Effects of applying biochar to soils from Embu, Kenya : effects on crop residue decomposition and soil fertility under varying soil moisture levels

Abstract: Global warming is a challenge the world is facing today. All countries won’t havethe same potential to adapt to future climate. The economic situation is determiningon how well the country can adapt. Therefore, this will be a bigger challengefor developing countries. Many of these countries are situated near the equator andare relatively dry. They are also predicted to become warmer and dryer in the future.Due to high weathering rates and erosion soils in these countries are poor innutrients. Fertilizers are expensive and therefore in limited use. In many areas alsoinfrastructure is limiting the availability of fertilizers. Rapid decomposition of organicmatter causes carbon content rarely to be maintained in soils. Carbon is importantfor water and nutrient holding capacity and is therefore affecting cropyields. If crop residues are combusted in absence of oxygen a part of that carbonremains as biochar. This biochar is more stable than crop residues and can therebybe added to soil for improving soil properties. Research on biochar is conducted inmany countries over the world, inspired by the black Terra Preta soils in Amazonas.Several field studies are run by Swedish University of Agriculture in collaborationwith International Center for Tropical Agriculture, Tropical Soil Biologyand Fertility (CIAT-TSBF) in Kenya. I performed my field studies in one of theseexperiments, at Embu, close to Mount Kenya. I studied the effects of biochar onplant growth and decomposition of crop residues under varying soil moisture levels.This study was conducted in pots in a greenhouse. The results indicate a positiveeffect of added biochar on plant water supply and nutrient availability afterapplication of biochar. Plants grown in soils not containing biochar suffered fromnitrogen deficiency and drought. Plants grown in presence of biochar had higherbiomass and showed less signs of nutrient deficiency and drought stress. Biocharcould be produced on the farms using organic materials that are commonly available.Therefore, biochar could be an option for improving soil fertility. The implementationof this technology could even become more important for food securityin the future due to climate change.