Biofertilizers

Mahesha Karunathilake

The use of chemical fertilizers, high yielding varieties and agricultural practices have resulted in tremendous develop in the agricultural sector. There is no doubt that use of chemical fertilizers has increased food grain production, but the excessive use is now leading to a decrease in crop yield, imbalance of nutrients in the soil, and an adverse effect on the soil's physiochemical properties. Also the use of chemical fertilizer leads to ecological disturbances and environmental pollution.

However, chemical fertilizers are not only short supply but also very expensive. At this critical stage biofertilizers are an excellent alternative for chemical fertilizers. They are low cost, renewable, and pollution free. Biofertilizers are useful as a supplement for chemical fertilizers.

Basically, biofertilizers are carrier based preparations containing specific strains of microorganisms like bacteria, fungi, algae or their combinations. Biofertilizers are categorized in to two main groups.

1. Biological N2 fixing biofertilizers
-Consist of microorganisms which have ability to fix N2 either symbiotically or a symbiotically.
2. PO43- Solubilizing biofertilizers
- Consist of microorganisms which have ability to solubilize fixed insoluble phosphates of the soil.

The use of biofertilizers has following advantages. They are cheap and can help to reduce chemical fertilizer consumption. They provide biological nitrogen directly to the plants. They help in solubilization and mineralization of other plant nutrients like phosphates. They enhance plant growth due to release of hormones, vitamins, auxins and other growth promoting substances. They control and suppress soil borne diseases .They increase crop yield by 10% -20 %. They improve soil properties and maintain soil fertility.

The production of biofertilizers is totally based on efficient strain of microorganisms. To select the efficient strains, different procedures are used. These procedures have three main steps called as isolation, identification and maintenance of the strain.

Microorganisms are isolated from the places which they are naturally live. Then it’s necessary to identify the microbial strains with good qualities. Since isolation and identification of any strain tedious and time consuming job it’s important to maintain the strains without loosing their characters.

The production technology of biofertilizers must be done under aseptic conditions and using sterilized media and equipments.

There are some disadvantages of biofertilizers such as contaminations and mutations during the production process. Also the presence of overpowering antagonistic microorganisms in the soil suppresses the establishment of the biofertilizers. Also the application of pesticides limits the nitrogen fixation capacity of them.

At present the biofertilizer industry is in its developing phase. Still farmers do not want to take the risk of reducing the application dose of chemical fertilizers. So there is a need to promote the biofertilizers among farmers as pollution free, productive and economically sound product.