CULTURAL METHODS IN ORCHARDS 



167 



to a tree annually), the trees often show considerable gain, 

 and when nitrate of soda is also used the orchard will not 

 infrequently do as well as when tilled. It then becomes 

 largely a question of soil and amount of available moisture 

 during the critical season of growth. 



Woodbury and associates report that "Trees grown un- 

 der a clean culture cover-crop system or under a heavy mulch 

 made 44.5 per cent greater average yearly gains in trunk 

 girth than trees grown in grass with a light mulch or no mulch 

 at all. There has been no significant difference between the 

 three varieties in their response to soil management treat- 

 ments. The Stayman variety made slightly greater gains in 

 girth of trunk on all plots than did Grimes or Jonathan." 



In support of this conclusion, the following data are sub- 

 mitted : 



Table XLV 

 detailed growth record of permanent trees for five-year period 



(after WOODBURY ET AL.) 



1 Girth. 1913. 



Gain in girth, 1914 to 1916. 



