Progress report for LNE23-477R
Project Information
Sphagnum peat moss is an important component of greenhouse and nursery plant potting media, but mining of the material is unsustainable due to its negative environmental impacts. Several European countries have banned the sale of peat to consumers, and restrictions are likely to be extended to the horticultural industry. Restrictions on the sale of peat are expected to expand to Canada, which is the major supplier of peat to the United States. Hurd is a byproduct of all hemp growing operations (fiber, grain, medicinal) and is an untapped renewable material. Milled hurd is similar to peat in many characteristics (porosity and water-holding capacity) and can likely serve as a substitute in container media. The novel approach is to repurpose hemp hurd fiber as a substitute for peat moss in container growing media for the production of horticultural crops. Research is needed to ascertain the amount of hurd that may be substituted for peat, what crop groups may be grown using hurd, and the impact hurd will have on nutrient availability. Outdoor nursery and indoor greenhouse production studies will be conducted to evaluate if hemp hurd can be used to fully or partially (33% or 66%) replace peat in growing media for crops of woody plants (evergreen and deciduous), herbaceous perennials and ornamental grasses, bedding plants, and vegetables. The availability of nutrients in hurd substituted media compared to peat-based media will be evaluated. The horticultural industries recognize that regulation of peat is on the horizon and alternatives must be identified that make their crop production more sustainable. In a recent survey of southern New England growers, 100% responded that they were extremely or strongly interested in research evaluating sustainable alternatives to peat in growing media. All growers surveyed agreed that the use of hemp hurd, a renewable resource, for plant production would be viewed favorably by the public. As part of the process of fully evaluating hurd as an alternative to peat, a nursery producer will grow plants on farm using hurd substituted media. Growers will participate in annual on-site demonstration events where they will view the outdoor nursery and greenhouse trials, receive preliminary research results, and provide feedback on the project. To reach a broader stakeholder audience, short educational videos that serve as “Reports from the Field” will be developed to highlight research activities and results and shared via UConn Extension, advisory committee member, and grower social media accounts.
Evaluate hemp hurd as a substitute for sphagnum peat moss in growing media for container production of horticultural crops. Knowledge will be acquired about what crop groups may be grown using hurd, the amounts of hurd that may be combined with traditional media components, and the impact hurd substitution has on the availability of nutrients. If it can be shown that hurd may be successfully substituted for peat during production of horticultural crops, then growers will seek to use this byproduct of the hemp industries.
Peat is an important component of greenhouse and nursery plant potting media, but mining of the material is unsustainable due to its negative environmental impacts including emission of carbon dioxide, the major greenhouse gas driving climate change. The damage caused by peat mining has prompted several European nations including the United Kingdom, to enact bans on the sale of peat to gardening consumers beginning in 2024 (Carrington, 2021). Climate scientists and conservationists are calling on governments to place limitations on the use of peat by the horticulture industry. In discussions with representatives from horticultural product supply companies, it was shared that similar restrictions on the sale of peat will be enacted in Canada in the near future. Peat bans will significantly impact greenhouse and nursery container growing operations in the United States (US), since nearly all of the peat sold in the US comes from the peat bogs of Canada (Higgins, 2017). Hemp produces two types of stem fibers. The first is high quality long fibers (bast) that are used for textiles and the second is shorter more lignified fibers (hurd), which has few identified uses. Only 3.5% of the hemp stem consists of bast, which means that 96.5% of a hemp fiber crop is hurd byproduct. Hurd is a byproduct of all hemp growing operations (fiber, grain, medicinal) and is an untapped renewable material. Milled hurd is similar to peat in many characteristics (porosity, water-holding capacity, bulk density) and can be expected to serve as a substitute in container media. Hurd will likely resist breakdown and provide structure for longer than other components, which is desirable for container production. Greenhouse and Nursery Products are the number one agricultural commodity in five (Connecticut, Massachusetts, New Hampshire, New Jersey, and Rhode Island) of the 12 Northeast SARE states (Census of Horticultural Specialties, 2019). It is number two in Maryland and New York and number three in Maine, Pennsylvania, and Vermont. In Connecticut, Greenhouse and Nursery Products contribute 51% of the value of agricultural production, with Dairy a distant second at 14%. There are 2,452 wholesale operations in the 12 Northeast SARE states that produce bedding plants, herbaceous perennials and/or woody ornamentals. The majority are family or individual owned and range from 50 to 500 acres. A 500-acre outdoor container production nursery utilizes approximately 17,500 cubic yards of peat annually. The nursery industry recognizes that alternatives to peat must be developed and is interested in new products that make their crop production more sustainable (Jackson, 2022). The demand for alternative media components has never been higher and will only increase exponentially in the future. Many parts of the hemp industry are expanding rapidly and there will be significant amounts of hurd produced directly from fiber production or as a byproduct of grain and flower production. Developing end product and markets for the hurd material now will prove helpful to hemp farmers as well as greenhouse and nursery growers in the future.
