20 



BULLETIN 675, U. S. DEPARTS KXT OF AGRICULTURE. 



nation of higher water-holding capacity and higher percentage of 

 available water when the soils are saturated there remains for the 

 plant L6.7 per cent more water in the noneroded than in the eroded 

 soil. 



Tables 8 and 9 and figures i and 5 summarize the results as to vege- 

 tative growth and the water requirements of Held peas, native brome- 

 grass, and cultivated wheat grown in the two soils. In the case of 

 each of the three plants the table shows that a much greater amount 

 of water was required for the production of a unit of dry matter in 

 eroded than in noneroded soil. 



Tabi i 8. 



-Pounds <>f water rc<iuirc<J by peas, bromegrass, wheat, <m<i wheat 

 heads per pound of dty matter produced. 



Soil. 



Peas Brome 

 reas - ! grass. 



Wheat. 



Wheal 

 heads. 





841 1 1,339 

 467 | 1,110 



472 

 343 



1,370 





407 









80.3 



20.6 



37.6 2.66. 







Table 9. — Summary of vegetative growth and water requirements of peas, 



bromegrass, and wheat. 



Plant and soil. 



Number 

 of leaves, 



Leaf 

 length. 1 



Dry 



weight. 



Water 



used per 



plant. 



Milli- 







meters. 



Pounds. 



Pounds. 



791 



0.79 



667 



2,634 



6.55 



3,051 



2,902 



.41 



553 



5,218 



.85 



944 



4,474 



5.52 



2,516 



10, 080 



12.09 



3,820 



Water 

 used per 

 pound 

 dry mat- 

 ter pro- 

 duced. 



Peas: 



Eroded soil 



Noneroded soil . 



Native bromegrass: 



Eroded soil 



Noneroded soil . 



Wheat: 



Eroded soil 



Noneroded soil. 



42 

 712 



Pounds. 

 841 

 467 



1,339 



1,110 



472 

 313 



' In the ease of peas the length of stem is given instead of the leaf length. 



Figure 5, summarizing the vegetative growth and water require- 

 ment of peas on the eroded and noneroded soil, shows a remarkable 

 contrast in the vegetative growth and other activities. The number 

 of leaves is as 1 to 2.7; the leaf length, 1 to 3.3; the total dry weight 

 produced, 1 to 8.3; and the water used per plant, 1 to 4.6, all in favor 

 of the noneroded soil. In the water requirement per unit of dry 

 matter, on the other hand, the ratio is reversed, being as 1.8 to 1 on 

 the eroded and noneroded soils, respectively. Hence there are a great 

 many more leaves, greater stem and leaf length, and more dry mat- 

 ter produced on the noneroded than on the eroded soil, with a notably 

 -mailer amount of water (PI. IV). The latter fact, of course, is ac- 



