LABORATORY MANUAL 
 
 FOR 
 
 SOIL PHYSICS. 
 
 By J. G. MOSIER 
 
/ BERKELE Y \ 
 
 EAfiTH n 
 
 SCIENCES A , 4. n .. „ 
 
 -<k>^. ay. /9/o 
 
 EAflTH 
 CIENCE 
 LIBRARY 
 
 
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 SCIENCES 
 LIBRARY 
 
 PREFACE. 
 
 The laboratory practices described in this manual are designed for 
 one semester's work, during which it is hoped to give the student a 
 knowledge of principles that underlie many common agricultural oper- 
 ations. No very complicated apparatus is required, but great care 
 must be used to have uniform conditions, especially where different 
 soils are to be compared. 
 
 In this second edition many changes have been made that the 
 experience of the past three years seemed to indicate as best. Some 
 new Practices have been added, together with cuts, descriptions of 
 apparatus and forms for the data obtained. 
 
 In a number of practices students may work together in groups 
 not so large, however, but that each one may have a distinct problem 
 to work out in each practice. This will enable the class to complete 
 the work in one semester which otherwise might not be possible. 
 
 ACKNOWLEDGEMENTS. 
 
 These laboratory practices were not all originated in the Univer- 
 sity of Illinois. Nos. 9, 11, 14, 18, 20, 21, and 22 have been adapted to 
 our work from Ohio State University Bulletin No. 6 by Professor 
 William D. Gibbs, formerly of that institution, and Practice 23 was 
 taken from the Manual of Soil Physics of Purdue University. A few 
 of the practices in this manual had been arranged for student use by 
 the late Mr. H. E. Ward, formerly instructor in Soil Physics in the 
 University of Illinois. 
 
 I also wish to acknowledge the valuable suggestions received from 
 Professor Clifford Willis, now of South Dakota Agricultural College, 
 and Mr. A. F. Gustafson of this University. 
 
 The Author. 
 College of Agriculture, 
 
 University of Illinois, 
 Urbana, Illinois, June, 1908. 
 
LIST OF APPARATUS FOR EACH STUDENT. 
 
 1 
 
 Ring stand 
 
 
 1 
 
 Yard cheese cloth 
 
 3 
 
 Rings (3 sizes) 
 
 
 6 
 
 Pint jars 
 
 1 
 
 Bunsen burner with rubber 
 
 1 
 
 Pair crucible tongs 
 
 
 tubing 
 
 
 
 
 1 
 
 Desiccator 
 
 
 1 
 
 100 cc. graduate 
 
 L2 
 
 Soil pans 
 
 
 1 
 
 Wash bottle, 500 cc. 
 
 12 
 
 Crucibles, 25 cc. 
 
 
 1 
 
 Nest of beakers Nos. 
 
 6 
 
 Crucibles, 50 cc. 
 
 
 2 
 
 Funnels, 4 inch 
 
 1 
 
 Spatula 
 
 
 1 
 
 Trinagle, pipestem 
 
 1 
 
 Camel's hair brush 
 
 
 2 
 
 Test tubes 
 
 1 
 
 Towel 
 
 
 1 
 
 Box matches 
 
 
 
 STOCK SOILS. 
 
 1 to 
 
 The soils commonly used consist of a (1) sand, (2) loam, (3) silt, (4) 
 clay, and (5) peat. 
 
 The sand is a white quartz of medium fineness. This is en- 
 tirely free from organic matter and of course represents an extreme. 
 A sand soil as taken from the field is occasionally used for purpose of 
 comparison. 
 
 The loam is a mixture of sand (not over 50 percent) silt, clay and 
 organic matter. This represents a good type. 
 
 The silt soil is one in which silt of different grades forms 70 per 
 cent or more of the constituents. It is a very common type of soil, 
 especially in glacial or loessial soil areas. The timber phase of this 
 type is used in the laboratory because it contains less organic matter 
 than the prairie phase. 
 
 The clay soil used is a heavy, plastic, sticky, clayey soil, frequently 
 found in bottom lands along large streams. The samples used should 
 contain 30 percent or more of clay. 
 
 The peat soil is obtained from peaty swamps or bogs, which are 
 especially common in north central United States. Organic matter 
 usually constitutes about 75 percent of this soil. (Where decomposi- 
 tion has gone on far enough and much clay is mixed with the organic 
 matter, muck soil is found.) 
 
 The soils are prepared by being dried and pulverized until they 
 pass through a 2 millimeter sieve. 
 
 M593629 
 
PRACTICE 1 
 Determination of Capillary Moisture* in Soils. 
 
 Use soils collected according to method given belowf and make 
 the determinations in duplicate for surface, subsurface and subsoil. 
 Weigh carefully six soil pans. Place in each from 100 to 200 
 grams of the soil and weigh pan and soil quickly to prevent loss of 
 moisture. Let it dry at room temperature for 72 hours, after which 
 weigh at intervals of about 24 hours till a practically constant weight 
 is obtained. The loss of weight is the capillary moisture. Express 
 your results in grams, and after the completion of the next exercise 
 express the results in percent of the water-free soil. Use these air-dry 
 soils for Practice 2. 
 
 Express in tabular form the capillary moisture in grams and per- 
 cent of water-free soil. 
 
 *The moisture content will always be expressed as percent of the water-free soil 
 in these exercises unless otherwise stated. 
 
 tFor this practice and also for Practice 5 the students are required to collect their 
 own samples. For this purpose a one and one-half inch or a two-inch auger with an 
 extension making it 40 inches long is used. In collecting samples for moisture determin- 
 ations, expose the soil as little as possible to the air before putting in jars. Collect the 
 surface soil to the depth of the plow line, usually about 7 inches. After this part of the 
 sample is removed, the hole is enlarged sufficiently so that the subsurface soil may be 
 taken without coming in contact with the surface soil. Take the subsurface sample to 
 the subsoil line as indicated by the change in color, texture and physical composition. 
 Commonly this line is found at a depth of 16 to20 inches, Enlarge and clean out the hole as 
 before. Since the change from subsurface to subsoil is not a sharp line but usually 
 somewhat gradual, we discard about two inches of the intermediate mixture. The sub- 
 soil is then collected to a depth of 40 inches, if possible. 
 
 In some soils the subsurface layer may be absent, the subsoil being reached by 
 the plow, while in others, as in peaty and sandy soils, no true subsoil may be found 
 within 40 inches of the surface. In such cases only two samples are taken. 
 
PRACTICE 1 
 
 Stratum 
 
 Surface 
 
 Subsurface 
 
 Subsoil 
 
 Sample 
 
 1 
 
 2 
 
 1 
 
 2 
 
 1 
 
 2 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Capillary moisture in % of 
 
 
 
 
 
 
 
 
 
 
 
 
PEACTICE 2 
 Determination of Hygroscopic Moisture. 
 
 Use air-dried soils from Practice 1. Mark and weigh the neces- 
 sary number of crucibles to run duplicates of each stratum. Place 
 about 10 grams of air-dried soil in each crucible and weigh. It is best 
 to weigh all of the duplicate samples out at the same time so as to 
 get them under the same conditions as to moisture. The hygroscopic 
 moisture of a soil varies with the relative humidity and temperature 
 of the atmosphere. Heat in an oven at about 100° C. for at least five 
 hours. Cool in a desiccator and weigh rapidly to prevent absorption 
 of moisture from the air. The loss of weight is the hygroscopic mois- 
 ture. 
 
