POTASH SULPHUR. 
POTASH. 
The relation of potash in the soil is almost exactly the same as 
that of phosphorus. It comes primarily from the rocks where it 
exists largely in the form of silicate of potassium. This is an insoluble 
salt, and soils may contain it in large quantity and still suffer from 
lack of available potash. It is rendered available in very much the 
same way as in the case of phosphorus, largely through the action 
of the decomposition produced by the soil bacteria. 
SULPHUR. 
Sulphur is one of the ingredients of protein, and, therefore, 
is necessary to plant life. Ordinary plants obtain it only in the form 
of sulphate, which they absorb from the soil. But microorganisms 
are concerned in the transformations by which the soil is properly 
stocked with the sulphates. The transformations show at least two 
different steps: 
i. Sulphur is set free from its combinations. 2. Sulphur is 
rccombined into sulphuric acid that unites with mineral matter to 
form sulphates. 
Liberation of Sulphur as H 2 S. All proteid matter contains 
sulphur, and when its decomposition takes place through the agency 
of bacteria the sulphur is liberated in the form of hydrogen bi- 
sulphid (H 2 S) which vile- smelling gas may usually be detected 
around decomposing proteid. This same gas is liberated from the 
decomposition of sulphate of lime that is carried in drainage waters 
to the ocean. Several kinds of bacteria have been found capable 
of liberating H 2 S from such deposits. In certain parts of the world 
large deposits of such sulphites (gypsum) have accumulated and 
are constantly acted on by bacteria which liberate H 2 S, producing 
the "curative muds" of the Black Sea and other localities. Such 
muds are saturated with hydrogen bisulphid gas. This reduction 
of sulphates is, in a way, comparable to denitrification since it is 
the result of deoxidation and since it also destroys substances that are 
already plant foods. Some species of bacteria appear able to attack 
pure sulphur, causing it to combine with hydrogen as H 2 S. From 
