Agricultural Production and Soil Nutrient Mining in Africa: Implications for Resource Conservation and Policy Development
| Author | Julio Henao | |
| Author | Carlos Baanante | |
| Jurisdiction: | Africa | |
| Date of acession | 2024-03-20T06:27:13Z | |
| Date of availability | 2024-03-20T06:27:13Z | |
| Date of issue | 2006-05 | |
| Abstract | The economic development of Africa, more than any other region, depends on the development of the agricultural sector and the agro-industry, which is fundamentally affected by the productivity of land resources. This is particularly true for countries in sub-Saharan Africa. Agriculture accounts for more than 25% of the gross domestic product (GDP) of most African coun- tries, and is the main source of income and employment for at least 65% of Africa’s population of 750 million. Thus, agricultural development is vital to Africa’s economic growth, food security, and poverty alleviation. By 2020 Africa is projected to import more than 60 million metric tons (t) of cereal yearly to meet demand. Africa’s food security situation has deteriorated significantly over the past two decades. With population growth of about 3% yearly, the number of malnourished people in Africa has grown from about 88 million in 1970 to more than 200 million in 1999–2001. Agricultural production in much of Africa is also hampered by the predominance of fragile ecosys- tems, low inherited soil fertility, and low use of modern inputs such as mineral fertilizers and improved crop varieties. Crop production in a region can increase through higher production per unit of land, or by increasing the area cultivated. The dramatic increases in agricultural production in Asia—known as the Green Revolution—were mostly through higher yields. But Africa’s far lower increases have mostly been through expansion of the cultivated land (Figures 2 and 3). Farmers in sub-Saharan Africa have traditionally cleared land, grown crops for a few cropping cycles, then moved on to clear more land, leaving the land fallow to restore soil nutrients and regain fertility. But population pressure now forces farmers to grow crop after crop, “mining” and gradually depleting the soil of nutrients. With little access to fertilizers, the farmers are forced to bring less fertile soils on marginal land into production, at the expense of Africa’s wildlife and forests. The fact that fertilizer use in Africa is less than 10% of that in Asia explains much of the contrasting trends in these regions. The declining fertility of African soils because of soil nutrient mining is a major cause of decreased crop yields and per capita food production in Africa and, in the mid to long term, a key source of land degradation and environmental damage. Methodology The methodology for monitoring of nutrient mining is based on the estimation of soil nutrient balances. We determine the sum of nutrient inputs such as through fertilization, use of organic residues and manures, nitrogen fixation, and sedimentation. We then subtracted nutrient losses such as through erosion, leaching, and volatilization. Crop uptake is another important loss of nutrients which are then exported from farmers’ fields for human and animal consumption. Balances are evaluated at spatial scales that range from small soil aggregates to regions, countries, and even the African continent. The evaluation process includes use of spatial analysis through geographic information systems to identify crop areas, analyze and classify production, predict erosion and leaching, interpolate nutrient mining, and display regional assessments. Simulated modeling and transfer functions were used to evaluate nutrient losses in soils, assess current yields, and estimate and predict potential yields and nutrient uptake across Africa. Management information systems allowed the interaction and consolidation of data series with primary and secondary information on soils and crops, input consumption and use, and crop production. In this paper we assess the status of food production associated with land degradation and estimate indicators of soil nutrient mining by country and region. We examine factors and circumstances that affect nutrient mining by predominant crop production systems in key agro-ecological zones and re- gions, and we review policy measures and investment strategies that can reverse current trends in nutrient mining and increase land productivity in a sustainable way. We also evaluate evolving trends in crop productivity in different regions and in land degradation caused by nutrient mining. Agricultural Production, Soil Nutrient Mining, and Land Conservation Soil nutrient mining, the result of overexploitation of agricultural land, is in fact consumption of a key component of the soil’s natural capital. The propensity for nutrient mining of Africa’s agricultural land and the severity of its consequences are the highest in the world. Soil nutrient mining is usually associ- ated with low agricultural production and land productivity under severe constraints of poverty in terms of physical capital (infrastructure) and human capital (health and education). Continued nutrient mining of soils would mean a future of even increased poverty, food insecurity, environmental