Sustainable agricultural production
MetadataShow full item record
CTA. 1988. Sustainable agricultural production. Spore 16. CTA, Wageningen, The Netherlands.
Permanent link to this item: http://hdl.handle.net/10568/44874
Will the present rate of expansion in global agricultural output be sufficient to satisfy the future demands of the world's burgeoning population and, more importantly, can improvements in productivity be sustained. Agriculturalists, ecologists and...
Will the present rate of expansion in global agricultural output be sufficient to satisfy the future demands of the world's burgeoning population and, more importantly, can improvements in productivity be sustained. Agriculturalists, ecologists and policy-makers concerned with the future have yet , to agree on an answer, for sustainability means different things to different people. Long-term viability is often sacrificed' in the scramble for short-term results. But productivity without sustainability is destructive. Modern, intensively-managed agricultural systems differ from natural ecosystems in many ways, but there is one basic rule that cannot be ignored -- the productivity of a system cannot be maintained if an unacceptable burden is placed on the natural resource base. Yet, in pursuit of agricultural productivity improvements, farmers all over the world are being forced to deplete renewable resources such as soils, water, and forests at ever-increasing and alarming rates. Fertile land is an essential requirement for intensive agricultural systems. Of the 1.5 billion ha of land in the world currently being farmed, only about half are considered suitable for agriculture. Paradoxically, at a time when more agricultural production is needed, vast quantities of valuable land are being destroyed by human activity. More and more marginal land is being cultivated, often by impoverished people using inappropriate methods and technology. Overgrazing and overcultivation are leading to serious soil erosion. Nowhere is the problem more acute than in the tropics where a combination of increasing slash and-burn operations and the timber industry is denuding the land of forests and vegetation. Sadly, the lessons of the past are being ignored. Compared to the 1.5 billion ha used for crop production, nearly two billion have already been ruined. According to a UNEP-FAO report, around six million ha of cultivable land are being lost each year through soil degradation. If present trends continue, newly-cultivated land will not replace that being lost. The FAO's Agriculture: Toward 2000 report calculated that soil and water conservation measures would need to be extended to 25% of all farmland by the end of the century, and that flood control would need to be extended to 20 million ha, to bring about equilibrium. It is estimated that these measures would cost in the region of $2.5 billion, money which is unlikely to be forthcoming. Worldwide, eight million ha of land are lost annually to non-agricultural conversion, in addition to those lost to erosion, desertification and toxification. Consequently, agricultural production is having to rely more and more on fossil fuels to produce the agricultural chemicals used to replenish soil fertility on farmland that is still being used, a situation which cannot last indefinitely. In Africa, the worst affected continent, the situation is acute. Most African soils are low in clay and organic matter and are thus particularly susceptible to erosion. According to UNEP figures, 742 million ha -more than a quarter of the continent -- are undergoing moderate or serious desertification and may soon be totally unproductive. Soil erosion rates in Africa have increased 20-fold in the last 30 years. In Ethiopia, rates as high as 200 tonnes per ha have been observed. In Madagascar figures of around 300 tonnes per ha per year are commonplace. In tropical Africa agriculture and livestock production is curtailed by other constraints. Diseases such as onchocerciasis and trypanosomiasis effectively remove vast amounts of land from agricultural production. So, can any agricultural production system be sustainable under African conditions? Indeed, which of the world's farming systems are truly viable in the long-term? Irrigation potential In Asia increased production has relied on the 'Green Revolution', based on the use of high-yielding varieties (HYV) and two-thirds of the world's irrigated land. However, irrigation is not a universal answer to the quest for sustainable agriculture. Irrigated land in the world tripled between 1950-85, the 177 million ha of newly irrigated land drawing heavily on both surface and underground water resources. Globally, 1.3 billion cubic metres of water is used for irrigation annually, but 3 billion cu.m is withdrawn. So over half of the water is lost during storage or transport. Moreover, poorly-managed irrigation systems can prove counterproductive, because of waterlogging, build-up of salts and eventual loss of soil fertility. Major problems are now appearing in Asia and a Club du Sahel study of irrigation in the Sahel concluded that 'the development of new irrigation areas has barely surpassed the surface area of older ones which had to be abandoned, In North America, intensive monoculture farming has been a major factor in agricultural development. Expanding food production by mining the soil and depleting underground water supplies can produce results, but for how long? In many parts of the US groundwater withdrawals for agricultural purposes are exceeding the aquifer recharge rates In Europe, farmers have turned to mixed-farming as a means of intensifying production. This maximizes land use but poses several problems, notably weed and pest control. In addition, almost all of the steps which have led to the increase in agricultural production in the developed world have had high energy requirements -- and have thus been extremely costly. The FAO estimates that energy consumption to accommodate agricultural development in developing countries will increase 50% by the year 2000. Fertilizers will account for 60% of this increase, mechanization, irrigation and pesticide use will account for the rest. Financially-poor Third World countries have tended to subsidize fertilizer and pesticide use as a means of encouraging the adoption of new technologies to stimulate cash crop production and move towards food self-sufficiency. Yet, such action has frequently