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Citation: Hoidal, N.; Bugeja, S.M.;
Lindenfelser, E.; Pagliari, P.H. Soil
Health Practices and Decision Drivers
on Diversified Vegetable Farms in
Minnesota. Sustainability 2025,17,
1192. https://doi.org/10.3390/
su17031192
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Article
Soil Health Practices and Decision Drivers on Diversified
Vegetable Farms in Minnesota
Natalie Hoidal 1, *, Shane M. Bugeja 1, Emily Lindenfelser 1and Paulo H. Pagliari 2
1Department of Agricultural and Natural Resource Systems, University of Minnesota Extension,
St. Paul, MN 55108, USA; sbugeja515@gmail.com (S.M.B.); hans6005@umn.edu (E.L.)
2Department of Soil Water and Climate, Southwest Research and Outreach Center,
Lamberton, MN 56152, USA; pagli005@umn.edu
*Correspondence: hoida016@umn.edu
Abstract: Soil health is at the root of agricultural sustainability, and small-scale vegetable
farmers are becoming an increasingly important part of the US food system. These farmers
face unique challenges when it comes to managing soil on their farms. These challenges
include reliance on intensive production practices, the use of primarily organic inputs
with difficult to calculate nutrient concentrations, and lack of access to formal education
tailored to their needs. We surveyed farmers at 100 small-scale vegetable farms in Min-
nesota to
(1) develop
a better baseline understanding of how small-scale vegetable farmers
utilize key soil health practices including nutrient management, cover crops, and tillage;
(2) explore
how farm demographics influence the adoption of soil health practices; and
(3) determine
educational priorities to better support these growers. Here, we report a lack
of understanding about the nutrient contributions of compost, which is often applied at
very large volumes without guidance from soil test results, with implications for nutrient
loading in the environment. Farmers in our study had high rates of cover crop adoption
relative to other farmers in the region despite several barriers to using cover crops. More
experienced farmers were more likely to utilize more tillage, with more use of deep tillage
implements on larger farms. Overall, organic certification was correlated with higher
adoption of soil health practices including utilization of soil tests and cover crop use, but
it was not correlated with tillage. Other demographic variables including land access
arrangement and race did not meaningfully influence soil health practices. Our findings
suggest a need for more research, outreach, and education targeted to vegetable farmers
about how to interpret laboratory soil test results, and how to responsibly utilize organic
inputs including vegetative compost and composted manure at rates appropriate for crop
production in a diversified farm setting. We also report a need to compensate farmers for
their labor to incentive cover crop use on small farms, and a need for more research and
support for farmers in the 3–50-acre range to utilize reduced tillage methods.
Keywords: compost; cover crops; emerging farmer; tillage; nutrient management; small-
scale farming; fruit and vegetable
1. Introduction
Sustainable agriculture is defined as the ability of a crop production system to contin-
uously produce food without environmental degradation [
1
]. A sustainable agricultural
system integrates biological, physical, chemical, and ecological principles to utilize prac-
tices that are not harmful to the environment [
2
]. Soil is at the center of sustainable farming
Sustainability 2025,17, 1192 https://doi.org/10.3390/su17031192
Sustainability 2025,17, 1192 2 of 22
systems: sustaining soil health and fertility is key to maintaining food production as well
as agricultural ecosystems [3].
Small-scale vegetable production is a growing industry in the Upper Midwest, but the
soils and soil management strategies on these farms are understudied. With each recent
census cycle, Midwest states such as Minnesota and Wisconsin lost thousands of farmers
overall but gained hundreds of small-scale (<50 acres) fruit and vegetable farmers [
4
–
6
].
Due to lower barriers to entry than other types of farm enterprises, beginning farmers
who do not come from farming backgrounds and who lack formal training often grow
vegetables [
7
–
10
]. Increasingly, small-scale vegetable farms grow in both open fields and
high tunnels. High tunnels are defined as plastic-covered enclosed growing structures
without supplemental heating, and in-ground crop production [
11
]. To date, the United
States Natural Resource Conservation Service has funded 26,216 high tunnels nationally,
including 694 in Minnesota [12].
