Leveraging Biodiversity to Improve Profitablity on a Small-scale Vegetable Farm

What we wanted to do

Wild Pansy Farm set out to make compost using the neighboring livestock farm’s spent bedding. The goal was to produce compost that had enough diversity and quantity of microbiology that it could eliminate the need for the farm to buy in fertilizers and pesticides, while producing healthy plants with high yields. This had the potential to reduce costs of production and enable reliable, local access to compost. 

In January 2021, Wild Pansy Farm purchased compost from a Michigan-based producer, with a combined order representing several farms. The product traveled over 400 miles to reach Wild Pansy Farm and was the closest we could source in quantities needed. This is the context in which Wild Pansy Farm decided to pursue on-farm compost production with Nightfall Farm’s spent livestock bedding. 

Adding another task to our operation seemed daunting, so we sought to develop a workflow that could keep the labor cost involved with producing the compost to a minimum. The Johnson Sue Bioreactor static pile composting system seemed to match this need. To further reduce labor, we wanted to use the compost in tasks already being performed on the farm, including it with soil blocks for transplants and applying soil drenches. Soil drenches are simple extracts of compost into water that are immediately applied to the field through drip tape or sprinklers. To determine if the desired microbiology was present in the compost, we needed to be able to look at it under a microscope. Ann enrolled in Dr. Ingham’s Soil Food Web Schools program to learn about the soil microbiome and how to conduct a quantitative analysis with the microscope. 

What we did 

Over the course of 2021, we built Johnson-Su Bioreactors and filled them with spent livestock  bedding. The Bioreactors use fencing to create a doughnut shaped cylinder to house the feedstock so that all the material is no more than one foot away from an air source. This is to prevent the static pile from becoming anaerobic during decomposition. The pile needs consistent moisture and as a final stage it goes through a vermiculture process. More information about Bioreactors and the building process can be found on YouTube and past SARE projects. To better fit with the farm’s footprint and flow, we made several changes to the Bioreactors’ proposed build (see Outcomes). By the autumn, we had six Bioreactors filled, two with chicken bedding and four with sheep bedding. The remainder of the bedding went straight onto the field. Some compost was tilled into a new plot, and some integrated into a no-till raised bed that is planted with perennials. Overall, we estimate that 18,062 pounds of bedding were delivered in 2021. Of which, we utilized about 10,200 pounds in the Bioreactor system. 

At the end of 2021, Ann completed the Soil Food Web School’s Foundation course and began their Growers Training Program, which includes practical coursework with a microscope for analyzing microbiology and making compost recipes that encourage microbiome development. During 2022, Ann used the Soil Food Web School’s (SFWS) approach to produce the compost. 

The SFWS thermal composting method requires time, specific temperature targets, and turning to encourage decomposition in a way that supports helpful microbes. The temperature of the piles and the length of time the piles maintain that temperature affect when the pile gets turned. Specifics of this process can be found in the USDA organic compost guidelines for making thermal compost. Follow this link for a tipsheet on compost with further references, https://www.ams.usda.gov/sites/default/files/media/Compost_FINAL.pdf

We experimented with several recipes that combined waste materials from the farm, as well as leaves from a suburban neighborhood. With the support of a mentor from the SFWS program, we were able to successfully produce a compost that met the thermal standards. The recipes varied in their percentages of brown (carbon), green (plant matter), and high nitrogen (manure) materials. By late fall, Wild Pansy Farm had constructed three compost piles, of which one met the time, temperature, and turning requirements stipulated by the  program. The 5,100 pounds of feedstocks used in these piles reduced to about 2,000 pounds of compost– a 60% reduction. However, only 700 pounds of this compost met the SFWS thermal composting requirements. Going into 2023, we have approximately 13,000 lbs of bedding remaining to turn into compost in the upcoming year, using the recipe developed from the successful pile. 

Outcomes, Pivots, and Challenges

The most important outcome of the project for Wild Pansy Farm was learning to incorporate compost production into the farm’s workflow. To that end, the Johnson-Su Bioreactors did not work for several reasons and we decided to pivot to the SFWS method. Many of our critiques of the Johnson-Su method can be reduced to issues with the bioreactors’ structure. Our partners from Nightfall Farm reported difficulty shoveling bedding from their pickup into the 4ftx6ft cylindrical bioreactors, due to the size of the opening at the top not accommodating their tools and the material. We adapted the design to account for this, creating a larger bioreactor prototype 6ft in diameter. This expanded design was not as structurally sound and would collapse while being filled. Additionally, the fencing was difficult to disentangle from the compost material, requiring an additional time cost. Following the first year of the project, it was evident the Johnson-Su Bioreactor method would not integrate with either farms’ needs, particularly given the volume of material available for composting. 

