Progress 07/15/24 to 07/14/25

Outputs
Target Audience:The target audience is small and medium-sized farms. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? Invited presentation to host a field day for USDA Research and Extension Experiences of Undergraduates (REEU). REEU students were provided with hands-on experience collecting SRA mushrooms in experimental plots, and learned about the project relevancy and how SRA might be used to recycle on-farm waste (July 2024) Invited presentation to direct stakeholder audience at UVM Extension Field Day (July 2024) Invited to deliver a workshop at Mycology Outside: A Weekend Mushroom Retreat in Saco, Maine (August 2024). The workshop focused on the problem of agricultural waste and how companion cropping with mushrooms can facilitate recycling waste and promote soil health. What do you plan to do during the next reporting period to accomplish the goals? Submit a manuscript of research results for review and publication in a peer-reviewed journal article. Present research results at the Global Soil Biodiversity Conference (April 12-15, 2026) in Victoria, British Columbia. Dissertation defended and published by graduate student, Noah Olson.

Impacts
What was accomplished under these goals? Year 2 of 2 of the field experiment was conducted on the same three farms, two in Vermont and one in Minnesota.Lessons from Year 1 were implemented to better manage weed pressure, provide more accurate estimates of mushroom yield, and quantify plant pathogens and disease progress.Weed management added the use of weed trimmers and weed removal weekly rather than biweekly. Number of weeds per plot were counted in triplicate 0.5 square meter quadrants per plot and classified as either monocot or dicot. Mushroom yield estimates were modified to enumerate numbers of Stropharia rugosoannulata (SRA) mushrooms per plot on a weekly basis. We estimated that medium-sized 'grade A' mushroom each weigh 20 g wet, and counts were converted to yield (kg/ha) accordingly.Septorialeaf spot lesions were visually estimated as a proportion of total leaf area for each plant, and a mean severity across treatments was reported in July, August, and September. Nematodes were extracted from 250 g of soil using a modified Cobb's sieving and decanting method. Nematodes were identified to family and assigned a trophic group, and ratios of fungivores to bacterivores quantified. Plant-parasitic nematodes were identified and enumerated by genus. A laboratory experiment was conducted to quantify the relationship of temperature with mushroom yield to aid in interpreting field results. Four replicates malt extract agar were seeded with plugs of SRA and incubated at 10, 15, 20, 25, 30 or 35 °C. Mycelial growth was measured to the nearest 1 mm with a stereo microscope and expressed as mean distance from the plug through time (alternate days for 2 weeks). Across all sites and treatments, mean waste was ~30% of total biomass with maximum waste production reaching 2,100 kg/ha. A positive linear relationship was observed between total biomass and waste generation. SRA beds were established successfully at all locations. Mushroom production was more consistent as the SRA bed establishment progressed into 2024. Optimal SRA growth occurred at 25 to 30 °C which helps explain relatively low yield in cooler soils of Vermont. Decomposition of hemp mulch was faster in SRA plots than control plots. SRA reduced severity of Septoria leaf spot (Septoria cannabis) and abundance of lesion nematode (Pratylenchus sp.) compared to landscape fabric. Leaf tissue potassium content was greater in mulched plots with SRA than without SRA. Marketable hemp yield was greater under landscape fabric than SRA likely a result of warmer soil temperatures and less weed pressure. The yield advantage of landscape fabric over SRA was less produced in 2024 than 2024. In conclusion, this study demonstrated that growing gourmet "winecap" mushrooms (SRA) with hemp plants promoted faster decomposition of hemp mulch compared to uninoculated control plots and did not negatively impact plant health or yield.

Publications

• Type: Theses/Dissertations Status: Under Review Year Published: 2025 Citation: Olson, Noah E. 2025. On-farm bioconversion of organic wastes into fertility inputs for sustainable agriculture. Dissertation, University of Vermont, Burlington, VT.