damage, and social and political instability. The findings and conclusions of this paper result from the monitoring of nutrient mining in agricul- tural lands of key agro-ecological regions and countries of Africa, and have implications for policy development. Sound policies and investment strategies are key contributors to the joint goals of in- creased agricultural production, food security, economic development, land conservation, and environ- mental protection. African countries today face not only the challenge of increasing agricultural production with scarce overall resources but must raise productivity in a way that conserves the natural resource base and prevents further degradation that has characterized African soils for generations. Agricultural production has particularly stagnated or declined in important food crops such as cere- als, tubers, and legumes. Crop yields and productivity in most African countries are about the same as 20 years ago. African cereal yields, particularly in the Sudano-Sahelian region, are the world’s lowest (Figure 10). In 1998, cereal yields in sub-Saharan Africa averaged 1 ton per hectare (t/ha)—15% lower than the world average of 1.2 t/ha in 1965. Africa’s low crop productivity, especially in densely popu- lated areas, is seriously eroding its economic development and the competitiveness of its agriculture in the world market. Africa’s share of the total world agricultural trade has fallen from 8% in 1965 to 3% in 1999–2000. During the 2002–2004 cropping season, about 85% of African farmland (185 million ha) had nutri- ent mining rates of more than 30 kg/ha of nutrients yearly, and 40% (95 million ha) had rates greater than 60 kg/ha yearly. These 95 million ha are reaching such a state of degradation that to make them productive again would frequently require investments so large that it will not be economically feasible to implement. Escalating rates of soil nutrient mining make nutrient losses highly variable in agricultural areas in the Sub-Humid and Humid savannahs of West and East Africa, and in the forest areas of Central Africa. Depletion rates range from moderate, about 30 to 40 kilograms (kg) of nitrogen, phosphorus, and potassium (NPK)/ha yearly in the Humid forests and wetlands of Southern Central Africa and Sudan to more than 60 kg NPK/ha yearly in the Sub-Humid savannahs of West Africa and the highlands and Sub-Humid areas of East Africa. The lands in these areas are typical for the tropics: weathered soil, with low productivity. Estimates by country show that nutrient mining is highest (more than 60 kg NPK/ha yearly) in agri- cultural lands of Guinea, Congo, Angola, Rwanda, Burundi, and Uganda (Figure 5, Table 7). Fertilizer use is low in those countries, and the high nutrient losses are mainly the result of soil erosion and leaching. Other regions, such as most countries of the North Africa region and South Africa, although constrained by harsh climate, have lower nutrient depletion rates, varying from 0 to 30 kg NPK/ha per year. Agriculture in the coastal areas of Libya, Egypt, Tunisia, and Algeria is characterized by high mineral fertilizer use and appropriate crop management. Nutrient mining across Africa ranges from 9 kg NPK/ha per year in Egypt to 88 kg in Somalia in East Africa. Nitrogen losses range from 4.1 kg/ha yearly in South Africa to 52.3 kg/ha in Somalia in the Sudano-Sahelian of East Africa. Losses of phosphorus range from none or minor losses in the Mediter- ranean and Arid North Africa to 9.2 kg/ha per year in Burundi and Somalia in East Africa. Potassium losses range from 6.5 kg/ha per year in Algeria to 30.4 kg/ha in Equatorial Guinea and Gabon in Humid Central Africa. The main factors contributing to nutrient depletion are loss of nitrogen and phosphorus through soil erosion by wind and water, and leaching of nitrogen and potassium. Nutrient losses due only to erosion in African soils range from 10 to 45 kg of NPK/ha per year. If erosion continues unabated, yield reduc- tions by 2020 could be from 17% to 30%, with an expected decrease of about 10 million t of cereals, 15 million t of roots and tubers, and 1 million t of pulses. Based on nutrient mining estimated by country, total annual mining of nutrients (NPK) is about 800,000 t for Humid Central Africa; 3.0 million t for the Humid and Sub-Humid West Africa; 600,000 t for the Mediterranean and Arid North Africa; 1.5 million t for the Sub-Humid and Mountain East Africa; 1.7 million t in the Sudano-Sahel; and 1.4 million t in Sub-Humid and Semi-Arid Southern Africa. Total nutrient mining in the sub-Saharan region may be about 8 million t of NPK per year. The evidence leaves no doubt that the very resources on which African farmers and their families depend for welfare and survival are being undermined by soil degradation caused by nutrient mining and associated factors such as deforestation, use of marginal lands, and poor agricultural practices. About 50,000 ha of forest and 60,000 ha of Africa’s grassland are lost to agriculture yearly. Intensifica- tion of agriculture with low fertilizer use and the clearing of forest lands are the main causes of nutrient mining and land degradation in the tropical forests and savannahs that are characteristic