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ILEIA Newsletter Vol. 11 No. 3 p. 12 Weeding on the forest edgeKojo AmanorOn the edge of the forest belt in Ghana weeds are becoming more and more of a problem due to soil and forest degradation caused by savannization and intensive agriculture. To reduce this problem farmers have developed several ecological management techniques investing in labour rather than in expensive inputs. Starting from the experiences of these farmers the author looks at new directions for weed research. Weeds are a much neglected problem in farming systems. Approaches to sustainable agriculture have tended to focus on soil and water management or high input packages. Yet weeds are symptoms of environmental degradation and the problems related to some species can make farming uneconomic and sap farmers of their energy. Since major cereal crops are often related to weedy grass species, farm environments often create conditions in which weeds thrive. For some weeds, such as Rottboellia exaltata, it is difficult to find effective herbicides which will not also destroy cereal crops. In the African savanna, large areas of farm land are abandoned because of infestations of striga, a parasitic weed of roots of cereal and legume crops. It has been estimated that 40% of potential cereal crop yields in Africa are lost to striga. Farmers often spend the greater part of farm work in weeding. Timely weeding is critical and can adversely affect yields if delayed. Weed problems force farmers to increase labour inputs or their expenditure on hiring labour without a corresponding increase in returns. A common complaint among cultivators is that they are spending more time on weeding than in former times, because of deforestation and decline of the farming environment. Studies on traditional forms of shifting cultivation have often found that fields are long abandoned before soil fertility declines to critical levels. The main factors influencing the return of land to fallow are problems in dealing with weeds and pests, which result in falling yields and more work (Nye and Greenland, 1960). In the transitional forest areas of Ghana there are two main types of weed problems. The first results from a process of savannization. Grassy species invade from neighbouring savanna areas and gradually spread along roads and paths into cleared farm plots, replacing the multitude of forest shrubs with a few gregarious species. The second is associated with intensive cultivation resulting in deteriorating soil conditions and land degradation. Savannization The edges of the rainforest are often the areas in which the heaviest commercialization of agriculture occurs. Intensive maize cultivation encourages the spread of grasses from neighbouring savanna areas. The corridors of grass, which intrude into the forest, create a highway down which bush fires spread during the dry season, annually destroying the regenerating forest flora and encouraging the further spread of grasses. Common invading savanna species in the southeast transition zone of Ghana include Panicum maximum and Digitaria ciliaris. While they do not necessarily have a poor impact on soil regeneration, the annual bushfires associated with them prevent the build-up of organic matter. Forest farmers who use the machete for both clearing land and weeding and farm in a minimum tillage style often adapt poorly to the invasion of grassy weeds. They spend considerable time in weeding and often fail to keep the farm free of grass species. The end result is a poor yield. Intensive cultivation Since independence, the state had attempted to promote the northern transitional zone, in Brong Ahafo and Northern Ashanti, as the bread basket of Ghana. State farms were developed in these areas as shining examples of modernization. Extension programmes were fostered to encourage farmers to use tractor services, and packages of fertilizers, pesticides and modern varieties planted in monocrop lines. This new source of technology enabled farmers to cultivate larger areas more intensely. Farmers who invested in clearing and stumping their land for tractor ploughing tended to engage in intensive permanent cultivation to recoup this large investment. State subsidized inputs encouraged this strategy. However, the soils in this area are highly fragile and not suited to the existing ploughing techniques (Obeng, 1973). Many unskilled tractor operators use deep ploughing techniques turning the subsoil over the top soil. This destroys the structure of the soil and the soil seed mat and encourages the spread of nefarious weeds. Today, most of the natural vegatation of these mechanized farms has been degraded into a uniform cover of Imperata cylindrica which offers little protection to the soil. Many farmers have a detailed conception of patterns of degration and corresponding changes in the environment. Elizabeth Nketia, a highly articulate woman farmer at Jensoso in the Wenchi area of Brong Ahafo, was able to succinctly chart the course of weed infestation resulting from intensive cultivation or ploughing. She narrated that with the opening up of well rested land the first dominant weed to apear is Penisetum purpureum (elephant grass). With more intensive cultivation this is replaced with Imperata cylindrica, and then later with Commelina sp. and Cyperus sp., which indicate the exhaustion of the soil. Combatting weeds Farmers sometimes hit upon ingeniously simple solutions that take much of the tedious