19 1 6] 



SHU LL— SOILS 



17 



The general situation is strikingly illustrated by table VI, which 

 combines the results of the 4 experiments of table V. While there 

 are a number of discrepancies, as one might expect, it is evident 

 that the method can be used in measuring approximately the forces 

 residing on the surfaces of soil particles at various soil moisture 

 contents. For instance, when this soil contains about 9.36 per 



502i 



45- 

 40- 

 35 

 30 ■ 

 25 

 20 H 



15 



10 



5 



10 



20 % 



Fig. 4. — Curves showing relation of moisture intake by seeds to increasing soil 

 moisture, plotted from experiment 4, table V; abscissae, percentage of soil moisture 

 in terms of absolute dry weight; ordinates, percentage of increase of soil moisture 

 above air-dry weight for the soil moisture curve (straight), and percentage of intake 

 by seeds in terms of their air-dry weight. 



cent of moisture (3.5 per cent above air-dry), it is in moisture 

 equilibrium with seeds at 6.47 per cent above their air-dry weight. 

 The seeds attain about the same equilibrium point with saturated 

 NaCl solution, which has an osmotic pressure of 375 atmospheres, 



