FERTILIZERS AND pesticides are two principle agricultural inputs. Fertilizers are the food while pesticides act as medicine for the crops. After intensive and prolonged cultivation, agricultural lands becomes poor in fertility and need to be supplemented heavily with agrochemicals to fulfill the deficiency of nutrients resulted due to this conventional intensive agricultural system.
No doubt, the chemical fertilizers increase the productivity but they are no more cost effective. Moreover, they are the potential threat for human health as well as for the environment. Vegetables and cereals absorb the toxic elements present in these fertilizers and become the part of the food chain. Water pollution resulting from the seepage of the fertilizers in the ground water is also affecting human health. An answer to all these problems is the use of biofertilizers, a worldwide accepted ecofriendly technique.
Biofertilizers are the substances that encompass active microorganisms, become active only when applied seed or soil, make colonies in soil or in plant and enhances the growth and development by making available the primary nutrients to the host plant. There is great difference among biofertilizers and fertilizers. Later are the chemical substances which increase the soil fertility by adding nutrients in the soil while biofertilizers add nutrients by natural ways e.g. by fixing atmospheric nitrogen, solubilizing bound phosphorus and by the production of growth promoting substances. They are also called as “live fertilizers” and sometimes “biostimulants”.
Different types of biofertilizers are available that can enhance the nutrient use efficiency through aiding the availability and uptake of nutrients. These include nitrogen fixers (Rhizobium, Bradirhizobium, Azospirillium and Azotobacter) and phosphorus solubilizers and growth promoters (Pseudomonas, Bacillus and Aspergillus).
The nitrogen fixers act upon by fixing the elemental nitrogen in the root zone of plants. These microorganisms dwell in the root nodules or live freely in the rhizosphere. There is mutual relationship between these bacteria and plant. They fix the atmospheric nitrogen and in return they obtain carbohydrates from plants as their energy source. In this way both the plants and bacteria get benefits from each other.
Phosphorus solubilizers solubilize insoluble form of phosphate such as tricalcium phosphate and aluminum phosphates into the available form. The phosphorus solubilizers decrease the soil pH and thus render the soil phosphorus into available form. In addition to the enhancement of nutrient availability and uptake, they also decompose the organic matter thus providing the additional advantages.
Some important substances such as hormones and antimetabolites are also released by these microorganisms in the rhizosphere which play pivotal role in boosting the plant growth. Antimetabolites safeguard the plants against diseases and also provide competitive advantages. These microorganisms are beneficial to the plants from their part but are not harmful to the plants in any aspect.
Biofertilizers are available in powder as well as in liquid forms but liquid forms are not common. Biofertilizers can be used in many ways like seed treatment which is the most common, effective and economic method. In this method seed can be treated by inoculating the microorganisms residing in carrier material using sugar solution as sticking agent and initial food for microorganisms. For crops sown by nursery such as rice and vegetables, dipping their roots in cultural solutions is an effective method of biofertilizers application. However, it is not a common practice. Another way of biofertilizer application is soil application, in which biofertilizers are applied by mixing with carrier like farmyard manure, cattle dung and rock phosphate.
Biofertilizers are cheap, easy to use and effective source of fertilizers and thus reduce the cost of production. These improve the soil fertility and structure by enhancing the availability of nutrients. Furthermore, these are host specific, therefore, are not detrimental to environment as well as for human health. Despite of immense benefits, some constraints are also linked to biofertilizers that limit their use by the farmers. Lack of infrastructure, poor technology (improper and less efficient strains, short shelf life of inoculants), poor human resources (lack of technically qualified staff and their proper training, adoption problems by the farmers), financial constraints (non-availability of sufficient funds and problems in getting bank loans), unawareness, poor marketing (no visual difference in the crop growth immediately as that of inorganic fertilizers) are some of the important constraints.
More research is needed in this field. Use of biofertilizers can be increased by the technical training of the staff, creating awareness and educating the farming community and by resolving the marketing problems. Government should take steps for the promotion of biofertilizers by subsidizing the products and provide modern equipment for farming community at extension stations.