132 EXPERIMENT STATION RECORD. 



"From tiiu(} to time tbe Hasks were gently shiikeu, and after 21 days their contents 

 were filtered and the residues, without washing, were brought back into the liasks 

 with 300 cc. of water and the same quantities of tobacco ash, sodium carbonate, 

 and putrefyiug solution as l)efore aud let stand for 52 days longer. 



•'luthe filtrates just meuti<med were determined both the total nitrogen and that 

 portion of it which was volatile when distilled with magnesium oxid. . . . 



"To conclude the experiment, the contents of the Hasks Avere again filtered, the 

 residues were thoroughly Avashed, aud the filtrates with the v/ashiugs Avero examined 

 as above described. The nitrogen of the residues Avas also determined. . . . 



"In a considerable number of cases the (piantity of nitrogen dissolved by putre- 

 faction duriug 7 months does not agree Avith or bear any A'ery definite relation to 

 the (|uantity dissolved by pepsin solution. 



'•'The most striking discrepancies are observed Avith ground bone, . . . and espe- 

 cially with the samples of hard raw bone, which it is evident are likely to be less 

 finely ground thau the steamed or soft bone, and, if pulverized to the same degree, 

 are less easily penetrated aud dissolved by the putrefactive agencies. . . . 



"The nitrogen of cotton-seed meal, linseed meal, aud castor 2)omace Avas (piite 

 readily dissolved during i)utrefaction, though not to the same extent as Avith pepsin 

 solution. 



"It is noticeable that the nitrogen of the two samples of undecorticated meal is 

 jnuch less soluble than that of clear decorticated meal under putrefaction as well as 

 in pepsin solution. 



"In the single samples of fish, blood, and ammonite there was substantial agree- 

 ment between the results of the two methods. . . . 



"Lastly, the two methods of determining uitrogen-8o]ul)ility fairly agree in the 

 case of three nitrogenous materials, known to be of inferior quality, as appears 

 below:" 



Cotnparative nitrof/en-.solubiH I y in 2>ep''ii>i <"*<' under jfnt refaction. 



Nitrogen-solubility- 



In pepsin 

 solution. 



Under pu- 

 trefaction. 



Tankage 



Ground annual niatter. 

 Animouite A 



Per cent. 

 37.7 

 32. 2 

 41.8 



Per cent. 

 35. 2-37. 

 41. 5-42. 7 

 37. 1-47. 6 



111 tests on mixed fertilizers there was "a ]»ra('tical coiiforinity 

 between the indications of the two methods, though in many cases the 

 agreement is not close." 



" While the ])ei>siu method is more convenient and rapid, the putrefaction method 

 might be regarded as a nearer approach to the 'natural' method by Avhich organic 

 nitrogenous matters are disintegrated in the soil and prepared for appropriation by 

 l^lants. It is not certain, however, that putrefaction gives a better indication of the 

 relative value of fertilizers as a nitrogen supply to plants than the })epsin method." 



To determine "whether either treatment is tlie proper criterion of 

 tlie availability of the nitrogen of fertilizers" G of the materials exam- 

 ined by both methods were selected for culture tests. For this purj)ose 

 galvanized iron pots in. in diameter and 9 in. deep were filled with 

 2,300 gm. of an artificial soil, very poor in nitrogen, consisting of coal 

 ashes and peat moss (5 per cent) mixed with 4 gm. of Thomas slag and 

 1 gm. each of jdiosphatic gaiano and muriate of potash. 



