New horizons for African rice
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CTA. 1996. New horizons for African rice. Spore 64. CTA, Wageningen, The Netherlands.
Permanent link to this item: http://hdl.handle.net/10568/47378
Every year more and more Africans are choosing to eat rice. Consumption is rising by 5% a year and although this is a decelerating increase compared to the '70s, there is an ever-widening gap between demand and local supply. Until now this gap has...
Every year more and more Africans are choosing to eat rice. Consumption is rising by 5% a year and although this is a decelerating increase compared to the '70s, there is an ever-widening gap between demand and local supply. Until now this gap has been filled by imports of rice from the distant horizons of Asia but the economic climate in Africa has changed considerably within the last few years. While imports may remain the most sensible option for the vast urban populations who live close to an ocean port, people who live in towns far from the coast may find themselves increasingly dependent on local rice production. In West Africa, the most significant rice production area of sub-Saharan Africa, the majority of rice farmers are poor, cultivating no more than one hectare, and yet the most sophisticated tools and techniques available anywhere in the world are being used to help such farmers. It is with Africa's own genetic resources that their problems are being solved. Rapid urbanization has created the increased demand for rice. Quicker and easier to prepare than traditional staples such as sorghum or millet, rice is the cereal that urban working people prefer. Rice in Africa is no longer a luxury food and a survey in Burkina Faso, typical of several other West African states, shows that the poorest third of urban households obtain 33% of their cereal-based calories from rice. Availability and price are major issues for consumers, and therefore also for rice producers, in West Africa. Liberalization While governments were able to import rice from South East Asia at very low prices there was little incentive to farmers to increase production beyond their own needs. State monopoly on imports was an opportunity to balance a controlled price to concentrated and politically active urban consumers, and a controlled profit to the government exchequer. Those who did not prosper were rural producers. The effect of devaluation has been to strengthen rice production in areas where it is already successful, such as in Mali. Where production is weaker, for example in Senegal where production has been in decline since 1991 and in Niger where the public sector has been experiencing some difficulties, devaluation has made the situation worse. Structural adjustment has loosened the grip of government on pricing, as it affects both producers and consumers. If producers can sell their rice at the farm gate to whichever trader will pay the best price, and if consumers can choose the quality of rice they consume according to preference and ability to pay, does this mean that local production will improve? Results of recent research conducted by WARDA (West Africa Rice Development Association) show that it is unrealistic to believe that local rice production can ever meet the demand of the coastal capital cities. Even if it were possible to raise production levels sufficiently, the cost of transporting rice from the hinterland to the coast, for the most part on inadequate roads, would quickly price it above imported rice. However, there are viable opportunities for local farmers to supply the many cities and towns away from the coastal ports. This means that the cost of transport is transferred to the imported rice, favouring the competitive edge of the local supplier. The economic prospects for rice production are in a state of transition. It is not easy to exchange decades of state control to a private sector where, by and large, market forces will determine the direction of development. But for farmers, the day to day farming constraints that they face may be more immediate and more challenging than the effects of fiscal policy. Environmental pressures Throughout much of Africa soil fertility is in decline. Adding imported inorganic fertilizer has never been an option available to most farmers in the region. It has cost too much in the past and now it costs even more. Pressure on land in the last two decades has had the effect of reducing the fallow period of forest bush from 12- l 15 years to 3 - 5 years in high population areas, 5-7 years elsewhere. In the savanna, similar pressures are forcing farmers to double (4-6 from 2-3) the number of crossings between fallow periods. Not only has this had the effect of depleting the soil of nutrients, reducing organic matter and increasing soil erosion, but farmers now have an even greater struggle with what has always been a major problem with rice production: weeds. The upland soils on which rainfed rice has traditionally been grown are inherently fragile. Currently upland rice represents nearly 60% of the total regional rice area. Forced to intensify cultivation without access to improved inputs, farmers' current practices are degrading these soils and contributing to declining productivity. What hope is there that such farmers could increase rice production without exacerbating an already destructive system? New demands In the first place, farmers need upland rice varieties that yield more for less. In other words they must produce better yields than those achieved with present varieties under the same poor growing conditions. At the same time, any new varieties must have the capacity to reward farmers with much higher yields in return for modest improvements to their farming system. In the second place, there are areas of land that at the present time are under exploited. If the constraints which currently inhibit rice production in such areas are overcome, not only is there potential for dramatically increasing overall rice production, there is also the considerable benefit of helping to protect the fragile upland environment on which the demand for rice production currently falls. The most sophisticated tools available to plant breeders today are being used to develop varieties that meet the needs of resource poor farmers. Unless those needs are met through the seed that farmers plant, there is very little hope of increasing productivity because farmers cannot afford fertilizers, fungicides, insecticides, herbicides or machinery. One of the most exciting achievements has been the successful crossing of African and Asian rice species at WARDA. This work is receiving international recognition for its importance, not only by rice breeders within Africa but also by breeders in other major rice producing areas of the world, notably China and Vietnam. Throughout Africa it is the Asian rice species, Oryza sativa, that has predominated in modern times. This is because it has much higher yield potential than the indigenous African rice, Oryza glaberrima. O. glalberrima is now grown only in small pockets of land for domestic consumption, because many people prefer its taste. The principal reason