 Express in tabular form the loss in grams and in percent of the 
 water-free soil. Also the total moisture of the samples in percent of 
 water-free soil. 
 
PRACTICE 2 
 
 Stratum 
 
 Surface 
 
 Subsurface 
 
 Subsoil 
 
 Sample 
 
 1 
 
 2 
 
 1 
 
 2 
 
 1 
 
 2 
 
 
 
 
 
 
 Weight of crucible+air-dry soil 
 
 Weight of crucible + water-free 
 soil 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Hygroscopic moisture in Jo of 
 
 
 
 
 
 
 
 Av. per cent, of hygroscopic 
 
 
 
 
 
 
 Av. per cent, of capillary water 
 
 
 
 
 
 
 
 
 
 
 
8 
 PRACTICE 3 
 
 Effects of Drainage on Temperature of a Soil.* 
 
 Two wooden trays 3 by 4 feet and six inches deep, one lined with 
 zinc to prevent the loss of water and the other made so as to allow 
 drainage, are filled with the same kind of soil. Water is added to each 
 till drainage begins in the latter. After three or four days the tem- 
 perature of each at 1, 2, and 4 inches in depth is determined hourly 
 on a clear day. 
 
 Explain differences in temperature. 
 
 Why is clay land liable to be cold? 
 
 "This and the following Practice logically come later in the course, but the season 
 here makes it necessary to give it early in either semester. Better results may be ob- 
 tained by conducting these experiments before the weather gets too cold in the fall or too 
 hot in the spring. 
 
PRACTICE 3 
 
 Time 
 
 Ther. 
 1 inch deep 
 
 Ther. 
 2 inches deep 
 
 Ther. 
 4 inches deep 
 
 
 Drain'd 
 
 Un- 
 drained 
 
 Drain'd 
 
 Un- 
 drained 
 
 Drain'd 
 
 Un- 
 drained 
 
 
 
 
 
 
 
 
 9 li 
 
 
 
 
 
 
 
 10 " 
 
 
 
 
 
 
 11 
 
 12 " 
 
 
 
 
 
 
 
 
 
 
 
 
 
 1 " 
 
 
 
 
 
 
 
 2 " 
 
 
 
 
 
 
 
 3 " 
 
 
 
 
 
 
 4 " 
 
 
 
 
 
 
 
 
 
 
 
 
 
 1 
 
 
 
 
 
10 
 
 PRACTICE 4 
 
 Effects of Color of Soil on Temperature. 
 
 Fill large wooden tray 6 feet long, 3 feet wide and 6 inches deep with 
 very light colored soil, gray silt loam, well pulverized. Divide the tray 
 lengthwise into halves and divide each half into six plots and plant 
 the same kind of seed in the opposite plots putting the same number 
 in each but covering those in one half of the tray I inch and the 
 other, $ inch deep. Then cover the latter with I inch of black 
 soil so that all of the light colored soil is covered. Observe the num- 
 ber of plants up each morning and evening, keeping a careful record 
 of the number coming up each day. 
 
 Select a clear day and make observations on the temperature of 
 each half of the tray. Insert thermometers 1, 2, and 4 inches in depth, 
 also place one, one inch above surface of each kind of soil, and take 
 hourly readings from 8 a. m. to 5 p. m. Keep all parts of tray 
 equally moist. 
 
 Each student may look after the planting of a single plot but he 
 must make observations on all plots in the tray and keep results in 
 tabular form. 
 
 Which tray shows the higher temperature? Why? 
 
 Why can you see the corn rows on the low black land sooner after 
 planting than upon the higher lighter colored soil? 
 
11 
 
 PRACTICED 
 
 
 Location 
 
 of 
 
 Ther. 
 
 
 
 Time 
 
 5 
 
 
 8 
 
 9 
 
 10 
 
 11 
 
 12 
 
 1 2 
 
 3 
 
 ! 
 
 
 1 inch 
 above 
 
 
 
 
 
 1 
 
 
 
 
 
 Dark 
 
 1 inch 
 below 
 
 
 
 
 
 
 
 
 
 
 Soil 
 
 2 inches 
 below 
 
 
 
 
 
 
 
 
 
 
 1 inches 
 below 
 
 
 
 
 
 
 
 
 
 
 
 
 1 inch 
 above 
 
 
 
 
 
 
 
 
 
 
 
 Light 
 Soil 
 
 1 inch 
 below 
 
 
 
 
 
 
 
 
 
 
 
 2 inches 
 below 
 
 
 
 
 
 
 
 
 
 
 
 
 4 inches 
 below 
 
 |.... 
 
 
 
 
 
 
 
 
 
 
 Number of plants up after number days indicated below: 
 
 
 Light Soil 
 
 Dark Soil 
 
 Number of 
 days 
 
 c 
 
 M 
 O 
 
 O 
 
 4^ 
 
 s 
 
 GO 
 
 c 
 
 0i 
 
 cq 
 
 a 
 
 o 
 O 
 
 
 
 o 
 O 
 
 4^ 
 C« 
 
 03 
 
 s 
 
 ffl 
 
 CD 
 
 — 
 
 O 
 
 O 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
12 
 
 PRACTICE 5 
 
 Determination of Total Moisture in the Same Soil Under Dif- 
 ferent Conditions. 
 
 Collect samples of surface, subsurface and subsoil* from the fol- 
 lowing places: (1) Sod, (2) Tilled field, (3) Forest. In collecting these 
 samples care should be taken to secure them from as small an area as 
 possible so that soil conditions may be uniform. Expose the samples 
 as little as possible to the air while taking them. After taking them 
 to the laboratory, the contents of the jars should be thoroughly mixed 
 by shaking. The condition of the weather at the time the samples 
 are taken and also the amount of rainfall within the week previous 
 should be noted. 
 
 Make the determinations in duplicate. Weigh 6 soil pans and use 
 100 grams or more of each soil. Weigh rapidly to prevent loss by evap- 
 oration. Place in an oven and leave at least five hours. Cool to the 
 room temperature and weigh at once. The loss of weight represents 
 the total water content. 
 
 It would be well for three students to work together, one taking 
 the surface, another the subsurface, and the third the subsoil. These 
 results may be compared. 
 
 Explain differences in moisture content of the soils. 
 
 PRACTICE 5 
 
 Sod 
 
 Student 
 
 Stratum 
 
 Wt. of 
 
 moist 
 
 soil 
 
 Wt. of 
 water- 
 free-soil 
 
 Loss 
 
 in 
 Grams 
 
 Percent 
 mois- 
 ture 
 
 Surface . . . . 
 Subsurface . 
 1st Subsoil. . 
 2nd Subsoil. 
 
 *In collecting the subsoil for moisture determination it is sometimes well to divide it 
 into two equal parts as to depth. 
 
13 
 Tilled Field 
 
 
 Surface . . . . . 
 
 
 
 
 
 
 Subsurface . . 
 1st Subsoil. . . 
 
 
 
 
 
 
 
 
 
 
 
 2nd Subsoil.. 
 
 
 
 
 
 
 
 
 
 
 
 Forest 
 
 
 Surface 
 
 
 
 
 
 
 
 
 
 
 
 
 1st Subsoil.. . 
 
 
 
 
 
 
 2nd Subsoil. . 
 
 
 
 
 
 
 
 
 
 
 
14 
 
 PRACTICE 6 
 
 Determination of the Variation in the Hygroscopic Capacity 
 of Soils. 
 
 In this exercise each student will use air-dried soils provided for 
 the purpose. These are sand, loam, silt, clay and peat. 
 