Studies of beginning small-scale vegetable farmers with limited agricultural back-
grounds have characterized them as people with a desire to positively contribute to the
natural environment while providing nutrient-dense fresh fruits and vegetables to their
communities [
13
]. These farmers often lack both formal and informal training in produc-
tion, stewardship, and business practices [
9
]. In Minnesota, these farmers are often referred
to as “emerging farmers”, defined as “those who traditionally face barriers to the education
and resources necessary to build profitable agricultural businesses, including immigrant
farmers and farmers of color” [
7
]. These farms tend to be highly diverse, with farmers
growing many, sometimes dozens of crops at a time [7,9,13].
The United States Natural Resource Conservation Service has determined key soil
health principles to guide their work, which include minimizing disturbance, maximizing
soil cover, maximizing biodiversity, and maximizing the presence of living roots [
7
]. The
agency posits that healthy soils contribute to agricultural sustainability by producing high
yields, reducing production costs, and therefore improving profits, protecting natural re-
sources on and off the farm, reducing nutrient loading and sediment runoff, and sustaining
habitat for wildlife and microorganisms [
14
]. Two key practices for achieving these goals
are the use of reduced tillage and cover crops. The benefits of these practices are well
documented: conservation tillage practices can increase soil microbial activity, soil moisture,
organic matter, aggregate stability, cation exchange capacity, and crop yield [1,15–18].
While the benefits of reduced tillage and cover crops are well documented, small-scale
vegetable farmers face unique barriers to implementing these practices. Many small-scale
farmers do not inherit land from family and, therefore, must farm in a way that allows them
to be profitable with limited land, infrastructure, and equipment [
9
,
13
]. Therefore, small-
scale direct market vegetable production is typically characterized by intensive cultivation
methods to produce high yields on a limited scale with tools that allow for season extension
(e.g., high tunnels), succession planting to achieve multiple crop cycles per season, and
reliance on hand tools or light machinery [
19
]. Due to the intensive nature of production,
small-scale vegetable farms often have few opportunities for fallow periods (including
cover crops), particularly in the context of high tunnels, which are most profitable when
farmers take advantage of off-season production windows [
20
]. Despite the intensive
nature of production, these farmers often prioritize soil health and reduced chemical
inputs, and conceptualize their own practices as being directly in opposition to a more
harmful paradigm of industrial agriculture [
10
,
13
]. For all of the above reasons, small-scale
vegetable farmers represent a unique demographic of farmers with unmet educational
needs. Understanding their practices and motivations can inform educational outreach
programs, as well as research priorities and the development of best practices.
Sustainability 2025,17, 1192 3 of 22
University Extension programs across the country have begun to invest in local foods
programs with dedicated local foods educators and researchers, urban agriculture pro-
gramming, and small farms content [
21
–
23
]. However, small-scale direct market vegetable
farmers have historically been underrepresented in university outreach programs. In
Minnesota, three needs assessments shed light on the lack of contact between university
and extension programs and this growing sector of the farming population. A 2019 needs
assessment of mostly white fruit and vegetable farmers in Minnesota found that only 19%
sought information from Extension or a university entity about farming practices [
24
]. An-
other survey of Hmong and Hispanic farmers in Minnesota found that only 5% would turn
to Extension or a university entity about farming practices [
25
]. Finally, the 2020 emerging
farmers report to the Minnesota state legislature cited that while Extension is a key resource,
small-scale farmers felt that Extension needs more educators who could better support
nontraditional farms [
7
]. Rather than seeking support from traditional “experts” or support
people, farmers are likely to turn to each other as sources of information [
24
]. They also
often turn to “master classes”, YouTube, and podcasts led by “celebrity” farmers who have
an outsized influence on small-scale vegetable production, as evidenced by subscriptions
to these channels. A study of beginning farmers in the Southeastern United States found
that YouTube videos, inspirational speakers, and books were some of the most common
sources of inspiration for first-generation farmers, both to start farming and to influence
their practices [
13
]. Another study of farmers in Hungary and the UK found that farmers
increasingly trust one another over “experts”, and that farmer influencers are becoming a
more important source of information and influence [
26
]. As of March 2024, The No-Till
Growers YouTube channel had 315K subscribers, Neversink Farms channel had 74.1k
subscribers, and JM Fortier’s Market Gardener Institute’s channel had 59.8k subscribers. A
common theme tying these channels and celebrity farmers together is vegetable production
systems based on reduced or no tillage, intensive production on a small scale, and heavy
inputs of compost.
