66 DRY LAND FARMING 



ent, clayey particles are worked down, so as to aid in 

 forming so firm an under-soil that, the roots of plants 

 may not easily penetrate it. Such a condition of the 

 subsoil may frequently be removed by tillage that is 

 deep and judiciously given. Such tillage facilitates the 

 downward movement of water to an extent that tends, 

 to break up the hard-pan even at distances far below the 

 surface soil. 



When a gravel seam has been deposited not far dis- 

 tant from the surface, it facilitates the downward move- 

 ment of water in the soil and cuts off the upward move- 

 ment of the same, on the principle known as capillarity. 

 In dry areas such a condition is greatly harmful to vege- 

 tation. If the gravel seam is of great depth, the harmful 

 influence referred to is intensified, and if the subsoil con- 

 sists almost entirely of coarse sand grains, similarly ad- 

 verse influences will follow. It may be impossible in 

 some instances to obtain satisfactory production from 

 soils thus underlaid, but should the sand or gravel be 

 interspersed with clay particles, these harmful results 

 will be reduced proportionately to the extent to which the 

 clay particles are present. 



In some instances fine clay particles are carried down 

 from the surface and left to mingle with the substances 

 composing the subsoils so as to form a mass that is not 

 easily penetrated by the roots of plants. Opening up the 

 surface soil so as to admit more readily the descent of 

 water will usually help this condition, and it may be 

 still further aided by the decay of deep rooted plants, as 

 those of alfalfa, which to a greater or lesser extent may 

 have penetrated these soils. 



In some instances, especially in the soils adjacent to 

 higher lands, seepage waters come down from the 

 former and to such an extent as to rise to the surface 

 at certain seasons of the year. These may exclude the 

 air from both soil and subsoil to such an extent as to 



