266 SOILS AND FERTILIZERS 



Experiment No. 8. 

 Movement of Air Through Soils. 



Fill a tube 12 inches high and 3 inches in diameter with sifted 

 loam soil without compacting. Attach the soil tube to the aspira- 

 tor by means of a rubber tube. Note the time required to draw 5 

 liters of air through the soil. In like manner fill tubes with sand, 



Fig. 40. Apparatus to Determine Rate of Air Movement Through Soils. 

 (Adapted from Bui. 107, U. S. Dept. Agr., Office of Expt. Stations). 



gravel, peat, and clay, and determine the time required for 5 liters 

 of air to be aspirated through each. In filling the tubes, care 

 should be taken that all are treated alike. Repeat the experiment 

 using soil from your own farm loosely filling one tube, and mod- 

 erately compacting another tube with the compacting machine. 

 Note the difference in the time required for the air to pass through 

 the loose and the compact soil. 



Experiment No. 9. 

 Separation of Sand, Silt and Clay. 



For this experiment, the student should use some of the soil 

 from his home farm. Ten grams of soil which have been passsd 

 through a sieve with holes .5 mm. in diameter are placed in a mor- 



