There is a growing realisation that current agricultural production practices in Nepal are not sustainable. We are witnessing a scenario where the misuse of agrochemicals, mainly pesticides, chemical fertilisers, and growth regulators/hormones, are pervasive, leading to irrevocable human health risks, degradation of soil qualities, and several other environmental hazards. Their economic and environmental impacts could be huge, if not addressed timely.

The reduced amounts of farmyard manure and compost on the one hand and increased cropping intensity and use of high yield crop varieties on the other have augmented the demand of plant nutrients in Nepal. Chemical fertilisers were recently considered a major source of plant nutrients. It is projected that about 500,000 metric tonnes of chemical fertilisers are required annually.

However, no such fertilisers are manufactured in the county and all fertilisers are imported. Currently, less than half of the total requirement is supplied through imports. There is an ever-growing shortage of fertiliser in the country. This also costs the country huge amounts of foreign currency. Over Rs 5 billion is estimated to be spent annually to supply only 50 percent of the total fertiliser required. Even if the negative effects of chemical fertilisers, such as increase in soil acidity, soil qualities, and environmental effects, are set aside, it is certain that the country will incur a huge economic burden over the long run. The time has therefore come to think, explore, and utilise alternative sources of plant nutrients that are safe, economically viable, and environmentally sustainable.

Bio-fertiliser switch

Bio-fertilisers can be one of the best alternative sources of plant nutrients to supplement chemical fertilisers. Bio-fertilisers are substances that contain living microorganisms, which, when applied to soil or inoculated to seeds or plant roots can colonise the rhizosphere, or the interior of the plant, and promote growth by increasing the supply of nutrients to the host plant or release in the soil. A large number of beneficial microorganisms exist in our soil, which enhance soil productivity by either fixing atmospheric nitrogen, by solubilising soil phosphorus, or by stimulating plant growth through synthesis of growth-promoting substances. They occur naturally in soil or plants but are invisible and their value is largely overlooked.

Several microorganisms and their associations with plants and soil are being exploited in the production of bio-fertilisers. The most common bio-fertilisers are nitrogen-fixing bacteria like Rhizobium, Frankia, Anabaena azollae, Azotobacter, Clostridium, and Azospirillum; phosphorus solubilising bacteria like Bacillus megaterium var. phosphaticum, Bacillus subtilis, Pseudomonas striata; fungi like Penicillium, and Aspergillus); and phosphorus-mobilising fungi such as Arbuscular mycorrhiza. Mycorrhizae are fungi that form mutualistic relationships with the roots of several plant species and promote the absorption of nutrients and water, and improve soil structure. Some other micro-organisms in bio-fertilisers also help to decompose or breakdown organic matter and release plant nutrients.

Beneficial micro-organisms are generally prepared in certain medium (inoculants or carriers) in solid or liquid forms. These inoculants are the substances containing microbial populations of bacteria and fungi, which are used for seed inoculation or mixed in soil or manures. To date, mainly Rhizobium inoculants are used in some legume crops in certain areas of Nepal, but their use is negligible and erratic.

Another potential bio-fertiliser is Azolla. This is a free-floating water fern that fixes atmospheric nitrogen in association with blue green alga (Anabaena azollae). Azolla is commonly found in many wetland rice ecosystems of the foot-hills and Tarai regions of Nepal. However, its wide-scale utilisation is very limited.

Benefits and limitations

The advantages of bio-fertilisers are that small amounts of inoculum can cover a large area. They can be produced within the country at low production costs and incur negligible transportation cost, compared to chemical fertilisers. Once inoculated or applied, the microorganisms can survive and multiply naturally in most environments. They do not have adverse effects on the soil or crops. Therefore, bio-fertilisers are cost effective, ecologically safe, and a renewable source of plant nutrients that can supplement the use of chemical fertilisers. They should be considered an important component of integrated nutrient management.

No technology can be expected to be free from all constraints. The most common limitations to the widespread adoption of bio-fertiliser technology in Nepal seems to be a lack of awareness among farmers about the benefits of technology; slow action of bio-fertilisers as compared to chemical fertilisers; unavailability of right inoculant at the right time; lack of qualified technical personnel and appropriate training on production application, and maintenance techniques; short shelf-life of inoculants and lack of proper storage (freezer) and transportation facilities; and faulty inoculation techniques. The success or failure and acceptance or rejection of any technology by farmers depends on its efficacy. Lack of regulatory compliance and quality control mechanisms have resulted in ineffective inoculants. Similarly, adverse soil conditions (too acidic or contaminated with pesticides) can affect the survival and efficacy of the microorganisms in soil. Some technologies, such as multiplication of Azolla, are temperature dependent and require water. Therefore, they cannot be used at higher elevations or during the cool season and in upland conditions.

Sustaining the land

It would not be sensible to argue that bio-fertilisers alone can replace all chemical fertilisers in Nepal. But it is certain that they can substantially reduce the dependency on chemical fertilisers. They should be considered one component of organic agriculture, facilitating the capture of atmospheric nitrogen for plant use, solubilising phosphorus and breaking down organic matter to release nutrients into plant available forms. Emphasis should be given to maximise the use of appropriate bio-fertilisers where they are technically feasible. We can learn much from India where several types of bio-fertilisers have been commercially produced in different formulations and are being used in a wider scale.

Although some research efforts have been made in Nepal, the commercial production, distribution, and utilisation of bio-fertilisers is vastly inadequate. It is time to invest more on research, production, and transfer of such technologies to growers. The government should invest more in such low cost, sustainable technologies. Programmes and policies should embrace research, production, quality control, assured supply of inoculums, training, and promotional activities. For the long-term sustainability of land, safer foods production, including organic foods, environmentally-friendly agriculture, and wide-scale utilisation of bio-fertilisers seems to be a prospective technology that should be invigorated in Nepal. This will help realise a green future for the country.

Subedi works for Agriculture and Agri-Food Canada