188 DRY-FARMING 



vated soils, though the direct evaporation was no 

 smaller, the number of pounds of water for each 

 j^ound of dry substance was as low as 265. 



One of the chief values of fallowing lies in the 

 liberation of the plant-food during the fallow year, 

 which reduces the cpiantity of water recjuired the 

 next year for the full grcjwth of croj^s. The Utah 

 exj)eriments to which reference has already been 

 made show the effect of the previous soil treatment 

 upon the water requirements of crops. One half of 

 the three ty]3es of soil had been cropped for three 

 successive years, while the other half had been left 

 bare. During the fourth year both halves were 

 ])lanted to corn. For the sandy loam it was found 

 that, on the part that had been cropped previously, 

 659 pounds of water were required for each pound of 

 dry matter ]5roduced, while on the j^art that had been 

 bare only 57.'] ])ounds were required. For the clay 

 l(jam 889 pounds on the cropped part and 550 on 

 the ])reviously l)are ]?art were required for each pound 

 of dry matter. For the clay 7466 pounds on the 

 croj^jDed i)art and 1739 ])ounds on the previously bare 

 l^art were required for each pound of dry matter. 

 These results teach clearly and emphatically that 

 the fertile condition of the soil induced by fallowing 

 makes it ]X)ssible to pr{jduce dry matter with a smaller 

 amount of water than can be done on soils that are 

 cro]3ped continuoush'. The beneficial effects of fal- 

 lowing are therefore clearh' twofold : to store the 



