Planning, Preparing, and Planting Minnesota Biochar Test Gardens (Part 3)

In two previous blog posts, I gave an overview of what we are seeking to learn through this biochar research project, and how we chose and added biochar to the test gardens.  Early in the planning, we first needed to find three locations to implement the gardens.  Next Extension Master Gardener volunteers needed to be recruited and trained about the project.

As part of this CenUSA Bioenergy project, Master Gardener volunteers completed a specialized training to learn about biochar and the CenUSA grant that supports it.  Each of the three sites in Minnesota has one or two team leaders and approximately 10 other volunteers per site.  Master Gardeners were involved in many facets of the research including planting and maintaining gardens, collecting data measurements and harvesting crops as needed.  They were asked to share their observations at the State or County fairs, horticulture field days or other community events.

How We Selected the Minnesota Biochar Test Garden Sites

All of the sites in Minnesota and Iowa needed to be identical in size because the same number of crops needed to be grown at each site. All of the gardens are 1000 sq ft and each site is divided into three plots of 300 sq ft.  Each site has a control plot with no biochar added, treatment 1 has 150 pounds of biochar and treatment 2 has 300 pounds of biochar.

It was also important to have locations with different types of soil to see how the biochar would react with the crops.  All three sites in Minnesota had to be developed from its original condition, meaning two of them had turf that needed to be removed and one was actually in an area filled with underbrush, small trees and weeds.  Soil tests were also conducted at each site and the gardens were amended with fertilizer based on the recommendations of the soil tests.

Biochar Test Gardens and MN Landscape Arboretum
Biochar Test Gardens at the MN Landscape Arboretum

Each site had its own unique issues with watering.  While we tried to replicate what a typical homeowner would do,the Arboretum site became the most labor intensive.  There was a sprinkler head close by, but the Master Gardener volunteers needed to run hoses and water by hand. The other two sites had irrigation that was scheduled by timers.

1) The Minnesota Landscape Arboretum Test Garden

Selecting the Arboretum as a site for this project was a no-brainer.  The Arboretum gets well over a quarter million visitors per year.  It was a great location to showcase this research project.  A couple of site locations at the Arboretum were considered.  Ultimately, the final decision was made and the biochar test garden is located on the 3-mile drive next to the Dahlia Trial Gardens.

Thankfully, the Arboretum staff removed the sod and tilled the soil to loosen it before we began.  One of our fabulous Master Gardener volunteers also offered to install deer proof fencing…a must have.  My colleague Julie, and I, amended the soil with fertilizer and biochar on May 18th.  It also happened to be a 97 degree day with high humidity to-boot. Ugh! Our soil test recommended that we use a nitrogen-only fertilizer with a ratio of 23-0-0.  The soil at the Arboretum site is loamy clay – not too terrible to work in.  The biochar arrived in 50 pound bags, so we just opened the end of the bags and slowly dragged the biochar over the areas of the garden where we needed it, and then my colleague tilled the biochar and the nitrogen fertilizer into the soil at the same time.

2) The St. Paul Campus Test Garden

The garden at the St. Paul Campus located at the intersections of Gortner and Folwell Avenues, was another great location. It is in close proximity to the Display and Trial Gardens and is visited regularly by students, staff, faculty and visitors.   The actual site was a former low-mow turf trial plot.  The sod was not removed but instead was tilled into the soil, which in hindsight we should have asked that it be removed.  The soil also has a fair amount of clay in it.  Because this site was irrigated regularly and wet when we started, it was challenging to work in.

The soil test in this garden also recommended a nitrogen only fertilizer of 23-0-0, the same as the Arboretum site.  The tiller got its workout that morning when trying to mix in the biochar and the fertilizer in the lumpy wet clay mess.  Deer isn’t a problem at this site, but rabbits are so a short fence was installed.

Biochar Test Gardens in St. Paul, MN

3) Bunker Hills Park in Andover Test Garden

The Andover site was a last minute surprise and a very exciting prospect. We originally had a site selected at UMore Park in Dakota County which is on the south end of the Twin Cities.  A new mining operation expanded in that area and there was uncertainty about whether the biochar research garden could remain in the same location for four years.

