The 'fruits' of agroforestry - soil, milk and fish!
Increasing population pressure and decreasing availability of good land in many parts of Africa are forcing more and more subsistence farmers to cultivate crops on unsuitable marginal land. Growing annual crops, such as maize and beans, on steep slopes of up to 60%, takes a lot of effort and time and, during the rainy season, heavy downpours often wash the nutrient-rich topsoils down the steep hillsides into the streams, rivers, and eventually into the sea.
This is exactly what is happening around the Embu region in central
Kenya, where soil erosion from the highlands is causing severe
siltation of the dams on the river Tana. And, as the river flows into
the Gulf of 
Formosa
in the Indian Ocean, large amounts of silt are deposited on the coral
reefs, which then die. This in turn damages fish breeding and feeding
grounds and deprives local fishermen of valuable income. Now,
researchers from ICRAF (International Centre for Research in
Agroforestry), KARI (Kenya Agricultural Research Institute) and KEFRI
(Kenya Forestry Research Institute) are working with local farmers
around Embu in an agroforestry project that might help prevent further
soil erosion. And the agroforestry solutions that have resulted from
this Swedish-funded collaborative project to prevent soil and water
loss are providing farmers with additional benefits - not just for the
soil and the crops but also for their dairy cows.
A mixed approach
In the past, research efforts to prevent soil erosion have focused on engineering structures to terrace farm fields. But farmers have been reluctant to accept these labour-intensive and expensive strategies. Now scientists are concentrating on biological solutions in the form of contour hedges made up of plant species selected by the farmers and the researchers, such as Calliandra calothysus and napier grass (Pennisetum purpureum). These not only hold the soil in place but also provide excellent fodder.
Dairy cows are economically very important in the Embu region. Most farmers grow napier grass to provide fodder for their zero-grazed cows, but the protein content of napier is very low and few smallholders can really afford dairy meal. When looking at alternative fodder species to be grown as contour hedges, researchers must therefore take into account the protein content of each species they recommend.
A number of fodder species have been, and continue to be tested at the KARI Regional Research Centre in Embu, where the project is based. One of the most promising species is calliandra, a legume which has a protein content of up to 25 %. On-farm trials have found that 3 kg of fresh calliandra contain the same protein content as 1 kg of dairy meal, which means that, by using calliandra, farmers can cut their costs of buying dairy meal by 50% or more. Other advantages of growing calliandra are its fast, vigorous growth, its tolerance of hard pruning and its general resistance to pests and diseases. Trees can be grown along terrace edges to help stabilise the soil, along the farm boundaries or even intercropped between rows of napier grass. Research has shown that about 500-600 metres of calliandra hedge (the perimeter of a one hectare farm) is sufficient to replace the concentrates required by one dairy cow and will sustain, even improve, its lactation throughout the year.
Initial on-farm trials have been a success and Mr George Karanja, an agronomist with KARI, is keen to disseminate the information to more farmers in the area. He feels that the best way is to work with farmer groups and co-operatives and to hold more on-farm field days so that the farmers can observe what is already being done and, as he puts it, "see the benefits for themselves."
Dr Mick O'Neill of ICRAF, who is also working on the project, is hopeful that the technology will spread further afield to neighbouring countries such as Uganda and Ethiopia as well as help soil conservation efforts in West Africa where, according to O'Neill, "Different species may have to be used but the principles we've learned here could still apply."