One practice in particular, deep compost mulch, has emerged as a unique soil manage-
ment strategy among many influential farmers. Deep compost mulch involves using large
volumes of compost to quickly increase soil organic matter, suppress weeds, and improve
soil moisture retention [
27
]. This system was first popularized by books like Regenerative
Agriculture: A Practical Whole Systems Guide to Making Small Farms Work [
28
] and The Living
Soil Handbook: The No-Till Grower’s Guide to Ecological Market Gardening [
29
]. While this
system is aesthetically pleasing and can result in many soil health benefits (e.g., increased
organic matter, increased soil available water, improved nutrient retention, and increased
biodiversity such as more earthworms), researchers have begun to identify concerns about
the accumulation of nutrients, particularly nitrates and risks to surface and groundwater
from this practice [27].
A 2019 needs assessment of 315 fruit and vegetable farmers in Minnesota identified
soil health and fertility as the top educational priority [
24
]. Despite relatively low rates
of organic certification, the use of organic practices is common among emerging farm-
ers in Minnesota [
7
] and among fruit vegetable farmers in Minnesota [
24
]. Soil fertility
can be particularly challenging for farmers relying primarily on organic practices due to
nutrient imbalances between organic inputs and crop needs [
30
] and because macronu-
trient concentrations are highly variable across compost and manure products, and, thus,
more expensive and time-consuming to calculate [
31
]. A recent survey and focus groups
with emerging farmers in Minnesota identified significant confusion about inputs. The
term “compost” was used interchangeably among participants to describe composted yard
waste and food scraps, composted manure, and commercial fertilizer products containing
composted animal products [
32
]. Additionally, Extension educators at the University of
Sustainability 2025,17, 1192 4 of 22
Minnesota reported working with farmers who, between 2021 and 2022 experienced chal-
lenges after applying large volumes of compost on their farms. Examples included two
urban farms that applied multiple cubic meters of compost to plots less than ¼ acre in size
to mitigate compaction, resulting in high soluble salts that killed their plants. In another
situation, a farmer added >6 tons of composted poultry manure to a single high tunnel
attempting to use a deep compost mulch system, resulting in excessively high nutrient
concentrations and high soluble salts.
Small-scale vegetable farmers, therefore, face a series of unique challenges when it
comes to managing the soil on their farms: the influx of new farmers means this group
may have more educational needs than a typical farmer. Reliance on intensive production
due to space constraints limits opportunities for cover crops and fallow periods. The
tendency to use organic inputs reduces opportunities to employ reduced tillage strategies
and makes nutrient management more complicated. Finally, the lack of formal outreach
and education for these farmers is often replaced by previously mentioned “celebrity” or
otherwise influential farmers and “master classes”, which may or may not be based on best
management practices and research-based information.
Based on these experiences and identified needs, a project was developed to study the
soils at 100 diversified vegetable farms growing their crops in open fields or under high
tunnels. The objectives of this project were the following:
1.
To develop a better baseline understanding of how small-scale vegetable farmers
utilize key soil health practices including cover crops, reduced tillage, and nutrient
management (including how the use of organic inputs like vegetative compost and
composted manure factor into nutrient management decision-making).
2.
To explore how farm demographics such as size, organic status, experience, land
ownership, race and ethnicity, and production system (open fields vs. high tunnels)
influence soil health practices.
3.
To determine educational priorities for Extension and other farmer-focused
education programs.
