Soil moisture : Soil moisture governs microbial activity in two ways.
Since water is the major component of protoplasm, an adequate supply
must be available for vegetative growth and multiplication. But,
where moisture becomes excessive, microbial proliferation is suppressed
because the over supply of water limits gaseous exchange and lowers
the available oxygen supply, creating an anaerobic environment. Moisture
is present in the form of film in soil pores. The amount of water increases
with increase in porosity of soil. Soil moisture is affected through
irrigation, drainage or management practices.