proved counter-productive. Agriculture becomes more energy-intensive, and less land and labour-intensive. The use of locally available organic fertilizers is drastically reduced. Mindful of the costbenefit ratio, many African nations, including Senegal, Mali, Niger, Burkina Faso, Benin and Togo are severely restricting the use of chemical fertilizers. In Rwanda, attempts to introduce Western-style agricultural practices failed, due to a combination of the high cost of inputs and the difficulties in obtaining them. Efforts have been made to intensify farming, using primarily organic methods, although fallow periods, as else where, have been drastically shortened or abandoned. On some farms soils are protected from erosion by physical methods and the extensive use of tree and shrub crops, such as banana and cassava. Diversified cropping also helps to improve soil fertility. Controlled clearing and burning, careful tillage, agroforestry (see Spore 14), alleycropping, polyculture, and cover crops, all aid conservation. Properly integrated, they can sustain high yields whilst minimizing the risks of environmental degradation. Exploiting natural systems Over the centuries, natural terrestrial ecosystems have been adapted and developed by human beings for agricultural production. Yet today, even with all the modern scientific technology at our disposal, only a fraction of the productivity of these natural ecosystems is being exploited. The closer that any farming system comes to mimicking a natural ecosystem, the more likely it is to be sustainable. A good example of this is seen in south-eastern Nigeria where farmers have developed complex systems of tree and crop production that reflect the natural multi-storeyed structure of the rainforest. Breadfruit, raffia and pea' trees are planted below taller coconut and oil palms. A mixture of shorter trees, such as mango, lime and kolanut come next, followed by a lower layer of bananas, plantains and papaya. Cassava, cocoyam and pepper bushes grow to about two metres. Maize, groundnuts and other vegetables are grown in small clearings. In addition, labour is spread more evenly throughout the year, food is available year-round, and the soil is rarely exposed to the eroding effects of rain. This farming system is virtually self-sustaining. A relatively large population is being supported on fairly poor soil by combining livestock, use of organic fertilizers, high crop diversity and control of soil erosion. Investment and research into ecologically sound agricultural techniques designed for conditions in tropical countries is beginning to gather momentum. Agroforestry and intercropping, development of HYVs of staple crops that require low inputs, integrated pest management, and the prospects of biotechnology are being investigated. Organic farming, wind-powered irrigation, and the use of solar power and other energy-saving methods could provide partial answers. Pricing all inputs needed by the agricultural system at values in line with long-term supply and demand considerations or commodity price fluctuations, would help to prevent abuse and wastage. Unexpected drawbacks More research is urgently needed as possible solutions reveal unexpected drawbacks. In Africa, less then seven percent of the cultivated area is being planted with HYV seeds. Nevertheless, even this small shift to HYV has led to nutritional problems in some areas as indigenous crops become neglected. Many ecologically adapted native crops, such as cassava, millet and sorghum, are being supplanted by cheaply imported or food-aid grains such as wheat, less suited to local conditions. Minimum tillage helps to reduce erosion on fragile soils, but major drawbacks have been identified. Greater insect and disease presence in crop residues makes pesticide use unavoidable, and heavy use of herbicides is essential to control weeds. Agricultural residues can often be more valuable than the food or crop itself as they can be put to a variety of uses. For example, corn cobs can be processed into lubricating oil, acetic acid and formic acid. The residue from this process can then be used as a bulk filler for animals as well as a fuel. If residues can be seen as valuable raw materials rather than waste, pollution can be reduced, energy demands diminished, and the resource base for food production increased. The opportunities to make maximum use of agricultural residues are limited, however, by the lack of incentives and appropriate research and development. In future, productivity of existing cultivated areas will have to rise to meet growing demand. Crop yields and intensity must improve. Furthermore, productivity must improve where the food is actually needed. A balance between resource protection, foreign exchange earnings, and improving conditions for the poor and malnourished will have to be struck. When poorly used, chemical based, energy-intensive agricultural methods can be detrimental to human health and the environment, and appear to be incapable of producing the necessary food, cash crops and by-products on a sustainable basis. Agriculturalists will thus have to create integrated agroecosystems that are designed to be self-reliant, resource-conserving, and productive under local conditions in both the long and short term. To do so they must identify and adapt the best components of ancient and modern agricultural methods, combining traditional wisdom with the most advanced scientific knowledge. Sustainability must be based firmly on the protection of the resources underpinning production and must incorporate the means for conserving them. As Stephen Gliessman, Director of Agroecology at the University of California affirms, 'the goal is to optimize productivity on a long-term basis rather than maximize it in the short term' SOURCES El-Hinnawi, E and M. Hashmi, 1987 The State of the Environment UNEP/Butterworth Scientific Dover, M. and L. Talbot, 1987. To Feed the Earth. World Resources Institute. Washinoton Lal, R., 1987. 'Sustainable agriculture and natural resource management for sub-Saharan Africa ' IN: BOSTID Developments. Vol. 7(3), Washington For more information, contact: AGRECOL (Information Centre on Sustainable Agriculture in the 'Third World ) Okozentrum CH-4438 Langenbruck SWITZERLAND ILEIA (Information Centre for Low External Input Agriculture) PO Box 64 3830 AB Leusden NETHERLANDS
SubjectsCROP PRODUCTION AND PROTECTION;
- CTA Spore (English)