 Determine the percent of moisture lost when heated for 5 hours 
 at 100° C. This is the hygroscopic moisture. Express in percent of 
 water-free soil. Care must be taken to weigh out all samples at the 
 same time to avoid any change in the amount of moisture due to a 
 change in relative humidity. 
 
 Explain differences between clay and sand. 
 
 Between peat and sand. 
 
15 
 PRACTICE 6 
 
 Soil 
 
 Sand 
 
 Loam 
 
 Silt 
 
 Clay 
 
 Peat 
 
 Sample 
 
 * 
 
 2 
 
 1 
 
 2 
 
 1 
 
 2 
 
 1 
 
 2 
 
 1 
 
 2 
 
 
 
 
 
 
 
 
 
 
 
 
 Weight of water-free soil. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Percent of hygroscopic 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
16 
 
 PRACTICE 7 
 
 Determination of Flocculating Action of Lime. 
 
 Take four bottles and in one put 200 cc. of distilled water, as a 
 check, in another 200 cc. of .1 percent solution of lime, in another 200 
 cc. .01 percent and in the fourth .001 percent solution. Add to each, 
 three grams of finely ground clay and shake for ten or fifteen minutes. 
 After shaking take out a drop from the check and .1 percent solution 
 and examine under a microscope with a high power. Then pour some 
 of the contents of the bottles into tubes and whirl in the centrifuge, 
 stopping every two or three minutes to note the effect upon the clear- 
 ness. Whirl for at least fifteen minutes. After centrifugation, pour 
 the contents of the tubes into their respective bottles, shake thor- 
 oughly and set aside, observing them occasionally to determine the 
 time required for complete sedimentation in each case. 
 
 Make sketches of the appearance of the check and the 0.1 per- 
 cent solution under the microscope. 
 
 Which is thrown down first by the centrifuge? Why? 
 
 What practical application of this principle in farm practice? 
 
17 
 PRACTICE 7 
 
 Time to Centrifugate Time for Sedimentation 
 
 0.1 % solution . . . 
 
 0.01 % solution.. 
 
 0.001 % solution. 
 
 Check 
 
18 
 
 PKACTICE 8 
 
 Determination of the Effects of Lime on Plastic Soils. 
 
 Two students may work together in this experiment. 
 
 Weigh out 6,300-gram samples of the clay soil using them as follows: 
 To sample 
 
 No. 1, check, add no lime. 
 
 No. 2 add .5 gr. of air slacked lime. 
 
 No. 3 add 1. gr. of air slacked lime. 
 
 No. 4 add 5. gr. of air slacked lime. 
 
 No. 5 add 10 gr. of air slacked lime. 
 
 No. 6 add 10 gr. sand. 
 
 Mix each sample thoroughly in a soil pan with the lime and add 
 just enough water to make plastic. 
 
 Fill the semicircular moulds, first placing a damp thin cloth in it 
 to facilitate the removal of the clay. Make duplicates of each number, 
 being careful to compress each to the same degree. Place on a cloth 
 in a soil pan and dry in an oven for 5 hours at 100° C. 
 
 Test the strength of each brick by supporting the ends so as to 
 allow just 3 inches between points of support. Hang weight pan in 
 middle of brick and determine the weight necessary to break each. 
 
 Explain the effect of lime. 
 
 Why does the sand not have as much effect as the lime on the 
 breaking strength? 
 
19 
 PRACTICE 8 
 
 1st Trial 2nd Trial Average 
 
 Check.— No. lime 
 0.5 grams of lime . 
 1. gram of lime . . 
 5. grams of lime . 
 10. grams of lime 
 10. grams of sand . 
 
20 
 
 PRACTICE 9 
 
 Determination of the Volume Weight and Apparent Specific 
 Gravity of Soils. 
 
 The volume weight of a soil is the weight of a certain unit of 
 volume and the cubic centimeter is taken as this unit. In determin- 
 ing the apparent specific gravity, the pore space is not taken into ac- 
 count. This gives a result much less, numerically, than the real spe- 
 cific gravity. 
 
 Find the volume weight and apparent specific gravity of sand, loam, 
 silt, clay and peat. 
 
 Weigh an empty and thoroughly cleaned soil tube.* Fill the 
 tube with one of the soils to be tested by simply pouring the soil in 
 loosely till it reaches the crease near the top, being careful not to com- 
 pact the soil by jarring or jolting. Weigh, empty and then fill again 
 with the same soil in the same way, using the average of the two 
 weights of soil from which to determine the volume weight and ap- 
 parent specific gravity. Treat each soil in the same way. Determine 
 the amount of water-free soil in each case by using the percent of hy- 
 groscopic moisture found in Practice 6. Find volume of soil tube by 
 filling with water to the crease and weighing. The weight in grams 
 will give the volume in cubic centimeters since one cc. of water 
 weighs approximately one gram. The weight of the soil divided by 
 the volume of the tube will give the weight of one cubic centimeter 
 of soil or the volume weight of soil. Numerically, this is the appar- 
 ent specific gravity. 
 
 Volume weight of soil ~ ._ _, . ~ ., 
 
 — Apparent Specific Gravity of Soil- 
 
 Repeat the above process with each soil but use the compacting 
 machine in filling the tubes, allowing the weight to fall three times 
 from the 12-inch mark upon each measure of soil. 
 
 The volume weight and apparent specific gravity of soils varies 
 with the amount of compaction. A freshly plowed field is much 
 lighter per cubic foot than one compacted by rains, tramping or by 
 means of the roller. 
 
 Why is the apparent specific gravity of sand higher than that of 
 loam? 
 
 Why is the apparent specific gravity of peat so low? 
 
 Sand has less pore space than clay. 
 
 How will this affect the apparent specific gravity? 
 
 What would be the weight of a cubic foot of each kind of soil both 
 compact and loose? 
 
 A galvanized iron tube two inches inside diameter and 12 inches long, closed at one 
 A crease one inch from the top indicates the height to which ii may lie tilled- 
 
21 
 PRACTICE 
 
 Soils 
 
 Sand 
 
 Loam 
 
 Silt 
 
 Clay 
 
 Peat 
 
 Cora pact ion 
 
 L* 
 
 C 
 
 L 
 
 C 
 
 L 
 
 C 
 
 L 
 
 C 1 L C 
 
 Weight of tube 
 
 
 
 
 
 
 
 
 
 
 
 Weight of tube] 1st trial. 
 
 
 
 
 
 
 
 
 
 
 
 + air-dry I 
 
 soil J 2nd trial 
 
 
 
 
 
 
 
 
 
 
 
 Av. of trials 
 
 Percent of hygroscopic 
 
 moisture 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 No. of cc. of water to fill 
 tube 
 
 
 
 
 
 
 
 
 
 
 
 Apparent specific gravity. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 • 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 *L = loose, C = compact. 
 
PEACTICE 10 
 
 Determination of the Apparent Specific Gravity of Surface 
 Soil Under Field Conditions. 
 
 Take a tube* provided for the purpose and force it into the ground 
 to the depth of six inches. Bemove soil to a weighed pan and dry in 
 the oven at 100° C. for at least ten hours. Find volume of the soil 
 taken and divide the weight of the water-free soil by this. The re- 
 sult will be the apparent specific gravity. 
 
