Agricultural and Research Applications of Radiation
By Dr K S Parthasarathy
In 1911, George de Hevesey, a Hungarian student working in Manchester University suspected that some of the meals that appeared regularly might be made from leftovers from the preceding days or even week. He put a small amount of naturally radioactive material into the leftovers of a meal. Many days later his land lady served the same food again. He confirmed his suspicion by using a simple radiation detection instrument- a gold leaf electroscope. The landlady sacked him.
Every one forgot the landlady! But George de Hevesey went on to win the Nobel Prize in 1943 and "Atoms for Peace Award" in 1959. He probably carried out the first experiment using a radioactive tracer.
Scientists and technologists use radiation and radioisotopes in a few hundred research and agricultural institutions in India.
Fertilizers are expensive; inefficient and improper use of fertilizers can damage the environment. We must release only minimum amount to the environment.
We can study how fertilizers move in the biosphere by labeling them with a radioactive tracer such as phosphorus-32. Simple experimental procedures show us where and how fertilizer should be placed in soil. We can quantitatively measure the amount of fertilizer used up by the plants.
Studies of pesticides, labelled with radioactive carbon, will help to optimize pesticide use.
Crop losses due to insect infestation are as high as 30 per cent in developing countries. Chemical insecticides are useful to eradicate insects; but are not often very effective. Some insects develop resistance. Insecticide residues are poisonous. Sterile Insect Technique effectively controls insect population.
Scientists rear male insects in the laboratory in large numbers and sterilize them with radiation before releasing them into the affected field. When these sterile males mate with females no offspring is produced. The insect population will reduce drastically. Scientists did such experiments in Mexico to eradicate Mediterranean fruit fly and the screw worm.
Ionizing radiation can be used in plant breeding. At one time, about 13 per cent of all the mutant plants released in the world came from India. Mutation breeding consists of choosing plants with desirable qualities and breeding them separately.
Mutations do occur in plants naturally. Irradiation speeds it up helping to enhance the range of variability of plants. Bhabha Atomic Research Centre (BARC) developed and released 35 mutant crops of ground nut, mung-bean, black-gram, pigeon pea, mustard, jute, rice and soya-bean for commercial cultivation.
A dosa or Idli from anywhere in Maharashtra will mostly contain urid dal (black-gram) produced by mutation breeding developed in BARC. Elsewhere in India, the chance of eating dosa containing BARC- technology-supported urid dal is nearly 50 per cent. Trombay Akola Urid (TAU-1) dal occupies 95 per cent of the area under black-gram cultivation in Maharashtra.
The average yield of Trombay Groundnut (TG-26) was high as 2,500 kg per ha; under improved agronomical practices yield was as high as 10,000 kg ha.
Since January 1, 1974, gamma sterilization of medical products started with the setting up of ISOMED at Trombay. Radiation sterilization ensures that disposable syringes, catheter and other medical devices are absolutely safe. ISOMED processed over 8200 cubic metre medical products during 2007-08.
The International Institute of Population Studies, Mumbai in a study found that the infant mortality rates in Rajasthan, Madhya Pradesh, Maharashtra and Uttar Pradesh fell by 25 to 30 per cent as a result of distribution of "Dai kits" which consist of basic radiation sterilized items required for delivery in rural homes.
Radiation sterilization is a simple process and is carried out at ambient temperature; it is highly reliable. It does not leave any residue. Sterilization is possible in packaged form.
BARC successfully demonstrated that radiation treatment of sewage removes 99.99 per cent disease causing bacteria. Drying the irradiated sludge on sand beds yields pathogen free dried sludge. BARC operates the Sludge Hygienization Research Irradiator (SHRI) at Baroda in collaboration with the Gujarat Government and Baroda Municipality. BARC supplied 600 tons of irradiated sludge as enriched manure for field applications.
Post-harvest losses of food-grains in India are as high as 20 to 50 per cent. Radiation processing of food eliminates insect infestation in food grains, reduces microbiological contamination in other foods, and inhibits sprouting of onion and potatoes and delays ripening of fruits such as mangoes. Radiation processing will never make any product radioactive.
India has exported 160 tons of radiation processed mangoes to USA for the first time in 17 years, starting from April 2007. Radiation processing is the only effective treatment against mango seed weevil and mango pulp weevil. USA approved six varieties of mangoes (Kesar, Alphonse, Banganppalli, Lagra, Dussehry and Neelam) for irradiation. The Krishi Utpadan Sanrakshan Kendra (KRISHAK) irradiation unit is the only cobalt-60 facility outside USA that was approved by the US Department of Agriculture.
Indian exporters of the king of fruits may now re-enter the large, premium markets of USA, Japan and other countries.
From April to November 2007, the radiation unit at Vashi processed more than 1000 metric tons of spices and allied products. Six out of 20 private companies with which BRIT signed Memoranda of Understanding (MOU) to set up radiation processing plants have started functioning in different parts of India.
The Ministry of Food Processing Industries (MFPI) provides substantial loans and grants to any private sector organization to start radiation processing units and or to build common facilities.
Since 1958, scientists have been using radiotracer methods to study silt movement in Indian harbours.
BARC scientists carried out 70 studies for harbour development and dredging programmes by using radioisotopes such as scandium-46 or Gold 198 in Kolkata, Kochi, Karwar, Mangalore and Marmagoa. Such studies helped to identify where silt must be placed after dredging.
Scientists and engineers use radioisotopic methods to trace and measure the extent of underground water resources.
Radioisotopes are useful in every field. We have not yet started using them on a massive scale, though we began activities in the field during the late 50s.
AERB web site www.aerb.gov.in. provides information on the regulatory requirements for using radiation sources in India. (PTI)
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