Progress report for FNE20-967
There has been substantial research into the accumulation of nutrients in plant tissue, with some plants widely championed as “dynamic accumulators” for their high concentrations of specific nutrients. This has led some farmers to grow dynamic accumulators for use in on-farm mulch and fertilizer production. However, there is a distinct lack of research establishing whether these nutrients carry over from plant tissue to soil health, and at present the claim that dynamic accumulators can be used to enrich the soil with specific nutrients is largely based on anecdotal reports.
This study aims to establish clear parameters for the identification of dynamic accumulators and perform on-farm trials to determine soil health impacts of six promising species available to Northeast farmers in zone 4 or greater. Soil tests will be performed to track nutrient values over two years of cultivation. Plant tissue will be heavily harvested and weighed to determine estimates for crop yields. Plant tissue will be used to produce both mulches and liquid fertilizers, and nutrient values tested to assess the soil health benefits farmers can expect from these practices.
Publicity through social media, fact sheets, media outreach, and speaking engagements will be used to raise awareness of dynamic accumulators and their potential applications; instruct farmers on best practices for the on-farm production and application of mulches and liquid fertilizers derived from six dynamic accumulators; and to make recommendations for further research.
This project seeks to assess six plant species for use as dynamic accumulators (DAs) on Northeast farms (zone 4 or greater). Rows planted with six potential DAs undergo soil testing over a two year period, tracking nutrient levels in three major soil horizons (0-6", 6-12", 12-24"). Nutrient levels in DA plant tissue and rows mulched with this tissue are measured, assessing the use of DAs for nutrient-rich mulch production. Liquid fertilizers produced from DAs are tested to assess nutrient carry-over to soluble fertilizer.
Farmers are then instructed on best practices for on-farm production and application of mulches and liquid fertilizers derived from these six DAs. Social media, fact sheets, media outreach, and speaking engagements are used to raise awareness of DAs and to make recommendations for further research.
If proven effective, DAs could provide economic and environmental benefits for farmers. Farmers previously reliant on purchased mulches or chemical fertilizers would be able to produce money-saving, plant-based alternatives on-site, choosing from a variety of DA species to address specific nutrient deficiencies. Deep-rooted DAs could be incorporated in farm plans to recover nutrients otherwise lost through leaching. Nutrient runoff, including nitrate runoff, could be addressed by planting riparian buffers that incorporate DAs.
Dynamic accumulators (DAs) are plants that gather certain nutrients from the soil and store them at high concentrations in their tissues. This plant material can then be harvested and used in organic liquid fertilizer or nutrient-rich mulch. Since the 1980s, farmers have been using DAs to draw up nutrients from deep underground and to recover soluble nutrients that would otherwise leach into the subsoil or run off into waterways (Brown, 2015). In recent years, both MOFGA (Maine Organic Farmers and Gardeners Association, with a membership of over 6,000 farms) and NOFA-Massachusetts (Northeast Organic Farmers Association, over 1,000 members) have promoted the use of DAs for sustainable nutrient management (Rawson, 2013; Walke, 2011).
However, there has been very little research to verify the claims surrounding DAs. Kourik (1986) is commonly cited as one of the first to compile a list of DAs and their benefits, with a similar list compiled recently by Hemenway (2009). But both of these authors have since stated that their lists relied on unproven, anecdotal reports (Kourik, 2014; Hemenway, 2015)
This presents a problem: dynamic accumulators are already being incorporated into nutrient management plans, but there has not been sufficient research to prove the merit of this practice. Until this research is done, the use of DAs is not a viable nutrient management practice.
