PHILIPPINE SOILS. 327 



centimeters, and place these together as representing the surface soil. 

 In no case is the sample to he taken to a greater depth than 30 centi- 

 meters {12 inches). 



If the surface soil extends to a greater depth than 30 centimeters, take 

 a separate sample below the depth of 30 centimeters to a change between 

 the surface soil and the subsoil, or to a depth of a meter if no change 

 occurs. This sample of the subsurface soil should be obtained in other 

 respects precisely like that of the surface soil. 



Subsoil. The depth to which the sample of subsoil should be talcen 

 will depend on circumstances. It is always necessar}' to know what 

 constitutes the foundation of a soil to the depth of 1 meter at least, but 

 in ordinary cases 25 or 30 centimeters will be sufficient for examination in 

 the laboratory and should be taken in precisely the same manner as the 

 surface soil. 



If the surface soil extends to a considerable depth below 30 centi- 

 meters, the sample of subsoil may be taken with less exactness, perhaps 

 at some ditch or other accessible point, and its physical characteristics 

 noted, i. e., whether a clay, rock, sand, etc. 



Combine the borings of a given depth. Empty these large composite 

 samples in turn upon canvas, oilcloth blanket, large heavy paper, or 

 floor so as to protect the sample as much as possible. Break all lumps 

 and mix thoroughly. Divide the sample by "quartering" and discard 

 the two diagonally opposite quarters; mix the remainder and again 

 quarter, repeat the process until only about 1^ to 2 kilograms are left, 

 and place in cans or in tight canvas or muslin sacks for the laboratory. 



Each sample should have duplicate labels, one to be placed inside the 

 bag and the other to be tied on the outside. A number may be marked 

 on the bag and a descriptive letter prepared, but the label to be placed 

 within the bag should, under no circumstances, be omitted. This process 

 of taking samples may be modified as the exigencies of the work neces- 

 sitate, but only those taken as above will be entirely satisfactoiy. Any 

 departure from this method of sampling should be carefully noted. 



Describe accurately the location of the field from which the sample is 

 taken and the actual depth represented by each sample. It is often 

 desirable to relocate a field and repeat the analyses after the fields are 

 \inder irrigation or have been cropped for a long time. Add any statis- 

 tics regarding the land as to crops, years under cultivation or since culti- 

 vation, etc., or any topographical information which is easily available. 

 The above directions for taking soil samples are represented graphically 

 in fig. 10. 



104660 4 



