WATER OF SOIL IN ITS RELATION TO PLANTS 249 



greater is likely to be the wind velocity. All this would 

 tend to raise the transpiration ratio. 



171. Effect of soil moisture on transpiration. — From 

 the soil standpoint, however, the factors inherent in the 

 soil itself are of more vital importance as regards tran- 

 spiration, since they can be controlled to a certain extent 

 under field conditions. An increase in the moisture con- 

 tent of a soil usually results in an increased transpiration 

 ratio. The work of Hellriegel l with barley grown in 

 quartz sand containing a nutrient solution may be cited 

 in this regard, together with the data obtained by Mont- 



gomery 2 at 

 loam soil : — 



Lincoln, Nebraska, with corn grown in a 



Effect of Soil Moisture on Transpiration 



These data show clearly that an excessive amount of 

 water in the soil is not a favorable condition for the 



1 Hellriegel, H. Beitrage zu den Naturwissenschaftlichen 

 Grundlagen des Ackerbaus, Seite 639. Braunschweig. 1883. 



2 Montgomery, E. G. Methods of Determining the Water 

 Requirements of Crops. Proc. Amer. Soc. Agron., Vol. 3, 

 p. 276. 1911. 



