2 November 2011
ORGANIC food without the use of chemical fertilisers and pesticides is being promoted in the USA, Canada, Austria, Italy, Poland and Cuba. These are processed without artificial preservatives. The products are more nutritious and resistant to diseases. Organic fruit and vegetables contain around 40 per cent more anti-oxidants than those produced with fertilisers. The products are required to be certified by an accredited agency.
The Green Revolution of the 1960s needed high inputs in respect of quality seeds, chemical fertilisers, pesticides, irrigation, farm mechanisation, etc. As a result, the problems of that agricultural phenomenon are now emerging. It can have an adverse effect on agricultural development. There have been both qualitative and quantitative degradation of land, waste and bio-resources; fertile lands have become uncultivable due to waterlogging and salinity, and the post-harvest losses have been substantial.
Organic farming is now being promoted in India. It plans to cover a range of high-value crops, including spices, fruit, vegetables, milk, poultry products, etc. An estimated 3.8 million hectares are now under organic farming in different states. These products fetch 25-30 per cent higher value than non-organic products.
Earlier, India had earned foreign exchange worth $78 million in a year from export of organic products to European countries, the USA, Japan, Australia and the Middle East.
Organic farming does not cause environmental and social damage. It maintains soil fertility, reduces tilling, suppresses weed growth, promotes humus formation and enhances the water-holding capacity of the soil. It is less costly for sustainable agriculture. This may reduce rural poverty and distress among the poor and marginal farmers, and may improve their income and livelihood.
Natural farming is a boon to the hapless farmers in Punjab. No institutional credit is required and hired labour is reduced. Home-made preparations such as a mixture of cow dung, cow urine, water, lime and soil protects crops against harmful soil-borne and seed-borne pathogens. Kerala is converting 20 per cent of the cultivable land to organic farming. Farmers are being encouraged to use bio-fertilisers and bio-pesticides. Six thousand hectares of arable land in Sikkim are under organic farming. Farmers have succeeded in growing maize, paddy, ginger, cardamon and turmeric.
The use of bio-fertilisers for nitrogen is being encouraged these days. Agriculture today consumes high inputs of nitrogen. On an average, 100 kg of nitrogen fertilisers are consumed per hectare in the country. This requires a huge investment. The present needs of nitrogen are largely met from synthetic nitrogen fertilisers. A part of the requirement is met by imports. Their demand is expected to increase by 25 per cent in the near future.
These fertilisers are quite expensive because of high production cost. Their high inputs have considerably increased the cost of farm production. Production consumes a substantial volume of energy. Given the energy constraints, attempts are being made to tap alternatives and supplement nitrogen resources by directly utilising atmospheric nitrogen through the biological procedure.
In view of fast depleting resources and to avoid depletion of fossil fuel and damage to environment from excessive use of synthetic nitrogen fertilisers, exploitation of the biological nitrogen procedure has gained special importance. A national project on the development of bio-fertilisers is being promoted to produce over 10,000 tonnes of bio-fertilisers. The commonly used varieties are rhizobium, azotobacter and blue green algae. The first two stem naturally from the soil. The blue green algae grows in the stagnant water of ponds and rice fields. Their efficient strains are being isolated.
Azospirillum-based experiments have also shown promising results. Its use increases yields of cereals amounting to considerable savings.
In the symbiotic nitrogen fixing system, photosynthetically stored energy is utilised instead of fossil fuels. In this process, atmospheric nitrogen is converted to ammonia with the help of biological catalysts, which are present in some of the plants or in the bacteria in the soil. In this system, certain nitrogen fixing bacteria (rhizobium species) grow in close association with a higher plant (leguminous), usually with its roots, where nodules are formed. The process takes place in these nodules through an enzyme system. Nitrogenase is the key enzyme. The efficiency of the process and the amount of nitrogen fixed depend on synthesis, control and regulation of the enzyme.
One major limitation of nitrogen fixation in legumes is the availability of photosynthetate which is dependent on the efficiency of the process of photosynthesis. Therefore, increased nitrogen fixation must be accompanied with more photosynthetic activity. The fate of nitrogen fixation also depends on how regulation of nitrogenase is effected under environmental factors such as oxygen concentration, ammonia in concentration and the presence of certain metabolites.
In the non-symbiotic process, there is a wide variety of “free-living organisms” such as azotobacter or clostrida, which fix atmospheric nitrogen under aerobic (presence of oxygen) conditions, depending on the organism and conditions like proper moisture, temperature, acidity and source of energy.
Blue-green algae also possess the nitrogen-fixing ability. These algae are now commercially grown, dried and sold in packets as bio-fertilisers. Application of a combination of blue-green algae at a rate of 10 kg of soil containing 5 per cent algae per hectare is commonly used. This saves about 30 kg fertiliser nitrogen per hectare.
The application of blue-green algae has an additional advantage. It reduces salinity. It is successful with the rice crop because it gets favourably submerged conditions for growth. These algae could not be exploited in wheat fields. However, its use would largely depend on developing efficient strains for adverse environments to ensure better success.
The long-term future of Indian agriculture will thus depend on the success of these efforts, which will ultimately mean going back to nature and reducing the dependence on synthetic chemical fertilisers.
The writer is ex-Principal Scientist, IARI, New Delhi