The Use of Biochar in Agroforestry to Promote Soil Microbial Health, Tree Productivity, and Carbon Sequestration

Progress report for LNE22-452R

Project Type: Research Only
Funds awarded in 2022: $154,586.00
Projected End Date: 11/30/2025
Grant Recipient: Arthur's Point Farm
Region: Northeast
State: New York
Project Leader:
David Newman
Arthur's Point Farm
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Project Information


According to previous scientific studies, biochar’s vast surface area, porosity, and durability provide habitat for beneficial microbes, increase soil water-holding capacity, and enhance soil health and carbon storage (Brewer, et al., 2014; Yao, et al., 2012). Because biochar is fairly easy to produce and can utilize local biomass waste streams, it has the potential of being a widely available renewable resource. It has been studied in annual systems, but rarely in the perennial context of tree crops. Increased interest in regenerative farming and agroforestry to bolster the viability of agriculture in the region and to provide ecological benefits require new data to guide application and usage. Farmers are interested in biochar but have not widely adopted the practice due to a lack of practical knowledge on optimal management. This project will assess the effects of different treatments of biochar, compost, micronutrients, minerals, and microbes on the establishment and growth of a chestnut orchard over a three-year period. 

At the main research site, five treatments will be applied to 120 chestnut trees across three planting rows during the initial planting and on an annual basis thereafter, using locally-produced, lab-tested biochar from sustainably-sourced wood. The study will analyze 60 individual trees divided into 20 experimental units. The research will isolate the effects of straight biochar, straight compost, biochar mixed with compost, and biochar mixed with compost and amended with a mix of micronutrients and microorganisms. We hypothesize that the introduction of organisms and nutrients carried by biochar at establishment, and the subsequent annual treatments of biochar mixed with compost, will have the synergistic effects of increasing soil organic matter, microorganism abundance, plant uptake of nutrients, and the growth and productivity of the subject chestnut trees. Additionally, the use of biochar will return a stable form of carbon to the soil, which we expect will build soil carbon by increasing root growth and soil biota. 

A survey of Northeastern farmers conducted for this proposal showed broad interest in biochar’s potential as a soil amendment, but hesitancy due to a lack of information and data. This study will facilitate farmer engagement by convening a Farmer Working Group of 10 farmers to implement a small-scale trial of the five research treatments on their own farms. Over the duration of this project, farmers will attend two workshops at Arthur’s Point Farm and will collect visual observations on their chestnut trees. This group of farmers will be critical in providing the feedback that will assist in creating a pathway to farmer adoption of this novel approach to regenerative, climate-friendly farming.

Project Objective:

Interest in biochar is increasing as a means of enhancing long-term soil fertility and carbon sequestration. A lack of data and farmer experience related to biochar’s benefits and optimal management practices, especially regarding tree crops, is a significant constraint on broader adoption. This project aims to quantify the relationship between inoculated biochar and chestnut trees to provide farmers with a regenerative tool to increase crop vigor and yield. With growing interest in chestnut agroforestry in the Northeast, this project comes at an opportune time for farmers establishing new orchards and for future regional studies with biochar and other tree crops.


Materials and methods:

Treatments: The biochar used in this research is produced at Arthur’s Point Farm using low temperature pyrolysis (~450℃) from sustainably-harvested trees and waste wood from a local lumber mill. Compost is also produced on our farm from a mix of livestock manures, animal bedding, wood chips, and scraps from a local vegetable processing plant. Biochar-compost is produced by adding biochar into the compost mix at the beginning of the compost process. All trees throughout the five treatments will be mulched annually with 10 gallons of wood chips. Treatments 3, 4, and 5 require annual top dressings of compost variations, and all annual applications will occur in the spring, starting in 2022. Hand-weeding will occur as needed. Application rates are based on typical quantities recommended by leading biochar products. 

Treatment 1 (T1): Hybrid Chestnut (Castanea spp.) and Black locust (Robinia pseudoacacia) trees planted into native soil. This treatment represents the most commonly employed method of planting chestnuts. Planting into native soil provides a control for the other treatments.

Treatment 2 (T2): Four cups of raw biochar mixed with native soil in the planting hole. T2 analyzes how biochar reacts with native soil unaccompanied by introduced microbial life. 

Treatment 3 (T3): One gallon of compost mixed with native soil in planting holes, top-dressed annually with two gallons of compost. T3 tests the benefits of an accessible and commonly used soil amendment and controls for the effects of compost in the biochar treatments.

