long if exposed to the sun or wind. Sand is useless for agricultural 

 purposes unless mixed with clay, peat or large quantities of organic 

 matter. 



Clay 



Pure clay is kaolin, which is formed by the disintegration of feldspar. 

 Clay as found in soils is composed of silica, feldspar, limestone, mica, 

 kaolin and other like formations. Particles are much finer than sand, 

 being less than 0.005 mm. in diameter. 



Clays are very compact, many being practically impervious to 

 water. Clay soils are usually cold when wet, and the tempera- 

 ture remains lower than lighter soils in the same field. If culti- 

 vated while wet, they become puddled. When the moisture 

 evaporates, they contract, crack and become extremely hard, rendering 

 cultivation very difficult. 



Silt 



is composed of particles which vary in size between sand and clay. The 

 particles being smaller and lighter than sand and larger and heavier than 

 clay, they settle, when soil is roiled in a stream or ditch, on top of sand. 

 The beds of irrigation ditches usually have an accumulation of silt, 

 especially if the water carries soil in suspension. Silt soils are quite 

 pervious to water, and usually, they are very fertile when they carry 

 organic matter. 



Loam 



is a mixture of sand and clay. If clay predominates, it is called a clay 

 loam; if the amount of sand exceeds the clay, it is called a sandy loam, 

 and if organic matter exceeds in abundance, it is called black-sandy or 

 clay loam, as the case may be. 



Weight of Soils 



Soils vary in weight according to the size of the particles and the 

 composition. A fine sandy clay will weigh more than any of the others 

 mentioned. Peaty soils, which contain a large amount of organic 

 matter, are the lightest. The more organic matter soil contains, the 

 more water it will absorb. The weight of soils as given by Snyder is as 

 follows : 



Soil Pounds Per Cubic Fo6t 



Clay Soil 70 to 75 



Fine Sandy Soil 95 to 110 



^ Loam Soil 75 to 90 



Peaty Soil 25 to 40 



Average Prairie Soil 75 



Uncultivated Prairie Soil 65 



12 