 The apparent specific gravity of soils in the field may be taken as 
 an approximate indication of the tilth, since the better the tilth the 
 less the apparent specific gravity for the same kind of soil. This is 
 due to the fact that soils in good tilth are looser on account of the 
 presence of a larger percent of organic matter and better granulation. 
 The apparent specific gravity of a continuously cropped soil is higher 
 than one having proper rotations. Why? 
 
 What would be the weight of a cubic foot of soil under the above 
 conditions? 
 
 ♦An iron or brass tube three inches in diameter with a cutting: edge. Very heavy 
 galvanized iron will do. 
 
23 
 PRACTICE 10 
 
 Sample 1 Sample 2 
 
 Weight of pan 
 
 Weight of pan + soil 
 
 Weight of soil 
 
 Weight of water 
 
 Weight of water-free soil. . 
 
 Volume of tube in cc 
 
 Apparent specific gravity. . 
 Weight of a cu. ft. of soil, 
 
24 
 
 PRACTICE 11 
 
 Determination of Real Specific Gravity of Soils. Picnometer 
 Method. 
 
 Use sand, loam, silt, clay and peat. 
 
 Fill a picnometer to the end of the capillary tube with distilled 
 water whose temperature is known. Wipe dry and weigh. Pour out 
 about half of the water and add about ten grams of soil (about half 
 as much peat) that has been carefully weighed. It is a good plan to 
 weigh the flask just before the soil is added and again just after, the 
 difference being the weight of the soil. In this case the soil need not 
 be previously weighed. 
 
 Boil gently for a few minutes in the water bath, sand bath or on 
 an asbestos mat to drive out the air from the soil. Refill with dis- 
 tilled water, bring to the same temperature as before and weigh. 
 Determine the amount of water-free soil, using the percent of hygro- 
 scopic moisture found in Practice 6. The weight of the flask of water 
 plus the weight of the soil, minus the weight of the flask containing 
 the soil gives the weight of water displaced by the soil. Calculate 
 the specific gravity and tabulate results. 
 
 Compare the real specific gravity with the apparent specific gravity. 
 
 Why is the real specific gravity higher? 
 
25 
 PRACTICE 11 
 
 Soils 
 
 Sand 
 
 Loam 
 
 Silt 
 
 Clay 
 
 Peat 
 
 Samples 
 
 1 
 
 2 
 
 1 
 
 2 
 
 1 
 
 2 
 
 1 
 
 2 
 
 1 
 
 2 
 
 Weight of picnometer 
 
 filled with water -f 
 wt. of water-free soil 
 
 
 
 
 
 
 
 
 
 
 
 Weight of picnometer 
 
 containing soil 
 
 
 
 
 
 
 
 
 
 
 
 Weight of water displaced 
 Weight of water-free soil 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
26 
 
 PRACTICE 12 
 
 Determination of Porosity. 
 
 first method. 
 
 "Weigh the Nessler's jar or graduated cylinder. 
 
 Use sand, loam, silt, clay and peat. 
 
 Fill to the 50 or 100 cc. mark with soil not compacted and weigh. 
 Compute the amount of water-free soil in this, using the percent of 
 hygroscopic moisture determined in Practice 6. 
 
 (Volume of soil x real specific gravity)-Wt. of water-free soil = nt Qf space 
 
 Volume of soil x real specific gravity 
 
 What effect does size of particles have on total amount of pore 
 space? 
 
 Does the amount of pore space increase or decrease with the 
 amount of organic matter? 
 
 Which of the soils have the largest pores? Does this mean the 
 greatest amount of pore space? 
 
27 
 PRACTICE 12 
 
 Soil 
 
 Sand 
 
 Loam 
 
 Silt 
 
 Clay 
 
 Peat 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Av. of two trials 
 
 Percent of hygroscopic 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Percent of pore space 
 
 
 
 
 
 
 
 
 
 
 
28 
 PRACTICE 13 
 
 Determination of Porosity, 
 second method. 
 
 Find what percent the apparent specific gravity is of the real 
 specific gravity and subtract this from 100 percent. The remainder 
 expresses the percent of pore space in the soil. 
 
 Use the results in Practice 9 and 11, and determine the pore space 
 for loose and compact soils and express the results In tabular form. 
 
 The porosity of soils varies as the apparent specific gravity. 
 
 Why? 
 
29 
 PRACTICE 13 
 
 Soil 
 
 Sand 
 
 Loam 
 
 Silt 
 
 Clay 
 
 Peat 
 
 Compaction 
 
 L* 
 
 C 
 
 L 
 
 C 
 
 L 
 
 C 
 
 L 
 
 C 
 
 L 
 
 C 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ' 
 
 
 
 
 
 
 
 
 
 *L^=loose. C=compact. 
 
30 
 
 PRACTICE 14 
 
 Determination of Loss on Ignition. 
 
 The loss that a soil suffers when it is ignited is often taken as a 
 measure of the organic matter, but it can only be a very rough ap- 
 proximation at best for most soils. For some subsurface and nearly 
 all subsoils, it gives little or no idea of the amount of organic matter. 
 By igniting, the organic matter, volatile salts and water of hydration 
 will be driven off. In heavy clay soils and all fine grained ones, this 
 latter forms a very large part of the loss. Subsoils with little or no 
 organic matter may lose as much as surface soils, due to the larger 
 amount of clay and consequently a larger amount of water of hydra- 
 tion which is driven off by the heat. The more organic matter pres- 
 ent in a soil, the nearer the loss on ignition will correspond to the 
 real amount so that for peat soils, ignition may give a close approxi- 
 mation to the amount of organic matter present. 
 
 Weigh out 5 grams of water-free soil or air-dry soil calculated to a 
 water-free basis and ignite in a small crucible to low red heat for 15 
 to 20 minutes. Cool in a desiccator and weigh. Determine loss for 
 silt, loam, clay and peat. 
 
 Of which of the soils loses most? "Why? 
 
 How do coarse and fine grained soils compare in loss? 
 
31 
 PRACTICE 14 
 
 Soils 
 
 Loam 
 
 Silt 
 
 Clay 
 
 Peat 
 
 Sample 
 
 1 
 
 2 
 
 1 
 
 2 
 
 1 
 
 2 
 
 1 
 
 2 
 
 
 
 
 
 
 
 
 
 
 Percent of hygroscopic moisture. . . 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
32 
 
 PRACTICE 15 
 
 Determination of Humus in Soils. 
 
 Weigh out five or ten grams of water-free soil, the amount taken 
 depending upon the amount of humus in the soil. Plase in filter and 
 leach out the lime and magnesia with dilute hydrochloric acid.* 
 When the lime is all leached out, as shown by testing the filtrate with 
 ammonia and ammonium oxalate, wash out the hydrochloric acid with 
 distilled water. Dry the soil and filter paper in an oven at 100° C. 
 and put in a wide-mouthed bottle, carefully measure and add 150 cc. 
 to 300 cc. of dilute ammonia, the amount depending upon the richness 
 of the soil in humus. Shake for about three hours. Filter. Evapor- 
 ate 50 cc. or 100 cc. of filtrate to dryness. Dry at 100° C, weigh, ignite 
 and weigh again. The loss in weight is the humus. Calculate from 
 the part evaporated the total amount of humus and express in percent 
 of the water-free soil. 
 
 Of what benefit is a large amount of humus? 
 
 If an acre seven inches of soil weighs 2,000,000 pounds, how many 
 tons of humus per acre in the soil with which you are working? 
 
