In order to obtain most efficient strains of Azotobacter one has to conduct different tests or experiments in glass house, earthern pots and field under the guidance of micro-biologists, some of them are explained below;

Strain found efficient in acetylene reduction test are selected and multiplied in a pure form. The broth is mixed with liquite and inoculant so prepared is used to inoculate the seeds. Seeds are then dried in shed and sown in pots. Suitable inoculated control plants are kept for comparision. Plants are watered as and when required and allowed to grow for about 45-60 days. Differences between inoculated and uninoculated plants in respect of height, nitrogen content of plant and soil, dry weight of plants are noted. Efficient strains are used for field tests.

3. Field Test
: Strains found efficient under glass house conditions are required to undergo field test which is most important test from the farmer’s point of view. Strains found efficient in glass house and acetylent tests when used in field are required to compete with native flora for their nutrition. Efficient strains of Azotobacter are applied to seeds of particular and sown. An adequate control is kept for comparision. All other factors are kept similar except seed inoculation with efficient strains of Azotobacter.

After maturity yield figures are noted and comparision is made. Such experiments are repeated for 3 to 4 years at different places. From this data an efficient strain is selected and used for the production of Azotobacter on a large scale. Such strains are stored under cold storage conditions or in refrigerator. For production of bio-fertilizer, it is always advisible to use more than one strain on safer side.

Experience of biofertilizer: Field experiments using Azotobacter as a biofertilizer for wheat, barley, oat maize, sugarcane, etc. revealed that the performance of Azotobacter was medium to poor. Experiments on the use of Azotobacter for seed inoculation of various crops have also been conducted in other countries including India. The results of these experiments indicate that benefits obtained from inoculation of seeds with biofertilizer were marginal in soil with poor organic matter content. While in rich soils results were quite encouraging.