2. Materials and Methods
2.1. Recruitment
A team of 16 University of Minnesota Extension educators visited 100 small-scale
(
<50 acres
) diversified vegetable farms between April and June 2023 to conduct soil tests
and a soil management survey. In each region of the state, testing was completed as soon as
fields were dry enough to sample following spring snowmelt. The county-based educators
on the team first reached out to farmers in their local areas through local newsletters and
personal contact. Following this local outreach, statewide staff posted a recruitment flier
in the “University of Minnesota Fruit and Vegetable News” (1757 subscribers). Farmers
were accepted into the trial until a total of 100 participants joined. Recruitment was carried
out in this way versus a more random approach to ensure the geographic distribution of
farm sites and to match educator capacity for conducting soil tests. A total of 200 vegetable
sites (100 open fields, and 100 high tunnels) were identified on the participating farms.
Participants with both high tunnel and field-grown vegetables were prioritized and made
up the majority of trial sites (83 farms). On these 83 farms, one open field and at least one
adjacent high tunnel were sampled, reducing variability by sampling one of each treatment
group on the same soil type and location. The additional 17 farms did not have high
tunnels, so a second high tunnel from one of the nearby 83 farms was included. Figure 1
illustrates the geographic location of the sites used in this study.
Sustainability 2025,17, 1192 5 of 22
Sustainability 2025, 17, x FOR PEER REVIEW 5 of 25
high tunnels, so a second high tunnel from one of the nearby 83 farms was included. Fig-
ure 1 illustrates the geographic location of the sites used in this study.
Extension educators collected soil and water for testing at each site, and during each
visit, participants completed a survey collecting information on agricultural practices and
land use history, administered via Qualtrics. Participants were not directly compensated
for completing the project. Rather, they received free soil testing and consultation.
Figure 1. Location of 100 participating farm sites. Each farm site is indicated with a red dot.
Names of major cities are included in the map for reference, and dark gray areas on the map show
major bodies of water.
2.2. Survey
A 20-question survey questionnaire was developed using Qualtrics to learn about
soil health and nutrient management practices on small-scale vegetable farms in Minne-
sota. The first draft of the survey was developed by the PI, and then it was reviewed for
technical content and functionality by three University of Minnesota soil scientist col-
leagues, as well as four local Extension educators. The questionnaire was approved for
distribution by the University of Minnesota Institutional Review Board (study #00018630).
The survey was divided into five sections: demographics and site history, fertility
decisions and practices, soil health practices, compost use, and land tenure. It included a
mix of multiple-choice and fillable text questions.
Participants completed the survey online via smartphone while the educator visiting
their farm completed soil testing. In areas with limited internet access, they were given
the link via email and encouraged to complete the survey when they had access to the
internet. Participants completed a survey for each site sampled at their farm (e.g., one
survey for their field and another for their high tunnel). The survey had an 88% response
rate. Survey data were cleaned by the PI, which included de-identifying participants with
a code for each farm and formaing the data for analysis in R. Unanswered questions
were left blank in the dataset, and later filtered during statistical analysis.
2.3. Soil Tests
Figure 1. Location of 100 participating farm sites. Each farm site is indicated with a red dot. Names
of major cities are included in the map for reference, and dark gray areas on the map show major
bodies of water.
Extension educators collected soil and water for testing at each site, and during each
visit, participants completed a survey collecting information on agricultural practices and
land use history, administered via Qualtrics. Participants were not directly compensated
for completing the project. Rather, they received free soil testing and consultation.
2.2. Survey
A 20-question survey questionnaire was developed using Qualtrics to learn about soil
health and nutrient management practices on small-scale vegetable farms in Minnesota.
The first draft of the survey was developed by the PI, and then it was reviewed for technical
content and functionality by three University of Minnesota soil scientist colleagues, as well
as four local Extension educators. The questionnaire was approved for distribution by the
University of Minnesota Institutional Review Board (study #00018630).
The survey was divided into five sections: demographics and site history, fertility
decisions and practices, soil health practices, compost use, and land tenure. It included a
mix of multiple-choice and fillable text questions.
Participants completed the survey online via smartphone while the educator visiting
their farm completed soil testing. In areas with limited internet access, they were given the
link via email and encouraged to complete the survey when they had access to the internet.