 •For the dilute dydrochloric acid use 25 oc HC1 sp. grr. 1.19 with 808 cc of distilled 
 water. For the ammonia 178 cc saturated ammonia with 422 00 of distilled water 
 
33 
 PRACTICE 15 
 
 Soils 
 
 Loam 
 
 Silt 
 
 Clay 
 
 Sample 
 
 1 
 
 2 
 
 1 
 
 2 
 
 1 
 
 2 
 
 
 
 
 
 
 
 Weight of crucible + air-drj 
 
 
 
 
 
 Weight of water- free soil . 
 
 
 
 
 
 
 
 
 
 
 
 Weight after ignition 
 
 
 
 
 
 
 Loss of weight 
 
 Percent of humus 
 
 
 
 
 
 
 
 
 
 
 
 Average 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
34 
 PRACTICE 16 
 
 Determination of Conductivity of Soils 
 
 Use sand, loam, silt, clay, and peat. 
 
 In one end of tray* place the copper vessel for the water and put 
 asbestos plates on all sides except the one adjacent to the soil. Fill 
 the tray with the soil to be tested. Place thermometers at a depth 
 of 2i inches and 1, 2, 3, 4, 5 and 6 inches from the vessel with the water 
 and apply heat to the water through the opening in the bottom of 
 the tray. Read thermometers about every five or ten minutes for 
 about one hour. Tabulate results. 
 
 Students should work in sets of five, each student testing one 
 soil and giving data to other four for comparison. Is there any rela- 
 tion between porosity and conductivity? 
 
 *The tray is made of galvanized iron 18 inches long by 5 inches wide and 5 inches 
 deep. At one end of the bottom is a circular opening 2 inches in diameter through 
 which heat is applied to the copper vessel containing water. This is 4" X 4" and five 
 inches deep with a lid with two holes, one for a thermometer and one for the escape of 
 steam. 
 
 PRACTICE 16 
 
 
 Sand 
 
 Loam 
 
 Time 
 
 
 
 
 
 
 
 
 
 
 
 Temperature at 
 1" 
 
 
 
 
 
 
 
 
 
 
 
 2" 
 
 
 
 
 
 
 
 
 
 
 
 3" 
 
 
 
 
 
 
 
 
 
 
 
 4" 
 
 
 
 
 
 
 
 
 
 
 5" 
 
 
 
 
 
 
 
 
 
 
 
 6" 
 From source of heat 
 
 
 
 
 
 
 
 
 
 
 
35 
 
 
 Silt 
 
 Clay 
 
 Time 
 
 
 
 
 
 
 
 
 
 
 
 Temperature at 
 1" 
 
 
 
 2" 
 
 ... 
 
 
 
 
 
 
 
 
 
 3" 
 
 
 
 
 
 
 
 
 
 4" 
 
 
 
 
 
 
 
 
 
 
 5 
 
 
 
 
 
 
 
 
 
 
 
 6" 
 From source of heat 
 
 
 
 
 
 
 
 
 
 
 
 
 Peat 
 
 
 Time 
 
 
 
 
 
 
 
 
 
 
 
 Temperature at 
 1" 
 
 
 
 
 
 
 
 
 
 
 
 2" 
 
 
 
 
 
 
 
 
 
 
 
 3" 
 
 
 
 
 
 
 
 
 
 
 
 4" 
 
 
 
 
 
 
 
 
 
 
 
 5" 
 
 
 
 
 
 
 
 
 
 
 
 6" 
 From source of heat 
 
 
 
 
 
 
 
 
 
 
 
36 
 
 PRACTICE 17 
 
 Power of Loose Soils to Retain Water. 
 
 Fill tubes* with sand, loam, silt, clay and peat soils. (Fill tubes 
 about two-thirds full of peat.) 
 
 Place disks of damp cheese-cloth in the bottom of the tubes and 
 then weigh them. Fill the tubes up to the crease (except peat) one 
 inch from the top by pouring the soil in gently through a funnel as 
 the tube is held vertically, being careful not to compact the soil by 
 jarring. Weigh the filled tubes and place in an empty galvanized iron 
 box. Pour water in the box till it is on the same level with the soil 
 in the tubes, thus allowing the water to pass up through the soils. 
 
 Note time required for soils to become moist on top. When the soils 
 have become thoroughly saturated, remove the tubes and place them 
 in a pan to drain. Cover to prevent evaporation and weigh when 
 drainage ceases. 
 
 Determine the amount of water-free soil by using the percent of 
 hygroscopic moisture found in Practice 6. 
 
 Measure depth of the settled soils. 
 
 Calculate the percent of waterretained, the weight per cubic foot 
 of soil that this represents using the apparent specific gravity found 
 in Practice 9, and the acre inches of water. 
 
 Land recently plowed 6 inches deep will absorb how many inches 
 of rainfall without any run-off? 
 
 Is there any advantage in deep plowing on rolling or hilly land? 
 
 What is a saturated soil? 
 
 Why do they plow deep in semi-arid regions? 
 
 ♦Galvanized iron or copper tubes two inches inside diameter and twelve inohes long 
 with a crease one inch from the top. The bottom is perforated with numerous small 
 holes and is about one-half inch from lower end of tube. There are two or three holes in 
 main tube below this for water to enter. 
 
37 
 PRACTICE 17 
 
 Soil 
 
 Sand Loam Silt Clay Peat 
 
 Weight of tube 
 
 Weight of tube + air dry soil . . . 
 
 Weight of air-dry soil 
 
 Percent of hygroscopic moisture . 
 
 Weight of water-free soil 
 
 Time to become moist 
 
 Depth of dry soil 
 
 Depth of wet soil 
 
 Weight of water retained 
 
 Percent of water retained 
 
 Apparent specific gravity 
 
 Weight of cubic foot of soil 
 
 Pounds of water per cubic foot. . 
 Acre inches of water 
 
PRACTICE 18 
 
 Power of Compact Soils to Retain Water 
 
 Use same tubes and soils as in Practice 17 and run at, the same 
 time if possible. Prepare the tubes in the same way but compact by 
 letting the weight drop three times from the 12 inch mark upon each 
 measure of soil. Fill to the crease except peat and proceed as in 
 Pr&cticG 17. 
 
 Calculate the percent of water retained, the weight of water per 
 cubic foot of soil using the apparent specific gravity found in Practice 
 9, and the acre inches of water for each soil. 
 
 Which soil becomes wet on top first? Why? How does this cor- 
 respond with total pore space? Which soil is drained first? Why? 
 How does this correspond with total pore space? 
 
 How does rolling effect the water-holding capacity of a soil? 
 
39 
 PRACTICE 18 
 
 Soils 
 
 Sand Loam 
 
 Silt 
 
 Clay Peat 
 
 Weight of tube 
 
 Weight of tube + air-dry soil 
 
 Weight of air-dry soil 
 
 Percent of hygroscopic moisture . 
 
 Weight of water-free soil 
 
 Time to become moist 
 
 Depth of dry soil 
 
 Depth of wet soil 
 
 Weight of water retained 
 
 Percent of water retained 
 
 Apparent specific gravity 
 
 Weight of cubic foot of soil 
 
 Pounds of water per cubic foot.. 
 Acre inches of water 
 
40 
 
 PRACTICE 19 
 
 Effect of Organic Matter on Retention of Water 
 
 Use same tubes as in preceding practices but compact in one, 
 sand, and in the others sand and peat in the following proportions: 
 95 grams of sand and 5 grams of peat thoroughly mixed, 90 grams of 
 sand and 10 grams of peat, 80 grams of sand and 20 grams of peat and 
 60 grams of sand and 40 grams of peat. 
 