Progress 07/15/23 to 07/14/24

Outputs
Target Audience:The target audience is small and medium-sized farms. Changes/Problems:Weed pressure. Mowing and weed trimmers were insufficient in managing weeds. Weed pressure was a major issue in the treatment plots mulched with hemp biomass in the Vermont Farms, and likely responsible for reduced hemp yields. Control plots covered in landscape fabric had little to no weed pressure which correlates with greater yield in plots with fabric (controls) than without fabric. Adjustments to be implemented in year 2 (2024) are the following: Apply weed mat to all treatment plots two weeks prior to spreading mulch and inoculating beds to smother weeds before they can establish. Apply hemp mulch and inoculate beds earlier in the season (mid-May) to further smother weeds. Fertility Differences/Plant Stunting. Despite attempts to apply the equivalent of 100 lbs/N per acre, there were nutrient deficiencies observed for plants in mulched plots. Plants in control plots without mulch showed no signs of stunting and produced the greatest yields. We hypothesize that application of carbon-rich biomass tied up the soil nitrogen. Adjustments to be implemented in 2024 are the following: Rake away mulch in May and rototill nutrients into plots for deeper placement than in 2023. Deeper placement places more fertility in contact with plant roots than the microbial communities in the mulch layer. Apply nutrient requirement in two stages, i.e., spread half of nutrient requirement into rototilled lanes and the other half at planting (spread fertilizer into planting hole). Disease Pressure. Extensive prevalence of Septoria leaf spot likely reduced yields at the Vermont farms. Rain and wet conditions experienced in Vermont the summer of 2023 likely exacerbated this issue. Adjustments to be implemented in 2024 are the following: Record disease incidence and severity early in the grow season (mid-June/early July) and periodically thereafter to assess disease progress. Prune lower leaves of plants in July to reduce disease spread (if needed). Flower yield was less than commercial standards. Plant stunting, disease pressure, and competition of weeds negatively affected yield in treatment plots. Moreover, farms were hot and dry at the start of the season in Vermont, and throughout the season in Minnesota. We installed drip tape and sprinkler irrigation systems to even out moisture among farms. However, installation was weeks after planting and the drought damage had a lasting impact. Adjustments to be implemented in 2024 are the following: Install drip irrigation before planting at each farm. Adjust fertility application regime, weed management, and disease pressure as outlined above. Changes to fertility, weed, and disease management may alleviate some of these pressures. Disparate Mushroom Yield among farms. Mushroom production was unequal across the three farms. Eden outperformed all other sites with ~57 pounds of fresh mushrooms. Alburgh was second with ~8 pounds while Minnesota produced about a pound. Differences between the VT and MN sites were likely due to unequal precipitation (VT had more than typical; MN had less than typical). Despite differences in yield and rain, we were successful in getting mushroom beds established at all experimental locations. Adjustments to be implemented in 2024 are the following: Irrigation systems will be established after applying mushroom spawn to insure establishment of mushroom treatments. Reduce labor and increase accuracy of mushroom harvest by counting mushrooms rather than picking and weighing them individually. A subset of mushrooms will be harvested at the beginning of each flush and a mean weight per mushroom determined. What opportunities for training and professional development has the project provided?For professional development, a graduate student Attended a webinar "From bud to blend: Compost opportunities in Cannabis cultivation" sponsored by the U.S. Composting Council on 22 April 2024. The webinar explored best practices and technology in processing cannabis waste, uncovering potential opportunities in this flourishing field, and learn about successful marketing strategies. Additionally, you will hear experts discuss current regulatory frameworks around cannabis waste disposal, particularly in key states like Colorado and California. Attended and participated in the Vermont Organic Recycling Summit in Waterbury, 29 April 2024 How have the results been disseminated to communities of interest?Invited presentation to direct stakeholder audience at Annual Field Day at Borderview Farm (Alburgh, VT) on 27 July 2023 What do you plan to do during the next reporting period to accomplish the goals?The field experiment will be repeated at the same three farms. Additional measures will be taken to better manage weed pressure, more efficient and accurate estimates of mushroom yield, and quantify plant pathogens and disease progress. A greenhouse experiment will be conducted to quantify the relationship between depth of hemp mulch with mushroom yield. Aspects of Objectives 3 and 4 will be addressed, including quantification of aboveground disease severity, plant-parasitic and free-living nematodes in the soil, and estimating economic value of mushrooms and hemp flowers. The economist who was an original co-PI (School of Business, Western Colorado University) left the university at the outset of the project.

Impacts
What was accomplished under these goals? Year 1 of 2 of a field experiment were conducted on three farms, two in Vermont and one in Minnesota. Two undergraduate students gained research experience with this project. Using hemp waste as mulch for hemp plants and substrate to grow gourmet Stropharia mushrooms would allow smallholder farmers to restore fertility directly while generating an added source of income. Methods and year 1 (2023) results are presented below: Objective 1. Waste streams produced by medical hemp were quantified by weighing fresh and dry mass from flowers, stems and leaves. Flowers are the harvestable product while the remainder is considered waste. Objective 2. Effectiveness of SRA for nutrient recycling and availability to plants was measured through enzymatic activity that reflects lignin decomposition by soil microorganisms, percent mass loss in litter bags, and nutrient content of soil and plant tissue. Enzymes were quantified monthly and measures of decomposition, and nutrient content were measured in spring and fall. Nutrient content in soil was similar among treatments. Enzyme activity varied by sampling time and farm location without any consistent pattern among treatments. Decomposition was fastest in plots inoculated with mushroom spawn when compared to the other treatments. Objective 3. Aboveground Septoria leaf spot disease was extensive at one farm and less at the remaining two farms. Septoria leaf spot was the most prevalent pathogen at our Vermont sites which might have affected plant performance. Rain and wet conditions experienced in Vermont during the summer of 2023 likely exacerbated this issue. Objective 4. Yields of mushroom and hemp flowers were quantified by mass. The yield of medicinal hemp plants was measured as weight of flowers harvested, and mushroom yield quantified by fresh weight when picked and weighed. At the Vermont sites, hemp yield tended to be greater in the control plots covered with landscape fabric (negative control) when compared to plants grown in mushroom/microbially treated hemp mulch. The opposite effect was observed at the Minnesota site where plants grown in treated biomass yielded more than the control plots. Mushroom yield varied greatly by location. Stropharia treatment beds at Eden (VT) yielded the most mushrooms throughout the 2023 season followed by the beds at Alburgh (VT). Beds at the Minnesota site did not fruit until late fall and total mushroom production was significantly less compared to the Vermont sites.

Publications