The critical factors which are responsible for the effectiveness of a particular biofertilizer are as follows: 1.Suitability of the species to the target crop.
2. Suitability of the strain: There are specific strains of Rhizobium for different leguminous species like Cowpea, Red gram, Soybean, Alfalfa etc. Biofertilizer specific culture should be used for specific crop.
3. Identification of strains as suited to the agro eco system, particularly the soil pH moisture conditions.
4. Through research, specific strains as suited to a particular soil environmental conditions are usually identified and pure mother cultures maintained in research labs for supply to the commercial manufacturers.
5. The aseptic conditions of manufacturing, the cell count of living organism present the carrier material, purity and level of contamination.
6. The conditions of carrier material in which the culture is packed and the quality of packing material, which determine the shelf life.
7. The conditions in which the packed materials are stored, distributed and kept with farmers before it is applied. 8. Soil conditions particularly pH, organic matter content, moisture level and agronomic practices.