Sahelian parklands needs improved tree, crop and livestock integration for future productivity
In the agroforestry parklands of the Sahel, generations of farmers have integrated crops, livestock and trees. With increasing pressure on natural resources to provide fuel, food and fodder for a growing population, farmers and scientists are looking at how these systems can best be intensified to increase productivity.
“Trees, crops and livestock all benefit from each other in the parkland farming systems of countries such as Burkina Faso and Mali,” explains Jules Bayala, Senior Scientist in Ecophysiology with the World Agroforestry Centre. “But to ensure all components are as productive as they can be relies on better integration and increased knowledge about the dependency, competition and complementarity of each element.”
In the agroforestry parkland farming system, livestock – cattle, sheep, goats, pigs, camels, donkeys and foul – are kept as a source of food, transport, power and cash. During the dry season, livestock freely browse in the parklands, providing manure that improves soil fertility and helps nourish trees and crops. Livestock also disburse the seeds of trees and sometimes break seed dormancy.
Farmers select tree species from natural vegetation which they retain on their farms to provide food, fodder, medicine, fuel and timber. The trees are generally kept at low densities to ensure optimum crop production. Trees have many benefits to the health of the parklands, including decreasing the velocity of runoff, increasing the availability of water and improving soil fertility through greater organic matter and nutrients, in particular leguminous species which fix nitrogen. The leaves and fruits of trees as well as crop residues constitute an important source of nutrients for both livestock as animal feed and for human nutrition.
The major crops grown in the parklands include cereals (maize, millet, and sorghum), cowpea, sesame, cotton and groundnut, most of which are grown during the rainy season. The common parkland tree species in Burkina Faso and Mali are Vitellaria paradoxa, Parkia biglobosa, Faidherbia albida, Adansonia digitata, Hyphaene thebaica, Borassus aethiopium, Balanites aegyptiaca, Sclerocarya birrea, Acacia raddiana and Anogeissus leiocarpus.
“Despite the many ecological and economic benefits of integrating trees, crops and livestock, the intensification of agroforestry parklands in the Sahel faces many challenges, most importantly competition for natural resources,” says Bayala.
Farming in the parklands is dependent on rainfall which tends to be variable. Water shortages cause losses to crop production and affects tree growth as well as the amount of fodder available to livestock. Short fallow periods, low fertilizer use, overgrazing and fuel wood harvesting have all contributed to soil degradation, deforestation and a reduction in vegetation cover which has led to poverty, food insecurity and conflict in the region.
Currently, the number of livestock and the way in which they are managed does not provide sufficient manure and nutrients to maintain fertility. Animal diseases and poor health are also reducing manure production.
Trees in the parklands are suffering and there has been a decline in species composition and density in recent years. Old trees are often removed when they are no longer productive and replaced by cereal crops. Dead and felled trees are not always replaced, and farmers sometimes prefer to plant faster growing exotic trees. In some places, livestock are hampering regeneration through trampling seedlings or causing the partial or complete elimination of tree shoots. The excessive pruning of trees for fodder can reduce the amount of organic matter made available to the soil as well as impede fruit production and impact on natural regeneration.
Another issue affecting the productivity of the system is that there are competing demands for crop residues and manure. As well as providing fodder and nourishing soils, crop residues can be traded, sold or used for fuel and fencing materials. Manure is also a useful building material (especially cow dung), household energy source and used for trapping termites to feed poultry.
Bayala is optimistic that many of these constraints can be overcome through more research on the most appropriate ways to sustainably intensify trees, crops and livestock in the agroforestry parklands of the Sahel.
“We need to develop technological alternatives which promote better resource use to take advantage of the benefits of each of the 3 components in the system.”
This would involve techniques for controlling resource competition among the 3 components, optimizing the impact of trees on crop yield and livestock production, better animal husbandry and methods for providing sufficient organic fertilizer from manure and crop residues and ensuring its strategic application.
Bayala and colleagues are working to develop an occasional paper based on their research into integrated tree-crop-livestock systems in Burkina Faso and Mali under a project funded by the McKnight Foundation.