44 Practical Farming 



soil. This can be readily seen in a deep, sandy soil after 

 a rain. The rain water disappears very quickly, while 

 on a more loamy soil the surface will remain wet for a 

 much longer time and on a compact clay the water may 

 stand for a time on the surface if special means have not 

 been provided for sinking it in the soil by underdrainage. 

 Even in a sandy soil the rate of percolation downward 

 depends largely on the fineness of the sand. There are 

 soils in some sections which are known as pipe-clay soils, 

 which drain very slowly and become very hard in dry 

 weather, when the soil is really not properly a clay but 

 sand of great fineness and has just enough of clay to bind 

 these very fine particles closely together. They are really 

 quicksand soils and are among the most intractable of 

 soils for cultivation since they hold water till evaporation 

 takes place from the surface, making the soil cold and 

 unfavorable to vegetation. When soils of this nature 

 are well stocked with humus or organic decay they are 

 made more porous, and the downward percolation is more 

 rapid. Yet the retention of soil moisture is increased, 

 though it may seem paradoxical, for the hardening of such 

 soils in dry weather is due to the extreme fineness of the 

 particles favoring rapid evaporation from the surface, 

 unless the formation of a crust is stopped by frequent 

 shallow cultivation. Free percolation of water through 

 the soil is essential to the keeping of the aeration of the 

 soil perfect, provided the percolation is not too deep and 

 a more retentive stratum is not far below. But the rapid 

 percolation in a coarsely granulated sandy soil under 

 which there is no retentive subsoil is excessive, and makes 

 what is known as leachy soil in which the plant food is 



