Black is the New Green: SHI Field Staff Learn the Benefits of Biochar for Agriculture
written by Julie Cornell, Cornell University
During the annual Board and staff meeting held in January in Honduras, field staff from Honduras, Nicaragua, Belize and Panama attended a workshop on managing soils with biochar. Biochar can be made simply and cheaply from any organic material, just by piling it, covering it up with soil to exclude air and setting it on fire. During the workshop biochar was made from rice hulls and pieces of pine wood for demonstration, but any crop residue or plant waste can be used to make biochar, such as coffee pulp, sawdust, sugarcane bagasse, etc.
Applying biochar to soil provides great advantages in terms of crop productivity, often more than doubling yields. Numerous field and greenhouse studies have shown that adding biochar to soil increases the yields of all plants, but most importantly food crops such as rice, beans, maize and horticultural crops. Most of these studies were carried out on poor, acidic soils of the tropics.
How does biochar improve crop yields?
Research so far has shown that biochar acts as a soil conditioner, not as a fertilizer. Indeed biochar improves the efficiency of fertilizers, be they chemical or organic. It acts as a sponge to retain applied nutrients in the rooting zone, whereas these would be flushed deeper into the soil without biochar. Biochar also likely improves water retention in sandy soils and likely has beneficial effects on the microbial communities in the soil. Research has shown that when biochar was applied to soil, the emission of greenhouse gases such as nitrous oxide was reduced. This means that we can retain much-needed nitrogen in the soil for plant growth, while reducing the contributions of soils to global climate change.
A different kind of organic matter
It is widely known that adding organic matter to soil helps improve soil fertility. So, why go through the trouble of making biochar instead of just applying crop residues to soil directly? The answer is that biochar lasts in soil for hundreds of years, whereas “fresh” organic matter decomposes almost completely within decades, especially in tropical climates. So, by making biochar with biomass and applying it to soil, we can capture carbon and sequester it into the soil over extremely long time scales. Not only is carbon sequestered, but biochar added to soil progressively improves and has a better potential to increase crop yields.
A powerful soil management tool
After listening to a talk on the benefits of biochar, field staff set out to install two demonstration plots, at the “Florence Reed” demonstration farm as well as on a farmer’s field. Knowledge was shared between participants as they ground biochar, prepared some for demonstration, turned up the soil on the plots, and tilled in the biochar. Crops will be planted on these plots and Honduras staff will monitor yields.
Biochar is most directly beneficial to small farmers because it improves crop yields. However, several environmental benefits are also associated to its use: decreased water pollution from farming, carbon sequestration, and reduced greenhouse gas emissions. Biochar production is an energy-yielding process, and with improved technology biochar soil management could be a way to produce energy in a carbon-negative way. This means that while energy is being produced, carbon is actually taken out of the atmosphere through biochar application to soil and increased plant productivity. This is an opportunity offered by no other technology.
Julie Major is a Ph.D. candidate in soil fertility at Cornell University and recently volunteered her time and talent to lead a biochar workshop with SHI’s field programs in Central America. Visit the International Biochar Initiative at www.biochar-international.org.