Enset: Food Security and SustainabilityHow do enset-based farming system contribute to food security in Ethiopia?
How does the quantity and quality of human food produced from enset in enset- based systems affect potential human carrying capacity as compared to other systems?
How does the quantity and quality of animal feed produced from enset in enset- based systems affect potential human carrying capacity as compared to other systems?
How does enset contribute to the stability of the annual food supply, and reduce food shortages, particularly during drought years?
How does enset contribute to the sustainability of food production?
Enset-based farming systems play an important role in food security in Ethiopia. The exact role and value relative to other farming systems cannot be addressed without examining enset production and consumption in relation to the concept of food security. Food security can be explained in terms of: 1) adequate availability of food in line with present population and demographic growth; 2) the nutritional adequacy of food intake; 3) annual stability of the food supply; 4) access to food (through production or the market) (Brandt, 1990; Webb and von Braun, 1994; and FAO, 1996); and 5) the sustainability of the food production capacity over the long term. Each of these five features relating to food security is discussed briefly.
Some of the most dense rural populations of Ethiopia are located in regions practicing enset-based farming in the southwestern highlands. Rahmato (1996) notes that among the Wolayta, as landholding size declines, there is an increase in the cultivation of enset. These observations indicate that the human carrying capacity (i.e., the number of people per unit of land area that can be adequately fed by the food produced on the same land area) of enset and enset-based farming systems is high and is likely greater than other crops and cropping systems for the same agroecology and inputs.
How does the quantity and quality of human food produced from enset in enset-based systems affect potential human carrying capacity as compared to other systems?
Although enset-based farming systems seem to support higher population densities than other farming systems, it is difficult to compare these systems, because of a lack of quantitative research data. The human carrying capacity of enset-based agricultural systems is more difficult to quantify than systems based on annual cereal crops for at least four reasons: 1) enset yields are difficult to determine and have not been quantified; 2) enset food products have a low, inadequately-verified, protein content with an unknown amino acid distribution; 3) enset's low protein content necessitates that the protein contribution from associated foods be more diligently considered; and 4) nutrient cycling among enset fields and other fields are not yet evaluated.
Enset yields are difficult to measure and evaluate because: 1) plants are grown for multiple and variable numbers of years; 2) the spacing of individual plants may be changed several times; 3) enset may be grown in complex mixtures with other species, as well as other enset clones and other sized enset plants; 4) the weight gain of food in an enset plantation for a year may not be the same as the amount harvested by the farmers during that year; and 5) in addition to human food, there are many other enset products obtained from each plant. Also, the huge volume harvested from one plant and from an area, particularly in relationship to cereals, contributes to the perception among both farmers and scientists that the yield of enset is tremendous. However, in reality, the content of water, energy, and protein, the area and time use by the plants, as well as other aspects must be considered in order to interpret the actual food yield from this huge volume. Box 11.1 and Figure 11.1 provide an example of the complexity of evaluating enset yield. This example shows that the average annual yield of 34 farms was 5,000 kilograms of kocho per hectare, in addition to other products that were not measured, such as fiber and animal feed.
Yield and human carrying capacity of enset and annual crops under the same conditions have not been compared. In such a comparison, at least two considerations must be made. First, enset usually grows in regions with a long growing season, commonly nine months. In the environments where it is possible to double crop and get two annual crops, yield and human carrying capacity of enset should be compared to a sequence of two crops. Second, comparisons of human carrying capacity should consider the abilities of the systems to supply the nutrients, particularly energy and protein, required by humans.
The importance of considering the requirements and supplies of both energy and protein in determining human carrying capacity are illustrated in Box 11.2 and Figures 11.2 and 11.3 with a comparison of two hypothetical cropping systems, i.e., 1) enset and dry bean and 2) maize/sweet potato and dry bean. To simplify the example, only crops are included; but the relevance of consuming high-protein animal food products with low-protein kocho is apparent.
From the comparison of enset and bean with maize/sweet potato and bean (Box 11.1 and Figures 11.2 and 11.3), it can be seen that comparing just the yields or energy content of enset with maize/sweet potato is inadequate for determining the ability of the crop to support dense human populations. Even at the highest protein content, the enset, at 5,000 kilograms of kocho per hectare per year, and bean support 15.5 adults per hectare, while the maize/sweet potato, at 4,000 kilograms per hectare per year, and bean support 18.2 adults per hectare. Another concern is the amount of bean required in the enset diet. The required bean consumption of 53 to 71 kilograms per year is two to three times greater than the amount provided by a typical African diet, which is 10 to 26 kilograms per year of pulses plus groundnuts (Aykroyd et al, 1982). Thus a diet with a large proportion of enset may require the addition of a higher protein source than bean, which is why high- protein animal food products are so important in this system. A serious concern in enset producing regions, is that as population density or poverty increases, the opposite may be occurring--consumption of kocho increases while consumption of animal products decreases.
How does the quantity and quality of animal feed produced from enset in enset-based systems affect potential human carrying capacity as compared to other systems?
The low-protein portion of an enset plant is eaten by humans and the high-protein portion is either recycled to the soil, used as a wrapping material, or fed to animals. Thus the entire cycling of protein through other components of the system, particularly animals, has a greater impact on human nutrition and human carrying capacity than in cereal-based systems, in which the high-protein portion is eaten by humans.
