Learning How To Measure Carbon In Soils

Hudson Carbon has developed a set of monitoring protocols aimed at developing a greater understanding of how carbon cycles through an agricultural ecosystem. Our monitoring methodology is based on measuring the fluctuations of carbon at each testing site, from season to season, and correlating these changes to specific agricultural practices. With this data, we can then develop a set of metrics to employ in a large-scale monitoring program, in order to allow farmers to demonstrate quantifiable ecosystem services that their managed land is providing, for which they can seek compensation in a voluntary ecosystem service market. See more about how our results are impacting Policy at a national level.



Field Sampling


At each testing site, we gather data from sampling points laid out in a triangular grid pattern. We gather plant biomass and surface litter samples once a month during the growing season, from April to November. We take soil core samples once every spring. With a portable greenhouse gas analyzer, we are able to measure the flux of carbon dioxide, methane, and nitrous oxide, in and around the plant canopy – giving us the ability to calculate the rates of photosynthesis and respiration, as well as methane and nitrous oxide emissions.



Lab Testing


In our lab, we air and oven dry our plant biomass and litter samples, and calculate carbon content from dry-matter weight. We have also implemented a set of soil classification testing protocols, carried out in our lab, that we perform on our soil core samples from each testing site. To determine organic matter content, we calculate bulk density and perform loss-on-ignition testing. We perform a water-stable aggregation test to measure aggregate stability. We also apply wet and dry sieving, and elutriation, to determine the sand, silt, and clay content. These tests are performed every season on each meter-deep core sample, which is divided into 5 layers. With this data, we are able to observe both the fluctuation in carbon content throughout the soil horizons, as well as fluctuations in sand, silt and clay content over time. We can also draw correlations between soil composition and rate of soil carbon build-up over time.





In order to draw correlations between our carbon cycle data and our farming practices, we keep detailed records of all agricultural tasks performed on each site. Season to season, we keep track of tillage type, depth, and frequency, cash crop and cover crop seed variety and planting rates, fertilizer and amendment application, stocking densities, grazing periods, and harvest yields. We also track fuel consumption of our equipment. We record this information using agricultural data management programs, which allow us to create detailed timelines for each field, planting, application, and yield maps, as well as to track fuel consumption of our equipment.



Moving Forward


In 2018 we significantly expanded the scope of our carbon cycle data collection, in partnership with Dr. Jianwu Tang of the Woods Hole Marine Biological Laboratory. We began a three-year project using the Li-Cor Eddy Covariance method to enhance our measurements of greenhouse gas flux, as well as launching specialized cameras to measure Solar Induced Fluorescence, or SIF, in plants, a process directly influenced by photosynthesis. This project is designed to compare two separate fields: one under organic management, and one under conventional management, implementing an identical, three-year cropping rotation. A Li-Cor Eddy Covariance tower equipped with a SIF camera will be positioned at one of our existing sites at Stone House Farm, and another will be positioned at a site at the neighboring Kukon Brothers Farm, our newest research partner.


At each site, we gather a set of data points that measure both the carbon and nitrogen cycles. The Eddy Flux tower and the SIF lens, in tandem with portable greenhouse gas flux monitoring, measure the rate of photosynthesis and respiration across the entire field over the growing season. Plant biomass, litter, and soil are sampled throughout the growing season and tested for carbon content, as well as nitrogen content. Using custom lysimeters, we test leached water coming off the field for nitrate, phosphorus, and dissolved organic carbon. Our portable greenhouse gas analyzers will also measure nitrous oxide emissions to complete the picture of nitrogen loss at each site. With this data, we are able to measure the difference between an organic management system and a conventional management system in their impacts on nitrogen and carbon cycling. A third Eddy Flux tower will be positioned in a pasture under intensive grazing management at the Churchtown Dairy. This study will focus heavily on the methane cycle, as well as CO2 and nitrogen, in order to better understand the impact of intensively managed ruminants on pasture.


We are also working with the Woods Hole Marine Biological Laboratory to create an aerial monitoring program using SIF and UAV technology. We are devising a hardware mounting system and a data collection platform to attach an SIF camera to a drone to remotely measure photosynthesis over our testing sites. In combination with a RGB and Infrared imagery, we will use the aerial SIF camera to map our testing sites from the air. Using data gathered by the Eddy Flux system and supporting ground data, we can accurately create a model that will allow us to remotely monitor the carbon cycle from the air over larger tracts of land.


See our latest results, live

We're collecting a variety of data in relation to our carbon sequestration project. We are working to publish this data regularly. But we also want  to share real time results so you can watch the trends we are seeing. Check out this page for our latest results.



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Hudson Carbon works to demonstrate the powerful role of regenerative agricultural practices in reviving ecosystems and mitigating the effects of climate change.

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