38 



MASS. EXPERIMENT STATION BULLETIN 209. 



on plots 2, 3, 4 and 5 since 1911 was due mostly to the stimulus of culti- 

 vation which lasted through 1915. From 1915 to 1919 the check plot 

 maintained just about the same growth as plot 1, while plots 2, 4 and 5 

 fell away. This may indicate an effect of the withdrawal of the fertilizer 

 applications, though, as stated above, the fact that it is seen in 1916 indi- 

 cates that it is not wholly due to that cause. 



Fm. 



2. — Relative irunk circumferences. Circumferences on plot 1 taken as 100 per i 

 Plot numbers are shown at the right. 



Varietal Response to Treatynent. 



Turning now to the question of whether all varieties have responded 

 in the same manner to the various fertilizer treatments, we may examine 

 Fig. 3. This shows the average trunk circumferences of the four varieties 

 at three periods: first, in 1902, at the end of the period of hay removal; 

 second, in 1911, at the end of the sod mulch period; third, in 1919, after 

 nine years of partial or strip cultivation. 



An examination of these graphs shows that the several varieties have 

 maintained about the same relative positions during the entire period for 

 which growth records have been kept. With increased size of the trees, 

 the absolute differences have naturally increased. Rhode Island Greening 

 has done better on the manure and ashes plots than on the other three 



