Enset Agronomy and Production Management
Compared to most crops, particularly annuals, the production of enset involves many more steps. Suckers are usually produced from the two- to four-year-old corms (10 to 20 centimeters in diameter) and the true stem. (The mother corm piece may be a whole corm or some portion of it.) These mother corm pieces are obtained by harvesting healthy plants, cutting off the pseudostems, removing the roots, and cutting out the center or apical bud, from which leaves and the flower stalk develop. Because of dominance by this apical bud, lateral buds on the true stem do not usually develop; but once the apical bud is removed, these lateral buds form suckers around the periphery of the mother corm piece.
The mother corm pieces are usually planted in a nursery, often with manure, where they can receive extra care. Suckers are also formed from plants left in situ with the pseudostem and apical bud removed. It is common for a farmer to have 5 to 15 mother corm pieces each year. Usually from 20 to 100 suckers form per corm piece. These suckers are usually allowed to grow for one year before transplanting, although they may be transplanted sooner or even left for a second year if the farmer has excess planting material.
Suckers are transplanted using a hand hoe, usually to an area that has been well prepared with added animal manure. At and beyond this stage of sucker transplanting, there is tremendous variation in management. Plants may be transplanted only once or up to four times, at ever wider spacing. Not all plants within a farm or a field may receive the same transplanting management. Some plants may be harvested at a young age (two to three years) for amicho and some may later be harvested for kocho. This variation in transplanting and harvest management seems to be a function of ethnic group, household needs, and available resources (such as land, labor, capital, and other food crops in the system). Elevation primarily affects the number of years that plants are left at each stage, because cooler temperatures slow plant growth. By contrast, manure speeds plant growth and time to harvest.
A general objective of most enset transplant systems seems to be to maintain a leaf canopy that covers the soil for most of the year. Therefore, small plants are spaced close together, e.g., half a meter apart, and/or are intercropped with other species or larger enset plants. As increased plant size and leaf canopy allows for efficient use of a wider spacing, some or all plants in a field may be transplanted to another field. For example, there are up to three additional transplantings of all plants in the Gurage system, while in the Sidama system some plants are thinned and moved to another field. Whether taken from an area where all plants are removed or from an area where there is selective thinning, the plants may be: 1) transplanted to a uniform stand of only removed plants; 2) incorporated with plants of similar size but different ages and previous management; 3) planted in open spaces between taller (either uniformly sized or variably sized) plants; or 4) intercropped (e.g., with coffee or citrus trees).
Enset may be grown alone in uniform stands of similarly sized plants, in mixed stands of enset plants of different sizes, ages, and clones, or in a combination of these at different stages. Enset may also be intercropped with other species, in which case there is a tendency to intercrop younger enset plants with annual crops (such as maize and cabbage), and older enset plants with perennials (such as coffee and citrus). In either intercrop type, farmers recognize that the growth rate of enset is decreased. There are, however, no research data quantifying the effects of such cropping strategies on the performance of enset or other crops in the system, although some trials are underway at Areka Research Station (Plate 7). Also, there is no extension information available for a group of best management strategies.
The age of enset plants to be harvested may be uniform or variable. For example, most plants harvested by the Gurage are nearly mature (although poorer households may have to harvest immature plants), while the Sheko tend to harvest many young plants for amicho. The Gamunya harvest plants of varying ages. Within an ethnic group, duration to harvest is affected by elevation (temperature), the age and characteristics of particular clones, the intended uses for food or cash, management (such as plant spacing and manure rates), and the wealth level of the household (addressed in more detail below under section on "Case Studies"). Farmers tend to believe that it is better to harvest plants at or near plant maturity, and that harvesting younger plants indicates an inadequate food supply or poverty. The importance of harvesting nearly mature plants is particularly stressed by male farmers, while female farmers in some of the same ethnic groups (e.g., North Omo) indicate they prefer to harvest smaller plants for better taste and ease of fermentation (Habte-Wold et al, 1996; Spring, 1996a; Tibebu et al, 1996; see also section on "Gender Issues," below).
