120 SOILS: PROPERTIES AND MANAGEMENT 



Approximate Number of Particles to the Gram in 

 Various Classes of Soil in the United States 



CLA8S 



Coarse sands . 

 Sands .... 

 Fine sands . . 

 Sandy loams 

 Fine sandy loams 

 Loams .... 

 Silt loams . . . 

 Sandy clays . . 

 Clay loams . . 

 Silty clay loams 

 Clays . . . . 



Approximate Number op 

 Particles 



2,299,145,360 



2,287,251,842 



1,826,176,893 



5,483,797,920 



5,485,069,147 



7,332,679,042 



6,868,546,664 



12,324,914,033 



11,877,875,092 



11,430,037,544 



19,177,571,994 



86. Surface exposed by soil particles. — Besides giving 

 an actual numerical figure and an insight into the prob- 

 able structural relationships of a soil, the approximate 

 number of particles may serve still another purpose — 

 that of enabling us to calculate the aggregate internal 

 surface exposed by the soil grains. The surfaces of the 

 grains hold more or less water according to their area, 

 and they increase the amount of chemical and biological 

 activities — functions so necessary to a continuous re- 

 placement in the soil solution of the elements withdrawn 

 by the plant. The minerals in the soil are all very re- 

 sistant to solution ; if they were not, they would long 

 ago have been leached away. Such materials, while 

 almost insoluble, allow the amount of material going 

 into solution to be notably increased by fineness of tex- 

 ture, although their solubility remains the same. The 

 fineness of the particles, then, presents another significant 

 feature besides those already pointed out. 



