36 
while Nos. 405 and 406 also contained many times as much ammonia 
as nitrates. 
The relative amounts of nitrogen extracted by hydrochloric acid 
also varied greatly. In soil No. 405, 92.18 per cent of the total 
nitrogen went into solution, while No. 447 yielded only 60.35 per 
cent of its nitrogen. Nos. 405 and 406 are soils that have been 
devoted to aquatic agriculture (rice and taro) for many years, while 
soils 379, 428, and 447 have been subjected to dry-land cultures. 
The chemical decompositions and hydrolyses that take place 
naturally in the organic matter of soils being brought about largely 
by biological agents, it is probable that the range and types of such 
reactions in submerged soils are somewhat different from those 
taking place in well-aerated soils. There are several lines of reason- 
ing not necessary to mention here that lead to this conclusion. 
From this point of view, then, the biological effects on soil nitrogen 
may reasonably be expected to be different in the two instances. 
The nature of the organic matter originally incorporated with the 
soil probably has some bearing on this question also. 
Among the several groups of nitrogen compounds brought into 
solution by hydrochloric acid it is noteworthy that the amids and 
monamino acids constitute the main portion. The latter comprises 
approximately two-third© of the total nitrogen dissolved. It should 
be borne in mind, however, that the monamino nitrogen was deter- 
mined by difference; that is, by subtracting the sum of the other 
groups from the total nitrogen in solution. It is known, however, 
that this difference is not made up entirely of monamino acids. 
Jodidi 1 found, for example, that the monamino nitrogen group 
in Iowa soils was made up of from 40.12 to 92.11 per cent of actual 
monamino acids, the variation in this respect being dependent 
in part on the treatment to which the soil had been previously 
subjected. It is of interest that the relative amounts of amids, 
monamino, and diamino nitrogen in Hawaiian soils were found 
similar to those of soils elsewhere. 
Turning now to the question of heat as affecting soil nitrogen, it 
was found that with the exception of No. 405 the average loss of 
nitrogen was about 25 per cent, but in certain soils the loss was 
much greater than in others. Soil No. 447 suffered a loss of prac- 
tically 50 per cent while No. 405 sustained almost no loss of nitrogen. 
It is also of interest that the reduction in the amounts of nitrogen 
extracted by hydrochloric acid was greater in two instances and less 
in three than the absolute loss of nitrogen occasioned by heat. In 
every instance enormous increases in ammonia and a total decompo- 
sition of nitrates took place. On the whole, the absolute amounts of 
neither the amids nor the diamino acids were greatly affected by 
'Iowa Sta. Research Bui. 1 (1911). 
