(i) Bacteria decompose dead bodies of plants and animals and mix them with soil. As a result, soil organic matter increases and fertility increases.
(ii) Bacteria like Azotobacter, Pseudomonas, Clostridium etc. capture nitrogen from air and mix it with soil. Rhizobium bacteria fix nitrogen from the air in the roots of leguminous plants. Currently, Rhizobium is used as a disinfectant. Three species of Rhizobium form nodules on lentil roots. These are Rhizobium bangladashense, Rhizobium bine and Rhizobium lentis. Bangladeshi scientist Dr. Haroon or Rashid discovered these three species.
(iii) Nitrification process produces nitrite from ammonia under the action of nitrifying bacteria. Nitrite is then produced from nitrite. Nitrate increases soil fertility.
(iv) Bacteria break down the organic wastes of the environment into simpler substances. Complex materials are oxidized making them suitable for reuse. This is why bacteria are called natural scavengers. Bacteria such as Pseudomonas, Nocardia, Mycobacterium etc. convert petroleum waste into simple compounds in the presence of oxygen.
(v) At present organic fertilizers are being produced by decomposing dung and garbage with the help of bacteria.
(vi) Genetic engineering using Agrobacterium tumefaciens and E. coli bacteria to develop disease resistant high yielding crops. These crops do not need to apply pesticides, fungicides and chemical fertilizers. As a result, the fertility of the land is not lost.