FERTILIZERS. 637 



Practically four-fifths of the brands of fertilizers examined contained 

 as much total plant food as was guaranteed, but in many cases it was 

 not distributed in the proportions claimed. 



The availability of organic nitrogen [New Jersey 8tas. Rpt. 1896, 

 pp. 110-117). — Two artificial methods for determining the availability 

 of organic nitrogen in fertilizing materials were tested, namely, diges- 

 tion in acid pepsin solution x and treatment with permanganate of pot- 

 ash according to Hayes. 2 



The first was tested on 49 brands of commercial fertilizers, and on 

 samples of bone sa wings, steamed bone, cotton-seed meal, dried ground 

 fish, tobacco dust, king crab (Limulus polyphemus), wool waste, hoof 

 meal, and certain special mixtures of ground hoof, tankage, leather, 

 ground horn, dried blood, sodium nitrate, ammonium sulphate, potas- 

 sium chlorid, and acid phosphate. 



Twelve per cent of the fertilizers examined showed a suspiciously 

 low solubility of nitrogen (50 per cent and less). The results of the 

 other tests "confirm on the whole the general belief that the nitrogen 

 of ground bone, blood, cotton seed meal, and high-grade tankage pos- 

 sesses a high degree of availability [ 77.1 to 94.5 per cent]; they also 

 show that the nitrogen of dried fish, tobacco dust, king crab, and hoof 

 meal is considerably less available [52.3 to 70.9 per cent], while that of 

 wool waste, raw leather, and ground horn is of very inferior quality 

 [14.9 to 29.9 per centj." 



The results of these tests are compared with those of vegetation 

 experiments on maize and oats made by the Connecticut State Station 

 in 1894 and 1895.'' The data thus obtained show that — 



" With the exception of raw leather, the pepsin method tends to give lower results 

 than were secured hy the vegetation tests. The pepsin results, however, are quite 

 satisfactory, except in the case of hoof meal, where the pepsin solubility is nearly 

 23 per ceut lower than by the actual culture test. These results, therefore, confirm 

 the conclusions of other investigators, namely, that, ' iu general, the solubility 

 of the nitrogen of these samples in pepsin solution was a fairly good measure of 

 the relative availability of the nitrogen to the plaut under the conditions of the 

 vegetation experiment.' In hoof meal, however, the solubility of the nitrogen in 

 pepsin solution is no indication whatever of its relative availability." 



The Hayes method was tested on 4 samples of complete fertilizers; 

 on dried blood, tankage, hoof meal, and raw leather in mixtures; and 

 on dried fish and steamed bone alone. Two solutions were used, oue 

 prepared by dissolving 10 gm. of potassium permanganate and 200 gm. 

 of potassium hydroxid iu 1 liter of water, the other by dissolving 16 

 gm. of permanganate in 1 liter of 10 per cent sulphuric acid. 



"The results secured both by the acid and alkali digestions are very satisfactory. 

 Wheu digested in alkali solution hoof meal and raw leather give too high results 

 while in acid solution all agree closely in comparison with the vegetation tests, 



1 Connecticut State Sta. Rpt. 1893, p. 218 (E. S. R., 6, p. 130). 



? U. S. Dept. Agr., Division of Chemistry Bui. 47, p. 112 (E. S. R., 8, p. 26). 



3 Connecticut State Sta. Rpt. 1895, p. 112 (E. S. R., 8, p. 387). 