backbreaking labour out of weeding. At Badu, in the Wenchi area, farmers discovered that if they cleared Rottboellia exaltata by slashing it half way up the stem (instead of at the roots), during the minor seasons, the upper part fell down to create a covering mulch that prevented its subsequent regeneration. This technique results in a good crop of maize without having to weed. However, it does not work during the major season, when the heavier rains promote rapid decomposition of the mulch and more vigorous undergrowth. In the Krobo settlements fringing the Afram Plains, farmers try out new techniques of conquering savanna grasses (Amanor, 1994). At Awoweso Sisi the Mensah brothers have developed a new technique of clearing grass. After the first bush fires which merely char the grass, they set about uprooting the grass clumps. These are spread flat on the soil creating a mulch, which prevents the further spread of bush fires, protects the soil from the sun and leaching, and suppresses the regeneration of grasses. The mulch gradually rots into the soil providing an enriched organic matter. They claim that they do not have to weed their farms. They are one of the few families in this area whose cassava yields have been improving. In the same settlement, Tekpeh Boboyoo has a strategy to prevent the spread of bush fires through grasses by extending the duration of cultivation. Instead of abandoning the plot after two years he continues to cultivate it into a third and fourth year, by planting long duration crops such as pepper. He rigorously weeds out grass species, but preserves regenerating forest trees and shrubs. These grow to suppress the regeneration of grass. By the fourth year there are not many crops left, but he has succeeded in creating an island of regenerating forest in a sea of grassland. He intends to extend this by methodically cultivating outwards from this area of regenerating forest. Within this region, there are many such experiments going on which are bearing fruit. Bush fires have destroyed many forest reserves in the outer perimeter of the Fanteakwa District which have been transformed into grassland. Yet in neighbouring settlements, many farmers have managed to preserve a woodland environment. Similar experiments can be seen in the more forested areas in the transition zone of Brong Ahafo where a growing number of farmers are consciously preserving small fast growing trees, such as Margaritaria discoidea, to halt the spread of savanna grasses and encourage fallow regeneration. In this respect the farms of Yaw Djan, at Badu are impressive. When clearing, he pollards the trees at quite a high level to encourage rapid coppice regrowth. After an early maize crop on the newly cleared farm, he preserves this coppice regrowth among egg plants and chili peper, conserving the land and minimizing weeds which are shaded out (Amanor, 1993). High input technology and weeds Some researchers argue that if farm land is used intensively, this will create less pressure on the rest of the land. Investment in high input technology will also lead to an increasing valuation of land that will assure that farmers will look after the land more carefully and with long-term considerations. However, if land degradation is examined at the level of flora transformation and spread of nefarious weeds, present high input technologies do not fare very well. They encourage the spread of grassy species, which promote bush fires and lead to further deforestation. They result in escalating costs of production with increasing amounts of labour invested in weeding and capital in fertilizers and related technologies. When inputs were subsidized by the state, many farmers took advantage of the cheap prices to get quick returns without counting the environmental cost. They now find the costs of inputs prohibitive when compared to the prices they receive for their crops. This suggests that farmers in other areas are producing crops more competitively without resource to high inputs. They prefer to invest their capital in hiring labour rather than in purchasing inputs, because they regard the labour/weeding problem to be the main bottleneck in farming. At present, investment in labour may pay better dividends than in expensive high input technology. Many farmers in the high input farming zone are now changing their strategies and using crop rotations with legumes (cowpea, groundnut and pigeon pea) instead of mechanized permanent monocultural production. The impact of these leguminous rotations on weed remains to be seen. Conclusions The weeding process is a useful entry point for approaches to sustainable agriculture based on natural resource management, since it represents a node at which labour and environmental concerns coalesce. An closer look at farmers’ experiences in weeding reveals rich traditions of experimentation and observation, in which techniques and the manipulation of ecological processes are as important as technology in finding solutions. The use of shade and the cutting of natural vegetation to provide a mulch are two important principles farmers utilize to protect the soil and minimize weeding. The timing of these techniques may have different impacts on their success. More research into the cropping calendar and the impact of timing on clearing, sowing and weeding is needed. Kojo Amanor, Institute of African Studies, University of Ghana, Legon, Accra, Ghana. References Back to Top |
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