Science

Irradiation makes cow dung bio-fertilizer safer

Cow dung compost is easy to process.

Cow dung compost is easy to process.   | Photo Credit: Rajesh Kumar Singh

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Do you know that the humble cow dung can be used in a high technology agricultural practice? Researchers from the Department of Agricultural Chemistry and Soil Science, Bidhan Chandra Krishi Viswavidyala and MSV Laboratories Private Ltd demonstrated the potential use of irradiated cow dung as a carrier of bio-fertilizers.

On July 9, this year the Board of Radiation and Isotope Technology (BRIT), Department of Atomic Energy (DAE) signed a Memorandum of Understanding (MOU) with MSV Laboratories Private Limited for setting up a radiation processing plant at Midnapur, West Bengal. The plant will process 60,000 Te of cow dung compost annually for use as a carrier of bio-fertilizers.

BRIT will offer technical guidance including dosimetry to the company and the company will bear the entire capital investment.

Mobilising nutrients

According to the International Crop Research Institute for Semi Arid Tropics (ICRISAT), “bio-fertilizers are ready to use formulates of such beneficial microorganisms which on application to seed, root or soil mobilize the availability of nutrients by their biological activity in particular, and help build up the micro-flora and in turn the soil health in general”.

ICRISAT lists the following: for fixing nitrogen, Rhyzobium for legume crops and Azotobacter /Azospirillum for non legume crops; Acetobacter for sugarcane only; Blue-green algae and Azolla for low land paddy; for phosphorus mobilization, phosphatika is to be applied with Rhizobium, Azotobacter, Azospirillum and acetobacter; for enriched compost, Cellulolytic fungal culture or Phosphotica and Azotobacter culture.

Researchers prepare bio-fertilizers as carrier-based inoculants containing effective microorganisms. This enables easy-handling, long-term storage and high effectiveness of bio-fertilizers. According to the FENCA's Bio-fertilizer Manual, a good carrier must be nontoxic; it should have good capacity to absorb moisture; it should be easy to process and should be free of lump forming materials.

The requirements

Good carrier material must be easily available in adequate quantities; it should be inexpensive and should have good adhesion to the seeds.

The carrier should be easy to be sterilized either by autoclaving or by gamma irradiation.

Charcoal, lignite and peat are costly and are not readily available in the market; so the scientists from the Department of Agricultural Chemistry and Soil Science, Bidhan Chandra Krishi Viswavidyala and MSV Laboratories Private Ltd chose low cost cow dung compost (CDC)as a satisfactory carrier material ( Journal of Interacademecia, Jan- Mar. 2011).

CDC is non toxic to the desired strains of the inoculants. It has good moisture absorption capacity and is easy to process. The authors found gamma sterilization is effective and less time consuming than autoclaving.

Normally, most carrier materials are contaminated with other bacteria. Sterilization offers nutrient and place to the inoculant bacteria against the occupation by the contaminated and/or native bacteria. This is important to keep the number of inoculant bacteria on carrier during the storage period before use.

Unsterilized carrier material will cause undesirable dispersion of pathogenic bacteria into agricultural fields.

Scientists exposed the samples of raw material in low density, 65 to 70 micron thick polyethylene bags to various doses of gamma radiation

They found that CDC, irradiated with a gamma dose of 50kGy, can be used as a carrier for bio-fertilizers (Gy is a unit of radiation dose. When the dose is one Gy the radiation energy absorbed per kilogramme of material is one joule; since during radiation sterilizing we use large doses of radiation, multiples of Gy such as kiloGy or 1000 Gy are used).

High initial cost

The initial cost of gamma irradiation installation will be high, at Rs.50 million compared to autoclave (Rs.20 million).

A ton of irradiated cow dung compost carrier will cost only Rs.2583 as against Rs.20,370 for a ton of sterilized charcoal. The major reason for this is the cost of charcoal (Rs.20,000) compared to cow dung (Rs.2, 250)

A major difficulty with the project may be the collection of enough “raw material”. MSV Laboratories Private Limited may have to set up a chain of cow dung collection centres to keep the programme running.

Raja Ramanna Fellow, Department of Atomic Energy ( ksparth@yahoo.co.uk)

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Printable version | Sep 16, 2019 7:20:04 PM | https://www.thehindu.com/sci-tech/science/irradiation-makes-cow-dung-biofertilizer-safer/article2319456.ece

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