Improving crop yields and livelihoods
MALAWI'S 'BLACK GOLD': TESTING THE EFFECT OF BIOCHAR ON CROP YIELDS
Richard Carpenter is a PhD student with the University of Reading, currently based in Lilongwe Malawi, studying the effect of biochar on crop yields. Food security in Malawi is highly dependent upon maize production. Ninety percent of Malawi’s rural population are smallholder famers who often cultivate crops in degraded soil, on less than one hectare of land (1). Intensifying maize production, while diversifying agricultural production to incorporate crops resilient to climate change, is an important step towards achieving food security, improving livelihoods and reducing deforestation.
Richard argues one realistic way for smallholders to realise these gains is through application of biochar to soils; “We know that benefits of biochar are greatest in poor quality soils that have low organic matter content and low nutrient retention capacity. This makes biochar an ideal candidate as a soil amendment for nutrient poor soils in Malawi. Malawi currently produces over seven million tonnes of crop residues annually, 83% of which is attributable to maize (2). The application of maize biochar to degraded soils that has been pre-soaked in human urine to make it ‘biologically active’ therefore represents a viable, low cost way for smallholders to achieve yield increases on existing land”.
WHAT IS BIOCHAR?
Biochar is a carbon rich product obtained when biomass is heated in the presence of limited oxygen and then applied to soils to improve soil quality and/or sequester carbon (3, 4). When applied to soil, biochar has been shown to improve air filtration (5), increase cation exchange capacity (6), improve soil hydraulic conductivity (7), increase plant-available water contents (8), improve pH of acidic soils (9), and increase nitrogen and carbon content of soils (10). Research has shown that an increase of 1 ton of the soil carbon pool of degraded cropland soils can increase maize yields by 10-20 kg/ha (11). A meta-analysis of existing biochar trials has shown that biochar applied to acidic soils results in average yield increases of 10-14% (12).
Biochar can also be used to sequester carbon from the atmosphere. Biochar has an average carbon content of ~50% (13), which when applied to soil has a residence time of hundreds (14) to potentially thousands of years, making biochar, as a soil amendment carbon negative (15).
GASIFIER COOK STOVES
Richard previously conducted his MSc thesis in Malawi, researching environmentally sustainable cooking solutions for peri-urban communities around Lilongwe. The results of his study showed that biochar stoves have a positive impact on reducing forest based energy consumption and improving livelihoods. As part of his PhD, Richard will return to communities engaged within his MSc study and undertake qualitative research to facilitate a longitudinal study of cook stove use and adoption.
Richard also intends to advance gasification technology used within biochar stoves by developing and testing institutional scale gasifier burners that can be applied to a variety of settings, such as school canteens
Malawi: C/O Lilongwe Wildlife Centre, PO BOX 2140, Lilongwe, Malawi
UK: Energy and Resilience, University of Reading
Tel: Malawi: + 265 (0) 99 336 7831
UK: + 44 (0) 749 068 7956