Soil Talk: Preliminary Results for our Biochar-Enhanced Compost Return Praise

“It’s beautiful, light, dark, and rich!” - Sonder Farmstead (Image Source)

Preliminary results from our field trials are in! Partnering with Skagit Soils, KCT delivered biochar-enhanced compost (COMBI) to more than ten farms across Whatcom, Skagit, Island, Snohomish, and King Counties. Our goal: to measure the benefits of biochar for soil health and crop success when grown in COMBI versus traditional compost. 

Post COMBI delivery, here is what farmers are saying: 

  • "We are on our way to soil goodness!" ~Sonder Farmstead

  • "We just want to say how incredibly impressed we are with the quality and cleanliness of the biochar compost! It is the best we have ever seen delivered here or on other farms we have worked with!" ~Full Heart Farm 

  • "Our biochar came this week and it's beautiful...It is my understanding that it's magic!" ~East of Eden Farm

  • Onsite at the Cloud Mountain Farm Center, staff noted that COMBI smells different – that pungent, earthy, and sometimes acrid smell that often wafts from compost was remarkably less. 

Our biochar came this week and it’s beautiful...It is my understanding that it’s magic!
— East of Eden Farm

Preliminary sampling numbers tell the same story:

We sent soil samples to the lab for preliminary analysis. (Drumroll, please…) When evaluating the results produced by the biochar-enhanced compost, nearly all indicators of compost maturity and health improved, compared to standard compost made at the same time. (Raise your glasses – this is what we hoped would happen!) These indicators, such as nutrient retention, water holding capacity, and organic matter content, mean that the ability of the compost to benefit crops and sequester carbon is higher in COMBI. For you science enthusiasts, some of our specific test results showed the following: 

KCT staff and interns collecting soil samples

  • Total Nitrogen and organic Nitrogen increased to a healthy level 

  • Ammonia decreased, signaling compost maturity 

  • Nitrate increased

  • Phosphorus and Potassium decreased

  • pH decreased to a more crop-beneficial value 

  • Bulk density and carbonates decreased

  • Organic matter and stored Carbon increased, while CO2 respiration decreased

  • C: N ratio/composting efficiency increased

  • Metal content decreased

  • Fecal coliform significantly decreased

If you are interested in receiving a spreadsheet of full test result values, please let us know! 

Both anecdotally and in the lab, the biochar-enhanced compost looks better, smells better, and supports optimal growing conditions better – it’s like a five-star meal for plants. This is a huge step for KCT and our partners, in proving that excess biomass on farms (e.g. inedible stems, leaves, and weeds) and in forests can help increase food security through higher yields, and simultaneously draw down carbon from the atmosphere. 

We are thrilled about these initial results, and we cannot wait to see what happens in our next round of sampling.

We would like to send out a special “thank you!” to our farmer-producer participants for your invaluable observations of the compost. 

Hannah Stone

Hannah is the KCT Science Communications Coordinator, infusing her background in journalism, environmental studies, and experiential education to curate content and strategy for KCT. She graduated from U.C. Berkeley with a B.S. in Conservation and Resource Studies, with an emphasis on environmental justice, creative writing, and ecological dynamics. She also holds minors in Forestry and Food Systems. Hannah is passionate about deepening human-nature relationships to inform systems change.

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