Allison gets her hands dirty on the job
My seventh interview has certainly been a long time in coming, but I think it will definitely be worth the wait. The funny thing is that I originally asked Allison for an interview last winter, and she enthusiastically agreed. It was solely my scatter-brain tendencies that caused such a long delay in getting this to you. This fall I decided to send Allison an email to gauge her interest in giving it another shot. Thankfully she was as enthusiastic as ever, so here we are!
I first learned about Allison via an article she wrote for Vermico’s Casting Call newsletter (Volume 8; Issue #3). The article demonstrated her passion for academic vermicomposting literature (an interest I certainly share), providing a fantastic overview of the important findings in the field gathered for her Masters thesis literature review. Allison has since moved on to a PhD project, and her passion for compost science certainly hasn’t waned.
Can you tell me a little about your background? How did you become interested in compost (and the field of composting in general)?
I grew up in the San Francisco Bay Area suburbs and although my family’s house is on a sixth of an acre, my Mom is an amazing gardener. We had fruit trees (orange, Meyer lemon, lime, tangerine, plumb, apple, and apricot), berries, vegetables, beautiful flowers and of course a compost pile. So I grew up in a composting family with a “pit pot” in the kitchen. Even my pet rabbit contributed his manure to the pile!
My waste management experience started when I was 16 and volunteering as a community health worker in rural Paraguay through the Amigos de las Americas program. My partners and I helped build 40 latrines in the small town of Espinillo and educated children about the fecal / oral disease cycle. At the time Paraguay was just coming out of a long dictatorship that had a very negative effect on rural development. The second leading cause of death for young children when I was there in 1996 was diarrhea due to improperly managed human and livestock wastes. I saw first hand how important human and livestock manure management was to the overall health of rural communities.
My senior year of high school, I was the co-president of the environmental club and became intimately familiar with the trials and tribulations of running a campus recycling system with little to no support from the administration. I learned a lot about how hard it is to change ingrained behaviors. After college I served for two years as an AmeriCorps volunteer at an environmental science magnet school in Portland, OR. As the service learning coordinator, I helped students manage the composting and recycling systems including a large worm bin. I became a Master Recycler through Oregon State Cooperative Extension and was fascinated by the unit on composting. I helped the school’s science teacher design and teach several labs based on the decomposer food web in our vermicomposting system.
So when I saw the announcement for the 2001 Earthworms in Ecotechnology conference, I signed right up! This even was put on by Peter Bogdanov of VermiCo and I got to meet Clive Edwards and Mary Appelhoff and learn more about the science of vermicomposting. At this point I had a BA in biology from Reed College, but I wasn’t sure which direction I wanted to take my career as a scientist. This conference really clinched it for me. Within a year I was visiting the soil science department at Cornell for a workshop on molecular techniques used to study soil microbes. I started my M.S. in soil science in fall 2002.
What is the current focus of your PhD research at Cornell?
After completing my M.S. in 2005, I moved to the Department of Plant Pathology and Plant-Microbe Biology at Cornell. The goal of my dissertation research is to understand how the microorganisms in composts can prevent plant diseases. I’m extremely fortunate to be working with one of the leaders in this field, Dr. Eric Nelson, who has been working with disease suppressive composts and biocontrol microorganisms for several decades. I’m focusing on a model system in order to uncover the microbial mechanisms involved in compost-mediated disease suppression. As it stands now, preventing plant diseases with composts is not consistent enough for commercial growers to rely on this practice. Once scientists understand how suppression works, we’ll all be in a much better position to make and use consistently suppressive composts.
The model system I’m working with involved the complex interactions between a germinating cucumber seed, seed-colonizing microbes from vermicompost and the swimming zoospores of the damping off pathogen, Pythium aphanidermatum. I want to find out how the microbes present in vermicompost prevent zoospores from finding and/or infecting their host.
Can you share some interesting/important findings from your work?
First of all, the vermicomposted dairy manure that I work with consistently suppresses Pythium damping off in my model system. When I inoculate seeds grown in soil with swimming zoospores I get a high level of disease and most of the seedlings die. However when I amend the same soil with 40% vermicompost, seedling survival is significantly higher. We’ve been able to show that this case of disease suppression is biological in nature, meaning that it relies on the microbes and is not due to the chemical nature of the vermicompost. When we heat sterilize the vermicompost and use it in our bioassays, it offers no protection from disease.
I wanted to know how quickly Pythium zoospores could find germinating seeds in my experimental set up. By removing seeds at various time intervals, I documented that zoospores had arrived at the surface of most seeds sown in soil within 24 hours. This time point is very important, because whatever interactions are taking place to prevent disease must occur within this short amount of time. Because the zoospores are motile and can “swim” towards a germinating seed using chemical cues, we can use them in experiments to find out if this chemical signaling has been disrupted. We have preliminary evidence that microbes from the vermicompost are modifying the chemical cues released from germinating seeds in such a way that the zoospores can no longer find their host. So as we understand things right now, the zoospores are not killed by these microbes, they simply end up lost and swimming aimlessly due to the disrupted signaling between the host and the pathogen. I’m currently working to document this interaction in greater detail.
Some other findings your readers might be interested in are from my M.S. I worked on a project evaluating potting media amendments for organic tomato production with Dr.’s Anu Rangarajan, Janice Thies, Thanwalee Sooksa-Nguan, and Steven Culman (2004-2005). We found that a 20% vermicompost amendment to potting media produced the largest seedlings compared to other plant and compost based amendments. This was exciting for me because we were also using thermophilic compost made from the same starting materials in the study and the vermicompost performed better in this production system. Because the seedlings in the vermicompost treatments grew so fast, if they weren’t transplanted to the field right away, they could run out of nutrients. Remember, this is a certified organic system, so no synthetic liquid fertilizers were used and all of the nutrients had to be provided in the potting media. So Anu Rangarajan and Betsy Leonard conducted a follow up study where they evaluated mixtured of composts and vermicomposts with bone meal and other amendments. Mixing vermicompost with bone meal led to the highest quality transplants. We’re following up on this finding in on farm field trials this season as part of a larger vermicompost project. We found that seedling performance in vermicompost amended potting media depends on species. So while 20% amendments were great for tomato, we had to scale down to 10% or less for cabbage and delphinium. This is all information we’re hoping will be helpful for both organic and conventional growers developing their own potting media recipes.
