38 
250° C. considerably increased the solubility of alumina, manga- 
nese, potash, and phosphoric acid and at the same time effected 
a reduction in the solubility of lime and magnesia. Upon ignition 
the solubility of silica, alumina, potash, phosphoric acid, and sul- 
phates was increased, while the solubility of lime and magnesia 
underwent a corresponding decrease. 
(6) The solubility of soils used in aquatic agriculture is abnor- 
mally high, but upon drying out these become much less soluble 
and approach a state similar to that existing in aerated soils. When 
such soils are heated after drying they seem to undergo changes of 
the same order as are produced in dry-land soils. 
(7) No single factor is sufficient to cover the solubility effects 
resulting from heating Hawaiian soil. On the other hand, the 
subject is very complex and involves many factors. Among the 
more important of these may be mentioned flocculation, deoxida- 
tion of manganese dioxid, oxidation, particularly of iron, double 
decomposition, dehydration, and the attending physical alterations 
of soil films. Such alteration would destroy film pressure, thus 
allowing the solvent to come into more intimate contact with the 
soil constituents. At the higher temperatures bicarbonates become 
converted into normal carbonates, thus effectively lowering the solu- 
bility of lime and magnesia. 
(8) Nitrates undergo decomposition with heat, a decrease in 
nitrate content having been found to take place at 150° C, while 
at 200° or 250° C. practically total destruction of nitrates took 
place. 
(9) One of the noteworthy effects of soil heating is the production 
of ammonia, which at 200° C. was formed in abnormally large 
amounts. Soil subjected to heat from brush burned in the field 
was found to undergo stimulated ammonification after heating. 
Nitrification, on the other hand, was not restored after the lapse of 
two months. 
(10) Heating to 200° C. caused a loss of approximately 25 per 
cent of the total nitrogen. A loss of nitrogen and the ammonia 
formed by the action of heat came largely from the monamino 
acid group, while the amids and diamino acid sustained much less 
loss. 
(11) The results of these studies are believed to throw important 
light on the subject of soil aeration and consequently have a direct 
bearing on the practical question of soil management. 
