4 



MISC. PUBLICATION 194, U. S. DEPT. OF AGRICULTURE 



that growing bliiegrass or lespedt^za loses less than a ton per acre. 

 Similar results were obtained in a comparison of the native-grass sod 

 and clean-tilled kafir in central Kansas. The loss from the land 

 growing kafir was 21 tons per acre of soil and 12 percent of the rainfall. 

 On natural-grass sod the loss was 5 pounds per acre of soil and 0.5 

 percent of the rainfall (fig. 2). 



These results, obtained by actual measurements in different sec- 

 tions of the United States, indicate the usefidness of grasslands not 

 only in preserving soil resources but also in protecting storage reser- 

 voirs from destruction through the gradual accumulation of silt. 

 Many such reservoirs have been constructed for irrigation purposes 

 and power development. The capacity and consequent usefulness 

 of these expensive public utilities is lessened each year by the move- 





t,, VP\ »i -sf>^>-»»^' 



Figure 2. — Steep hillsides in southwestern Virginia, showing perfect control of soil erosion by pasture. 

 Where phosphate has been applied, clover is abundant. 



ment of soil from the surrounding watershed. Any increase in pas- 

 ture acreage \\ill tend to extend the period during which these reser- 

 voirs will fulfill their purpose. 



In addition to losing less soil by erosion than cultivated land, well- 

 managed grazing land loses less fertility because less is taken from 

 the soil by pasture plants and part of that which is removed is restored 

 directly through the excrement of grazing animals. Theoretically, 

 the soil should lose only the fertilizing constituents contained in the 

 carcass or in the milk that has been produced. However, if the 

 grazing is not well managed the losses of fertilit}^ on grazed land may 

 be much greater than is at first apparent. Observations show that 

 on good pasture cattle spend only about one third of their time 

 grazing. Therefore, if most of the remainder of the time is spent in 

 barns, in lots, at watering places, in lanes, under trees along streams, 

 or in brush or wooded places, as much as two thirds of the manure 

 may never be returned to the pasture. 



