New York Agricultural Experiment Station. 549 



Incidentally there is evidence here to show that the quantity 

 of the chief food elements is a minor matter in this experiment. 

 Of the eight plats in the orchard, the one changed from sod to 

 tillage has least humus, as gaged by carbon, and is next to the lowest 

 in nitrogen and phosphorus. Yet without additions of fertilizers in 

 the change from sod to tillage, the plat almost immediately became 

 the most productive in the orchard. It is doubtful if the humus or 

 the available food turned over in the sod wholly accounts for the 

 increased productivity of this plat. 



The change from, tillage to sod. — Plats 4, 6 and 8, constituting 

 the northeast quarter of the orchard, were cultivated the first half 

 of the ten years and were in sod the last half. The change for 

 the worse was quite as remarkable in this quarter of the orchard 

 as it was for the better in the quarter turned from sod into tillage. 

 The trees began to show the effects of the grass in their foliage before 

 mid-summer of the first season. The deterioration of the trees as 

 a whole began this first season and became increasingly greater from 

 year to year until the end of the experiment. In the quarter of the 

 orchard ten years under tillage the average yield per tree for the 

 last five years was 5.03 barrels per tree; in the quarter five years 

 in sod followed by five years of tillage the average yield per tree 

 was 5.17 barrels for the same period; but in the quarter five years 

 in tillage followed by sod the average yield was but 2.32 barrels per 

 tree for the five years of sod — not half that of either of the other 

 two sections. These figures are modified somewhat to the advantage 

 of sod by the application of nitrate of soda in Plat 6. 



In accounting for the all but fatal effects of grass on the treet: 

 in this orchard we are almost forced to assign the toxic effect of 

 grass as one of the causes of grass injury. One of the chief evidences 

 that grass has a toxic effect on apples is to be found in the behavior 

 of the trees in this newly sodded area. It does not seem possible 

 that drought, lack of food, lack of air, or any other assignable cause 

 than some toxic property, acting before mid-summer — almost 

 immediately, — could have caused the trees in this plat to have taken 

 on the symptoms of sod-bound trees as soon as the roots of the young 

 grass came in contact with those of the trees. 



The use of nitrate of soda in the sod plats. — Potassium, phosphorus 

 and lime were all used liberally in the first half of the ten-year period, 

 as we have seen in the discussion of fertilizers, page 256. Nitrogen 



