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2008 / 2009
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Genetic Diversity in the Lowlands of South Bengal
(Variétés indigènes dans la riziculture pluviale au Bengale -1- La diversité génétique dans les terres basses du sud Bengale)
09 / 1997
The village of Naltala lies in the deltaic region of South Bengal, in the district of South 24-Parganas. Marshy lands with high salinity levels are not uncommon in this part of the state, where rice is the predominant crop. Every year during and after the monsoon rains, water stagnates in the fields, with up to four or five meters accumulating in the lower lying areas.
Farmers have adapted their agricultural practices to these conditions. Over the years, they have also identified and selected rice varieties that grow tall and fare well in inundated terrain. Sturdiness is another trait that farmers have aimed for : local landraces do not lodge easily during a rainfall or a storm, and they can also withstand sudden temperature changes. Further, in the event of erratic weather patterns such as rain failure, between 70% and 80% of a crop of local cultivars would still come to maturation whereas most of a crop of high yielding varieties would be ruined. Indeed, the modern high yielding varieties that have been spread throughout the state are rarely suited to specific agro-climatic constraints.
For aman cultivation (May to October-November), virtually all farmers rely on indigenous rice varieties. Farmers whose fields are located in the lower areas have to cultivate varieties which mature within 140 to 150 days. Thin-grained varieties, which mature faster, are grown on highland plots.
The six following varieties are the most popular in Naltala among small farmers : Auspajal, Dorani, Patnai, Doodheswar, Shamarmani, Nikunj. The first three varieties have thick grain, and yield around 1. 6 t/ha. They are sold for Rs. 9 or 9. 5/kg on the market. The other three are thin grain varieties. They do not yield more than 1. 3 t/ha, but can be sold for Rs. 12/kg. Auspajal and Dorani were introduced in Naltala some fifteen years ago as improved indigenous varieties.
All farmers know of Shabita, a high yielding variety for aman, which hardly anyone grows. The extra yield its procures fails to compensate for a high production cost. Moreover, its taste is inferior to that of indigenous landraces.
Like all small farmers, Deepak, who owns 4 bighas (a little under one hectare)cultivates 5 or 6 different varieties. On each of the small plots, he grows a variety suited to the landtype of that plot. Every year, for two similar plots, the seeds are rotated. They are replaced every 2 to 3 years.
It is important to note that the quasi exclusive cultivation of indigenous varieties during aman season in Naltala is not representative of the entire district. Hence, in Chandi, another village located some thirty kms North of Naltala, 30 to 40 % of the land is cultivated with high yielding varieties in aman season. These varieties are grown in the least water-logged areas.
The winter crop, or boro rice (December to February-March)thrives on water supplied by a canal directly linked to the Hooghly River (the Ganges). Towards the middle of February, the spring tide comes in, ensuring a large supply of water to the paddy fields. At the end of March, however, the salinity of the water increases drastically. Hence, it is of prime importance to harvest the fields before that time. The tide, which comes in twice a day, floods the fields morning and evening. The floodgate is manually opened and closed to regulate the inflow of water. Where necessary, a waterpump is used to irrigate certain fields.
All varieties cultivated during boro season are high yielding varieties. Since water supply is only ensured for three months, farmers tend to go for short duration varieties, such as Lolat, Rashi (IET 1444), Ratna (CR 44-11), IR 36 (thick rices)or Khitish, Rajbogh 381 (thin rices). The local names are most commonly used than the numbered appellations. These mature within 90 days and yield on average 3. 2 t/ha. They fetch prices ranging between Rs. 9 and 11per kilo. IET 723, also known as Joya has a greater yielding potential. Yet few farmers can cultivate it, because due to its long maturation period (120 days), it must be transplanted one month before the canal irrigation water is available.
Of his 4 bighas, Deepak only uses 2 for boro rice. The other 2 bighas are used to grow vegetables or mustard seeds. Similarly, Hidoy, whose family of 11 people cultivates 8 bighas (almost two hectares), grows rice on 6 bighas only in boro season.
Usually, the entire aman crop is saved for the yearly family consumption, and if that is not sufficient, part of the boro crop is also kept. The rest is sold on the market.
In Naltala, farmers can not do without indigenous rice varieties due to the agronomic constraints. This does not mean, however, that farmers will not readily adopt suitable modern varieties when they are introduced. What is needed, perhaps, is a thorough scientific endeavor to upgrade indigenous varieties, as well as a conscious effort to preserve the local genetic diversity of rice.
Personal study on biodiversity in India. A book is on the point to be published in India. For further information, please contact the author (see address)or Fph.