The Bioreactors were left to passively produce compost for a year. Upon examination in the spring of 2022, we found that there was not a sufficient level of microbiological activity or biodiversity to merit our using this approach. The failure of this technique was largely due to the adjustments necessary for integration with the farms’ workflows. We isolated feedstocks, rather than mixing them, so the soil microbes had a less diverse mix of foods available, inhibiting their growth. After a year of passive management, we observed a very low level of decomposition in the Bioreactors. 

Another reason these did not decompose effectively was our failure to effectively manage moisture levels. Johnson-Su Bioreactors need regular, short periods of misting frequently throughout the day. At Wild Pansy Farm, our key constraints in the field are access to electricity and shelter, both of which were critically necessary for this  method. Our original plan was to house the bioreactors in a caterpillar tunnel, to protect them from the elements and control the water dispersed on the pile. The Bioreactor design was not configured to the equipment available to the livestock farm, as the 12-ft clearance was not enough space in the tunnel to drive in the materials to fill the bioreactors. Neither did we have reliable power for automatic watering. Without an indoor watering space available, we built the piles outside and were unable to maintain the consistent moisture level through the pile that is necessary for decomposition, even as we watered during dry periods. 

After training on SFWS approach to composting, we determined it was more effective and consistent with Wild Pansy Farm’s workflow. Producing SFWS compost required more time, attention, and effort, but the result will be a compost with a diverse microbiome. In our recipe, animal bedding from Nightfall Farm constituted 62% of the feedstock mix. The other ingredients included green matter grown in the course of producing vegetables on Wild Pansy Farm, and leaves gathered from a suburban neighborhood. The livestock bedding was a mix of both woody/brown (cardon) material and high nitrogen content (manure). Determining the ratio between the two helped to ensure we would be able to reach the 132F temperature for the 72 hours necessary to meet the thermal composting requirements. The SFWs piles required three turns to achieve the minimum temperature across all the material. Importantly, the green inputs grown by Wild Pansy Farm were a critical food source for the microbiome in the piles. 

We made notable mistakes in two of our SFWS composting efforts. In the first case, the pile reached 172F degrees within 24 hours and, in our haste to moderate the temperature to a range safe enough for the microbiology, we over-vented the pile. As a result, the pile did not have sufficient heat following its third turn to maintain the 132F for the 72 hours required. The second case, the pile was constructed too late in the season to achieve the necessary temperature for the required duration. In October, 2022, a period of frost and unseasonable cold suppressed the internal temperature of the pile and the decomposition cycle could not be sustained. 

Despite the above failures, one pile did successfully meet the criteria. It took around three weeks to achieve this process. About a month after the final turn, the compost returned to ambient temperature. However, at that point  it was too late in the growing season to test if it would have any effect on plant growth or yield. 

Future Work

Our ‘small batch’ approach with the SFWS’s compost recipe development required the use of five gallon buckets that necessitated manipulating the materials by hand. For the small quantity of final compost, this was inappropriately labor intensive and time consuming. The principle of assembling a recipe using ratios of material is challenging and starting small is a sound approach. Still, given the inefficiencies introduced in operating by hand, Wild Pansy Farm will seek ways to scale up production to an appropriately sized skid steer or tractor, with a bucket attachment that can handle cubic yard quantities of material.

For both the SFWS and JSB methods, the compost product was coarse, too coarse for use as a potting soil. The successful batch of thermal compost from our second pile would need to go through a vermiculture system, or be machine screened, prior to being used in soil blocks for transplants. Additional aggregates would also need to be mixed in to create a product applicable to that part of the farm’s operation. We do not think the number of transplants in our operation (~32,000) justifies the additional work and expense to use the compost as a potting soil. The plants will be better served by watering them at time of transplant with a compost extract. This, we feel, will help establish a healthy microbiome and provide a better workflow for our farm. 

The SFWS provided instruction in the use of a microscope to observe the soil microbiome and conduct a quantitative analysis. We learned that our field has extremely low levels of microbiology and almost no biodiversity within the microbiome. Only some bacteria were present in the samples we pulled from many different points in the field and pasture. This helped explain the poor plant growth and yields we achieved during our first seasons, even after having applied organic fertilizers. Having established the baseline for our acreage, we can observe how adding the compost changes the populations of the soil microbiome going forward. The Bioreactors did have nematodes, amoebas, and fungal hyphae present, just not at levels we wanted. Moving forward we will be able to observe the effects the compost has had with these quantities.