Cooperators
- (Researcher)
Research
The research objective is to ascertain if hemp hurd fiber can be used to fully or partially (at 33% or 66%) replace sphagnum peat moss in container potting media and how broadly it can be applied to different crop groups including annual bedding plants, vegetables, herbaceous perennials and woody ornamentals. The degree to which the hemp substitute effects the availability of nutrients compared to peat will be determined.
2023 Greenhouse studies (proposed study 3)
Treatments
The experiments conducted in 2023 were part of proposed study 3, which involved bedding plants. Experiments were conducted in the greenhouse at the UConn Floriculture Greenhouse Facility in Storrs, CT. Both experiments were conducted with petunia started from seed (Petunia Spreading, Shock Wave Series). There were four different treatment medias in both experiments: the control media consisted of 1:1 peat: vermiculite, which is representative of media typically used to grow greenhouse crops. The three other treatment media were as follows: 1:1 peat: vermiculite (full replacement); 0.66:0.33:1 hurd: peat: vermiculite (high rate replacement); 0.33:0.66:1 hurd; and 1:1 hurd: vermiculite (low rate replacement). In experiment 1, the hurd product had a particle size of 8 to 10 mm (Biocomposites Inc.) and the vermiculite used was medium grade for texture. In experiment 2, the hurd product had a particle size of 2 mm (Hemp Trader Inc.) and the vermiculite used was fine grade for texture.
Methods
For each experiment, the experimental unit was an individual potted plant. Experimental units were arranged in a randomized complete block design with 10 replications. Three week old seedlings were potted into 6.5-inch azalea containers and top-dressed with 3 g (the manufacturer’s recommended low rate) of controlled release fertilizer (15-9-12 Osmocote Plus 3 to 4-month formulation). Plants were grown and evaluated for six weeks.
Data Collection
The porosity and water-holding capacity of each treatment media was determined. Pour thru (PT) testing was conducted weekly and the pH and electrical conductivity of the leachate was measured. Plant canopy width (the average of two perpendicular widths) was recorded weekly. Data was collected on the number of days until first open flower, the number of open flowers and flower buds at 21 days after potting and at harvest, and the above media fresh weight at harvest.
Data analysis and presentation of results
Data analysis is being conducted.
2024 Outdoor Nursery Study, Woody Plants (proposed study 1) and Greenhouse Study (proposed study 3)
Treatments
The experiments conducted in 2024 completed proposed studies 1 and 3, which involved woody shrubs and bedding plants, respectively.
Study 1 was conducted in an outdoor container nursery at UConn in Storrs, CT. The species tested included Forsythia (deciduous), Northern Bayberry (semi-evergreen), and Microbiota (evergreen). There were three different media treatments, which is a departure from the proposed work, that had planned for four media treatments. This change was made because three different mediums provided for a better proportional spread between treatments because the peat portion of a standard woody plant container mix is less than for bedding plants. The control media was 4:2:1 bark:peat:sand and then for the other two treatments, the peat was replaced fully (100%) or partially (50%) with hurd. The hurd product had a particle size of 2 mm (Hemp Trader Inc.).
Study 3 was conducted in the greenhouse at the UConn Floriculture Greenhouse Facility in Storrs, CT. Geranium plants were started from seed (F1 Hybrid, Maverick Series, Red). There were four different treatment medias: the control media consisted of 1:1 peat: vermiculite, which is representative of media typically used to grow greenhouse crops. The three other treatment media were as described in 2023 for petunia experiment 2 and abbreviated here as follows: full hurd replacement, low rate of hurd and high rate of hurd. The hurd product had a particle size of 2 mm (Hemp Trader Inc.) and the vermiculite used was fine grade for texture.
Methods
For each study, the experimental unit was an individual potted plant. Experimental units were arranged in a completely randomized design (CRD) with 10 replications.
For study 1, species were propagated in house during late winter to early spring 2024 from stem cuttings or tissue culture micropropagation. In mid May rooted cuttings of Forsythia and Northern Bayberry were transplanted into #2 trade containers and Microbiota into #1 trade containers. Plants were top-dressed with the manufacturer’s recommended low rate of controlled release fertilizer (15-9-12 Osmocote Plus 5 to 6-month formulation). Plants were grown and evaluated for 12 weeks. Each species was arranged as a separate CRD.
For study 3, four week old Geranium seedlings were potted into 6.5-inch azalea containers and top-dressed with the manufacturer’s recommended low rate of controlled release fertilizer (15-9-12 Osmocote Plus 3 to 4-month formulation). Plants were fertigated with a 13-2-13 formulation at 250 ppm N for the first 4 weeks and at 125 ppm N for the rest of the study. Plants were grown and evaluated for 10 weeks.
