120 



SOIL PHYSICS AND MANAGEMENT 



In some cases areas of five acres or even less are shown, but only 

 when the area is a very distinct type. In states where no land 

 surveys have been made the roads form convenient lines from which 

 to work. 



3. Sampling of Soils. In. collecting soil samples for analysis 

 each investigator has used his own method. Uniformity is very de- 

 sirable for purposes of comparison. Since the samples are to be the 

 basis of investigations and plans for soil improvement, it is highly 

 important that they should be representative of their respective area 

 or type. Whatever the stratum divisions made, they should be se- 

 cured without mixing or contamination in any way. Various de- 

 vices have been used, but the soil auger (Fig. 64), 40 inches long, 

 seems best for the purpose in humid climates. 



The total depth to which the sample is taken varies with the 



Weight of Soil^trata 



