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Agronomic Rationale for the Genetic Diversity in the Drylands of West Bengal
(Variétés indigènes dans la riziculture pluviale au Bengale -2- Facteurs agronomiques en lien avec la diversité génétique dans les régions sèches de l’ouest du Bengale)
09 / 1997
The district of Bankura in West Bengal is known for its arid land and erratic rain patterns. Along with two neighbouring districts, Purulia and Western Midnapore, Bankura is consequently known as one of the poorest regions of West Bengal.
The Damodar river and its two tributes, the Bodai and the Sali are the only waterways of the state. Except for villages linked to these water sources through canals and reservoirs, the district is rainfed. The main rice season is aman, from July-August to November-January, but aus rice, which has a shorter period (June-July to September-October)is also found. Boro rice is only cultivated in pockets of irrigated land. Unlike in the more favourable irrigated areas of the state, the farmers of Bankura still cultivate a fairly large number of traditional rice varieties, not necessarily out of choice, but rather because the agronomic conditions leaves them little choice. The modern high yielding varieties launched during the Green Revolution are for the most part unsuitable for tropical uplands and lowlands, which characterize the topography of Bankura district.
The farmers of Ukhradihi, a village located in the Northern half of the district, distinguish three subtypes of land : "bhaid", the high land, "kanali", the middle land, and "sol", the low lying areas more prone to water logging. A lateritic soil gives the land its red colour throughout the district.
On the high lands, farmers tend to grow local aus varieties of short duration which come to maturation within ninety to a hundred days. These varieties of rice, among which Ashinlaya, Kelas and Kaya, have been cultivated in the area for over a hundred years according to the older farmers. Kelas and Kaya are known for their tolerance to drought, and they can be grown on upland plots that would otherwise be unproductive.
The middle lands, which remain flooded for a longer period of time than the high lands, are sown with varieties that mature in 150 to 180 days, such as Nona, or Kalamkatti. Some high yielding varieties, such as IR36, Rotna or Lalat, which only require 120 days to reach maturation are also grown.
The high level of standing water which accumulates in the low lying areas make the cultivation of traditional varieties compulsory on this landtype. Dohar Lagra is the most commonly used. It can survive in as much as 5 feet of water (1.5 m), whereas high yielding varieties do not survive in more than 2.5 feet (75 cm).
As most landowning farmers possess several plots in the high, middle and low lands, they cultivate at least three or four varieties during one season. Moreover, farmers attempt to alternate the cultivation of modern and folk varieties on a given plot every year so as to minimize losses in soil fertility and a hardening of the land due to the application of fertilizers on modern varieties. The latter also require frequent spraying of pesticides.
Indeed, pest diversity is significantly higher with high yielding varieties than with indigenous cultivars, which often feature an inherent resistance to specific pests and diseases. Thus, Kelas has been shown to be resistant to blasts and farmers report that Kaya and Chandrakanti are rarely infected by fungi and bacteria. Finally, folk varieties are better able to resist sudden water shortages than their modern counterparts, so that if the rains are not sustained throughout the monsoon period, the entire crop of HYV’s threatens to be lost.
Despite this major drawback - rains have been known to partially or entirely fail every third or fourth year - an increasing number of small farmers (owning between 5 and 7 bighas, or 1.4 and 2 hectares)choose to grow high yielding varieties on their high land plots. The main incentive is the difference in output : HYV’s have the potential to yield between 6 and 7 quintals a bigha (approximately between 2.2 and 2.5 tons/hectare), which is considerably more than the 2 to 4 quintals per bigha (between O.8 and 1.5 t/ha)harvested in the case of indigenous varieties. Two local landraces, Chandrakanti and Murgisal, are said to yield as many as 4.5 quintals per bigha, which makes them very popular among poor farmers.
This account shows to what extent agronomic factors shape individual cultivation practices. We are far from the irrigated and well controlled environemnts of the deltaic areas of central and South Bengal. In the dry environment of Bankura, the farmers-breeders have selected folk varieties suited to the local hydrologic conditions and to the wide range of landtypes. Knowing well that an indiscriminate use of modern varieties would lead to a disaster, the farmers grow the latter with parcimony and caution.
Calculations of areas and yields based on 1 bigha = O.66 acre in this part of Bankura.
The names of local rice varieties have been gathered during my fieldwork with farmers and double-checked in the existing literature on indigenous rice.
See Deb, Debal, 1995, Sustainable Agriculture and Folk Rice Varieties : Agronomic, Ecological and Cultural Aspects, World Wide Fund for Nature - Eastern Region, Calcutta.
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.