58 



SOILS AND FERTILIZERS 



LABORATORY EXERCISES 



Exercise I. — Examination of soil for organic matter. 

 Materials. — Samples of clay soils respectively low and high 

 in organic matter, hand lens, flame. 



Procedure. — Examine a soil rich in organic matter under the 

 hand lens. Observe character of the organic matter, its color and 

 its effect on structure. Compare the structure of the soils high and 

 low in organic matter. What effect does the organic matter ap- 

 pear to have upon granulation ? How should the organic matter 

 influence the ease of preparing a seed bed? How does organic matter 

 influence percolation of water through a soil ? How does it affect its 

 water capacity ? 



Place a small portion of the soil rich in organic matter in the 

 flame. Observe and explain the results. 



Exercise II. — Examination of peat and muck. 

 Materials. — Samples of peat and muck, hand lens, flame. 



Procedure. — Examine samples 

 under lens and describe and make 

 drawings. What is the origin of 

 the materials, their structure, com- 

 position and degree of decay ? 

 What is the value of peat and 

 muck ? 



Place a small portion of each in 

 the flame. Observe and explain 

 results. What is shown regarding 

 the composition of peat and muck ? 



Exercise III. — Estimation of 

 organic matter. 



Materials. — Soil samples, cru- 

 cible, stirring wire, flame, tripod, 

 clay triangle, balance. 



Procedure. — Place a five-gram 

 sample of dry soil in a weighed 

 crucible. Ignite with frequent 

 stirrings at a low red heat over a flame until original dark color has 

 disappeared. Cool and weigh. The loss has been largely organic 

 matter. Calculate the percentage based on the original sample. 

 Find in this way the percentage of organic matter present in several 

 different soils. 



Fig. 11. — Apparatus for the esti- 

 matiqn of organic matter in soil. 

 (A) crucible, (B) clay covered tri- 

 angle, (C) tripod, (D) Bunsen burner. 