 Treat as in the preceding and determine the grams of water re- 
 tained, also the percent of water retained based upon the total 
 amount of sand and peat used in each tube. 
 
 How many grams of water did the 5 grams of organic matter re- 
 tain? The 10 grams? The 20 grams? The 40 grams? 
 
41 
 PRACTICE 19 
 
 Soils 
 
 Prac- 
 tice 18 
 Sand 
 
 Sand 
 
 — % 
 Peat 
 
 Sand 
 
 % 
 
 Peat 
 
 Sand 
 -% 
 Peat 
 
 Sand 
 -% 
 Peat 
 
 Weight of tube 
 
 Weight of tube + air-dry 
 soil 
 
 Weight of air-dry soil 
 
 Percent of hygroscopic 
 moisture 
 
 Weight of water-free soil.. 
 
 Time to become moist 
 
 Depth of dry soil 
 
 Depth of wet soil 
 
 Weight of water retained . 
 Percent of water retained. 
 Apparent specific gravity. 
 
 Weight of cubic foot of soil . 
 
 Pounds of water per cubic 
 foot 
 
 Acre inches of water. 
 
 Grams of water retained by 
 one gram of peat 
 
42 
 
 PRACTICE 20 
 
 Determination of the Rate of Percolation of Air Through 
 Soils 
 
 This experiment requires the utmost care in order to obtain 
 satisfactory results. Use the same aspirator* for all of the soils. 
 Be sure that all connections are air tight. Use pressure tubing. 
 
 Fill the tubes very carefully without compacting, holding them 
 vertically while filling. Attach the tubes successively to the aspirator 
 after the can has been lowered in the water to the zero mark. Allow 
 at least 4 litres of air to pass through each soil and express results in 
 time required for 10 litres of air to pass through. Empty tubes and 
 refill and run again as a check. 
 
 Use sand, loam and clay, compacting by letting the weight fall 
 three times from the foot mark upon each measure of soil. Tabulate 
 your results for both loose and compact. 
 
 What bearing has this experiment upon aeration? 
 
 What effect does organic matter have on aeration? 
 
 What effect will moisture in the soil have upon aeration? 
 
 Try it by wetting the tube of sand and then drawing air through 
 it. 
 
 One student may run sand with 10 grams of organic matter (peat) 
 and another clay with the same proportion and compare with the 
 results from the stock sand and clay. Give to the class for compari- 
 son. 
 
 ♦The aspirator B is made of galvanized iron, 8 inches in diameter and about 18 inches 
 long fitted with a stopcock to which the rubber tube is attached that runs to tube D in 
 which the soil is placed. The aspirator fits loosely in a can C filled with water. Tube D 
 is made of galvanized iron and is 2 inches in diameter and 18 inches lonif with a tube for 
 attaching to the rubber tube from the aspirator. A is the weight and should be at least 
 twice as heavy as can B. 
 
43 
 PRACTICE 20 
 
 
 Sand 
 
 Loam 
 
 Clay 
 
 
 Loose 
 
 Com- 
 pact 
 
 Loose 
 
 Com- 
 pact 
 
 Loose 
 
 Com- 
 pact 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 1 
 
 
14 
 
 PRACTICE 21 
 
 Determination of the Rate of Percolation of Water 
 Through Soils. 
 
 Fill the tubes* provided for the purpose with the soils, without 
 compacting, to within a half inch of the overflow tube and place a 
 layer of coarse sand one half inch deep on top to prevent the dis- 
 turbance of the soil by the flowing water. 
 
 Connect the tubes as in the figure by means of short rubber 
 tubes. Attach a to the water supply and b should lead to the waste 
 pipe or sink for taking off the overflow. Allow the water to flow 
 over the surface of the soil just fast enough to keep it constantly 
 flooded. Place flasks under the tubes c to catch any drainage water. 
 Note the time when water is turned on and also when percolation 
 begins. When the flow becomes constant, the quantity of water 
 draining from the soil in 30 minutes is determined. 
 
 Use the same soils in the same way but compact them in the 
 usual manner. 
 
 What application of this experiment do we see in farm practice? 
 
 From this experiment, would it be advisable to plow deep? 
 
 Would there be any advantage in fall plowing? 
 
 What objection to a sandy soil does this experiment show? 
 
 fr\ 
 
 X 
 
 = ^ 
 
 *The tubes are of galvanized iron 2 inches inside diameter. The overflow tubes, 
 about % inch in diameter, are 1 inch from the top and the M inch bent drainage tube is 
 Vi inch from the bottom. 
 
45 
 PRACTICE 21 
 
 
 Sand 
 
 Loam 
 
 Silt 
 
 
 Loose 
 
 Com- 
 pact 
 
 Loose 
 
 Com- 
 pact 
 
 Loose 
 
 Com- 
 pact 
 
 Time when percola- 
 tion begins 
 
 
 
 
 
 
 
 Amount of water 
 percolating 
 in 30 min 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
46 
 
 PRACTICE 22 
 
 Testing the Tenacity of Moist Soils. 
 
 Use clay, silt and loam. 
 
 Weigh out about 200 grams of each soil to be tested. Pour the 
 soil in a pan and mix with it by hand enough water to bring it to 
 maximum adhesiveness as near as you are able to judge. 
 
 Note amount of water used. 
 
 Now holding the cages firmly together, pack the mud into them 
 and scrape the top off level. Attach the weight pan and carefully 
 pour sand or fine shot into it until the soil column breaks. Weigh pan 
 and sand. Put the movable cage in place but not having the soil 
 surface in contact, and determine the weight necessary to overcome 
 friction. 
 
 Subtract this from the previous weight. The result represents 
 the tenacity of a column of moistsoil one square inch in cross section. 
 
 With the same roll of mud, make three tests, using different 
 amounts of water, noting the amount added for each soil each time. 
 
 How does fineness of grain effect tenacity? 
 
 What effect would undecomposed organic matter have on tena- 
 city? 
 
 What term is applied to very tenacious soils? 
 
 What differences in the working of these soils? 
 
47 
 PRACTICE 22 
 
 Soils 
 
 Silt 
 
 Loam 
 
 Clay 
 
 
 
 
 
 
 
 
 
 
 
 Weight to overcome friction. . 
 
 
 
 
 
 
 
 
 
 
 Breaking force I 
 
 2nd trial 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
48 
 
 PRACTICE 23 
 
 Eefbct of Organic Matter on Kise of Water. 
 
 Class exercise in which each member of the class is to take daily 
 observations on the height of the water in the tubes and note effect 
 of organic matter on rise of water. 
 
 After tying a cloth firmly over the ends of two glass two-inch tubes, 
 18 inches long, fill them to the height of one foot with soil compacted by 
 letting the tube drop four times on a book for a distance of six inches 
 for every six inches of soil put in the tube. 
 
 In one tube put about an inch of cut straw or sawdust, in the 
 other about a half inch of well decomposed manure or peat. Fill the 
 tubes with soil. Place the ends of the tubes in a tray and note the 
 effect of the organic matter. 
 
 What is the effect of plowing under poorly rotted manure in the 
 spring? 
 
 What advantage in this respect in fall plowing? 
 