All along I had my eyes on the Regional and County Extension office location in the Anoka County Bunker Hills Park in Andover as a potential site for the biochar project.  The reason I was hoping for this site is because it is on the north end of the Twin Cities and in the middle of the Anoka sand plain.  Since biochar is known to have positive benefits in nutrient depleted soils, this sandy site was a good option. When I explained the issues about the Dakota County site to the Anoka County Parks Department staff, they were more than willing to accommodate the needs of the project.  Not only did they bring in a Bobcat and clear out an existing area of small trees and underbrush, they also enhanced their irrigation system to allow us to set a sprinkler that was set-up on a timer.  In addition, they brought in a couple of loads of mulch to help beautify and complete the project.  Since this garden is in a large suburban park, a deer fence needed to be constructed there as well.

Biochar Test Gardens at Andover
Biochar Test Gardens at Andover

The soil test recommended a well-rounded fertilizer with a 10-10-10 ratio. One variable in this garden, that presumably will affect the research, and that isn’t present in the other sites, is that one end of the garden gets shade in the morning hours, but full sun the rest of the day. Because of this, it was anticipated that crops would not get as much heat stress as the rest of the garden and the water would not evaporate as quickly, so there was a good chance those plants would be healthier overall from the other two treatments.

What’s next?

We learned a lot the first year (2012) about the sites themselves, how the biochar interacted with the soils, and how data is best collected.  Next week, we’ll share what we learned from our 2012 data collection and research with the CenUSA Bioenergy project.

by Lynne Davenport-Hagen
University of Minnesota Extension
Master Gardener Program Coordinator-Anoka County
CenUSA Biochar Research & Display Garden Project Coordinator-USDA NIFA Grant

“The CenUSA Bioenergy project is supported by Agriculture and Food Research Initiative Competitive Grant No. 2011-68005-30411 from the National Institute of Food and Agriculture.”

Choosing and Using Biochar for Research in Biochar Test Gardens (Part 2)

U of MN Extension Master Gardener applying biochar in test gardens

As I mentioned in my last blog post, Extension Master Gardeners in Minnesota and Iowa are researching whether biochar would be a suitable soil amendment in home gardens.

Biochar can come from many different products, from grasses to hardwoods, and from most anything that can burn.  Before I move forward, I need to back up here a little. In the bigger picture of the CenUSA Bioenergy project, one of the goals is to develop sustainable perennial grasses as primary energy crops for the purpose of developing biofuels. (Learn more in this Harvesting Native Grass for Biofuel Production YouTube video.)

When the time comes that perennial grasses will be used on a regular basis for biofuel production, there will be a lot of byproduct that could be repurposed in the form of granulated biochar, and one way that biochar be can used is as a soil amendment.

What Biochar Are We Using in Test Gardens? Why?

Biochar used in test gardens

Now, you might be thinking there is a twist to this story because the biochar we are using and evaluating in test plot gardens is not from grasses, but actually from hardwood (shrub and tree) species! Why, you ask?

Ideally we were hoping to find biochar that was processed from switchgrass or other perennial grasses.  Since biochar is a relatively new product and very few processing plants are licensed to produce it, especially in the quantities we needed, we welcomed the next best option.

We did find biochar in the granular size that we needed from Royal Oak charcoal company.  The biochar they had was processed from hardwoods. The decision makers at Royal Oak were interested in being part of our research project so they were gracious enough to donate it.

The grass and hardwood biochars may not be the same, but at least they are similar. It’s not like using biochar from feathers, manure or pine needles. And, since there is much we (researchers) do not know about using biochar in gardens, researching one type of biochar across multiple test plots in several states will give us clues to see how the same biochar reacts in different soils and climates.

Remember, our overall objective is to replicate gardens that a typical homeowner would have, so we wanted a variety of soil types to test and while we are testing only one form of biochar, there are other researchers testing many other kinds.

Adding Biochar to Gardens Using Biochar Safety Sheets and Guidelines

Following health and safety guidelines for applying biochar to test gardens

The biochar was shipped in 50 pound bags.  It had a granular texture and was about the size and consistency of course fertilizer.  I have been asked if biochar has an odor…and the answer is YES. It smells like burnt wood but it wasn’t too strong, and the odor doesn’t linger.  You may get an urge to roast some hot dogs and marshmallows initially, but not for long.

Before we could apply the biochar to the test gardens, we asked some of our CenUSA Bioenergy partners to develop safety guidelines for applying it. Since this product is not on the consumer market, those kinds of things had not taken place yet.

We did learn that biochar is considered a combustible material and there are specific guidelines on how best to store anything ignitable.  In addition, biochar can be dusty so it was recommended to not apply it on a windy day. We were also advised to wear dust masks, gloves and protective clothing….mostly to protect from the dust.