Kourik (2014) identifies three research steps that should be taken to verify the efficacy of using a plant for dynamic accumulation. The first step is to determine nutrient values for plant tissue samples of potential DAs and compare these with established averages among plants, using USDA’s “Phytochemical and Ethnobotanical Databases" (Kourik, 2014; Duke, 2016). During the first stage of research for SARE Grant FNE20-967, a list was assembled of over 100 plant species that have reportedly been used as DAs worldwide. After selecting for plants that would be viable on Northeast farms (zone 4 or greater), plants’ nutrient values were compared with averages drawn from the thousands of plant species in the USDA databases. This resulted in a list of 6 plant species that demonstrate very high concentrations of specific nutrients: Amaranthus retroflexus (Redroot Amaranth), Chenopodium album (Lambsquarters), Symphytum peregrinum (Russian Comfrey), Taraxacum officinale (Dandelion), Trifolium pratense (Red Clover), and Urtica dioica (Stinging Nettle). The results of this analysis were published to the Permaculture Research Institute website in March 2020.
Now that Kourik’s first research step has been addressed, the next step is to perform on-farm trials. These trials are currently being carried out at Unadilla Community Farm over a 2-year period. During the first year, test rows are planted with each of the species listed above. These rows are cared for and allowed to establish over the course of the first year. In the second year, the rows will be harvested, and harvested material weighed. This will address Kourik’s second research step: to establish estimates for crop yields.
Kourik’s third research step, to establish the changes in soil nutrient values resulting from DA cultivation, will be addressed in 3 parts. First, nutrient levels in rows planted with DAs will be tracked over a 2-year period, to assess the use of DAs to prevent nutrient leaching or runoff. Second, nutrient levels in rows mulched with DA plant tissue will be tracked, to assess the use of DAs for nutrient-rich mulch production. And third, liquid fertilizers produced from DAs will be tested to assess nutrient carry-over from plant tissue to soluble fertilizer.
With this information, farmers will be instructed on best practices for the on-farm production and application of mulches and liquid fertilizers derived from these six DAs. Publicity through social media, fact sheets, media outreach, and speaking engagements will be used to raise awareness of dynamic accumulators and their potential applications, and to make recommendations for further research.
For researchers, this study would be the first that examines DAs following Kourik’s recommendations, setting a new precedent for accurate and consistent DA research moving forward. The methods used could then be replicated with other potential DAs around the world.
For farmers, this study would prove or disprove the efficacy of a widely known nutrient management practice. If proven effective, DAs could become a valuable resource for farmers, with economic and environmental benefits. Farmers previously reliant on purchased mulches or chemical fertilizers would be able to produce money-saving, plant-based alternatives on-site, choosing from a variety of DA species to address specific nutrient deficiencies. Deep-rooted DAs could be incorporated in farm plans to recover nutrients otherwise lost through leaching. Nutrient runoff, including nitrate runoff, could be addressed by planting riparian buffers that incorporate DAs.
Greta Zarro is currently serving as the President of the Board of Directors and as the Internship Coordinator at Unadilla Community Farm, a 12-acre off-grid organic farm and nonprofit permaculture education center in West Edmeston, NY. Founded in 2014, the farm currently runs a seasonal accredited beginning farmer training program as well as a veggie box delivery program. As a center for sustainable education, the farm showcases a diversity of USDA NRCS conservation practices, such as rainwater collection, multi-story and alley cropping, no-till management, wildlife habitat planting, heavy mulching, on-site composting, crop rotation, and high tunnels. The farm grows 200+ varieties of organic annual and perennial vegetables, mushrooms, herbs, and cold-hardy fruits, nuts, and berries. The farm is currently serving as the research site for SARE Project FNE20-967, "Researching and Raising Awareness of Dynamic Accumulator Plants in the Northeast."
- - Technical Advisor
- (Educator and Researcher)
During the first stage of research for this project, a list was assembled of over 100 plant species that have reportedly been used as DAs worldwide. After selecting for plants that would be viable on Northeast farms (zone 4 or greater), plants’ nutrient values were compared with averages drawn from the thousands of plant species on file in the USDA’s “Phytochemical and Ethnobotanical Databases." This resulted in a list of 6 plant species that demonstrate very high concentrations of specific nutrients: Amaranthus retroflexus (Redroot Amaranth), Chenopodium album (Lambsquarters), Symphytum peregrinum (Russian Comfrey), Taraxacum officinale (Dandelion), Trifolium pratense (Red Clover), and Urtica dioica (Stinging Nettle). The results of this analysis were published to the Permaculture Research Institute website in March 2020. This project seeks to assess these six plant species for use as dynamic accumulators (DAs) on Northeast farms (zone 4 or greater).
