PREHARVEST APPLE DROP 



Table 4. Number of Roots Less than 2 mm. 

 Diameter Exposed by Excavations 



in 



in Table 4. The total number of roots less than 2 mm. in diameter 

 ranged from 54 under tree #90 to 417 under tree #10, yet both of 

 these trees were heavy droppers. On the other hand, there were 378 

 of these small roots under tree #18 while only 79 were encountered 

 under tree #64, both trees being light-droppers. The ditlerence be- 

 tween total number of such roots under heavy-and light-dropping 

 trees was not statistically significant. 



The percentage of the total number of small roots located in each 

 soil zone is shown in Table 5. Although variation between trees was 

 large, it is evident that two-thirds of the small roots were located in 

 the combined C and D zones, and approximately one-fourth in the 

 combined A and B layers. Yet it must be remembered that the com- 

 bined C and D layers occupy a much larger volume of soil than the 

 A and B zones. Few small roots penetrated the E layer except where 

 this layer was closest to the soil surface (trees 44. 62, 64, 88, 90, 94). 

 Light-dropping-and heavy-dropping trees had the same percentage 

 of roots located in like soil zones ; hence, differences in the location 

 and thickness of the soil zones apparently were not a factor in 

 causing dift'erential dropping. 



Table 5. Per Cent of Total Number of Roots Less than 2 mm. Diameter in 

 Different Soil Zones (Average Per Tree) 



A + B 



Zone 

 C + D + SC 



Light-Dropping Trees 

 Heavy-Dropping Trees 



26 

 27 



68 



68 



6 



5 



