i84 



CONTROL OF EROSION ON RANGE AND PASTURE 



In all of the constituents examined, except potash, the non- 

 eroded soil was much the richer. The greatest difference was 

 found in the total content of nitrogen, one of the most im- 

 portant plant foods. A considerable proportion of the nitrogen 

 content was soluble in water and hence was subject to appre- 

 ciable loss through run-off. 



In addition to the decreased fertility of the eroded soil, it was 

 found that this soil had a maximum water-holding capacity of 

 46.8 per cent, as compared with 76.2 per cent for the non- 

 eroded soil. That part of the soil moisture which cannot be 

 absorbed by the roothairs of the vegetation — termed " non- 

 available water " — was found to be 15.6 per cent in the eroded 

 soil and 19.3 per cent in the noneroded soil. Accordingly, on 

 the basis of saturation, the noneroded soil was capable of yield- 

 ing to the vegetation 25.7 per cent more water than was the 

 eroded soil. 



Erosion and Plant Growth. — In order to determine the 

 difference, if any, in the crop-producing capacity and water 

 requirements of plants grown on typical eroded and noneroded 

 soils, blocks of these two kinds of soil were sifted and thus 

 freed of the larger pebbles, moistened moderately to the same 

 percentage basis, and tamped firmly into large galvanized-iron 

 cans. In one set of cans containing these selected soils was 

 grown pedigreed Canadian field peas, in another set native 

 bromegrass (Bromus marginatus), and in the third set a pedi- 

 greed wheat known as Kubanka. The pots were hermetically 

 sealed and so arranged that all the water removed from the 

 soil had to pass through the plants in the form of transpiration 

 or " evaporation." Water was added from time to time so 