Another interesting finding from the 2004-2005 tomato study was that the choice of potting media amendment impacted the bacterial community living on the tomato plants’ roots. We expected the different amendments to impact root-zone bacteria in the transplant plugs where roots were in direct contact with these materials. However, we tracked root bacteria after the seedlings were transplanted to field soil and were somewhat surprised to find significant treatment differences a month later. This means that even as the roots grow out of the original transplant plug and into the field soil, the bacterial communities continue to be influenced by the tablespoon or so of amendment that was in the plug. We found that in this case, tomato root bacteria were different depending on if they were grown in dairy manure that was thermophilically composted vs. vermicomposted. I found this interesting, but we would a lot more information before we can draw definitive conclusions about what effect the composting process has on the microbial communities present in these materials. Overall, we found that growers can influence the root zone bacteria for the life of the tomato plant just by choosing one type of potting media amendment over another. Once we understand more about how these changes in bacterial communities can translate into plant growth, yield and health, then we have the possibility of actually managing the rhizosphere, or root zone of our crop plants for optimum production.
You’ve worked with both thermophilic composts and vermicomposts – are there any consistent differences between these two end products in terms of disease suppression?
It’s really too early to draw these kinds of conclusions. There have been very few studies that effectively compare the different composting processes. Many of the scientific papers available say that they make this comparison, but then use a food scrap vermicompost and a sheep manure thermophilic compost. So this is like comparing apples to oranges. This is a great question, and I hope to provide some useful data in this area, but we need a whole team of compost scientists working on this one!
How important a role does the staring material play in disease suppression? (ie would a manure compost offer different disease fighting ability than a compost made from food waste?)
I’m only working with one type of feedstock, but I have seen some good comparisons in the literature. Polish scientist, Magdalena Szczech, and colleagues found that vermicompost made from cow, sheep and horse manure suppressed disease caused by Phytophthora infestans in tomato, while vermicomposted biosolids did not. There is a large body of scientific literature on disease suppressive thermophilic composts that deals with a range of feedstocks. However, it’s difficult to compare between studies because experimental methods can differ widely.
It’s my understanding that you’ve collaborated with RT Solutions (Worm Power). Can you tell us a little about that?
Sure. Scott Subler (now of Environmental Credit Corp. and previously a vermicomposter) introduced me to Tom Herlihy of RTS right after my talk at the U.S. Composting Council conference in Las Vegas in 2003. At that time Tom was a consulting engineer and the facility was just a gleam in his eye. Tom and I corresponded throughout my M.S. and we ended up using his material in our tomato study when his facility was up and running in 2005. Since then we’ve done a lot of grant writing together, successfully and unsuccessfully of course, which is how it goes! Right now Tom is on the advisory board for our NY Farm Viability Institute funded project “Potential use of vermicompost as a substitute for synthetic inputs to horticulture and nursery production”. My advisors, Eric Nelson and Anu Rangarjan are co-PI’s (principal investigators) on the project and Chuck Nicholson from Applied Economics and Management and Jean Bonhotal from Cornell Waste Management Institute are also involved. This season we put in 7 on-farm field trials with RTS’ “Worm Power” vermicompost and I’m continuing my work with disease suppression for this two year project. Tom, Eric and I also applied for the USDA’s Small Business Innovation Research (SBIR) program and were funded to develop biocontrol products out of vermicompost and non-aerated vermicompost extracts. We received matching funds for this project through Cornell’s Center for Biotechnology and the NY Science to Achieve Results Center for Advanced Tecnhology (NYSTAR CAT).
When I started my M.S. I was making my own vermicompost in the barn at Dilmun Hill student farm, so having the opportunity to collaborate with one of the largest vermicomposting businesses in North America is very exciting! Now I don’t have to say “Hey, it would be neat if someone would produce this material on a large scale so growers have access to it and we can learn more about how it performs in different systems.” Because that’s exactly the situation right now! It’s been a pleasure collaborating with RTS, because Tom and his team really value rigorous scientific inquiry. We’ve all learned a lot from each other. I can talk with confidence about sub-surface injecting liquid manure with a chisel plow and cap and trade carbon incentives for dairies, and I think you’d be impressed if you asked Tom about Pythium aphanidermatum zoospores!
Is there anything else you’d like to share?
As part of the NYFVI funded vermicompost study we’ll be hosting a workshop summer ’09 geared towards growers who are interested in learning more about vermicompost in different plant production systems and the results of ours and other studies. More information TBA!
Also, I have to say that I’m incredibly proud to live in Tompkins County, which has one of the highest home composting rates in the country thanks to the Tompkins County Cornell Cooperative Extension Compost Education Program. I took the Master Composter training in 2003 and have been involved in the program one way or another since then. It’s a great program run by my friend Adam Michaelides that has a huge impact in our community. I would encourage all hobby composters to talk to their county extension offices about starting up a Master Composter program if they don’t already have one. It’s a great way for composters to pass on their knowledge to people in the community who may be interested in composting, but don’t know how to get started.
I’d like to take this opportunity to once again thank Allison for her participation in this interview. If you would like to learn more about Allison’s work, be sure to pay a visit to the Cornell Vermicompost page.