46 SOILS AND FERTILIZERS 



LABORATORY EXERCISES 



Exercise I. — Examination of soil particles. 



Materials. — Samples of soil, hand lens, high power microscope. 



Procedure. — Examine various sizes of soil particles under the 

 hand lens and later under the microscope. Observe shape and 

 color. If possible measure size of particles. Try to distinguish 

 between silt, clay and sand particles. 



Exercise II. — Examination of soil separates. 



Materials. — The seven separates into which a soil is divided in 

 making a mechanical analysis. 



Procedure. — As a soil is made up of the seven grades of parti- 

 cles in varying amounts, the characteristics of the grades will 

 determine the characteristics of the soil. 



Observe the cohesion and plasticity of each grade. The finer 

 grades are usually richer in plant food. Therefore try to imagine 

 the physical and chemical properties of different mixtures. Study 

 the separates with a view to identification if presented unlabeled. 



Exercise III. — Simple mechanical analysis. 



Materials. — Sandy loam well pulverized, 8 oz. bottle, funnel 

 with filter paper, torsion balance, ammonia. (See Fig. 7.) 



Procedure. — Place 50 grams of a dry and well-pulverized sandy 

 loam in a bottle of about 8 ounces capacity. Add a few drops of 

 ammonia and fill two-thirds full of water. Shake five minutes to 

 break up all granules. Then allow sample to stand until the 

 various grades of sand have settled to the bottom, after which de- 

 cant the silt and clay. Add water and repeat this until the water 

 clears as soon as the sands have settled. Then wash the sands 

 out into a weighed filter paper held in a funnel. Allow sands to 

 drain. Then dry sands and filter paper thoroughly and weigh. 

 This weight, less the weight of the filter, will give the weight of the 

 sands. Fifty grams, less the weight of the sands, will give the 

 weight of the silt and clay. Calculate the percentages of sand and 

 of silt and clay respectively in the sample of sandy loam. 



Exercise IV. — Study of soil class and its determination by 

 examination. 



Materials. — Hand lens, a number of different soil classes (sand, 

 sandy loam, clay loam, loam, silt loam, muck, etc.) labeled for study 

 and a set of unknown specimens for identification. 



