90 DRY-FARMING 



the spring and summer is as large or larger some feet 

 below the surface than in the ujjjjer two feet. The 

 tendency of the root is, then, to move downward to 

 depths where there is a larger supply of water. 

 Especially is this tendency increased by the avail- 

 able soil fertility found throughout the whole depth 

 of the soil mass. 



It has been argued that in many of the irrigated 

 sections the roots do not penetrate the soil to 

 great depths. This is true, because by the present 

 wasteful methods of irrigation the plant receives so 

 much water at such untimely seasons that the roots 

 acquire the habit of feeding very near the surface 

 where the water is so lavishly apj^lied. This means 

 not only that the plant suffers more greatly in times 

 of drouth, but that, since the feeding ground of the 

 roots is smaller, the crop is likelj' to be small. 



These deductions as to the depth to which plant 

 roots will penetrate the soil in arid regions are fully 

 corroborated l^y experiments and general observa- 

 tion. The workers of the Utah Station have repeat- 

 edly observed plant roots on dry-farms to a depth 

 of ten feet. Lucern roots from thirty to fifty feet 

 in length are frequently exposed in the gullies formed 

 by the mountain torrents. Roots of trees, similarly, 

 go down to great depths. Hilgard observes that 

 he has f(iimd roots of grapevines at a depth of 

 twenty- two feet below the surface, and quotes Aughey 

 as having found roots of the native Shephercha in 