Treatment 4 (T4): One gallon of compost and four cups of biochar mixed with native soil in planting holes, top dressed annually with two gallons of biochar-compost. T4 is distinguished from T3 by the addition of biochar, both in the planting hole and mixed into annual top dressings.

Treatment 5 (T5): One gallon of compost, four cups of biochar, and four cups of an amendment of micronutrients, minerals, and beneficial microbes (“amendment”) mixed with native soil in planting holes, top-dressed annually with two gallons of biochar-compost. The amendment consists of alfalfa meal, oat meal, kelp meal, azomite, soil bacteria (Arthrobacter globiformis; Azospirillum brasilense; A. lipoferum; Azotobacter chroococum; A. paspali ; A. vinelandii; Bacillus amyloliquefaciens; B. atrophaeus; B. Licheniformis; B. megaterium; B. pumilus; B. subtilis; Brevibacillus brevis; Micrococcus luteus; Pseudomonas fluorescens; P. putida; Rhodopseudomonas palustris; Rhodospirillum rubrum; Streptomyces griseus) and soil mycorrhizae (Glomus intraradices; G. deserticola; G. etunicatum; G. clarum; G. claroideum; G. mosseae; Gigaspora albida). 

Methods: The main statistical research is being conducted on a field that has been continuously used for hay and pasture since at least the mid-19th century, resulting in compaction, nutrient deficiencies, and low organic matter. Three 800 foot rows spaced 20 feet apart were planted in the April 2022 with Hybrid Chestnut (Castanea spp.) and Black locust (Robinia pseudoacacia), alternating at 10 foot spacing (see Figure 1, Site Design). The field was prepared in the fall of 2020 with keyline plowing and planting rows were constructed using a single moldboard plow to create berms and swales to increase water infiltration. Each experimental row has 80 planting holes spaced 10 feet apart. The three research rows are divided vertically into twenty 12-tree blocks of 40 feet each to make one experimental unit in which all 12 trees within each unit will receive one of the five treatments (see Figure 2, Experimental Unit Design). Each experimental unit will have four iterations, meaning that each treatment will be applied to one 12-tree block four times. Three chestnuts per experimental unit will be studied, resulting in 60 total study trees in the experiment.

Figure 1 - Site Design Figure 2 - Experimental Design

Data Collection: Soil samples were taken taken in April, 2022 (and will be done again in 2024 and 2025) with a 1.5 inch diameter handheld corer to a depth of 30 centimeters. Three samples are taken per study tree and combined to submit one sample per tree for analysis. Soil sampling will occur semi-radially around the first chestnut in each experimental unit on each of the three rows (See Figure 3, Soil Sampling Design). The sampling circle has a radius of two and a half feet. Soil samples taken from around the study trees were analyzed for microbial abundance, carbon storage, and basic soil health. Microbial abundance consists of the quantitation of 17 soil microbial functional groups and 16 relationship indices which demonstrate the direct correlation between soil chemistry and microbial groups. Carbon tests include water soluble carbon and total organic carbon. Other soil health tests include potassium (K), sodium (Na), calcium (Ca), magnesium (Mg), storage phosphorus (P), Solvita CO2-burst, Solvita labile amino-nitrogen (SLAN), a volumetric aggregate stability test (VAST), nitrate, soil organic matter, pH, C:N ratio, and soil bulk density. To assess nutrient bioavailability, leaves were collected from a combination of the six chestnut trees in each experimental unit and Wood’s End Lab conducted a plant tissue test to measure levels of nitrogen, phosphorus, potassium, magnesium, calcium, sodium, sulfur, boron, zinc, manganese, iron, copper, and aluminum. Leaf tissue samples were collected in August 2022 and will be repeated again in August 2024 and 2025. Tree health and vigor was assessed in August 2022 by applying standard tree assessment protocols adapted from the Forest Ecology Monitoring Cooperative (Duncan, 2019), which includes live crown ratio, vigor, dieback, foliage transparency, defoliation, and foliage discoloration. Above ground biomass was determined using a generalized biomass equation (Chojnacky, 2014). Tree health and vigor will be assessed again in August 2024 and 2025. Deep carbon core samples were taken in March 2022 to a depth of one meter using a Geoprobe 54DT drill rig. Two deep carbon samples were taken in each experimental unit, between the rows, five feet above and below the central row, for a total of 40 samples. Deep core carbon samples will be taken again in the spring of 2025. All data will be collected using standardized data sheets in the field and will be transferred to Excel. Please note that we decided not to collect data in 2023 to save costs and allow us to do the full suite of tests in 2024 and 2025 (growing seasons 3 and 4 of the project). We're hoping this provides greater contrast in the results given the longer timeline without any impact in completing the project by the end of 2025.

