122 HATCH EXPERIMENT STATION. [Jan. 



during the past five j^ears. Experiments in continuous 

 potato culture witliout manures in tlie Cornell University 

 Experiment Station have shown in a striking manner the 

 dependence of this crop upon the presence of a suitable 

 proportion of organic matter in the soil.^ The common 

 observation that potatoes thrive exceptionally well in virgin 

 soils and upon sod land points in the same direction. 



The superiority of the yield on Plot 10 also is striking. 

 This, in tlie \vriter's opinion, is due to the fact that the pota- 

 toes on this plot were covered by hand, while those on the 

 other plots were covered by the use of the plow. The 

 potatoes on this plot came up much more quickly and more 

 vigorously than those on the others, and showed decided 

 superiority in growth from the start. 



The average yields of this year on the several fertilizers 

 are shown in the following table : — 



As the result of all experiments previous to this year, it 

 is found that the materials furnishing nitrogen have produced 

 crops in the following relative amounts : — 



Per Cent. 



Nitrate of soda, 100.00 



Barnj-ard manure, ....... 94.00 



Dried blood . . . 90.40 



Sulfate of ammonia, . . . . . . 90.30 



No nitrogen, ........ 72.80 



Similar averages for this year are as follows : — 



I'er Cent. 



Nitrate of soda, 100.00 



Barnyard manure, ....... 124..S0 



Dried blood, 96.80 



Sulfate of ammonia, . . . . . . G5.30 



No nitrogen, ........ 62.50 



As was the case last year, the nitrate of soda stands rela- 

 tively lower than in experiments of previous years, although 



1 Bulletin No. 196, Cornt-ll University Experiment Station, p. 52. 