49 
 
 PRACTICE 24 
 A Study of tiie Capillary Power of Soils. 
 The capillary power of soils is influenced by several factors, the 
 most important of these being the physical composition, texture and 
 compactness of the soil. In field soils all of these are changed by con- 
 tinuous cropping and capillary action is therefore altered. Of these 
 factors, physical composition is most important. 
 The soils selected are as follows: 
 
 1. Peat. 
 
 2. Sod, preferably an old blue grass pasture. 
 
 3. Heavily cropped soil as near (2) as possible so that the type of 
 soil will be the same. 
 
 4. Clay. 
 
 5. Silt. 
 
 6. Loam. 
 
 7. Loess. 
 
 8. Sand that will pass a 100 mesh sieve but not a 120. 
 
 9. Sand that will pass an 80 mesh sieve but not a 100. 
 
 10. Sand that will pass a 60 mesh sieve but not an 80. 
 
 11. Sand that will pass a 48 mesh sieve but not a 60. 
 
 12. Sand that will pass a 20 mesh sieve but not a 40. 
 
 13. Sand and clay equal parts by weight. 
 
 14. Loess and clay equal parts by weight. 
 
 15. Loess and sand equal parts by weight. 
 
 16. Loess with 10 per cent of well ground peat. 
 
 17. Sand with 10 per cent of well ground peat. 
 
 18. Clay with 10 per cent of well ground peat. 
 
 19. Silt and 5 per cent peat. 
 
 20. Silt and 10 per cent peat. 
 
 21. Silt and 15 per cent peat. 
 
 22. Silt and 20 per cent peat. 
 
 23. Silt and 35 per cent peat. 
 
 24. Silt and 50 per cent peat. 
 
 One end of the large glasstubes is closed by means of a piece of 
 muslin firmly tied on. These tubes are then filled with the finely 
 pulverized and sifted air-dried soils. Great care must be exercised 
 in filling these tubes so as not to separate the coarse and 
 fine particles. This may best be accomplished by holding the tube 
 vertically during the process of Ailing. When the tubes are filled, 
 the soil is compacted slightly by letting each tube drop 4 times, a 
 distance of 4 inches upon a book. The tubes are now placed in the 
 supporting frames in such a manner that the ends shall dip one half 
 inch beneath the surface of the water contained in the tray. The 
 water should be turned in all trays at the same time. The exper- 
 iment is now ready for observation and the data to be obtained at 
 each reading is the total hight to which the water has risen. The 
 readings are to be taken as nearly as possible at the intervals stated 
 below and tabulated. 
 
50 
 
 Observe night after $ hour, 1 hour. 2 hours, 3 hours, 6 hours, 9 
 hours, 12 hours, 24 hours, 36 hours, 48 hours, 3, 4, 5, 6, 7 and 8 days. 
 
 Make a close comparison of the different tubes. 
 
 Which shows the most rapid rise, 8 or 11? 6 or 7? Why? 
 
 Plot the bights of the water of the different tubes at different 
 times? 
 
 Why does loess show a greater and more rapid rise than clay? 
 
 At the end of one hour which shows the greater rise, clay or 20 
 sand? Which at the end of a week? Why? 
 
 What effect does organic matter have as shown in 2 and 3, 4 and 
 18, 7 and 16 and 12 and 17 and 19 to 24? 
 
 What effect does size of particles have on rapidity of capillary 
 movement not taking bight into account? 
 
51 
 
 +3 4-3+^+3 
 
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 go c3 c3 c3 c£ tj 
 
 GO GO CO CO g 
 
 O O c= O o e3 
 
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 . a a a a 
 
 *| *fc ^ 4R S? 
 
 CD o iO O 
 
 ^ lO H H N 
 
 +3 43 
 
 CO ■* <M 
 
 
 W o 
 
 J ft ft ft ft ft vx 
 
 CO GO CO 
 CD CD CD 
 O O " 
 
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 M CO IB CC W OQ 
 
52 
 
 PRACTICE 2j 
 
 Effect of Soil Mulches on Evaporation of Water from Soils. 
 
 Fill all of the tubes* with the same kind of soil compacting each 
 three inches of soil added. The enlarged bases of the tube are then 
 partially filled with water and the tubes are left 
 till the surface soil becomes moist. The tubes are 
 then ready for use. The water must be replaced 
 from day to day, as it evaporates from the surface 
 by refilling the base, the exact amount of water 
 added in each case being noted. 
 
 The loss of water is determined by the loss in 
 weight of the tubes. Weigh each day. 
 Tube 1. Check (no cultivation). 
 Tube 2. Cultivated 1 inch deep. 
 Tube 3. Cultivated 2 inches deep. 
 Tube 4. Cultivated 3 inches deep. 
 Tube 5. Cultivated 4 inches deep. 
 The cultivations should be made every other 
 day to the required depth. 
 
 Each tube has an area of thirty-six square 
 inches and the results are to be computed in tons of water evapo- 
 rated per acre per week. 
 
 It is very necessary that the tubes all have the same exposure to 
 heat and air currents. 
 
 Upon what principle does a soil mulch conserve moisture? 
 What effect will cultivation have on a very wet soil? 
 If the water table were 12 inches from the surface instead of what 
 it is, what difference would there be in your results? 
 
 Is there any argument in the experiment in favor of fall plowing? 
 What argument for cultivating as soon after a beating rain as 
 possible? 
 
 *The tubes may be made of galvanized iron, zinc or copper. Each tube consists of 
 two parts, a straight tube 28" long and 6%" in diameter for holding the soil and an 
 enlarged base 9" in diameter and 3" high for holding the water. The former is olosed 
 by tying a piece of muslin over the end- The opening of the basal part Is olosed by a 
 flange about 3" from the end of the large tube. The small tube is for adding water as it 
 evaporates. 
 
53 
 PRACTICE 25 
 
 Soil 
 
 
 
 
 
 
 Depth of Cultivation 
 
 No 
 Culti- 
 vation 
 
 linch 
 deep 
 
 2 inches 
 deep 
 
 3 inches 
 deep 
 
 4 inches 
 deep 
 
 Total evaporation in grams. 
 Tons per acre per week 
 
 
 
 
 
 
 
 
 
 
 
 
54 
 
 PRACTICE 26 
 
 Effect of Artificial Mulches upon Evaporation of Water 
 from Soils. 
 
 Fill tubes as in preceding exercise to within one inch of top and 
 then fill the remaining part with material for mulch. Proceed as in 
 Practice 25. 
 
 Tube 1. Check (filled to top with same kind of soil). 
 
 Tube 2. One inch of sand. 
 
 Tube 3. One inch of gravel. 
 
 Tube 4. One inch of peat. 
 
 Tube 5. One inch of sawdust or cut straw. 
 
 The area of each tube is thirty-six square inches. 
 
 Compute loss of water in tons per acre per week and tabulate 
 results. 
 
 What will be the effect of these mulches on temperature? 
 
 What is the principle of the growing of "Straw potatoes," i. e. 
 covered with straw and not cultivated? 
 
Soil 
 
 Mulch 
 
 55 
 PRACTICE 26 
 
 No 
 
 mulch 
 
 1 inch 
 sand 
 
 1 inch 
 gravel 
 
 1 inch 
 peat 
 
 1 inch 
 saw- 
 dust 
 
 Total evaporation in grams. 
 Tons per acre per week 
 
56 
 
 PRACTICE 27. 
 
 Effect of Different Surfaces upon Evaporation. 
 
 Fill all tubes with the same kind of soil to within one inch of top 
 by compacting. 
 
 Fill one tube to the top with the same kind of soil and the others 
 with the material desired. 
 
 No. 1. Check (filled to top with same kind of soil). 
 
 No. 2. One inch of sand. 
 
 No. 3. One inch of peat. 
 
