28 



CIRCULAR 303, U.S. DEPARTMENT OF AGRICULTURE 



was carefully picked from the roots and rootlets to a thickness of 

 about 2 inches. These were then sketched as shown in figure 17. 



The enormous extent of the roots of a large apple tree in a soil of 

 this kind is much greater than is often realized. A conservative esti- 

 mate indicates that the roots 

 of this tree thoroughly per- 

 meate and draw moisture and 

 some plant food from at least 

 14,400 cubic feet of soil, 

 enough to cover, to a depth 

 of 1 foot, one third of an 

 acre. The function of these 

 deep roots is not definitely 

 known, but records show that 

 trees which root deeply not 

 only produce well but also 

 are consistent producers un- 

 der varying seasonal condi- 

 tions. In the Hilton area it 

 was found that roots in the 

 deep subsoil seem to have a 

 stabilizing influence on or- 

 chard performance and prac- 

 tically all deep-rooted or- 

 chards were found to be 

 productive. 



These graphs show that 

 in the soils of group 3 roots 

 extend sufficiently deep for 

 good production, but that 

 so many of the roots are 

 dead or in bad condition that 

 high production or long life of 

 the tree cannot be expected. 

 In the soils of group 2, 

 trees on the till ridges with 

 compact till subsoil, and on 

 the less well drained natter areas of the lower gravelly slopes root to 

 an average depth of about 3 feet. On the level imperfectly drained 

 soils developed from water-laid material there is wide variation in 

 depth and extent of rooting, the maximum penetration being about 

 6 feet, but in many places rooting is not abundant below 4 feet. 



Figure 16.— Baldwin apple tree with a trunk 100 inches 

 in circumference. 



