13. Find out the role of microbes in the following
(b) Soil
Microbes decompose complex organic debris into a dark amorphous substance called humus and degradation products which can be used as manure to increase the fertility of soil. The manure can loosen the soil and increases aeration in the soil. It contains many organic substances which are easily assimilated by plants. Some microbes are used for enriching soil fertility. Microorganisms like Azatobacter and Rhizobium can be used as nitrogen fertilisers. Thus, it can be said that microbes play an important role in improving the quality of the soil.