This project spans a two-year period: during the first year (2020), these six species were planted in twelve test rows, two rows dedicated to each species. A thirteenth row was left fallow for the duration of this project, to serve as a control group. Test rows measure 2.5 feet wide and 30 feet long, equaling 75 square feet each. Soil testing at depths of 0-6 inches, 6-12 inches, and 12-24 inches was conducted in May 2020, prior to planting.
During the second year (2021), these test rows will be heavily harvested to produce mulches and liquid fertilizers for subsequent testing. Soil testing will be repeated in May 2021 (after one year of cultivation), and again in the autumn of 2021 (after two years of cultivation). The thirteenth row, left fallow, is also being tested at these times. The objectives of soil testing are as follows:
- To determine whether deep-rooted DAs are primarily gathering nutrients from the upper 6 inches of soil, or from deeper underground, to assess the application of deep-rooted DAs for subsoil nutrient accumulation.
- To measure the rate of accumulation for DAs absorbing specific nutrients in the topsoil, to assess the application of DAs to address leaching or runoff of specific nutrients.
- For rows that are being mulched with DA plant tissue (explained in detail below), these soil tests will measure the release of nutrients from this mulch into the topsoil, to assess the use of DAs for nutrient-rich mulch production.
During 2021 (the second year of cultivation), all twelve test rows will be harvested and plant material weighed. This will be done up to four times throughout the second year, as appropriate for each species, to determine annual crop yield estimates. That harvested plant material will be used in one of three ways:
1. Plant tissue samples from each of the six species will be tested through ash analysis, conducted by Cornell, to determine nutrient values. This data will help to assess the carryover of nutrients from plant tissue to mulch and liquid fertilizer.
2. For six rows (one row of each species), immediately following each harvest, plant material harvested from that row will be applied as a mulch, 2-3 inches thick, following NRCS’s recommendations for mulching with fresh plant material. The effects of this practice on nutrient levels in the topsoil will be determined through soil testing, as mentioned earlier.
3. For the other six rows (one row of each species), plant material will be used to produce liquid fertilizer after each harvest. 275-gallon IBC totes and 5-gallon plastic buckets will be used to produce liquid fertilizer, as the global ubiquity and low cost of these containers make them ideal for on-farm use. Following the recommendations of Brinton (2011), non-aerated liquid plant extracts will be produced from each of the six species being tested: fresh plant material will be combined with rainwater at a ratio of 1:10 by weight.
Rainwater will be used to minimize the presence of dissolved solids in the water, which could affect test results. The rainwater will be tested prior to use in this study. There is already a rainwater catchment system on-site at Unadilla Community Farm.
Batches of liquid fertilizer will be left to steep for 5 days without agitation. Brinton recommends a steep time of 3 days with a temperature of 72 degrees, but up to 5 days of steeping may be required at lower temperatures. We will monitor the liquid temperature of these tanks and test fertilizer nutrient content and pH after 3 and 5 days to determine more specific recommendations for Northeast farmers who may be operating at less than ideal temperatures.
Liquid fertilizer test results will be used to determine optimal steep times at a range of temperatures, as well as optimal dilution rates to avoid excessive nitrogen, sodium, or chloride. The resulting liquid fertilizer nutrient values will demonstrate the efficacy of using DAs for the on-farm production of liquid fertilizers high in specific nutrients.
Education & Outreach Activities and Participation Summary
In 2020, we presented our ongoing research on the Plant Cunning podcast, through a webinar with the Finger Lakes Permaculture Institute, during two on-farm seminars as part of Unadilla Community Farm's beginning farmer training program (Permaculture Internship), and through an article published by the Permaculture Research Institute.
Furthermore, the 2020 cohort of 25 interns in Unadilla Community Farm's internship program from May-September 2020 participated in all aspects of the research process carried out at the farm, from soil test sampling to direct seeding and transplanting seedlings of dynamic accumulator test crops to weeding, mulching, and irrigating the test rows throughout the season.