12 MASS. EXPERIMENT STATION BULLETIN 320 



tinued for a relatively short period. In Table 8 the average annual yields in 

 bushels per tree for a four-year period previous to the differential pruning treat- 

 ment is compared with the two-year period during which part of the trees were 

 not pruned. 



Table 8. — The effect of pruning on average annual yields — Clark 



Orchard. 



The number of trees of each variety is small. Allowing these trees to go un- 

 pruned for two years has apparently increased the yields of Ben Davis slightly, 

 and of Mcintosh and R. I. Greening considerably, and made no material difference 

 with Wealthy. It is interesting to note that the results with Wealthy are similar 

 to those shown with younger trees in Table 7. These Wealthy trees like the others 

 are only moderately vigorous. 



In view of the short period and few trees, it cannot be said that there is here 

 any conclusive evidence that pruning has affected yields. More evidence is needed 

 to prove that the increased yield of Mcintosh and R. I. Greening is due to leaving 

 the trees unpruned. 



The trees in Block O are old and have declined in vigor during the period of 

 this experiment though they produced by far their largest crop in 1930. This 

 heavy crop seems to be largely due to a light yield in 1929 and very favorable 

 weather while the buds and fruit of the 1930 crop were developing. 



Table 9 shows the average annual yield of these trees by varieties in pounds of 

 fruit per tree for six years of differential pruning. This is compared with the 

 yields of the same trees for the previous six-year period when they were all pruned 

 alike. The gain or loss in the second period as compared with the first is the sig- 

 nificant figure. This is given in percentage of gain over the yield in the earlier 

 period. 



Table 9. — The effect of pruning on average annual yields — Block O. 

 (Pounds per tree) 