 No. 4. One inch of sawdust or cut straw. 
 
 No. 5. One inch of gravel. 
 
 No. 6. Pan of same area filled with water. 
 
 The area of each tube is thirty-six square inches. 
 
 Conduct this practice similar to preceding, computing loss of 
 water in tons per acre per week. Tabulate results. 
 
57 
 PRACTICE 27 
 
 Surface 
 
 Soil 
 
 Sand 
 
 Peat 
 
 Saw- 
 dust 
 
 Gravel 
 
 Water 
 
 Total evaporation in 
 grams 
 
 
 
 
 
 
 
 Tons per acre per 
 week 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
58 
 
 PRACTICE 28 
 
 Use eye-piece and stage micrometers. Place both micrometers 
 in position and determine the number of divisions or spaces of the 
 eye-piece micrometer that correspond tol, .1, .01 and .001 millimeters 
 of the stage micrometer for each of the objectives. 
 
 By means of this table and the microscope with the eye-piece 
 micrometer, it may be determined whether the separations are prop- 
 erly made in the following Practice. 
 
59 
 PRACTICE 28 
 
 Grades 
 
 Diameter in 
 millimeters 
 
 inch 
 
 objective 
 
 inch 
 
 objective 
 
 inch 
 
 objective 
 
 Clay 
 
 .001-less 
 .001- .01 
 .01 - .1 
 
 
 
 
 Silt 
 
 
 
 
 
 .1 -1.0 
 
 
 
 
 Gravel 
 
 1.0 -more 
 
 
 
 
 
 
 
 
60 
 
 PRACTICE 29 
 Mechanical Analysis. 
 
 Four samples of from five to ten grams of the prepared soil are 
 weighed out and the hygroscopic moisture determined. 
 
 Two of these are then ignited and the percent of loss on ignition 
 is found based upon the water-free soil. Each of the other two sam- 
 ples is placed in a shaker bottle and about 200 cc. of distilled water 
 and from 5 to 10 drops of ammonia are added. The bottles are then 
 placed in the shaker and agitated till a microcopic examination of a 
 drop of the contents shows that the soil particles are completely sep- 
 arated and no granules exist. When this condition is reached, the 
 individual particles will appear clear or semi-transparent in the field 
 of the microscope while any remaining granules will be dark, irregular 
 and opaque. It may be necessary to continue the shaking for twelve 
 or even twenty-four hours tocompletely disintegrate the soil granules. 
 As the determination is quantitive, but a small amount of the liquid 
 is taken from the bottle with a small glass tube and mounted on a slide 
 for examination. When the examination is completed, the slide and 
 cover glass are carefully rinsed with distilled water back into the bot- 
 tle to recover the small portion of soil taken. Great care is necessary 
 throughout the analysis to prevent the loss of any part of the sample, 
 and for purposes of comparison and greater accuracy in results, dupli- 
 cate samples are used. 
 
 ^mi 
 
 i \ 
 
 V 
 
 * * 
 
 \ ) 
 
61 
 
 When the microscope reveals that no compound granules remain, 
 the samples are ready for separation into the different grades. Re- 
 move stoppers from the shaker bottles and wash them off carefully 
 with distilled water so as to save all of the adhering particles. Make 
 an apparatus similar to figure using an inverted 2-hole rubber stop- 
 per so large that it will close the mouth of the bottle without going 
 in. Place in one hole a short bent tube and in the other a long tube 
 that reaches near the bottom of the bottle. The lower end of this 
 tube should bend suddenly upon itself so that the opening shall be 
 upward and not downward. Adjust this tube when the apparatus is 
 in place on the bottle so that the opening in the long tube will be H 
 inches from the bottom of the bottle. Make a mark on the bottle 3 
 inches from the bottom. Fill the bottles to this mark by means of a 
 small stream of water of sufficient force to thoroughly stir up the con- 
 tents. 
 
 After the liquid has stood long enough for the fine sand to settle 
 below the end of the tube as shown by a microscopic examination of 
 a sample compared with the sizes of the grades in the preceding exer- 
 cise, the liquid is blown off into a beaker provided for the purpose. 
 This operation of filling, settling and blowing off is repeated until 
 the grades that settle are free from silt and clay. The liquid blown 
 off contains silt and clay and no effort is made to separate them here. 
 For separating the fine sand, fill the bottles as before and allow 
 to stand long enough for the sand (.1-1 mm.) to settle below the tube 
 as shown by the microscope and then blow off the fine sand. Repeat 
 until all the fine sand is blown off. The sand and gravel may be sep- 
 arated by the use of the millimeter sieve. 
 
 If at any time during the analysis, it is found that some of the 
 wrong grade is blown over, it will be necessary to recover this. The 
 water containing the silt and clay is poured into a large bottle and 
 thoroughly shaken when an aliquot part or 500 cc. is taken and evap- 
 orated to dryness, placed in a crucible, ignited, weighed and the total 
 amount of clay and silt determined and the percent found. 
 
 The water containing the fine sand, sand and gravel is decanted, 
 each grade is put in a weighed crucible, dried, ignited and the percent 
 of each grade is determined. 
 
62 
 PRACTICE 29 
 
 Soils 
 
 Grams 
 
 Percent 
 
 Grams 
 
 Percent 
 
 Wt. of crucible 
 
 Wt. of cru.+air dry soil. 
 Wt. after drying in oven. 
 
 Hygroscopic moisture 
 
 Wt. after ignition 
 
 Loss on ignition 
 
 Clay, less than .001 
 
 Silt .001-.01 
 
 Fine sand .01-1 
 
 Sand .1-1 
 
 Gravel 1-more 
 
63 
 
 PRACTICE 30 
 
 The last two weeks of the semester will be devoted to the estima- 
 tion of the constituents of a larger number of soils. It is quite im- 
 portant that one should be able to estimate approximately the amount 
 of gravel, sand, silt, clay and organic matter in soils and it is the ob- 
 ject of this exercise to enable the student to do this. Each one will be 
 given a sample of soil to be studied according to the outline below. 
 The work is to be done rapidly and the graduated cylinder may be used 
 as an aid in estimating the amount of each constituent. 
 
 In using the graduated cylinder, place 10 cc. of soil in it and almost 
 fill with water. Shake thoroughly and allow it to stand for one-half 
 minute or longer. Note the amount of sand in cubic centimeters. 
 Soil No. 
 Dry 
 Color 
 Odor 
 
 Pulverulent, crumbly, cloddy. 
 Moist 
 Color 
 Odor 
 
 Floury, mealy or gritty 
 Friable or plastic 
 Composition 
 Organic matter (estimated) in percent 
 Gravel (estimated) in percent 
 Sand (estimated) in percent 
 Silt and clay (estimated) in percent 
 Name of soil. 
 
64 
 
 PRACTICE 31 
 
 Determination of the Effect of Cultivation and Mulches 
 upon Temperature and Moisture. 
 
 A number of students may work at this experiment, each one be- 
 ing assigned a definite problem. 
 
 Select a level area of four or five square rods and remove any veg- 
 etable matter, such as weeds, etc. Break up with plow or spade all 
 but one square rod. Place a mulch of straw or leaves several inches 
 deep upon a half square rod of both the plowed and the unplowed. 
 Roll a portion of the plowed area. 
 
 Determine temperature at one, two and four inches in depth 
 on days when the sun is shining. Read the thermometer every two 
 hours. 
 
 Determine moisture to a depth of forty inches once each week for 
 at least four weeks. 
 
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