250 SOILS: PROPERTIES AND MANAGEMENT 



economic use of water, as the plant, in order to supply 

 itself properly with food, must transpire excessive amounts 

 of water. As soil moisture may be controlled, this waste 

 may to a certain extent be eliminated. 



172. The influence of fertility on transpiration. — The 

 amount of available plant-food is also concerned in the. 

 economic utilization of water. In general the data along 

 these lines show that the richer the soil, the lower is the 

 transpiration ratio. Therefore a farmer, in raising the 

 general fertility of his soil by drainage, lime, good tillage, 

 green manures, barnyard manures, and fertilizers, provides 

 at the same time for a greater amount of plant production 

 for every unit of water utilized. Again, quoting from 

 Hellriegel and Montgomery, the following figures are 

 available : — 



Effect of the Supply of Plant-food Materials on the 

 Transpiration Ratio of Barley grown in Quartz Sand 

 with a Nutrient Solution; Calcium Nitrate being in 

 the Minimum. Hellriegel x 



1 Hellriegel, H. Beitrage zu den Naturwissenschaftlichen 

 Grundlage des Ackerbaus, p. 629. Braunschweig. 1883. 



2 A unit of Ca(N0 3 ) 2 equals 1 mg. -equivalent. A mg.- 

 equivalent of Ca(N0 3 ) 2 equals 82.1 mg. 



