KEGULATING THE TRANSPIRATION 187 



recommended for the prevention of the direct evap- 

 oration of water is of itself an effective factor in set- 

 ting free plant-food and thus in reducing the amount 

 of water required b)'' plants. The experiments at the 

 Utah Station, already referred to, bring out very 

 strikingly the value of cultivation in reducing the 

 transpiration. For instance, in a series of experi- 

 ments the following results were obtained. On a 

 sandy loam, not cultivated, 603 pounds of water were 

 transpired to produce one pound of dry matter of 

 corn; on the same soil, cultivated, only 252 pounds 

 were required. On a clay loam, not cultivated, 535 

 pounds of water were transpired for each pound of 

 dry matter, whereas on the cultivated soil only 428 

 pounds were necessary. On a clay soil, not cultivated, 

 753 pounds of water were transpired for each pound of 

 dry matter ; on the cultivated soil, only 582 pounds. 

 The farmer who faithfully cultivates the soil through- 

 out the summer and after every rain has therefore the 

 satisfaction of knowing that he is accomplishing two 

 very imjjortant things: he is keeping the moisture 

 in the soil, and he is making it possible for good crops 

 to be grown with much less water than would other- 

 wise be required. Even in the case of a peculiar soil 

 on which ordinary cultivation did not reduce the 

 direct evaporation, the effect upon the transpiration 

 was very marked. .-On. the soil which was not culti- 

 vated, 451 pounds of water were required to produce 

 one pound of dry matter (corn), while on the culti- 