All research to date on the yield of enset has been with nearly mature plants, and generally has been at spacings designed to maximize yield per plant in the minimum duration. However, this is not the apparent objective of most farmers' strategies. There are no data available to compare yield or land use when harvesting many closely spaced, younger, smaller plants versus fewer, widely spaced, older, larger plants. Studies on combinations of these and intercropping (either mixed sizes, clones of enset, or mixed species) strategies also are nonexistent. There is no extension information available on the spacing, timing, intercropping, and harvesting of enset, while for other crop species these facts are considered baseline extension information.
Ideally, farmers use cattle manure on enset (Plate 8). It is common for enset to receive available manure before other crops. In an ideal enset system, ruminant animals such as cattle, sheep, and goats graze on large areas of grassland and are then housed at night in corrals where manure is collected. This manure is then applied to enset and to a lesser extent to other crops. For many communities and individual households, however, manure is often scarce or nonexistent because inadequate grazing land or lack of resources limit animal numbers. In reality, increasing human population densities and/or the disappearance of grazing lands in poorer households lead to declining animal numbers and manure quantity per household, and in turn to decreasing enset yields.
In a few households with sufficient capital, fertilizer is beginning to be used on enset. This is particularly evident in the Sidama region, where farmers are accustomed to putting fertilizer on coffee, and have cash incomes from coffee sales. In the absence or shortage of cattle manure, some have tried inorganic fertilizer (diammonium phosphate) on enset. The results are mixed; growth is greater, but food yields do not increase correspondingly.
As available land per capita becomes more limited, the role of ruminant livestock for manure supply becomes one of the greatest threats to the future of this highly successful, sustainable, indigenous system. The potential for alternatives has not yet been researched. There are no research data available as a base to use for advising farmers on the rates of manure and inorganic fertilizer that should be applied to enset. Similarly, there is no information on the effect of soil type, environment, age and size of enset plant, harvesting management, intercropping, or any other variable on optimum rates of manure or fertilizer. Improved pasture and cut-and-carry systems to augment ruminant meat and milk production, let alone manure production, have not been implemented.
Diseases are collectively the most severe biological problem facing enset. The damage that diseases can cause and the lack of knowledge about or implementation of preventative strategies contribute to the severity of enset plant diseases. Diseases are caused by several bacteria, nematodes, fungi, and viruses. Bacterial wilt, caused by the bacteria Xanthomonas campestris pv musacearum, is the most threatening to the enset system. Bacterial wilt attacks plants at any stage, including full maturity. When bacterial wilt, or any other cause, kills an enset plant late in its life cycle, it is a particularly serious loss. The farmer has already invested several years of land, labor, and resources into the plant's production. In some enset-growing areas, such situations have caused farmers to abandon their enset farming and replace it with annual crops.
Enset is attacked by numerous diseases in addition to bacterial wilt. They include enset corm rot, enset sheath rot, and enset dead heart leaf rot, caused by an unknown bacterial pathogen and fungus, respectively, as well as root-knot, lesions, nematodes, and virus diseases.
The most important factors responsible for spreading disease of bacterial wilt include disease-infected planting material, contaminated farming and processing tools, and human and animal vectors. The only research-recommended control measures for diseases are cultural measures to prevent the movement of the causal agent. For bacterial wilt, these measures include the use of healthy, disease-free suckers for planting material; destruction and controlled movement of diseased plants; cleaning of equipment that has come in contact with diseased plant material; and rotation of crops. The specific practices required for realization of these control measures can require sizable investment of additional care and labor. If a farmer is not knowledgeable about the cause of disease, is not convinced that the additional effort will make a difference, or has insufficient labor, the control practices are not likely to be adopted. While there is still much to research about enset diseases, adoption of known preventions could be part of an extension campaign. However, the current lack of extension programs presents the main limitation to disease management.
Bacterial wilt is easily spread by any object touching the contaminated parts of the plant or processed enset (i.e., kocho). Contaminated cutting and processing tools, in particular, spread the disease. Cutting enset leaves for animal feed and wrappers may spread the disease from one plant to another. It is also postulated that mole rats, which burrow underground, can cause contamination as they tunnel from one plant to another. Similarly, snakes and insects going between plants, as well as the presence of cattle walking through fields, could also contribute to the spread of bacterial wilt. All of these transmission agents need to be researched.
