humus, or humus formed under anaerobic conditions, is thought to 
decompose more slowly than neutral humus. Thus it seems that 
conditions arise during the course of bacterial action which tend to 
check the process, or else some of the constituents of proteins are more 
difficult of hydrolysis and decomposition than others. 
Previous investigations on proteins throw much light on this sub- 
ject. It is known that proteins are composed of a number of amino 
acids and that different proteins undergo hydrolysis by acids, alkalis, 
and enzyms at different rates, yielding varying amounts of the several 
amino constituents. From limited study on the subject it seems 
that bacterial and enzymatic action bring about similar hydrolysis 
of proteins, with the important difference that the products of 
hydrolysis are subject to decomposition by bacteria. During the 
course of such action certain amino acids are split off more rapidly 
than others. Abderhalden and Reinbold 1 found, for example, that 
in the tryptic digestion of edestin from cotton seed, 97.6 per cent of 
the tyrosin had been split off at the end of 2 days, while only 7.4 per 
cent of the glutaminic acid had been hydrolyzed. 
From previous work in this laboratory 2 it has been shown that 
Hawaiian soils contain relatively greater amounts of amid and 
smaller amounts of basic (diamino acid) nitrogen than the vegetable 
proteins. From this it has been suggested that a study of the group 
changes produced under the action of bacteria might throw important 
light on both the availability of, and the nature of bacterial action 
on, nitrogenous fertilizers. Various factors, such as the degree of 
aeration, the acidity of the medium, the carbohydrates present, the 
synthesis of proteins in the body cells of the bacteria, the absorption 
of organic nitrogen compounds in varying degrees by plants, etc., so 
complicate the problem as to render very difficult an interpretation 
of the chemistry of bacterial action in soils. It has been suggested, 
however, that by also studying the rates of decomposition under 
varying conditions some light might be thrown on this question. 
AMMONIFICATION UNDER VARYING CONDITIONS. 
SERIES I — AMMONIFICATION IN SILICA SAND. 
The materials used in this investigation contained the following 
percentages of nitrogen: Casein (Eimer and Amend), 12.40 per cent; 
dried blood, 13.29 per cent; soy bean cake meal, 8.28 per cent; cot- 
tonseed meal, 5.10 per cent; linseed meal, 5 per cent. 
In order to insure maximum aeration the first series of tests was 
conducted with the use of silica sand. One gram each of the above 
nitrogenous materials and one gram of calcium carbonate were thor- 
oughly mixed with 100-gram portions of sand in tumblers. Ten cubic 
i Ztschr. Physiol. Chem., 46 (1905), pp. 159-175. * Hawaii Sta. Bui. 33 (1914). 
