34 Journal of Agricultural Research voi. iv, no. i 



SERIES IV.— COMPARATIVE AMMONIFICATION AND NITRIFICATION 

 OF MACROCYSTIS, FRESH, AIR-DRY, HIGHLY HEATED, AND PAR- 

 TIALLY DRY 



The results of Series III showed that the air-dry Macrocystis with which 

 we are principally concerned is a slowly available material. Series I and 

 II indicated that the kelp which had been dried to a constant weight for 

 a number of hours was less available. It therefore appeared desirable 

 to find what degrees of availability there would be between the thoroughly 

 dry kelp and the fresh material. It was quite possible that this might 

 throw some light on the most desirable method of handling the kelp com- 

 mercially. One patent has been taken out for a process by which the 

 kelp is heated to from 250° to 270° C. and thoroughly "parched." 

 Many advantages for this process are claimed. 



A series of experiments were therefore conducted at Pacific Grove. 

 In these Macrocystis pyrifera was air-dried completely, so that it con- 

 tained only 8.68 per cent of moisture. Duplicate portions were dried 

 so that they contained 28.63, 37-i5> ^^^ 55.32 per cent of moisture. 

 Fresh kelp was also gathered from the same bed. On returning to Berke- 

 ley, two duplicate portions of the air-dry kelp of 500 gm. each were heated 

 to from 250° to 270° C. till thoroughly parched. During this process 36 

 per cent of the organic matter present was lost, and in this organic 

 matter driven off 31 per cent of the nitrogen originally present in the 

 kelp was also lost. 



The materials were all used in an ammonification and nitrification study 

 which was conducted for three weeks. The soil used was clay adobe, as 

 in Series III. Two portions of each sample of kelp were added to trip- 

 licate sets of tumblers. One weight of kelp used contained just 0.27 gm. 

 of soluble salts, while the other contained just twice as much, 0.54 gm. 

 (See Table V.) 



It will be observed that the fresh kelp as before gave a very satisfactory 

 conversion to ammonia and nitrates. The air-dry Macrocystis with the 

 smaller quantity added gave a negative result. With double the amount 

 of kelp there was a small but consistent gain. The parched kelp gave no 

 conversion whatsoever. The partially dry kelp was all fairly available. 

 That which contained 28 per cent of moisture was, in fact, more readily 

 changed than the fresh sample. The evident conclusion is that Macro- 

 cystis will be more readily decomposed if it can be handled without 

 drying completely. It should be noted that the samples with 28 and 37 

 per cent of moisture could be kept without danger of decay or mold. 

 That with 55 per cent was too moist to be safely stored. 