of the Humid and Sub-Humid regions that predominate in Cameroon, Ghana, Nigeria, Gabon, Congo, Sudan, and parts of Uganda. Most soils are fragile and low in plant nutrients. The nutrient recycling mechanisms that sustain soil fertility are insufficient to support increased production without fertilizers. Land is being degraded, and soil fertility is declining to levels unsuitable to sustain economic production. Indicators of Soil Nutrient Mining, Population, and Nutrition Population growth and migration associated with drought, food shortages and land overuse have accel- erated degradation of agricultural land. Figure 11 gives estimates of the actual supporting capacity of land, calculated by use of crop suitability data and assuming limited use of inputs (rainfed production without mechanization, mineral fertilizers, and conservation practices). The average estimates of popu- lation density range from less than 0.1 to 5.0 persons/ha. This means that high population density in many countries already exceeds the long-term population carrying capacity of the land. Variation in population density is highest in the very fragile soils in the Semi-Arid areas of West and East Africa. Population density varies from as low as 5 persons/ha in Semi-Arid areas of East Africa to as high as 150 persons/ha in some Semi-Arid areas of West Africa. Population densities are also high in Humid and Sub-Humid areas in the west coastal areas and in some east fertile areas in Ethiopia, Kenya, Uganda, Mozambique, Tanzania, Burundi, Rwanda, Namibia, and Angola. Correspondingly, these ar- eas have high rates of nutrient mining. The production of cereals expressed in kilograms per hectare is particularly low in countries with high rates of nutrient depletion such as the Sudano-Sahelian and the Humid and Sub-Humid areas in west central and east Africa. Countries such as Congo, Gabon, Liberia, Sierra Leone, Eritrea, Rwanda, and Botswana continue importing large quantities of cereal food. Africa imported about 43 million t of cereals at a cost of $7.5 billion in 2003. The sub-Saharan African countries (excluding South Africa) imported 19 million t at a cost of $3.8 billion. Assuming that the current situation in agricultural land management will not change dramatically, Africa is pro- jected to import about 60 million t of cereals, at a cost of about $14 billion, by 2020. The sub-Saharan countries (excluding South Africa) will import about 34 million t of cereal at a cost of $8.4 billion by 2020. A part of the imports is used as animal feed, but most is to satisfy demands of an increasing popula- tion. The imports of cereals, along with imports of other food, have a great impact on economies of African countries, and make food security strategies difficult to accomplish. The influence of nutrient mining on the land’s capacity to sustain population and production has long-term impacts besides loss of soil productivity and the consequent exodus of farmers. About 33% of the sub-Saharan population is undernourished compared with about 6% in North Africa and 15% in Asia. Most of the undernourished are in East Africa, where nutrient mining rates are high. Malnutrition rates in these regions are from 10% to 50%. The nutritional level as measured in calories per person/day is lower than the basic level of 2,500 kilocalories. Crop cereals provide more than 60% of these calories in the Semi-Arid and Sub-Humid areas, while animal products provide 5% to 30%. Roots, tubers, and plantation crops provide most of the calories in Humid regions. Low yields in nutrient-mined areas seem to contribute to poverty and malnutrition. Soil Nutrient Mining and Policy Development Information about the extent and intensity of soil nutrient mining and a better understanding of its main causes are essential to design and implement policy measures and investments to reverse the mining and subsequent decline in soil fertility. Restoration of soil fertility is necessary to increase crop yields and food production in order to combat the worsening food security situation in Africa. Thus, these policy measures and investment strategies must be viewed as key contributors to the joint goals of increased agricultural production, food security, economic development, land conservation, and envi- ronmental protection. A better understanding of the economics of nutrient mining and of the agro-climatic and socioeco- nomic factors that explain why farmers mine and deplete the soil of nutrients provides the rationale for designing effective policy and investment strategies to reverse current trends. The main goal of such strategies is to prevent soil nutrient mining by making the use of external plant nutrient sources, par- ticularly mineral and organic fertilizers, more economically attractive. This implies implementation of policies and investments that increase the cost of mining plant nutrients from the soil while decreasing the cost and increasing the profitability of mineral and organic fertilizer use. These sources of essential plant nutrients, and other improved technologies, must be made available to farmers efficiently and timely. Key factors determining the extent of nutrient mining in many areas of sub-Saharan Africa are pre- vailing land