70 



THE PRINCIPLES OF SOIL MANAGEMENT 



23. Texture. The size of the individual particles 

 in a soil is a targe determining factor in all of its prop- 

 erties. The term texture is used to refer to the size of 



the individual par- 

 ticles of which a soil 

 is composed. 



In shape the 

 particles are very 

 irregular. Being 

 minerals or mineral 

 aggregates, they 

 tend to have the 

 characteristic lines 

 and faces of their 

 species. Ordinarily, 

 however, the nu- 

 merous forces that 

 have been at work 

 in the formation of 

 the soil have rounded or broken the mineral into angu- 

 lar, jagged or partially smoothed fragments. The relative 

 number of particles of corresponding sizes varies greatly 

 in different soils, some being composed largely of coarse 

 particles while others are made up largely of fine ones. 

 The relative proportion of these various -sized particles 

 influences greatly the physical properties of the soil. 



24. Textural classification. -When a soil is divided 

 into groups of particles of approximately one size, the 

 process constitutes a mechanical analysis and each 

 group is a soil separate. The limit in size of each of 

 these groups is arbitrarily arranged, and is determined 



Fig. 17. Fine sand, photomicrograph. Magni- 

 fied about 110 diameters. Differences in color 

 indicate differences in mineral composition. Each 

 particle composed of one mineral. 