Farmer Working Group Satellite Research: The ten Farmer Working Group participants were each asked to replicate the research treatments on their respective home farms and were provided with five chestnuts and five black locusts, along with all the materials necessary to apply the research treatments. Each farmer was asked to make visual observation on the health and growth rate of their trees and report back to the research team. Due to budget limitations and logistical challenges, the research was not designed to collect soil samples for these small satellite trials. The farmer observations have been documented in a survey form that follows the same protocol we will use in assessing tree health and vigor at the main research site at Arthur’s Point Farm. Three of the farm participants did not complete these tasks for different reasons - either because they did not manage to plant the research trees or neglected to care for them - and are no longer participating in the satellite trials or the Farmer Working Group. 

Research results and discussion:

The first year's data are intended to provide a baseline for future analysis and to identify underlying variables unrelated to the research treatments. Accordingly, there is little analysis to interpret and report. We have included a summary report from Woods End Lab describing the analysis that was conducted in the first year, as well as the raw data from the first year's sampling.

2022 Summary Data Report

2022 Visual Observations Data

2022 Total Carbon Macro-core Data

2022 Soil Sampling Data

2022 Leaf Tissue Data

Participation Summary
7 Farmers participating in research

Education & Outreach Activities and Participation Summary

Educational activities:

3 Curricula, factsheets or educational tools
3 On-farm demonstrations
6 Tours
2 Webinars / talks / presentations
3 Workshop field days
3 Other educational activities: Individual calls with the three Farmer Advisors reviewing the first year's work and discussing ways in which we can continue to engage farmers in the coming years.

Participation Summary:

15 Farmers participated
1 Number of agricultural educator or service providers reached through education and outreach activities
Outreach description:

We conducted an inaugural workshop with the Farm Working Group and collaborating research scientists in March of 2022 (slide presentation). We provided an overview of biochar and described the details of the research being conducted at Arthur's Point and the sample trials that the Working Group members are undertaking on their home farms. We toured the farm and showed the farmers how we currently make and use biochar. We had in-depth discussions about various related topics and then provided the farmers with their research kits (5 chestnut and 5 black locust seedlings, biochar, compost, soil amendment, tree tubes, weed mats, and written instructions). In late 2022, we sent an update to the Farmer Working Group on the research and outreach efforts. We also conducted one-on-one meetings with the three Farmer Advisory Group members.

We presented on the use of biochar and compost on a 2022 Connecticut Compost Webinar Series hosted by the CT Department of Resource Conservation & Development in March of 2022 with over 100 attendees. This presentation included an overview of the SARE project (video recording here).

We also published a blog on our website announcing the launch of the project as well as another blog promoting a bill in Congress that would create a national biochar research network. We discussed our use of biochar with the local USDA Natural Resource Conservation Service extension office during a visit to the farm this past summer. We discussed the newly established soil practice for biochar and was told that they hope to begin offering payment for services through CRP in 2023. 

In addition, we hosted two workshops in 2022 with substantial focusses on biochar, including the SARE project work, one for the Berkshire Botanical Garden and the other for the Climate Farm School (presentation).

The SARE research project was also referenced in a report by the American Farmland Trust, the National Center for Appropriate Technology, and the Foundation for Food & Agriculture Research entitled "Scaling Sustainable Biochar Research Commercialization for Agriculture Conservation," published in December of 2022.

In December of 2022, we were interviewed for the Nature Calls podcast, focusing on agroforestry, biochar, and ecological resilience. The episode can be accessed here

In September of 2022 and 2023, Arthur's Point Farm participated in the Chatham Area Farm Tour, which brought over 50 visitors to the farm each year. Participants were shown the biochar production process on the farm and were given an overview of the SARE research project. In 2022, Arthur's Point Farm also helped to organize the first ever Columbia County Climate Carnival, where we had a booth focused on climate-friendly farming, including with biochar and native perennial plantings. The County is planning another Climate Carnival in September 2024, which we plan to participate in. 

Information Products

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.