Participants completed a survey for each site sampled at their farm (e.g., one survey for
their field and another for their high tunnel). The survey had an 88% response rate. Survey
data were cleaned by the PI, which included de-identifying participants with a code for
each farm and formatting the data for analysis in R. Unanswered questions were left blank
in the dataset, and later filtered during statistical analysis.
2.3. Soil Tests
University of Minnesota Extension educators collected soil tests at each site between
7 April and 5 June 2023. Soil samples were collected with a standard soil probe from 0
to 15 cm, moving away any mulch present. Between 15 and 20 cores were collected from
Sustainability 2025,17, 1192 6 of 22
each site and aggregated into a single composite sample. The composite samples from each
location were sent to the University of Minnesota Research Analytical Laboratory (RAL) to
quantify Bray-P1 phosphorus, exchangeable potassium, and nitrate [
33
,
34
]. Additional soil
testing was completed, which will be reported in a future publication.
2.4. Tillage Score
The tillage score was calculated based on survey results and an equation developed
by the project team based loosely on the STIR rating [
35
], which attempts to assign a
quantitative value to tillage intensity rather than classifying farms into vague qualitative
groups like “no till”, “low till”, or “conventional till”. Following the approach of Büchi
and colleagues [
36
], a weight was assigned to different types of tillage, and participants
were asked to report the average frequency of each type of tillage. They reported on
the number of deep (rototiller or moldboard plow), shallow (e.g., harrow or tilther), and
manual (broadfork) tillage passes per year. The equation used was as follows:
Tillage score = (# deep tillage passes per year ×2) + (# shallow tillage passes
per year ×1) + (# manual tillage passes per year ×0.5) (1)
To further assess tillage differences, we created a farm size variable. Sites were grouped
by size and production type: high tunnels,
≤
1-acre fields, 1.1–3-acre fields, 3.1–5-acre fields,
and >5-acre fields. These categories were chosen based on equipment suitability at each
scale (based on author experience and observations): one can feasibly manage a 1-acre
farm using only hand tools, whereas two-wheel tractors and other motorized equipment
such as rototillers become more common at the 1–3-acre scale and larger equipment such
as tractors become more common around the 5-acre scale.
2.5. Statistics
Survey and soil data were analyzed using R v4.2.2 [
37
]. Graphs were generated
with the ggplot2 package, and summary statistics were generated using basic commands
within the dplyr package. A basic chi-square test was used to assess differences between
non-ordered categorical variables. For ordered categorical variables, we also used the
Spearman correlation coefficient. Variable levels were assigned a rank in R (e.g., for organic
certification, conventional = 1, using mostly organic practices = 2, using exclusively organic
practices = 3, and certified organic = 4). Finally, Kruskal–Wallis was used to compare
categorical values with continuous variables.
3. Results
3.1. Farm Demographics
Participating farms had an average of five acres in production, with fields in vegetable
production for an average of seven years. A total of 23% of participants had less than
5 years
of experience farming, 25% had 5–10 years of experience, and 49% had more than
10 years
of experience. Three percent did not share their level of experience. Participants self-
identified as belonging to the following racial and ethnic groups: white (75%), American
Indian or Alaska Native (6%), Asian, Native Hawaiian, or other Pacific Islander (4%), Black
or African American (5%), and Hispanic or Latino (1%). Nine percent chose not to answer.
While only 14% of participants were certified organic, 44% claimed to use exclusively
organic practices, and an additional 18% used mostly organic practices. In total, 11% of
participants used conventional practices, while 13% chose not to specify.
Land use history (how the site was managed prior to growing vegetables, as reported
by study participants) varied substantially. The largest category of previous land use was
row crop farming (32%), followed by “other” (16%), fallow (13%), grazing animals (9%),
Sustainability 2025,17, 1192 7 of 22
specialty crop production under a different manager or owner (6%), woodland (5%), prairie
(5%), and former industrial site (1%). The remaining respondents did not specify (13%).
Write-in responses included hay or alfalfa, lawn, mixed use, and fruit production (7, 4, 3,
and 2% of the total responses, respectively).
