SOURCES AND COMPOSITION OF FERTILIZERS 



301 



oats and Hungarian grass was made on 25 pounds sandy loam. 

 The results of Wagner were on small plots with summer rye, flax, 

 summer wheat, and carrots, and are the average of 3 seasons. 

 Pfeiffer and associates used 27 kgs. poor sandy soil, and the 

 effect of the residues for two years was considered, which in- 

 creased the value of stable manure decidedly. 



Voorhees at the New Jersey Experiment Station 1 made experi- 

 ments with out-of-door cylinders, 3 square feet surface area and 

 4 feet deep, with corn, oats, and millet, oats and corn. Considera- 

 tion of the second crop in each case increased the availability of 

 manure decidedly. Root residues and fertilizer residues probably 

 remained for succeeding crops, unless washed out during the 

 winter. Some of his results are as follows : 



Biological Methods of Availability. Since organic materials 

 must be transformed into ammonia and nitrates before being 

 taken up by plants, the quantity of ammonia and nitrates pro- 

 duced from a given amount of nitrogen in the soil, with not too 

 short a period, may be used for comparing nitrogenous materials. 

 The quantity of nitrates produced from 0.3 gram nitrogen in 500 

 gram soil in four weeks varied with different soils, and was not in 

 proportion to the value of the materials, but the quantity of nitro- 

 gen converted into nitrates and ammonia was in proportion to the 

 availability of the material. The following table gives some of 

 the results. 



1 Report, 1901, p. 144. 



- Voorhees and Lipman, Bulletin 221, New Jersey Station. 



