THERE were thousands of varieties of rice, the most important grain crop in Bangladesh, but more than 5,000 local rice varieties have become extinct in the past few decades. Nearly I0,000 landraces are considered to exist in Bangladesh and it is estimated that about 1,20,000 varieties of rice exist in the world.
About 8,200 germplasm have been preserved by the BRRI genebank till date. Available data of the Digital Herbarium of Crop Plants show that only 135 varieties are in cultivation now. The situation is alarming both for food security and biodiversity. Ongoing rapid changes in agricultural practice that favour agronomically improved varieties have become a serious threat to the persistence of indigenous rice varieties.
Thus, conservation and management strategies are urgently needed to prevent further loss of genetic diversity inherent in indigenous rice varieties in the region. A detailed understanding of the genetic structure and diversity is needed for the planning and implementation of effective conservation, management and use of rice germplasm in the whole region.
Therefore, along with the genetic forced crop improvement, climatic adaptation and improvement of environmental factors through climatic manipulation and aggregate farming using multiple varieties of crops, pets and aquatics etc are of utmost importance for food and nutrient security in this climate change situation.
To ensure the conservation of biodiversity, protection of soil health and water quality and ultimately for the betterment of human health, the government, researchers, research organisations and policy-makers should consider the direct and indirect benefits of rice landraces without further delay.
Rice has the wide adaptation ability under different agro-ecological niches of Bangladesh. It can be cultivated on the slope of the hill, plain lands, floodplains and semi-dry to very deep flooded areas. Widely adapted with different climatic seasons, it can be cultivated throughout the year. Rice is the best-adapted cereal crop in the lowland soil in the wet season. No other crops have this ability to cope with the situation.
When the vast areas of Bangladesh go under flood water for a considerable time in the rainy season, or when intermittent flash flood affects majority of the low land, or when tidal water rises and falls down twice a day, rice remains the only crop option in such conditions. Thus, rice can be cultivated in such vast areas in an unfavourable condition.
Traditionally, jhum or shifting cultivators had paid careful attention to soil resilience by practising short cultivation, following long fallow system with minimum of disturbance to the surface soil to avoid erosion and to help facilitate forest regeneration. Jhum as a means of slope-land cultivation has, thus, been traditionally quite sustainable.
Keeping to variations in climatic seasons and topography, there evolved different kinds of rice with many characters and specialities. Aromatic, non-aromatic, glutinous and non-glutinous, coarse and fine grain, long-, medium- and short-grain, with varied colours — brown, white, red and black, etc.
Rice is, perhaps, the most sustainable food crop in the world in providing energy and nutrition and has versatile food preparations, preservation and regeneration opportunities. Compared with vegetable crops, other grain crops, tuber and root crops and even fruit crops, rice is cheaper and handy.
Rice is considered to be an auspicious symbol of life and fertility. Starch is the most important source of carbohydrates in human diets and accounts for more than 50 per cent of the carbohydrate intake. It occurs in plants in the form of granules and these are particularly abundant in cereal grains and tubers, where they serve as a storage form of carbohydrates. Potato is often throught as a ‘starchy’ food, yet other plants contain a much greater percentage of starch — potatoes 15 per cent, wheat 55 per cent, corn 65 per cent and rice 75per cent. Although potatoes are cheaper than rice, they are one-fifth efficient compared with rice and, therefore, are costlier than rice.
Residue management practices affect physical properties of the soil such as soil moisture content, temperature, aggregate formation, bulk density, soil porosity and hydraulic conductivity. An increased amount of rice residues on the soil surface reduces evaporation rates and increases duration of first-stage drying. Thus, residue-covered soils tend to have greater soil moisture content than bare soil does except after extended drought.
The straws are very good fodder for cattle used in both green and dry conditions. Straws contain cellulose lignin and many minerals which decompose in the field or recycled via cattle through enzymatic and microbial process, enriching food chain adding value with protein, fat and minerals. The cellulose is the carbohydrate like starch with similar basic unit glucose. Therefore, both rice and straw contribute to energy conversion and nutrient supply chain and, in biogeochemical cycle, more efficiently than any other crop.
Usually the yield of vegetable crops is high and whole plants are consumed; thus, all nutrients are ingested by human. Very little of them are recycled through the involvement of other animals. As a result, short-cycled recycling of the human faeces or excreta is not easy especially in quickly growing urban areas. Therefore, nutrients do not get back to their origins and the soil nutrition status declines sharply mainly in vegetable fields.
Practically in urban and peri-urban areas, huge faeces are remained unused for years together in septic tanks; the black water overflows to rivers or wet bodies through the sewerage system. Unfortunately, most of the wet bodies are deadly polluted with chemicals, oils and other pollutants discharged from industries, transports, hospitals and tanneries, etc. As a result, the productivity of fish and other aquatics is also very poor in such wet bodies. On the other hand, urban green garbage is rarely recycled and is, rather, dumped in landfills. Other than the faeces, average urban waste generation rate is estimated at 0.41 kilogram per capita a day, with food and vegetable accounting for 67.65 ie about 0.28 kilogram per capita a day. For now, the urban 40 per cent of the total population produces 20,160 tonnes of green waste every day a very negligible quantity of which is recycled. Thus, the soil fertility status has on a sharp decline and farmers are becoming increasingly dependent on chemical fertiliszers. Rice-based home-centred farming system for short-cycled biomass recycling is, therefore, essential. The diversified landraces of rice have the ability to supply the necessary energy and nutrients to humans and other animals associated in the cropping circle in this region.
According to recent IPBES Global Assessment Report: Since 1970, trends in agricultural production, fish harvest, bioenergy production and harvest of materials have increased in response to population growth, rising demand and technological development. This has come at a steep price, which has been unequally distributed within and across countries. Many other key indicators of nature’s contributions to people such as soil organic carbon and pollinator diversity have, however, declined, indicating that gains in material contributions are often not sustainable.
The pace of agricultural expansion into intact ecosystems has varied from country to country. Losses of intact ecosystems have occurred primarily in the tropics, home to the highest levels of biodiversity on the planet. Bangladesh needs to revise its agriculture policy to save the ecosystem, biodiversity and to protect human health.
Professor Dr Mohammed Ataur Rahman, a crop climatologist, works at the International University of Business Agriculture and Technology.
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