Wadleigh and Richards 435 



to whether or not decreasing soil moisture content within the "availa- 

 ble range" will affect plant growth (u8, jo). If the level of soil mois- 

 ture approaches the wilting percentage while the plant is subjected to 

 a cool humid environment, an associated decrease in growth is much 

 less likely than if the plant is growing in a hot, dry environment. That 







I 



2 

 3 

 4 



OLYMPIC CLAY 

 ANTIOCH CLAY 

 YOLO CLAY LOAM 

 HANFORD FINE SANDY 



LOAM 

 INDIO SANDY LOAM 



10 20 30 40 50 60 70 80 90 

 SOIL MOISTURE- PERCENT OF TOTAL AVAILABLE 



100 



Figure 4. Relative loci of moisture retention curves presented in Figure 1. 



is, at the lower levels of "available moisture" the supply of soil moisture 

 in the former case could probably maintain turgescence, whereas it 

 would probably be insufficient in the latter instance. 



The evidence indicates that some species of plants, e.g., the tree fruits, 

 show no response in productiveness regardless of the level of soil mois- 

 ture maintained above the wilting percentage. There are productive 



