BENEFICIAL MICROORGANISMS IN AGRICULTURE
Microbes are an integral part of soil and contribute to soil and plant health. Microorganisms have the ability to fix atmospheric nitrogen, solubilize and mobilize phosphorus, produce antibiotics and disease suppressing molecules. Owing to these properties, they are used in agriculture as biofertilizers and biopesticides. They are also important in the treatment of solid waste and sewage. They clean up the environment by degradation of several pollutants like pesticides, hydrocarbons, dyes and paints.
They also help in the enhanced recovery of oil and metals from low grade ores or aqueous streams.
Man is a host to variety of pathogenic bacteria, protozoa and viruses. They can cause various infectious and non-infectious diseases. In order to control the disease and its transmission, it is essential to isolate and identify the causal agent from blood, sputum, urine, stool or pus. Various cultural and molecular methods can be employed for identification of pathogen. Sterilization techniques, use of disinfectants and vaccination can help control transmission of disease.
Biofertilizers
Biofertilizers are the products containing living cells of different types of microorganisms that enrich the nutrient quality of soil. The main sources of biofertilizers are bacteria, fungi and cyanobacteria (blue green algae). Most biofertilizers belong to one of the following categories: nitrogen fixing, phosphate solubilizing and mobilizing, and plant growth promoting rhizobacteria. Nitrogen fixing biofertilizers fix atmospheric nitrogen into forms which are readily useable by plants. These include Rhizobium, Azospirillum, Azotobacter, blue green algae and Azolla. WhileRhizobium requires symbiotic association with the root nodules of legumes to fix nitrogen, others can fix nitrogen independently. Phosphate solubilizing microorganisms secrete organic acids that enhance the uptake of phosphorus by plants by dissolving rock phosphate and tricalcium phosphate. Arbuscular mycorrhizal fungi are the most common phosphorus mobilising types that are omnipresent. A group of bacteria that enhance the growth of plant through nitrogen fixation, phosphorus solubilization or production of plant growth promoting metabolites are known as Plant Growth Promoting Rhizobacteria (PGPR). Many PGPR strains have a potential to be used as microbial inoculants to enhance crop productivity.
The growth in agricultural production in the last three decades has been accompanied by a sharp increase in the use of chemical fertilizers, causing serious concern. Foremost among these concerns is the effect of excessive fertilizers on the quality of soil and ground water. The use of environmental friendly biofertilizers can cut down the use of chemical fertilizers. Biofertilizers have definite advantage over chemical fertilizers. It is economical to use biofertilizers as they are a cheap source of nutrients when compared to chemical fertilizers. Biofertilisers in addition to nitrogen and phosphorus, also provides certain growth promoting substances like hormones, vitamins, and amino acids that improves the plant health and vigour. Continuous use of chemical fertilisers adversely affects the soil structure whereas biofertilizers when applied to soil improve the soil structure. The chemical fertilizers are toxic at higher doses where as biofertilizers have no toxic effects.