Data Collection
The porosity and water-holding capacity of each treatment media was determined. Pour thru (PT) testing was conducted biweekly for study 1 and weekly for study 3, and the pH and electrical conductivity of the leachate was measured. For study 1 data was collected on plant height and width, number of shoots per plant, and above media fresh weight at harvest. The nutrient content of leaves was measured by the UConn Soil Testing lab. For study 3, data was collected on plant height, width, number of days until first open flower, number of open flowers and flower buds, and the above media fresh weight at harvest.
Data analysis and presentation of results
Data analysis is being conducted for study 1.
Data analysis for study 3 was conducted using non-parametric Kruskal-Wallis rank-sum test and Bonferroni post hoc analysis and mean separation according to Tukey’s honestly significant difference (HSD) test at P ≤ 0.05.
Update on proposed studies 2, 4 and on farm trial
Study 4 was initiated.
Study 2 (herbaceous perennials) is planned for spring 2025. It will include ornamental switch grass, to be propagated in-house by division, and beebalm, obtained as rooted plugs from Prides Corner Farms Nursery, Lebanon, CT.
In 2025 we will work with Evan Brand, Nursery Manager at Prides Corner Farms, to grow Hydrangea on farm in their nursery mix amended to include hurd in partial replacement of peat.
2023 Greenhouse Study 3
The hurd product from Biocomposites had a higher pH of 7.0 then was expected. The Biocomposites product required washing prior to mixing treatment medium to remove debris. The product was also contaminated with hemp seed that sprouted in the first 1 to 4 days after potting. Hemp seedlings were easily removed by hand. Based on visual observations of the first petunia experiment it was determined that the particle sizes of the Biocomposites hurd (8 to 10 mm) and the medium grade vermiculite were too large, making the treatment medium too porous. For the second petunia experiment we used fine grade vermiculite (with smalle rparticle size) and a different hurd product by Hemp Traders with particle size of 2 mm, that more closely resembled the particle size and texture of sphagnum peat moss. The Hemp Traders product had a lower pH of 5.0 and was free of debris and seed. Petunias in all hurd treatment mediums grew better in the second experiment than the first experiment based on visual observations. Future experiments will utilize the Hemp Traders hurd product at 2mm particle size.
Figure 1. Peat and hurd substrates.
The tables below provide the physical properties of the four treatment mediums in experiment 1 (Table 1) that used ~10 mm sized hurd and experiment 2 (Table 2) that used ~2 mm sized hurd.
Table 1.
| Treatment | Container capacity (% volume) | Air-filled porosity at CCAP | Bulk density (g/cm3) |
| Control | 55.91 | 19.68 | 0.16 |
| 1H:1V | 40.9 | 41.27 | 0.03 |
| 33H:66P:1V | 54.09 | 26.21 | 0.02 |
| 66H:33P:1V | 48.12 | 34.54 | 0.02 |
Table 2.
| Treatment | Container capacity (% volume) | Air-filled porosity at CCAP (% volume) | Bulk density Final, at EWHC (g/cm3) |
| 1P:1V (Control) | 65.98 | 11.14 | 0.14 |
| 1H:1V | 69.10 | 14.7 | 0.16 |
| 33H:66P:1V | 68.23 | 11.29 | 0.16 |
| 66H:33P:1V | 68.29 | 10.92 | 0.14 |
The figures below shows petunia plants grown in 1:1 peat: vermiculite; 0.66:0.33:1 hurd: peat: vermiculite; 0.33:0.66:1 hurd; and 1:1 hurd: vermiculite (left to right) for experiment 1 using ~10 mm hurd (top) and experiment 2 using ~2 mm hurd (bottom).
2024 Outdoor Nursery Study 1
The woody shrubs evaluated all grew very well in the hurd amended media and were visually indistinguishable from plants in the control medium.
2024 Greenhouse Study 3
Petunia and Geranium were able to grow in substrates containing hurd as a replacement for peat. Petunia plants in media containing the low rate of hurd performed similarly and were visually indistinguishable from the control. Plants in the medium rate of hurd treatment had achieved similar plant width to the control. Geranium plants in the hurd treatments were larger than the control. Geranium plants in the low rate treatment were the most visually appealing. It is possible that geranium plants in the control medium did not grow well because the pH was too low or the medium remained too wet.
Education & Outreach Activities and Participation Summary
Educational activities:
Participation Summary:
1. Annual meeting (2023) about this NESARE project which included UConn extension educators and growers.
2. Presentation titled "Multipurpose Hemp: Cultivars and Breeding" at the UConn Extension event titled "Hemp Justice: Building a Circular Economy in CT".
3. Extension video "Report from the Field" about media mixing, pour thru testing, data collection and plant harvest of petunias.
4. Second annual meeting (2024) about this NESARE project which included extension educators and growers.
5. Presentation titled "Substituting Hemp Hurd Fiber for Peat in Plant Production" at the 2024 International Plant Propagators Society Conference - Northeast Region.