6 Contents 



PAGE 



Investigations at the Cornell University Agricultural Experiment 

 Station {concluded) : 



Nitrifying activity of soil under crops as shown by inoculation 



tests 81 



Formation of nitrates in soil after freezing and thawing 85 



The depressing influence of grass on nitrate formation a possible 



factor in orchard management 86 



The influence of a preceding crop on nitrate formation in soil .... 91 

 Is there a mutual stimulation of plant growth through root 



influence.'' 99 



Summary 106 



Acknowledgment 109 



Bibhography ' 110 