tenure arrangements and the lack of plant nutrients as mineral or organic fertilizers. There are differences between the cost of nutrient mining to individual farmers and to society as a whole caused mainly by land tenure arrangements that make the farmers indifferent to the loss of future economic returns to land. When the farmers’ possession of agricultural land is well established through property rights or land tenure arrangements, and there is a functioning market for agricultural land, farmers internalize costs associated with the loss of the land’s productive capacity. That significantly increases the cost to farmers of the mined soil nutrients. The opposite occurs when land tenure rights are not well established and there is no functioning market for agricultural land. Then, costs associated with the loss of the land’s productive capacity become an externality and thus, a social rather than a private cost. Then, from the farmer’s point of view, soil mining is perceived as the least expensive source of plant nutrients. This is particularly true for farmers who practice shifting cultivation. They often perceive that they are not significantly affected by the declining land productivity associated with nutrient mining. Design and Implementation of Policy and Investment Strategies—Policies and investment strat- egies to reverse soil nutrient mining should be designed and implemented nationally, and sometimes locally, but always in context, and as a key part, of a comprehensive policy approach to economic development. To facilitate the selection of a set of policy measures and investments as key components of an effective strategy to reverse soil nutrient mining, it is useful to describe and pre-assess them in terms of (1) expected outcomes; (2) impacts on the countries’ capital endowments (their natural capital, physical man-made capital, and human capital); and (3) change in the incentives or disincentives to mine soil nutrients. Summaries of key policies follow: Broad Scope Development Policies. These include investments in roads and associated infrastruc- ture, investments in schools and education, and measures to control corruption and promote good governance. Expected outcomes of these broad scope development policies are increased availabil- ity and lower costs of fertilizers and other agricultural inputs and significantly improved access of farmers to information and markets for their products. Land Tenure Policy. Measures or legislation to improve farmers’ long-term rights to own the land they use can significantly affect the importance of the benefit streams that farmers receive as a result of the long-term use of the land. This seriously affects farmers’ decision making in management and use of agricultural land, and in nutrient mining. Policies to Improve Agro-Inputs Supply Efficiency. The timely and efficient supply of agro-inputs such as seeds and fertilizers can be improved through provision of credit and technical assistance (TA) to farmers as well as the producers, importers, wholesalers, and dealers involved in the pro- curement and distribution of seeds, fertilizers, and other inputs. In this context, TA involves provid- ing technical and managerial assistance, as well as training and the dissemination of relevant infor- mation to business entrepreneurs and farmers. Policies to Expand the Demand for Agricultural Products and Stabilize Prices. The goal and expected outcome of this policy is to expand the demand for agricultural products that farmers can efficiently produce in a competitive environment and in a way that is consistent with price stability. Growth in demand for agricultural products that is consistent with stability in the prices that farmers receive for their products promotes the profitability of fertilizers and modern inputs and increases the productivity of agriculture and the incomes of farmer households. Expansion in the demand for agricultural products can be attained as a result of (i) policies and investments that increase the domestic demand for agricultural products and (ii) policies that increase the demand for exports of these products. Policy measures and investments include, but are not limited to, the following: Investments in marketing infrastructure for farmers, wholesalers, and retailers of agricultural products. This involves construction of properly located facilities for product trade among farm- ers, wholesalers, retailers, and consumers. Measures to facilitate credit and technical and managerial assistance to marketing intermediar- ies of agricultural products such as wholesalers and retailers, including those interested in in- vesting in marketing infrastructure. Provision of credit and technical and managerial assistance to exporters of agricultural products, and to agribusinesses involved in the processing and then the marketing of processed products in the domestic and export markets. All of these policies involve direct investments by the public sector and measures to create a policy environment that stimulates investments and dynamic participation of the private sector. Growth in demand for agricultural products that can stimulate sustainable growth in agricultural production and productivity can be a powerful