New York Agricultural Experiment Station. 553 



why is tillage better than sod for the apple? 

 In our first report on the Auchter orchard, Bulletin No. 314, 

 we discussed at length the question, " Why is tillage better than 

 sod for the apple." We were not then satisfied that the conclusions 

 reached answered the question as fully or as accurately as might 

 be wished, yet with five years' more work we have but few additional 

 facts to modify the conclusions of the first report. As we tried to 

 show in the previous report the ways in which grass militates against 

 apples growing in sod are probably several, which act together, as: 



(1) Lowering the water supply. 



(2) Decreasing some elements in the food supply. 



(3) Reducing the amount of humus. 



(4) Lowering the temperature of the soil. 



(5) Diminishing the supply of air. 



(6) Affecting deleteriously the beneficial micro-flora. 



(7) Forming toxic compounds that affect the trees. 



Each of these supposed causes of injury to the sodded trees in 

 this orchard may be briefly reviewed with such additions and cor- 

 rections as the five more years of experimental work suggest. 



Sod injures apple-trees by lowering the supply of water. — In the 

 preliminary report of this experiment (Bulletin No. 314, pages 115 

 to 121) the reduction of the supply of water was held to be the main 

 cause of the injury to the trees in sod. The results of 120 moisture 

 determinations in the orchard in 1907-08 gave evidence that there 

 was much less moisture in the sodded land than in the tilled soil; 

 the behavior of the trees in sod seemed to show that they were 

 suffering from thirst; and a consideration of the amount of water 

 used by an apple-tree and of the rainfall of the region made plain 

 that there was seldom a year when trees did not suffer from a 

 shortage of water even if the supply was not interfered with by 

 grass. 



It is not necessary to review further the data and reasons given 

 in the first report to show that injury by sod is at least in part a 

 question of water supply. We wish here only to reiterate our belief 

 that the great reduction of the water supply is the chief cause of the 

 extraordinary injury to the sodded trees in this experiment. The 

 results of a similar experiment in the Hitchings orchard, as set 

 forth in Bulletin No. 375 from this Station forced us to the same 



