POTASH—-SULPHUR I23 
similar activities. In short, while bacteria do not furnish phos- 
phorus, they are the active agents in rendering available the 
phosphorus from both organic and mineral sources. 
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 in- 
soluble 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 micro- 
6rganisms are concerned in the transformations by which the soil 
is properly stocked with the sulphates. The transformations 
show at least two different steps: (1) Sulphur is set free from its 
combinations. (2) Sulphur is recombined into sulphuric acid that 
unites with mineral matter to form sulphates. 
Liberation of Sulphur as H.S.—AII proteid matter contains 
sulphur, and when its decomposition takes place through the 
agency of bacteria the sulphur is liberated in the form of hydrogen 
bisulphid (H2S) 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 HS from such deposits. In certain parts of the world 
large deposits of such sulphates (gypsum) have accumulated and 
are constantly acted on by bacteria which liberate H2S, producing 
the “‘curative muds” of the Black Sea and other localities. Such 
