48 



SOILS AND FERTILIZERS 



Procedure. — By the use of the chart determine the class of the 

 following soils and describe their probable characteristics. 



u 



fr* 



Be ready to explain the practical value of a mechanical analysis. 



Exercise VI. — Soil structure. 



Materials. — Puddled and granular soils. 



Procedure. — Examine under hand lens a granular and a puddled 

 soil. Describe each and make drawings. Discuss each as to prob- 

 able relation to air and water movement, penetration of plant roots, 

 ease of making seed bed, etc. Be ready to suggest practicable reme- 

 dies for poor structure. 



Exercise VII. — Determination of apparent specific gravity of 

 a dry sand and clay. (See Fig. 8.) 



Materials. — Torsion balance, dry soils and a 100 c.c. graduated 

 cylinder. 



Procedure. — Apparent specific gravity is the weight of dry soil 

 compared to the weight of the same volume of water. 



Weigh the 100 c.c. graduate in grams, then fill to the 100 c.c. 

 mark with loose sand. Weigh and calculate the weight of the sand 

 in grams. The weight of the sand divided by 100 (the weight of 

 100 c.c. of water in grams) will give the apparent specific gravity of 

 the loose sand. Now compact the sand as much as possible by 

 jarring and read volume. Divide the weight of the sand by this 

 volume to obtain the apparent specific gravity of the sand compact. 



