Biochar as soil amendment : a comparison between plant materials for biochar production from three regions in Kenya

Abstract: The majority of the people living in sub-Saharan Africa earn their living mainly byfarming. Infertile soils and variable climate make it difficult to reach sufficientcrop yields every year and therefore food security can be low. Soil quality reductiondue to erosion and nutrient depletion due to limited addition and maintenanceof nutrients is a common problem. One feasible measure to increase soil fertility isaddition of biochar, charcoal produced during pyrolysis (organic material, usuallywood, heated under low oxygen conditions), which generally is used as fuel forcooking.This Minor Field Study is a BSc thesis based on studies of biochar as soilamendment in Kenya. The project had three main objectives. The first aim was to,through visits, describe smallholder farming systems in three areas in Western,Central and Eastern Kenya. Interviews, observation and sampling of characteristicorganic materials were performed in each area. The second aim was to measurewhether biochar application to soil can increase crop yields and if so, if there areany differences between biochar originating from different feedstock organic materials.The third aim was to return to the involved farmers and discuss and presentthe results as well as the possible practical benefits.All the visited farms were small-scale systems with no or few external inputs.The farming systems were similar in all three areas, though some differences werefound, e.g. dominating types of crops. Most of the farmers were interested in usingbiochar as soil amendment- if it would be proven to have beneficial effects and beeconomically viable.The results from analyses showed that nutrient concentration correlated with theyield from pot trials where three treatments stood out: biochar from cassava stems,coffee leaves and fresh banana leaves. Biochar from these materials in general hadthe highest nutrient concentration as well as pot trial crop yield, indicating a fertilizereffect. Plant materials with different properties may be important for plantgrowth, but biochar rate seems to be a more significant factor, confirmed by thestatistical test.The great need of improvement in soil fertility and the farmers’ interest towardsbiochar indicate that this approach might be possible to use in the future. However,more research on the subject is necessary if it is going to be implemented in thefield, since these farmers cannot afford failures.