New York Agricultural Experiment Station. 531 



Only in the amount of humus and nitrogen has the soil been 

 appreciably changed by the two treatments. The quantities of 

 humus and nitrogen in the plat tilled ten years are so much greater 

 that it is safe to assume that the tillage and cover-crop treatment 

 conserves humus and nitrogen better than the sod-mulch treatment. 



Grass militates against apples growing in sod in several ways 

 which act together, as: 



(i) 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 a toxic compound that affects the trees. 

 General statements are: 



Sod is less harmful in deep than in shallow soils. 



There is nothing in this experiment to show that apples ever 

 become adapted to grass. 



Sod may occasionally be used in making more fruitful an orchard 

 growing too luxuriantly. 



Other fruits than the apple are probably harmed quite as much 

 or more by sod. 



The effects of grass occur regardless of variety, age of tree, or 

 cultural treatment, and are felt whether the trees are on dwarf 

 or standard stocks. 



Because of their shallow root systems, dwarf trees are even 

 more liable to injury from grass than standards. 



Hogs, sheep or cattle pastured on sodded orchards do not over- 

 come the bad effects of the grass. 



Owners of sodded orchards often do not discover the evil effects 

 of the grass because they have no tilled trees with which to make 

 comparisons. 



It is only under highest tillage that apple trees succeed in nurseries 

 and all the evidence shows that they do not behave differently when 

 transplanted. 



Grass left as a mulch in an orchard is bad enough. Grass with- 

 out the mulch is all but fatal — it makes the trees sterile and 

 paralyzes their growth. It is the chief cause of unprofitable orchards 

 in New York. 



