FERTILIZERS. 



541 



The details of fertilizers applied aud the weight and nitrogen eon- 

 tent of the crop produced during 189-4, 1895, and 1896 are given in full 

 in a table. The principal results are summarized as follows: 



Availability of different forms of nitrogen, taking that of nitrate of soda as 100. 



Experiments 



of 1894. 



A verage of 



experiments 



of 1894 and 



1895. 



Average of 

 experiments 



of 1894, 1895, 

 and 1896. 



Nitrate of soda . . 

 Castor pomace, A 

 Cotton-seed meal . 

 Castor pomace, B 



Linseed meal 



Dried blood 



Dried fish 



Dissolved leather 

 Horn and hoof. . . . 



Tankage 



Steamed leather. . 

 Roasted leather . . 

 Raw leather 



100 



90 



87 



73 



74 



79 



69 



76 



77 



73 



8 



9 



2 



100 

 83 

 79 

 73 

 72 

 72 

 69 

 70 

 67 

 64 

 10 

 10 

 2 



"The availability of the nitrogen of roasted, steamed, aud raw leather, while not 

 alike in the 3 years, is so much lower than that of any other materials tested as 

 to demonstrate that the nitrogen in them is comparatively inert and of little effect 

 unless applied in large quantities. 



" The experiments also demonstrate that leather may be dissolved in oil of vitriol 

 so as to make its nitrogen nearly as available to the maize aud oat crops as that of 

 tankage. Samples of roasted leather, steamed leather, aud dissolved leather were 

 prepared each year from a common stock of raw leather, and slight differences in 

 their preparation might explain the differences of availability observed in different 

 years. 



"Of the 9 materials tested, other than leather, tankage certainly has the lowest 

 nitrogen availability, ranking seventh, ninth, and ninth in the 3 years' tests. 



" Regarding the nitrogen availability of the other organic matters, the experiments 

 are not altogether conclusive." 



As in previous years, the amount of water supplied to different series 

 of pots was varied. The largest assimilation of nitrogen took place in 

 the pots whose water supply was maintained between 40 and 80 per 

 cent of the water-holding capacity of the soil. 



In cooperation with the reporter on nitrogen for the Association of 

 Official Agricultural Chemists, a comparison was made of nitrogen 

 availability determined by vegetation experiments and by treatment 

 with chemical reagents (pepsin and potassium permanganate). The 

 materials tested were blood, tankage, horn and hoof, raw leather, and 

 a commercial fertilizer. The crop used in the vegetation experiments 

 was corn. The highest percentage of availability of nitrogen (47) as 

 determined by corn cultures was found in dried blood. The percent- 

 age of digestibility of the nitrogen of the same substance in pepsin 

 solution was 93. 



"If uow we call its percentage digestibility 47, to agree with the percentage 

 availability, and reduce the other figures for pepsin digestibility in the same ratio, 

 we have a set of numbers which show how the relative solubility and digestibility 

 compare with relative availability, as fixed by maize cultures." 



