204 NATURE AND PROPERTIES OF SOILS 



The quantity of water entering a soil is determined almost 

 entirely by the physical condition of the soil. If it is loose 

 and open, the water enters readily and little is lost over the 

 surface as run-off. If, on the other hand, the soil is com- 

 pact, impervious and hard, most of the rainfall runs away, 

 and not only is there a serious loss of water, but considerable 

 erosion may also result. The first step in checking run-off 

 losses, therefore, is strictly physical in nature. Good tillage 

 and plenty of organic matter by encouraging granulation have 

 much to do with the proper entrance of water into the soil as 

 well as with its economic utilization therein. 



108. Erosion by water and its control. 1 — While every 

 one is familiar with the importance of water in the forma- 

 tion of alluvial and marine soils, the concurrent destructive 

 action that is going on in the uplands is generally overlooked. 

 This is due to the fact that erosion is often considered as more 

 or less uncontrollable, an ill that can not be avoided. In 

 Wisconsin, for example, 50 per cent, of the tillable land is 

 subject to erosion of economic importance. 2 Even in as level a 

 state as Illinois, 17 per cent, of the area is detrimentally 

 eroded. 3 The waste by erosion is as great in other states, 

 even those of an arid climate. Davis 4 has estimated that 870 

 million tons of suspended material are carried each year into 

 the ocean by the streams of the United States. Since this is 

 only a very small fraction of the soil brought down from the 



1 Davis, E. O. E., Economic Waste from Soil Erosion; U. S. Dept. 

 Agr., Year Book for 1913, pp. 207-220. 



Ramser, C. E., Terracing Farm Lands; U. S. Dept. Agr., Farmers' Bui. 

 997, 1918. 



Eastman, E. E., and Glass, J. S., Soil Erosion in Iowa; la. Agr. Exp. 

 Sta., Bui. 183, Jan., 1919. 



Fisher, M. L., The Washed Lands of Indiana; Ind. Agr. Exp. Sta., 

 Circ. 90, Feb., 1919. 



3 Whitson, A. R., and Dunnewald, T. J., Keep Our Hillsides from 

 Washing; Wis. Agr. Exp. Sta., Bui. 272, Aug., 1916. 



3 Mosier, J. G., and Gustaf son, A. F., Soil Physics and Management, 

 p. 358, Philadelphia, 1917. 



4 Davis, R. O. E., Economic Waste from Soil Erosion; U. S. Dept. Agr., 

 Year Book for 1913, p. 213. 



