This work has been started in 2010 with a self-funded initiative to collect information from different sources like research publications, government and public research institutions, offices, books and journals, periodicals and also from the news media. Physical investigations were made visiting most part of the country meeting people of different ages and levels. Many changes are also shared from the author’s experiences at different work places and compared by revisiting. Since, there are marked changes of the landscape are found but not scientifically documented or studied, as it was less understood or overlooked in the past, so little data is available. However, this study has been done with care and given utmost importance on its scientific needs.
Ecotypes and Landraces of Rice in Bangladesh
According to climatic adaptation in the tropical monsoon four Ecotypes or Landraces of rice are grown in Bangladesh which are Aus, Aman, Boro and Jhumia.
Adaptability and Sustainability of Rice
Rice has a wide adaptation ability under different agroecological niches of Bangladesh. It can be cultivated on the slope of the hill, plain lands, floodplains, semi-dry to very deep flooded areas. Widely adapted with different climatic seasons; 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 our country go under floodwater for a considerable time in the wet season, or when intermittent flash flood affects the majority of the lowlands, or when tide water rises up and falls down twice a day, rice is the only crop option to be suited in those conditions. Thus rice enables to bring these vast areas under cultivation in unfavorable conditions.
An extremely high density of human population in Monsoon Asia has been supported by paddy rice cultivation developed exceptionally extensive lowlands that have resulted from erosions of uplifting Himalayas and erupting volcanoes under heavy monsoon rains. A native grass, Oryza Sativa, has many outstanding merits when cultivated in submerged soil, thus making the paddy rice/soil system highly productive and, at the same time, highly sustainable. High productivity and high sustainability are the outstanding merits of rice cultivation, while upland cultivation in Monsoon Asia for dry footed crops has been handicapped by low soil fertility and high susceptibility to soil erosion. In the future, rice would remain the most important crop in Monsoon Asia and further intensification of rice cultivation should be attained. To nourish the region’s increasing population, upland cultivation must also be intensified with adequate measures for soil amendment and conservation.
Traditionally in Bangladesh, Jhum or shifting cultivators had been paying careful attention to soil resilience by practicing short cultivation following long fallow system with a minimum of disturbance to the surface soil to avoid soil erosion and to help facilitate forest regeneration thus Jhum cultivation as a means of slope land utilization has traditionally been quite sustainable.
According to variations of climatic seasons and topography there evolved different kinds of rice with many characters and specialties. Aromatic, non-aromatic, glutinous and non-glutinous, coarse and fine grain, long medium and short-grain rice with varied colors: brown, white, red and black etc.
Perhaps rice is the most sustainable food crop in the world in providing energy and nutrition, has versatile food preparations, preservation and regeneration opportunities. Comparing to 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 the human diet and accounts for more than 50% of our 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. We often think of potatoes as “starchy” food, yet other plants contain a much greater percentage of starch (potatoes 15%, wheat 55%, corn 65%, and rice 75%). Commercial starch is a white powder. Although potatoes are cheaper than rice but it is one-fifth efficient to rice, therefore, costlier than rice.
Boiled and cooked rice, viz. Bhat, Polao, Biriani, Khichuri, fried and puffed rice: Chira, Muri, Khoi and Moa, fermented Bini Bhat, wine, bear and vinegar, rice bran oil, soup and many kinds of cakes and preparations with fruits, sugar, milk, chili and spices e.g. Pitah, Payesh, Kheer, Semai, banana leaf Puli, and bamboo Pitahs, different seasonal Pitah preparations like Taler (Palmyra palm) Pitah in Vadra, Vapa Pitah in Poush, Kolar (Banana) Pitah in Magh, Katal (Jackfruit) Pitah in Jaista and Ashar and coconut pitah throughout the year. Cooked rice is usually consumed with diverse recipes prepared with meat, fishes, prawns and vegetables and fruits as curries, Vorta and salads etc.
Residue management and biomass recycling
Residue management practices affect soil physical properties such as soil moisture content, temperature, aggregate formation, bulk density, soil porosity and hydraulic conductivity. Increasing amounts of rice residues on the soil surface reduce evaporation rates and increased duration of first-stage drying. Thus, residue-covered soils tend to have greater soil moisture content than bare soil except after extended drought. The straws are very good fodder for cattle used 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. Cellulose is the carbohydrate-like starch with similar basic unit glucose. Therefore both rice and straw are contributing in energy conversion and nutrient supply chain and in biogeochemical cycle more efficiently than any other crop.
Usually, the yield of the vegetable crops is high and consumed whole plant parts; thus all nutrients are ingested by humans, very few portions are recycled through the involvement of other animals. As a result, short-cycled recycling of the human feces or excreta is not easy especially from the quickly growing urban areas. Therefore, the nutrients are not getting back to their sources of origin and the soil nutrition status is declining sharply mainly from the vegetable fields. Practically in the urban and peri-urban areas, the huge faeces are remained unutilized years together in the septic tanks; the black water overflows to the rivers or wet-bodies through sewerage system. Unfortunately, most of the wet bodies are deadly polluted with the chemicals, oils and other pollutants discharged from the industries, transports, hospitals and tanneries etc. As a result, the productivity of fishes and other aquatics is also very poor from those wet bodies. On the other hand, urban green garbage is rarely recycled rather than dumps for landfills. Other than the feces, according to Waste Concern (2006), average per capita urban waste generation rate is estimated as 0.41 kg/capita/day of which food and vegetable comprises 67.65% i.e. about 0.28 kg/capita/day and for present urban 40% of the total population of the country producing 20,160 tons green waste every day by the urban people of which a very negligible quantity is recycled. Thus the soil fertility status of the country has been declining very sharply and the farmers are becoming increasingly dependent on chemical fertilizers. Therefore rice-based home-centered farming system for short cycled biomass recycling is of utmost essential. The diversified landraces of rice have the ability to supply the necessary energy and nutrients to humans and other animals associated with the cropping circle in this region.