3.2. Demographics and Soil Testing
Farmers in our study were equally likely to test their soil in high tunnels versus fields,
and the decision to collect soil for testing was not impacted by the farmer’s race or ethnicity
(Table 1). Across all testing sites (including fields and high tunnels), organic certification,
farmer experience, and land access situation were all significantly correlated with the
frequency of soil testing (Table 1). In general, certified organic farmers were the most
likely to test their soil at regular intervals. Farmers who claimed to use organic practices
without certification were not more likely than those who self-identified as conventional
farmers to do regular soil tests. Less experienced farmers were also less likely to have
tested their soil than those with at least five years of experience. While land access was
significantly correlated with soil testing frequency, it did not follow a clear pattern, and
having more stable land access did not necessarily make someone more or less likely to test
their soil (Table 1).
Table 1. Impacts of various demographic factors of survey participants on how often they test their
soil. For each variable, the chi-square test is reported. For ordered variables (e.g., experience), the
Spearman correlation coefficient is also reported. Responses (% of total response) for each category
are listed for variables that were significantly correlated with soil test frequency. Variables with
significant correlations are shaded in gray.
Soil Test Frequency Never Once 4+ Years 2–3 Years Every Year
Tunnel vs. field: χ2= 0.609, p= 0.9620
Race or ethnicity: χ2= 31.51, p= 0.1396
Organic certification χ2= 32.063, p=0.0014;rs=0.26,p= <0.001
Conventional 12% 24% 24% 29% 12%
Mostly organic 34% 14% 6% 40% 6%
Exclusively organic, not certified 20% 16% 22% 31% 11%
Certified organic 7% 0% 7% 52% 34%
Experience: χ2= 27.823, p= 0.0005; rs= 0.087, p= 0.265
<5 years 41% 16% 0% 38% 6%
5–10 years 16% 11% 11% 36% 27%
>10 years 11% 15% 24% 38% 11%
Land access: χ2= 47.843, p=0.03556
Informal lease 27% 18% 0% 18% 36%
Formal lease 30% 0% 0% 50% 20%
Own 21% 14% 17% 36% 12%
Land trust or community farm 0% 33% 0% 33% 33%
Tribal land 0% 33% 0% 67% 0%
3.3. Nutrient Management and Input Decision Drivers
Survey participants reported using soil tests as one of their top three decision-making
factors more than any other source of information when deciding which fertility products
to use (and how much) (61% in high tunnels, 55% in fields). Soil tests were followed by
observations of previous crop performance (55% in high tunnels, 52% in fields). Farmers
were more likely to seek advice from other farmers about fertility (40% in high tunnels,
41% in fields) than they were to ask private consultants (20% in high tunnels, 22% in fields),
Extension (14% in high tunnels, 16% in fields), co-ops or input sellers (10% in high tunnels,
9% in fields), or nonprofit support organizations (5% in high tunnels, 18% in fields). A
total of 14% of participants selected “other” in high tunnels and 18% selected it in fields as
one of their top decision-making factors. Write-in responses for “other” included applying
Sustainability 2025,17, 1192 8 of 22
based on observation of plant performance (n = 3), performing the same practices they have
used before (n = 2), not applying any fertilizer (n = 4), based on university or agronomist
recommendations (n = 4), personal or family knowledge (n = 5), “plant needs” (n = 3),
personal research based on books or online articles (n = 4), and applying as much as is
available n = 1) or as much as the participant could afford (n = 1).
3.3.1. Soil Testing
Since participants ranked their soil tests as the primary driver of nutrient manage-
ment decisions, we created a new binary variable based on whether a survey respondent
indicated soil tests as a factor in their decisions, then did basic t-tests to determine whether
using a soil test for fertility decisions impacted the amount of each macronutrient in the soil.
There were no significant differences in soil phosphorus (p= 0.1378), potassium (
p= 0.1284
),
or nitrate (p= 0.1285) between farmers who claimed to use soil tests as a basis for fertility
decisions and those who did not. This is consistent with the findings above, indicating that
the use of soil tests is not significantly correlated with soil macronutrient values, except for
people who had never completed a soil test in their high tunnels.
We also looked at whether soil test frequency influenced soil nutrient concentrations.