for the greater yield of O. sativa is the number of grain holding spikelets that form on the panicle. Unlike O. glaberrima, which has only primary branching, O. sativa forms secondary, grain-holding spikelets. The more spikelets there are, the more grain the panicle can produce. But O. glaberrima has advantages too. One advantage is that it has droopy leaves which shade the ground and reduce competition from weeds. O. glaberrima also has very rapid seedling growth and produces many more tillers than O. sativa. This too has the effect of reducing the space in which weeds can grow. Not only is weeding labour intensive but the three week window in the farming calendar when it must be done is too short for most farmers to finish the job. Rice which is weeded late does not recover, even if it is cleared of weeds later in the season. The droopy leaves of African rice also help to conserve soil moisture and, because it has evolved over 3,500 years in African conditions, O. glaberrima is better adapted to the biological stresses and poor soils of the African environment and is therefore more robust than Asian varieties. Breeding new varieties The successful crossing of African and Asian rice species using conventional breeding techniques has been a scientific achievement that owes much to the persistence of WARDA's team of breeders. They have achieved varieties which combine the best characteristics of the two rice types. What has astonished the plant breeding world is not that these new varieties show characteristics of both rice types but that they show changes in plant structure through the plant's development stages, from one plant type to the other. The new progeny develop like O. glaterrima in the early growth stages, with thin droopy leaves which help smother weeds. As the rice plant grows, becomes more like O. saliva. The leaves become thicker and more upright and so capture solar radiation more efficiently, a trait that is critical for high yield potential. The new varieties have also inherited the thicker stem of the sativa parent and are therefore less susceptible to lodging. Their panicles develop with secondary spikelets and most of the new progeny have substantially larger panicles than either of their parents. These new varieties, like their O. glaberrima parent, continue tillering even in drought conditions (O. sativas increases in height in preference to tillering when under stress). The new progeny have proved to be an excellent starting point for subsequent breeding programmes because they have within them genes from both O. glaterrima and O. sativa. The first season's field trials of the newly created plant types were conducted last year on two sites in Cote d'lvoire. One was on soil that had been continuously cropped for the previous three years and before that was on short threeyear fallow. Even on this exhausted soil, with no added nitrogen, the new progeny significantly outyielded the best O. sativa varieties. 011 better soil, with nitrogen added at 80kg/ha, yields of 5.6t/ha were obtained. Expanding the production area 1 here are 20-30 million hectares of inland valleys in West Africa of which less than 1 15% is cultivated and less than 5% is used for rice. It is not known precisely why these lowlands are so underexploited. There have been suggestions ranging from the risk of crop failure due to erratic flooding, the risk of diseases such as malaria or schistosomiasis or the traditional belief that men who work in the valleys risk impotence. The most likely reason is that uplands are easier to cultivate, requiring less land clearance because there is less weed growth than in the more fertile inland valleys. Population pressure, the need to protect fragile uplands and increasing demand for rice all make lowland cultivation more attractive. In a single decade, lowlands have the potential to produce ten crops of at least twice the yield compared to the three crops (allowing for fallow) achievable 011 uplands. The new varieties developed by WARDA have the genetic potential to resist some of the very different agronomic constraints experienced in lowland cultivation, particularly Rice Yellow Mottle Virus (RYMV), blast and African rice gall midge. Rice yellow mottle virus RYMV is a new threat to African rice production. First described in Kenya in 1966, it is Africa's only known rice viral disease and it has noow spread throughout most of sub Saharan Africa where rice is grown in lowland, humid conditions. It has spread very fast in the last five to seven years and affects the improved, irrigated varieties based on O. saliva. At its worst RYMV causes 100% loss. The virus is highly virulent. If inoculation by the virus occurs early in the life of the plant, its height is reduced by 60% and the number of tillers is also reduced. The panicles do not open up properly and the percentage of filled grain is very low. It is still not known for sure whether the virus can be transmitted within the seed. Sites where the virus is most persistent have been identified and varieties that are similar to those preferred in the region are being tested at these 'hot spore' with the help of national scientists through WARDA's Task Force mechanism which involves the NARS of its member states. These and a further 60 varieties (112 in total) are being tested in special screen houses. These varieties have been challenged with the virus by the simple process of grinding leaves from infected plants and wiping the crushed residue, by hand, on to the leaves of the varieties to be tested. Those that are most resistant have been selected and, provided they prove to be suitable in all other respects, will be available for release in 1997. Perhaps most promising of all are the new varieties, some of which carry not just resistance but natural immunity to RYMV. Farmer options for improving production are not limited to variety choice, even though this may be the single most significant decision. Whichever varieties are chosen, all will respond better if crop management is improved. To ensure that the shift to more intensified rice based cropping systems is sustainable, improved crop and resource management practices that are socially and economically acceptable are urgently required. Rice farmers in Africa have already demonstrated that they can respond to demand. What they need is continued support from the agricultural research conummunity to ensure that this response is not detrimental to the natural resource base of the region. Recent advances in rice research have the potential to deliver real improve meets to the rice production sector in Africa. This should benefit rural producers, l urban consumers and those between who are involved in trading and milling. The challellges that African producers face may, in l detail, be specific to their region, but some - of the solutions could find wider application, beyond the continent of Africa. New horizons could be opening up for African rice. Proportion of rice (hectares) grown under different production systems in W. Africa Proportion of regional production (tonnes) under different systems in W. Africa
SubjectsCROP PRODUCTION AND PROTECTION;
- CTA Spore (English)