52 



SUCCESSFUL FARMING 



films are thickest to a point where they are thinner, tending always to 



equality in the thickness of the 

 film, but gradually becoming thin- 

 ner as the distance from the 

 source of water increases. 



It is evident, therefore, that 

 the fine-textured soil will hold 

 much more water than the one 

 consisting largely of sand. Such a 



iggDATS 



soil can supply crops with more 

 water than a sandy soil, and such 

 a soil is adapted to grass, wheat 

 and other plants having fibrous 

 roots that do not penetrate to 

 great depths. 



If a glass tumbler is filled 

 with water and emptied, a thin 

 film of the liquid adheres to the 

 surface. This will equal only a 

 fraction of one per cent of the 

 weight of the tumbler. If the 

 tumbler can be pulverized into a 

 very fine powder and the particles 

 saturated with water and allowed 

 to drain, they may hold water to 

 the extent of ten to fifteen per 

 cent of the weight of the glass. 

 This change in the water-holding 

 power is the result of pulveriza- 

 tion and especially of the increase 

 of the exposed surface which is 

 brought in contact with the liquid. 

 The finer the degree of pulveri- 

 zation the larger the percentage 

 of water the glass particles will 

 retain. So we find that soils of 

 very fine texture will sometimes 

 hold as much as forty per cent 

 of their weight of water, while 

 some of the coarse, sandy soils 

 will not hold more than four or 

 five per cent of their weight of water. This water-holding capacity of 

 the soil is also modified by its content of organic matter. Organic matter 



. w UUA. 



Rate and Height of Capillary Rise of 

 Water in Soils of Different Texture. 1 



1 Courtesy of The Macmillan Company, N. Y. From " Soils," by Hilyard. 



