29 



Nitrogen: A good grade of dried red blood was selected as a 

 standard, one series received an application of .42 grams nitrogen 

 per pot, (59.5 pounds of nitrogen or 5G2 pounds of blood per acre). 

 Another series received .85 grams of nitrogen per pot, (127 pounds 

 of nitrogen or 1200 pounds of blood per acre). A third series received 

 1.12 grams of nitrogen per pot,(172 pounds of nitrogen or 1,625 pounds 

 of blood per acre). The two increased amounts of nitrogen were 

 used as checks to indicate whether the full action of the nitrogen was 

 obtained where the minimum quantity was used. 



(The fact that they gave larger yields proved that general condi- 

 tions were such that the smaller amount could exercise the full effect 

 of which it was capable.) 



A series of pots was used which contained 50 per cent more pot- 

 ash and phosphoric acid, in order to show that the nitrogen was the 

 only limiting factor. (The yields were not increased by this addition- 

 al application.) 



Other Sources of Nitrogen: In case of the commercial fertilizers 

 each one was washed out with distilled water so as to remove all sol- 

 uble nitrogen. The residue, dried at a low temperature, was tested 

 for its nitrogen and a calculation made to determine how much of 

 each fertilizer residue was to be used to furnish .42 and .85 grams of 

 nitrogen. Each fertilizer residue was again tested by the alkaline 

 permanganate method for its nitrogen activity so as to be able to 

 compare the laboratory method with the vegetation experiment by 

 using material produced under the same conditions. There was 

 another laboratory check secured when the fertilizers were analyzed 

 in our inspection work. 



Crop: Oats were selected as the crop to be grown and were 

 thinned to ten plants per pot. The crop was harvested when in milk 

 by cutting even with the ground. Dry matter determinations were 

 made on the air-dried products. The crop throughout the growing 

 season was in charge of Mr. R. L. Coffin, who has had much experience 

 in caring for vegetation experiments of this nature. Extreme care 

 was used in furnishing suitable temperatures and the supplying of 

 necessary water conditions was regulated by weighing each pot, water 

 being applied both to the surface and through sub-irrigation. 