Discussion/Recommendations/Next Steps

The microscope is a useful tool in the farmer’s toolkit, but we do not think it is realistic or practical for all farmers to conduct soil microbiome analyses. For the time and expenditure associated with compost production and oversight, and the additional specialized equipment, we feel this is an area where technically trained consultants or agronomists, whose focus is in microbiology, could effectively support farmers engaged in regenerative/restorative agricultural practices. Their expertise can offer a better understanding of soil health than chemical-based soil tests. 

Our partners at Nightfall Farm reported financial benefits from the sale of their spent bedding, equating to an average of 7% of the total cost of goods sold for their operation. Bedding costs comprise between 4% and 13% of COGS for the chicken, turkey, and lamb business lines. Nightfall Farm was able to capture this cost as revenue, without any additional labor. Wild Pansy Farm is located at Nightfall, so there were no additional expenses or time associated with spent bedding delivery. Distance of delivery should be a governing factor for other livestock farms considering selling their spent bedding, as it scales poorly and can require additional equipment to achieve profitability. 

As an interfarm partnership that eliminated Nightfall’s materials cost without additional labor or time, the benefit is clear. For Wild Pansy Farm, the fiscal value of the proposition is dependent upon our ability to effectively produce microbially living compost, something we are still working to accomplish at a scale appropriate to our needs.

There was a 60% reduction in the volume of material from its raw feedstock form to finished compost, using the SFWS method. Composting standards anticipate a 70% reduction of starting material to finished compost. By comparison, the bioreactors experienced a less than 20% reduction in volume. The material simply did not break down to the degree necessary for us to stick with the method, though it is important we acknowledge this could be due to the adjustments required for our working farm.

The cost of the spent bedding each year was $3,175 for just over 18,000 lbs of raw material. When composted properly, our expectation was to yield some 7,200 lbs of compost–about 5.75 cubic yards. During the 2021 season, we spent $2,000 on 5 cubic yards of a combination of seed starting mix and compost, which included renting equipment to unload the order and delivery costs. Comparatively, the price per cubic yard for the compost produced from Nightfall’s bedding was $552, while the cost of the Dairy Doo compost we purchased was $425, inclusive of the delivery expenses. We should note that by paying full price for the spent livestock bedding, which we agreed to do to incentivise Nightfall’s participation, was ultimately not a good financial fit for our vegetable farm. On a per-cubic-yard basis, the costs of processing the compost on farm were very nearly equivalent to those required for buying it, with additional labor required. However, since beginning this project, we have identified several regional sources of compost inputs that can be obtained at low or no cost to our farm, with bulk delivery of certain feedstocks possible for as little as $25 per cubic yard. As we move into 2024, Wild Pansy Farm is seeking to partner with the City of Seymour to purchase wood chips for roughly $35-$40 per ton ($0.02 per pound). While this may necessitate changing our compost recipe, it represents savings of over $5 a pound when compared to the price paid for spent livestock bedding. 

An additional expense was the $526 we spent on organic fertilizers over the two years of the project. As our yields indicate, it would have benefited the farm to spend more on fertilizer during the 2022 season. The comparatively lower cost of the fertilizers does not justify full reliance on the compost, particularly given the time and effort required to create it. However, when considering soil health, we believe that our observations of the microbiome indicate there is significant value in using compost that is active with diverse microbiology. Those products advertising microbial inoculants are extremely expensive and usually encourage growth of specific microbes. To achieve sustainable nutrient cycling for our plants requires a diversity of microbes. As we learned, Wild Pansy Farm’s acreage only has low levels of  bacteria, so introducing only one or a few new types of microbes would not provide enough diversity to achieve the population composition necessary for sustained nutrient cycling. As a result, we have concluded that the cost-effective path forward is to source cheaper inputs and scale up production with correctly sized and configured equipment. In the upcoming season, we intend to approach the supply-side issue with inputs from the City of Seymour and green material byproducts from operating our farm, and attempt a focused period of composting over one to two months, using a rented skid steer and bucket. We still feel that, given the available data from the SFWS compost method, we can reach a point where fertilizer and compost input costs are dramatically reduced, if not completely eliminated.

In conclusion, Wild Pansy Farm will continue to test if a diverse and abundant microbiome can eliminate or reduce the need for fertilizers and pesticides.