Human food from mature enset plants comes primarily from the corm and an extracted pulp from pseudostem leaf sheaths. Together the corm and leaf sheaths have 0.037 kilograms of protein per kilogram of dry matter (Fekadu, 1996). The remainder of the plant, which is mostly leaves, is about 26 percent of the plant, and contains 0.160 kilograms of protein per kilogram of dry matter. Therefore, both the protein content and the total amount of protein is greater in the portion not eaten by humans. The recycling of all these products (non-human portions, human foods, and animal manure) all have important consequences for the human carrying capacity of the system. By comparison, the stems and any remaining leaves of cereals and other tuber crops that are left for animal feed are usually of low protein value and in some cases are unacceptable as animal feeds. Nitrogen, which is 16 percent of the protein, is often the most limiting chemical element in a farming system. In the enset system, the larger portion of the nitrogen does not pass directly from the enset plant to humans. Rather, it is cycled through animals. Therefore a quantitative understanding of the cycling of nitrogen in the enset system is difficult to measure, but important.
How does enset contribute to the stability of the annual food supply and reduce food shortages, particularly during drought years?
The presence of enset in the farming system contributes significantly to the stability of the food supply by several mechanisms. Enset can: 1) be stored for long periods; 2) be harvested at any time during the year; 3) be harvested at any stage over a several year period; and 4) survive stress years that reduce other food sources. It could even be argued that since enset requires from three to over ten years to mature, the frame of mind required to produce enset contributes to a general prepare-for-the-future mentality, which has other behavioral consequences.
As described in the section on processing, kocho is stored in nearly-airtight "containers" (i.e., pits), in a fermented state, which greatly retards loss. Farmers report that kocho may be kept for several years in this way. It is important to note, however, that only the wealthier households may actually store kocho for more than one year (Spring et al, 1996; and above); this product may be a status symbol analogous to an aged wine for special occasions.
Mid-season food shortages can be alleviated because enset can be harvested at any time during the year. If kocho is going to be prepared, then the farmer must plan ahead by about one month as this is required by the fermentation process. If the plants are harvested for amicho, they may be used immediately. Because of the storage and harvest-timing characteristics of enset, if a farmer has enough enset plants, there is no "hunger period" as is common in cereal farming.
The last two mechanisms, which work together, are probably more important for adding stability to the year- to-year food supply. Enset can be eaten at any stage of growth, over a several-year period after the corm reaches about 10 to 15 centimeters in diameter. Under good growing conditions, this condition may occur during the first transplant stage. There is great variation among ethnic groups as to both the acceptability and the practice of harvesting young enset plants. In years when other foods are in short supply, usually caused by drought, more enset plants may be harvested than was originally intended. For example, in the system described in Figure 11.1, the harvest may include the 80 plants in the fourth year of the third transplant stage, as well as any number of younger plants. However, the younger plants harvested will not be available to harvest in the future. At the beginning of the next growing season, the farmer will likely need to implement a strategy to recover. The enset plants themselves may also contribute to the recovery, since the remaining enset plants in the "prematurely" harvested field may grow faster during the next season because of lower plant density and reduced competition. Although these last two mechanisms may provide great stability to the food supply in an enset-based farming system, no research has been conducted either on the effect of "early" harvest of enset on present and future food supplies or on strategies implemented by farmers that are facilitated by these enset characteristics.
In enset producing regions, no matter how small the land holding, enset is grown. Even families referred to as "landless" have a house with enset around it. Enset serves the multiple purposes described above, as well as providing a dependable food source.
The ability to provide a long-term, sustainable food supply, with minimum off-farm input, is probably the most noteworthy characteristic of enset, and is a primary motivation for this publication and current interest in enset. An obvious and principal contribution to sustainability is the minimal soil erosion involved in enset's cultivation. Enset provides a perennial leaf canopy over the soil and a heavy mulch cover from leaf litter. Soil erosion is not seen in enset fields. This situation is in stark contrast to fields of annual crops, particularly at the beginning of the rainy season when there is no soil cover by the annual crop. The perennial leaf canopy also may reduce maximum soil temperatures and, thereby, decrease organic matter decomposition rates. There are no research data to support these common visual observations of reduced soil erosion.
A curious aspect related to soil erosion is that enset is most commonly planted around the house, and the house is usually on the most level location on a farm. If there is slope variation on a farm, annual crops commonly occupy steeper fields than enset. Therefore the soil erosion observed in enset versus annual crops is not just related to the crop. There is a need for research comparing enset and annuals on sloping fields. If suspicions are confirmed, extension activities need to be implemented to encourage more production of enset on erosive locations.
Leaching losses of plant nutrients, particularly nitrogen, may be reduced by enset as compared to annual crops. This should be possible because of the continuous soil occupation by roots. At the beginning of the rainy season and after maturation, annual crops have little root proliferation and little affect on nutrient leaching. For established enset, roots already proliferate the soil profile at the beginning of the rainy season. Also the large mass of the plant should serve as a storage reserve, reducing the availability of the nutrients in the soil for leaching.
The main negative feature of enset, its low protein content in the human-food portion, may contribute positively to its sustainability. Soils are depleted with continual removal of crop products. This is common with off-farm sales or with on-farm consumption without recycling of waste products, including human excrement. Removing low-protein (low-nitrogen) kocho from a site should have less impact on the nitrogen status of the soils than removing cereal crops, as long as the high-nitrogen portion is cycled within the farm.
It is common to find enset fields that have been productive for decades. The mechanisms that allow this long- term high productivity with minimum external inputs need a great deal of future study with the objectives of improving the enset system and transferring components of its success to other systems.