Agricultural Classification of Soils 5 



shrinkage, resulting in the hardening of the surface 

 and the forming of openings or cracks in periods of 

 drought. These cracks admit the heated air, and the 

 contraction which produces them breaks the fibrous 

 roots of plants, thus intensifying the injurious effects 

 of drought. Owing to the slowness with which clayey 

 soils dry, they are often seriously injured by cultivation 

 while wet. This class of soil is not adapted to horticul- 

 tural use. 



Clay loam is clayey soil ameliorated by the presence 

 of sand and humus, but in which clay predominates. If 

 well supplied with humus, to increase its porosity, 

 darken its color, and thus increase its friability and 

 elevate its temperature, clay loam is well adapted to the 

 growth of many vegetables, but is not so desirable for a 

 garden soil as the following. 



Sandy loam is one in which sand predominates over 

 the clay. If kept supplied with humus, either by heavy 

 applications of animal manures or by proper rotation, 

 this constitutes the typical garden soil. The fine clayey 

 soil -particles fill the inter- spaces between the grains of 

 sand and, together with the humus, produce a soil of 

 good texture, favorable to proper tillage and cultivation, 

 promptly warmed in spring and hence favorable to early 

 gardening, admitting free percolation of rain-water, a 

 free circulation of air, and facilitating the ascent of 

 capillary moisture in periods of drought. 



Sandy soils, composed principally of small particles 

 of quartz rock, are objectionable in many respects. The 

 particles of quartz being impervious to water, the rain- 

 water passes too freely through, carrying the soluble 



