New Yokk Agricultural Experiment Station. 555 



vegetables require fertilization. From all sides, too, come reports 

 from apple-growers who augment, diminish or alter in various ways 

 manurial treatments of their trees without appreciable results. 



It must be borne in mind, however, that if these trees were in need 

 of more food, tillage would make available some of the unavailable 

 reserve food which the chemical analyses of the plat show to be 

 present. 



To the statements just made there is a seeming exception in the 

 case of nitrogen. The action of nitrate of soda in reviving the sodded 

 trees is almost instantaneous. Yet analyses show nearly as much 

 nitrogen, on the average, for the sodded plats, as for those that have 

 been tilled; indeed, in some of the sodded plats there is more. More- 

 over, as soon as the sod is turned under, without the addition of 

 commercial nitrogen, the trees revive, grow vigorously and show no 

 signs of the starvation they endured in grass. This behavior can 

 best be accounted for in one of two ways. Either the grass takes the 

 nitrogen, the cream of the land in this orchard, in which case appli- 

 cations of nitrate of soda would so supplement the natural supply 

 as to give the trees a fairer share and thereby give new life; or the 

 nitrate of soda may counteract a toxic effect of the grass. Of the 

 two explanations we are inclined to the first, although we can offer 

 no explanation as to how the grass can so completely exhaust the 

 supply of nitrogen in the soil for apples and yet in a ten-year period 

 not drain it of the fertility in this element upon which the grass 

 itself retains its pristine vigor. 



Lyon and Bizzell 1 have found that grasses have a strongly depres- 

 sive influence on nitrate formation and suggest that this is a possible 

 cause for the injurious effect of sod in orchards. Doubtless such 

 effects would differ with different grasses and with different soils, 

 thus accounting for the wide variations and seeming anomalies in 

 sod and tillage methods in different localities. Lyon and Bizzell's 

 work opens up a promising field for investigation in the relationships 

 of grass and trees. 



Sod has injured the trees in the Auchter orchard by reducing the 

 humus content of the soil. — The statement just made is an assump- 

 tion, pure and simple, so far as humus itself is concerned. It is 

 extremely doubtful if humus in the quantities shown to be present 



1 T. L. Lyon and J. A. Bizzell, " Some Relations of Certain Higher Plants to the 

 Formation of Nitrates in Soils," Cornell Exp. Sta. Memoir No. 1: 75-91. 1913 