Applying the biochar was fairly easy.  We just cut open the end of each bag and carefully dragged them across the areas we wanted it and then rototilled it in to a depth of about 6 inches.  If we were to apply this on a larger plot of land, it could be applied with a fertilizer spreader.  The way we did it had very little dust.   For the purpose of this research, biochar will only be applied the one time.

The next steps past amending the soil with biochar was in prepping, and planting the gardens, but we’ll get to that next week, as we continue to blog about our biochar research story through the CenUSA Bioenergy project.

by Lynne Davenport-Hagen
University of Minnesota Extension
Master Gardener Program Coordinator-Anoka County
CenUSA Biochar Research & Display Garden Project Coordinator-USDA NIFA Grant


“The CenUSA Bioenergy project is supported by Agriculture and Food Research Initiative Competitive Grant No. 2011-68005-30411 from the National Institute of Food and Agriculture.”

CenUSA Bioenergy Project: What Master Gardeners are learning about biochar, soils, and bioenergy (Part 1)


As part of the CenUSA Bioenergy research project, Extension Master Gardeners in Iowa and Minnesota are doing research to explore to see if biochar makes a good soil amendment for growing flowers and vegetables in the home garden.


What is biochar?  In a nutshell it is a new term for an old product…charcoal.  The soil scientists working on the CenUSA Bioenergy project are really good about explaining the differences between biochar based on the type of biomass it’s processed from or the way it is actually processed.

All Biochar is Not Created Equal, Which is Why We are Researching Its Use in Gardens

Because not all biochar is created equal,  when people get excited about wanting to add biochar to their gardens (or garden soils, technically), I try to encourage them to wait until there is more research and some credible labeling and standardization of biochar products before diving in.  There is a lot of  hype and misinformation that’s out there.  I can’t imagine what would happen if people started adding biochar to their soil every year much like fertilizer…if too much is added, it could prove to be pretty negative on the soil (with long term consequences).

Different materials and processing lead to variable biochar outcomes

Since biochar is a form of carbon, it can last in the soil for decades (depending on how it’s processed). Biochar is a complicated product. It can be processed from many materials.  There are many ways of processing it which also produces differing results.  When those variables are combined with a variety of soils, it results in many different outcomes. I have learned that in current research projects, there are some plants that have shown beneficial results from using biochar such as flowers or leafy kale and in other cases there were negative results such as tomatoes and in some trials, adding biochar as a soil amendment made no substantial difference in plant growth.

With that said, there is still a lot of research that needs to take place before using biochar to grow flowers and vegetables in the home garden.  Some careful research has shown that in some soils, especially sandy or nutrient-depleted soils, biochar has shown improved plant yields on select crops.  This may be due to better soil structure and improved moisture and nutrient retention from the use of biochar. On the flip side, there are some biochars that have been tested and had some negative results  – showing that it may actually rob the nutrients from already healthy soils, and some biochars may actually possess potentially toxic chemicals. Researchers on our project and elsewhere are also trying to measure if there is a net benefit of reducing atmospheric carbon dioxide when it’s weighed against the amount of carbon needed to produce it.

In closing my thoughts on biochar, I would encourage people to do their homework and search credible sources for research that has been conducted.  The use of biochar seems to raise more questions than answers. I believe it will take more time and research before “designer” biochars can be regulated and sold for the home gardener.

The Story of Extension Master Gardeners Researching Biochar Has Just Begun

In 2012, Extension Master Gardeners were asked to help support biochar research for this Cenusa Bioenergy project by planning, preparing, and ultimately planting test plots in concert with University of Minnesota and Iowa State University. I have been the project coordinator on this project for the past year for the University of Minnesota test plots.  It has been a year of learning and trial and error (which is really what is so fun and rewarding about this project)!

In the next couple weeks, I’ll get a chance to tell more about our research story on this blog, including how we selected our biochar, what safety recommendations we used, how we chose our test plots, what we planted, how it grew the first year and what we learned in our first season that will help us in the coming year’s research.

In the meantime, you can begin to see how Master Gardeners are involved in this much bigger project to create a midwestern regional system for producing advanced biofuels in this 2012 CenUSA Bioenergy Overview YouTube video


by Lynne Davenport-Hagen
University of Minnesota Extension
Master Gardener Program Coordinator-Anoka County
CenUSA Biochar Research & Display Garden Project Coordinator-USDA NIFA Grant


“The CenUSA Bioenergy project is supported by Agriculture and Food Research Initiative Competitive Grant No. 2011-68005-30411 from the National Institute of Food and Agriculture.”