Biochar as a carrier for bacterial soil inoculants
In my dissertation research, I investigate microbial interactions in biochar amended soils. In doing so, I incorporate plant growth promoting rhizobacteria (PGPR) into biochar. The pyrolysis of organic waste materials offers the potential to sequester significant portions of source carbon, hence it has been praised as a climate change mitigation strategy. The charcoal material resulting from this process, called biochar can be stored in agricultural soils where it often enhance their fertility. PGPR can serve as biological fertilizers and biological control agents because of their abilities to fix nitrogen, solubilize phosphorus, sequester iron, suppress root-growth inhibition, produce antibiotics and anti-fungal compounds, and out-compete pathogenic populations. My model organism interacts with a plant by producing a plant growth hormone, auxin, around its roots, thereby leading to increased root mass and structural integrity, resulting in a healthier plant. While biological fertilizers have been studied for decades, a major limiting factor in their use is poor survival. Basically, we see a sharp decline of our inoculum population size once added into a soil. We hypothesize that biochar, which has high microporosity, will serve as a solid structural support to shelter microbial colonies and thereby increase the longevity of the benefits associated with biological fertilizers. On the flip side, the incorporation of PGPR into biochar can serve as a value added component to this material making the use of carbon-sequestering biochar more desirable. My work is supported by an EPA STAR fellowship.
Our lab hosted two visiting scientists, a soil chemist from Brazil and a microbial ecologist from Mexico. Together, we investigated a sustainable phosphorus source that incorporates phosphorus solubilizing bacteria into what we hope will be a time-released P fertilizer. For this we encapsulated live microorganisms, biochar, and rock phosphate into small beads using sodium alginate. I use the most probable number technique to quantify the bacteria maintained within and released from these beads.
New Zealand Collaboration
Through a National Science Foundation fellowship, I took part in an interdisciplinary project with a biochar research center in New Zealand. I added a biological component to two on-going projects. This research center focused one study on the phosphorus (P) availability from different biochars included into their treatment soils. I assayed the capacity of the native soil bacteria in these treatments to solubilize phosphate from mineral complexes. This will play a significant role in P availability from their biochars and it was reassuring to observe that none of the biochar products selected against these organisms. The second project was a phytoremediation study that incorporated biochars into soils contaminated with heavy metals and pesticides. Here I assayed root-colonizing strains for ACC deaminase activity and auxin production; traits that play a major role in assisting survival of plants stressed from heavy metals. For more information on the program that granted me this opportunity check the NSF’s call for proposals.