New York Agricultural Experiment Station. 559 



also gradually been forced upon us by the appearance itself of the 

 trees throughout the years that they have been under observation, 

 namely, that this action of grass is not merely a question of star- 

 vation in any form, nor of any simple modification of the ordinary 

 conditions under which a tree can thrive, but that the grass has 

 some actively malignant effect on the tree, some action on it akin 

 to that of direct poisoning." 



Thus, it is seen that Pickering believes that there is but one 

 mportant factor in the injury of trees in sod; namely, grass " which 

 has some actively malignant effect on the tree, some action on it 

 akin to direct poisoning." But the case against grass as a poisoning 

 agent still rests largely on circumstantial evidence; or, rather, as 

 we understand Pickering's arguments, he arrives at his conclusions 

 as to the toxic effect of grass by eliminating all other possible causes, 

 admitting that he cannot present his supposition as a proved fact 

 " till the presence of such poison is definitely established." 



Pickering's work has been so long continued and so carefully 

 carried on that great weight must be attached to his opinion. Yet 

 we cannot agree with him that the malignancy of grass is wholly or 

 even in largest part due to a poisoning effect. Rather, we are 

 inclined to think toxicity one of several causes, awaiting more crucial 

 experiments before attempting to say how large a part it plays 

 in the malign influence of grass. 



GENERAL REMARKS ON TILLAGE AND SOD IN 



AN ORCHARD. 



The first report of this experiment has called forth many questions 

 and some objections which are not answered in the main body 

 of this report. It seems worth while to attempt to touch upon 

 the most important of these here. 



In deep, fertile soils where trees have a deeper root-run than 

 in the shallow soil of the Auchter orchard, competition between 

 apples and grass may be less keen and the grass therefore less harmful. 



There is nothing in this experiment to show that apple trees 

 eventually "adapt" themselves to grass — a statement often 

 heard. The sodded trees showed harmful effects from grass as 

 soon as sod formed and in every plat. The longer the trees remained 

 in sod the more exhausted and decrepit they became. 