In the case study areas (described in more detail below), virtually all enset fields of Gurage households are infected by bacterial wilt, while about half of the Hadiya households have infected enset fields. By contrast, the majority of Sidama households report no enset diseases on their farms, although a few households report wilt in the older enset plants. Farmers mention that bacterial wilt is more severe at high altitudes, but more research is needed to confirm this. The reason for these differences is probably related to farmers' knowledge of the methods of disease spread and contamination of tools.
Typical bacterial wilt symptoms in enset plants above two years old is that the innermost leaf sheaths become yellowish and droop. Usually only older plants are attacked; however, in one area studied the disease was observed attacking younger enset plants (even the one-year-old suckers).
The control measures used by farmers are inadequate, and seem to facilitate the distribution of the disease. In areas of greatest infestation, farmers loan or borrow farming and processing tools. Therefore both men and women engaged in cultivating, processing, and cutting leaves spread the disease.
Some households control bacterial wilt by uprooting and discarding infected enset plants as a cultural control measure; however, few households use sanitation methods for their tools. Too frequently, infected enset plants are disposed of near the enset farm, and, as such, they may be a potential source of the disease inoculum and its re-spread. Some farmers fallow the enset field and practice rotation with annual crops. By contrast, in the area that is relatively free of bacterial wilt, farmers practice control measures such as uprooting the infected bacterial wilt enset plants and keeping them away from the household, other enset plants, and cattle. Farmers also try to keep healthy plants away from contaminated farm and processing tools.
Some households decorticate and process infected enset plants at their early stage of infection. Some women separate the kocho from infected plants (bulla is never made from infected plants) from the kocho of healthy plants by putting them in separate pits. The wealthier households have the choice of utilizing diseased plants or not. They may chose to process this lower quality kocho separately and sell it. The poor have less choice and may use it for home consumption, purchase it, or receive it from more affluent households as payment for their labor or craft product.
Farmers note that certain enset clones have relatively high tolerance against bacterial wilt and that particular clones revive after infection has occurred, while other clones of similar age group are wiped out by the disease.
Many Gurage farmers report disease problems related to kocho stored in pits, especially for an extended period of time. A tooth-shaped fungal mycelial growth (species not identified) on the upper surface of stored kocho in the pit is reported. The disease starts around the wall of the pit, causes a bad small, and the kocho becomes highly compacted because of dehydration. Farmers report that this problem is common in kocho stored for extended periods of time and is easily transmitted from the nearby infected enset storage pits or pit lining materials. Farmers try to control this problem by regularly aerating the kocho and changing the pit.
Porcupine, mole rat, and wild pig attack enset plants in the field. They usually damage the plant by feeding on the corm and pseudostem. Among these pests, the mole rat ranks number one. Since these animals are not microscopic like the bacterial and viral diseases, farmers are knowledgeable about them, and many employ effective management practices. These practices include woven fences and ditches around enset fields, to retard the movement of animals into the field, and traps for catching them. Wealthier farmers use steel traps to snare wild pigs and monkeys, and others traps for porcupines and mole rats. Burning coals may be dumped into the rat tunnels. Farmers also protect against porcupines by digging pits around enset plants so that it is difficult for the animals to get in or to climb up and get away. In some areas, farmers organize themselves on a village basis to hunt wild pests with sticks, spears, and machetes.
Insects have been considered a minor problem in enset cultivation. However, over the last several growing seasons, mealy bugs have been identified as a serious problem in certain regions. Mealy bugs are soft-bodied insects that feed on the corm and roots. Enset plants infected by mealy bugs show stunted growth; the damage appears more severe during the dry season. Because they live underground, their damage often goes unnoticed until serious loss has occurred. As they are slow moving insects, mealy bugs are controlled with methods similar to those used against diseases such as bacterial wilt.
Weeds can cause greatly reduced plant growth while enset plants are small, i.e., during the sucker stage and for one or two years after the first transplant. The total land area used for production during these stages is usually relatively small compared to the farm size, and therefore weeding can be accomplished with available labor. As the enset plants become larger, the perennial leaf canopy and leaf litter on the soil surface prevent most weed growth. In annual crop production, the labor available for weed control can be a serious restriction to production. Although labor data are not available, there is probably much less labor required for weed control per ton of food in enset than on any annual crop. The reduction in labor for weed control may be offset in part by the additional labor required during harvesting and processing of enset.