source of agricultural and economic development. This is par- ticularly evident when demand growth is due mainly to expansion in demand for processed agricul- tural products. Then the growth in demand can result in rapid development of the agricultural sector and agribusinesses involved in product processing. Some countries in Latin America and Asia have experienced this kind of development as a result of growth in the export demand for processed agricultural products. Social Support Programs for Poverty Alleviation and Public Health. These programs are needed to combat poverty and malnutrition among both rural and urban populations, and to alleviate the HIV/AIDS epidemic. Policies that are primarily directed to promote economic development should be implemented, along with social support programs. These programs should be designed to reduce malnutrition and hunger, provide health care to combat the HIV/AIDS epidemic, and offer basic education and information to fight these two problems. Conclusions and Recommendations on Policy Development—To reverse and prevent soil nutri- ent mining, policies and investment strategies must be designed and implemented at the national level, focusing on well-defined target areas. Furthermore, it is evident that these measures must successfully promote the judicious use of mineral fertilizers in conjunction with sound soil conservation practices. Given the complex nature of the multiple constraints affecting the use of fertilizers, a well-integrated strategy involving the simultaneous implementation of all or some of the policy measures described above should be adopted to achieve the goals of increased fertilizer use and soil fertility conservation. Key conclusions and recommendations on policy development to combat soil nutrient mining and depletion in some agricultural land areas of Africa can be summarized as follows: Well-designed policy measures and investment strategies that target specific agricultural areas where soil nutrient mining is extensively occurring in a country can successfully increase the judicious use of fertilizers and the adoption of sound soil fertility management practices. These policies can re- verse soil nutrient mining and provide important and substantial benefits to farmers, on-farm work- ers, marketing intermediaries, consumers, the land resource base, and the countries’ economies. In the target countries, the implementation of policy strategies to reverse this process through mea- sures and investments that promote fertilizer use and soil conservation practices should be a national priority. To develop national policy reform and investment strategy programs for target countries, strategies must be tailored to overcome the constraints and circumstances prevailing in well-defined target areas within a country. Then, ex-ante assessments of alternative pre-designed policy strategies can be conducted to select or design policy and investment strategies with the highest probabilities of success in terms of impact, benefits, and costs for the target country. Results of ex-ante assessments can also be useful to derive estimates of the magnitude and bound- aries of the total expenditures that a country could incur in costs of implementation of a policy strategy in order to have satisfactory levels of expected benefit:cost ratios on those expenditures. Finally, it is important to note that national policy and investment strategies must include details about geographic coverage, the chronology of policy interventions and investments, and the specific modus operandi to be used in the implementation of policy measures, such as the provision of technical assistance and credit. Thus, the proper design of national policy and investment strategies to reverse soil nutrient mining in African countries can, in some instances, be involved and demanding. This paper represents a significantly enhanced update of a 1999 publication produced by IFDC, an International Center for Soil Fertility and Agricultural Development, as part of its efforts to provide additional information and develop strategies and policies for improved crop production in Africa. The dissemination of this information is crucial for the design and implementation of policy interventions that can prevent the continuous mining of nutrients and associated damage to the environment and the resource base. The information, methodologies, databases, and procedures described in this report should be viewed as components of an evolving process of continuous improvement and refinement. IFDC is interested and actively involved in developing and enhancing innovative approaches to improve the scope and quality of data, information, and technologies that are crucial for improving agricultural production and preserving the environment in developing countries. The monitoring of nutrient mining and the evalua- tion of fertilizer requirements for sustainable crop production in agricultural lands of the developing world is part of this effort. | |
| URL | https://hub.ifdc.org/handle/20.500.14297/2971 | |
| Subject | Production | |
| Subject | Soil | |
| Title | Agricultural Production and Soil Nutrient Mining in Africa: Implications for Resource Conservation and Policy Development |