Extraordinary biochar: an introduction, and results from the lab and field
the last four years I’ve been passionately investigating plant growth and physiological responses to biochar. The results have been interesting, surprising, and honestly quite extraordinary.
Let’s start with the basics:
“Biochar” is the term given to charcoal when it is intentionally used as a soil amendment. Biochar is typically made from the waste products of agriculture and forestry (such as woodchips, sawdust, animal bedding, corn stalks, etc.,). These products are called the “feedstocks” that are thermally degraded inside furnaces where oxygen is limited, so there’s no combustion that takes place. This process is called “pyrolysis”. The solid product of pyrolysis is charcoal, which are stacked, planar, aromatic carbons. This diagram explains the process using examples from one of our research partners: the Haliburton Forest and Wildlife Reserve Ltd., (Haliburton, ON):
This process happens naturally, of course. Wildfire is often associated with the burning of fuel material, but there’s actually a considerable amount of material that isn’t burned at all, it’s pyrolyzed, creating large amounts of charcoal. This charcoal is responsible for the spectacular re-generation following fire observed in essentially all terrestrial forests and grasslands. “Charcoal effects” are many and include: mineral element solutes from freshly produced charcoal can stimulate soil fauna and plant pioneers; high surface area and porosity enable charcoals to sorb a variety of compounds including phenolics, salts, root exudates, and the products of litter decomposition; and charcoals have incredible liming ability. Here is a photograph I took of regenerating Jack pines in the Canadian polar north following a stand replacing fire (Opapimiskan Lake, ON):
Biochar has received remarkable recent research attention and is heralded for its ability to increase productivity and ameliorate poor soil conditions, while mitigating anthropogenic climate change by enhancing soil carbon sequestration. Similar to wildfire-produced charcoal, many BCs exhibit high surface areas, pH, and cation exchange capacity, properties that can increase soil fertility, nutrient availability, and water retention.
Here are some results from several experiments using biochar:
1. Greenhouse experiments studying biochars potential to alleviate salt stress in temperate road-side pioneer plants. (Thomas, Frye, Gale et al. 2013, Journal of Environmental Management)
Another graph shows photosynthetic response to biochar in A. theophrasti grown in a temperate forest soil. (Gale and Thomas, in prep)
2. Another glasshouse experiment showing positive growth responses in 20 temperate mixed-wood forest trees. Results reveal positive growth responses in fire-adapted trees to biochar, and even negative growth responses in non-fire adapted tree species. (Thomas et al. in prep)
3. Results from our recently published review and meta-analysis of tree growth responses to charcoal show unbelievably high growth responses in tropical systems (Thomas and Gale 2015, New forests)
Final thoughts:
My own experimental results show very strong plant growth and physiological responses to biochar across a variety of systems. Plant responses in tropical systems other than agriculture have really not been studied, but we speculate that forestry, and agro-forestry responses will be tremendous. Please help support the next phase of this exciting research!
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