﻿6 



BULLETIN' li:«», U. S. DEPAl; I W KNT OF AGRICULTURE. 



There is an experimental error in sampling, depending: largely 

 upon the lack of uniformity of the soil. Different soils vary greatly 

 in this respect, Almost all soils in the Great Plains become less uni- 

 form in character and structure as distance from the surface in- 



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Fig. 1. — Diagram showing the percentage of water in the several foot sections of soil of 

 plat B in wheat at Williston, N. Liak., at each date of sampling In 1910. 



creases. Thus, any single sampling can not be taken as giving an 

 exact measure of the water content of a plat, but must be considered 

 as giving a close approximation, the closeness depending upon the 

 uniformity of the soil. In all of the years and stations under study 



