unimpeded). The beneficial effects of canopy decrease as the drop fall height increases and are negligible 
 when the drop fall height exceeds 33 feet. 
 
 ''Percent canopy cover is the portion of the total surface area that would be hidden from view by canopy from an 
 airplane (a bird's-eye view). 
 
 •^G indicates that the cover at surface is grass, grasslike plants, decaying compacted duff, or litter at least two inches 
 deep. W^indicates that the cover at surface is mostly broadleaf herbaceous plants (weeds with few lateral root networks 
 near the surface) or undecayed residues or both. 
 
 Table 8. C Values for Undisturbed Forest Land 
 
 Area covered by canopy 
 
 of trees and undergrowth 
 
 (percent) 
 
 Area covered by duff 
 
 at least 2 inches 
 
 deep (percent) 
 
 C value 
 
 20 to 40 
 45 to 70 
 75 to 100 
 
 40 to 70 
 
 0.006 
 
 75 to 85 
 
 0.003 
 
 90 to 100 
 
 0.0005 
 
16 
 
 Table 9. Conservation Practices (P) Values for Contour Farming and Contour Strip Cropping 
 
 
 Contour farming 
 
 
 Contour strip cropping 
 
 
 Slope 
 percent 
 
 P value 
 
 Maximum slope 
 length (feet)" 
 
 P value 
 R-G-M-M"' 
 
 P value 
 R-R-G-M'''='' 
 
 Strip width 
 (feet)« 
 
 lto2 
 
 0.60 
 
 400 
 
 0.30 
 
 0.45 
 
 130 
 
 3 to 5 
 
 .50 
 
 300 
 
 .25 
 
 .38 
 
 100 
 
 6 to 8 
 
 .50 
 
 200 
 
 .25 
 
 .38 
 
 100 
 
 9 to 12 
 
 .60 
 
 120 
 
 .30 
 
 .45 
 
 80 
 
 13 to 16 
 
 .70 
 
 80 
 
 .35 
 
 .52 
 
 80 
 
 17 to 20 
 
 .80 
 
 60 
 
 .40 
 
 .60 
 
 60 
 
 21 to 25 
 
 0.90 
 
 50 
 
 0.45 
 
 0.68 
 
 50 
 
 "Slope length limits are based upon limited data and field observations. 
 
 ''R = row crop; G = small grain; M = meadow. 
 
 *^Strip cropping is most effective when there are alternate strips and equal width of row crops and 
 sod crops, for example, corn-corn-wheat with meadow seeding, meadow, meadow. 
 
 **A strip cropping rotation of corn-corn-wheat-meadow is less effective. 
 
 *To accommodate widths of farm equipment, generally adjust strip width downward. 
 
 Table 10. Values Used in Determining P Values for Terraces Built 
 on Contour and Used in Combination with Contour 
 Farming and Contour Strip Cropping 
 
 Terrace interval 
 
 Closed 
 
 Open outlets with percent slope of 
 
 (feet) 
 
 outlets" 
 
 0.1-0.3 
 
 0.4-0.7 
 
 >0.8 
 
 Less than 110 
 
 0.5 
 
 0.6 
 
 0.7 
 
 1.0 
 
 110 to 140 
 
 0.6 
 
 0.7 
 
 0.8 
 
 1.0 
 
 140 to 180 
 
 0.7 
 
 0.8 
 
 0.9 
 
 1.0 
 
 180 to 225 
 
 0.8 
 
 0.8 
 
 0.9 
 
 1.0 
 
 225 to 300 
 
 0.9 
 
 0.9 
 
 1.0 
 
 1.0 
 
 300 and up 
 
 1.0 
 
 1.0 
 
 1.0 
 
 1.0 
 
 ■Values for closed outlet terraces also apply to terraces with underground 
 outlets and to level terraces with open outlets. However, closed outlet terraces 
 are not normally built in Illinois because of the large amount of rainfall in 
 Illinois. 
 
 The channel slope is measured on the 300 feet of terrace closest to the outlet or 
 on the third of the total terrace length closest to the outlet, whichever distance 
 is less. 
 
17 
 
 How to Make and Use a Slope Gauge 
 
 How to Make 
 
 1. Glue, tack, or tape the slope gauge 
 sheet (located on page 00) on a 9-inch by 
 12-inch board. A V,-inch plywood or %-inch 
 thick board works best. Also, you may want 
 to attach these directions to the opposite 
 side of the board. 
 
 2. Place a small eye screw or nail at Point 
 1 on the slope gauge sheet. 
 
 3. Hang a string from the eye screw or 
 nail. Let the bottom of the string hang 1 to 2 
 inches below the bottom of the board. 
 
 4. Attach a weight, such as a fish line 
 sinker, at the end of the string. 
 
 5. Place two small finishing nails or wire 
 brads at Points 2 and 3 on the slope gauge 
 sheet. These are the sighting pins. 
 
 How to Use 
 
 1. Keep the sighting pins in your line of 
 vision and aim at the point on an object or 
 person that is the same height from the 
 ground as your eyes. For example, let's as- 
 sume you're aiming at a person who is taller 
 than you. If that person's chin is the same 
 height from the ground as your eyes, aim 
 for his chin (see figure). If you're aiming at a 
 stick, tie a ribbon around the point on the 
 stick that is at your eye level; then aim at 
 the ribbon. 
 
 2. The person or object does not need to 
 be any particular distance away. 
 
 3. You can aim the slope gauge either up 
 or down the slope. 
 
 4. Hold the slope gauge as steady as 
 possible and make sure the weighted string 
 can swing easily across the scale. 
 
 5. After you have finished sighting, hold 
 the string at the point where it comes to rest 
 on the scale. 
 
 6. Read the percent of slope directly from 
 the scale and record your measurement. 
 You may want to take several measure- 
 ments on the same slope to check your 
 accuracy. 
 
Slope Gauge 
 
 19 
 
 Point 1 
 
 Hang weight on a string 
 
 from this point. 
 
 Point 2 
 
 Place sighting 
 pin here. 
 
 ^0 
 
 ^0 
 
 3S 
 
 Point 3 
 
 Place sighting 
 pin here. 
 
 Aim 
 
 «>^ 
 
 tf) 
 
 '' '' 20 IS 
 
 10 5 5 
 
 10 15 20 25 
 
 30 
 
 Read percent of slope directly on this scale. At the point 
 where string rests on scale, the number indicates 
 percent of slope. 
 
35^ 
 
 ^84i1lll 
 
Urbana, Illinois November, 1983 
 
 Issued in furtherance of Cooperative Extension Work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. 
 Department of Agriculture, DONALD L. UCHTMANN, Director, Cooperative Extension Service, University of Illinois at 
 Urbana-Champaign. The Illinois Cooperative Extension Service provides equal opportunities in programs and employment. 
 
 1 .5M— Rep.— 1 2-93— MO 
 

 II 
 
 ::»: