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



manner dried blood to furnish loo mg. of nitrogen was added to other 

 duphcate sets of kelp and soil. The above combinations were con- 

 trasted with duplicates containing lo mg. and loo mg. of nitrogen from 

 dried blood, and also with tumblers of untreated soil. 



The Macrocystis used contained 8.47 per cent of moisture, 0.90 per 

 cent of nitrogen, and 35.68 per cent of soluble salts. The composition 

 of the Nereocystis was 3.51 per cent of moisture, 1.70 per cent of nitro- 

 gen, and 46.47 per cent of soluble salts. The dried blood was the same 

 as in Series I and II. The fresh field soil employed was the clay adobe 

 from the campus botanical gardens. The ability to ammonify and nitrify 

 which was shown by this soil in Series II was considered thoroughly 

 satisfactory. It could be obtained readily in a fresh condition and for 

 these reasons was used in this and all further work. 



Several duplicate sets of tumblers with additions of Macrocystis and 

 blood were prepared. These were incubated for periods of 2, 4, ii, 

 and 1 5 weeks. Two sets of Nereocystis were incubated for 2- and 4- week 

 periods, respectively. (See Tables III and IV.) 



In Tables III and IV the total number of milligrams of nitrogen found 

 as ammonia and as nitrates has been given, as well as the number of 

 milligrams gained. This has been done because these data in some cases 

 give more information than those recorded under the head of gain. 



The results where the IMacrocystis is the only addition to the soil will 

 first be considered. The tumblers with 10 mg. of added nitrogen from 

 kelp have apparently too small an amount present to yield any definite 

 result. The variations in each period between the treated tumblers and 

 the untreated soil are insignificant. The addition of 50 mg. of nitrogen 

 in Macrocystis produces some striking changes. At the end of 2 and 4 

 weeks the result is the same; a small gain of ammonia has taken place. 

 This is accompanied by a great reduction in the quantity of nitrates 

 present. At 1 1 weeks there is not only an appreciable gain of ammonia, 

 but the nitrate production is almost normal. At the end of 15 weeks the 

 ammonia present is the same as in the blank, and 6 per cent of nitrogen 

 has been gained in nitrates. This is considered to be an appreciable 

 figure, especially in view of the improved nitrate content shown in the 

 previous set. The results from the tumblers with 100 mg. of added Mac- 

 rocystis nitrogen corroborate these from the 50 mg. portions. The 2- 

 and 4-week determinations show a trifling gain of ammonia and consid- 

 erable losses of nitrates. At 1 1 weeks there is an appreciable gain of 

 ammonia, which is larger at the end of 15 weeks. The nitrate content 

 remains low throughout all the sets, just as it did in Series I. It is, how- 

 ever, considered to be significant that with both of the larger amounts of 

 kelp a distinct ammonification appeared at the same period, 11 weeks. 

 This kelp had not been dried completely, as had that in Series I, a fact 

 which has apparently considerable bearing on the availability of Macro- 

 cystis. 



