iS 



SOILS AND FERTILIZERS 



boiling water, are placed in the sieve. Water is passed 

 through until the washings are clear. All particles 

 larger than 0.5 mm. remain in the sieve, and after dry- 

 ing and igniting, are weighed. The contents of flask r, 

 containing the particles less than 0.5 mm., are then 

 passed through a sieve having holes 0.25 mm. in 

 diameter. Finally a o. 10 mm. diameter sieve is used. 

 The fine sand and silt are separated by gravity. The 

 fine sand with some silt and clay are read- 

 ily deposited and the water containing 

 the suspended clay is decanted into a 

 second glass vessel. The residue is treated 

 b with more water and allowed to settle; 

 this operation is repeated until the micro- 

 d scope shows the soil particles to be nearly 

 all of one grade. 



Clav is obtained bv 

 evaporating an aliquot 

 portion of the washings 

 or by determining the 

 total per cent, of the other grades of particles and the 

 volatile matter and subtracting the sum from 100. 

 This is the Osborne sedimentation method with modi- 

 fications. 9 Hilgard's 10 elutriator, and the apparatus 

 of Shoen-Mayer are also used for separating the soil 

 particles. 



SOIL TYPES 



11. Crop Growth and Physical Properties. The 



Fig. 7. 



Figs. 8 and 9. 



