CHAPTER III. 



PHYSICAL PROPERTIES OF SOILS. 



Among the most noticaable or important physical 

 characteristics of soils are weight, color, adhesiveness, 

 fineness of division, and their relations to heat, to 

 moisture, to gases, and to dissolved solids. In regard 

 to all these, soils differ much, and these differences 

 have much to do with the differing capabilities of soils 

 in producing crops. Differences in physical proper- 

 ties depend largely on the proportion in which sand, 

 clay, lime, stones, and vegetable matter are combined 

 in the soil. 



Sand is heavy; is usually light colored; the grains 

 do not stick together. It has little power of attract- 

 ing moisture from the air, and allows water to run 

 through it readily. It absorbs and retains heat well. 

 A soil with much sand in it will be dry and warm; 

 easy to work; not sticky; will not "bake." In dry 

 weather crops on such soils will suffer from lack of 

 moisture. Soluble plant food will leach through such 

 a soil. 



Clay, or a soil with much clay, has a fine texture, 

 and the particles adhere tenaciously. It absorbs 

 moisture from the air readily, draws water from be- 

 low by what is known as capillary power, holds it well. 

 This tends to make such a soil cool, but it will absorb 

 heat readily. It absorbs and holds ammonia and other 

 gases readily. If stirred while wet it becomes hard; 

 often cracks in drying. It differs much in color. 

 The presence of iron will give a red color. Common- 



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