On the footslopes of Mount Kenya, soil erosion is a serious problem. The increasing population has made farmers abandon the system of shifting cultivation for more settled land use. In addition to heavy rainfall, the intensified landuse has increased the problem of erosion.
In an attempt to base a participatory approach on the real perceptions of farmers, Okoba looked for indicators of soil erosion that farmers perceive. It emerged that most farmers clearly see the damage that soil erosion is doing to their fields. Gullies and rills as well as indicators such as the colour of the soil and stones on the ground tell farmers that erosion is happening. Okoba drew maps of the eroded areas together with farmers. Okoba: ‘This turned out to be a good tool for discussing erosion among farmers, because many see it happening on their own fields, but didn’t know their neighbours had the same problem. Making maps allows them to discuss the issue and make a joint plan for the whole catchment area to so something about it.’
There appeared to be little difference between the farmers’ perceptions and the experts’ assessment of erosion. The difference is in the perception of the processes behind erosion. Experts think in technical terms and amounts of nitrogen lost. But that doesn’t tell a farmer what’s happening. Okoba gives one example of a farmer who believed that the stones grow out of the soil gradually over the years, instead of the soil being washed away and so exposing the underlying stones. But, says Okoba, these differences don’t matter as long as farmers see that they can stop erosion by taking measures. Scientists and extension officers need to learn that it is not their job to force farmers to do as they say, but to show them the differences in yield between conserved and eroded land and tell them about the experiences of other farmers with dealing with erosion. That helps to raise awareness among farmers, as it helps them to make the link between indicators of erosion and gradual decreases in yield over the years, which farmers otherwise may attribute to diminishing rainfall.
A colleague of Okoba, Dr Albino Tenge, developed a tool to put all this into practice. He worked in the Western Usambara mountains in Tanzania. After the farmers have mapped soil erosion based on their own indicators, the tool can be used by extension officers together with the farmers to make clear, field by field, what the costs of erosion are, and what the benefits of soil conservation measures can be in the future. Tenge found three major forms of conservation practised by farmers in the Usambara mountains. For each he calculated the costs of construction and likely benefits as a result of future increases in yield. The most drastic measure is the construction of bench terraces, which cost 215 dollars to make, mainly due to the high labour input required. On a yearly income of 200 to 300 dollars, this is a high amount, though the future benefits of terraces may be as high as 600 dollars. Cheaper options are the indigenous fanya juu, which are small hillside ditches, or grass strips, but these all have lower yield increasing effects. One strategy that makes things easier for farmers is a stepwise implementation of measures, as is the formation of a group in which all members work on measures for one member at a time. Both researchers will return to East Africa to work as researchers on improving farmer participation in combating soil erosion.
Dr Albino Tenge and Dr Barrack Okoba defended their theses on Monday 25 April. They were both supervised by Professor Leo Stroosnijder, professor of Erosion and Soil and Water Conservation at Wageningen University.