If someone had never taken a soil test in their high tunnel, their soil nitrate concentrations
were likely to be higher than someone who had taken a soil test, but farmers who tested
more frequently had similar nitrate concentrations to those who tested less frequently
(Figure 2). This same dynamic was true for phosphorus, but only in high tunnels (Figure 3).
Using the Bray-PI test for phosphorus, 41 ppm is considered “very high” for most vegetable
crops, and no additional phosphorus is recommended after 50 [
38
]. Of the 100 tunnels and
100 fields we sampled, 87% of tunnels and 84% of fields exceeded the “very high” threshold
for soil phosphorus. Even on farms that tested their soil every year, soil phosphorus
levels were on average well above the “very high” threshold at which no additional added
phosphorus is recommended (Figure 3). Potassium concentrations were similar across all
groups, including those who had never tested their soil (Figure 4).
Sustainability 2025, 17, x FOR PEER REVIEW 9 of 25
Figure 2. Frequency of soil testing vs. nitrate concentrations in the top 15 cm of soil (ppm) in 100
vegetable fields and 100 high tunnels in Minnesota. Box plots indicate the median, 1st, and 3rd quar-
tile for each group.
Figure 3. Frequency of soil testing vs. soil phosphorus concentrations in the top 15 cm of soil (ppm)
using the Bray-P1 extraction method in 100 vegetable fields and 100 high tunnels in Minnesota. Box
plots indicate the median, 1st, and 3rd quartile for each group.
Figure 2. Frequency of soil testing vs. nitrate concentrations in the top 15 cm of soil (ppm) in
100 vegetable
fields and 100 high tunnels in Minnesota. Box plots indicate the median, 1st, and
3rd quartile for each group.
Sustainability 2025,17, 1192 9 of 22
Sustainability 2025, 17, x FOR PEER REVIEW 9 of 25
Figure 2. Frequency of soil testing vs. nitrate concentrations in the top 15 cm of soil (ppm) in 100
vegetable fields and 100 high tunnels in Minnesota. Box plots indicate the median, 1st, and 3rd quar-
tile for each group.
Figure 3. Frequency of soil testing vs. soil phosphorus concentrations in the top 15 cm of soil (ppm)
using the Bray-P1 extraction method in 100 vegetable fields and 100 high tunnels in Minnesota. Box
plots indicate the median, 1st, and 3rd quartile for each group.
Figure 3. Frequency of soil testing vs. soil phosphorus concentrations in the top 15 cm of soil (ppm)
using the Bray-P1 extraction method in 100 vegetable fields and 100 high tunnels in Minnesota. Box
plots indicate the median, 1st, and 3rd quartile for each group.
Sustainability 2025, 17, x FOR PEER REVIEW 10 of 25
Figure 4. Frequency of soil testing vs. potassium concentrations in the top 15 cm of soil (ppm) in 100
vegetable fields and 100 high tunnels in Minnesota. The y-axis was limited to 1250 ppm, occluding
one outlier (high tunnel, once at the beginning, 2464 ppm) to improve readability of graph. Box plots
indicate the median, 1st, and 3rd quartile for each group.
3.3.2. Inputs
Inputs were similar across high tunnels and fields. Composted manure was the most
frequently used input in both systems, with over half of respondents using it every year
or more than once per year. This was closely followed by “organic supplemental fertilizers
like bone meal, fish meal, blood meal, feather meal, etc.” (Figures 5 and 6). Because edu-
cators have noticed confusion about the use of the term “compost”, and the fact that it is
often used interchangeably to describe composted manure and vegetable-based compost,
we asked participants to share where they source their compost, and what type of com-
post they most often use. A total of 29% of respondents said they use animal-based com-
post, 16% said they use plant-based compost, and 54% said they use a mix of the two.
Most compost was generated on the farm. Off-farm compost primarily came from com-
mercial facilities. Farmer participants were more likely to purchase compost from a coop-
erative or input store for use in their high tunnel, whereas, for use in fields, they were
more likely to source it from neighbors (Table 2).
Figure 4. Frequency of soil testing vs. potassium concentrations in the top 15 cm of soil (ppm)
in
100 vegetable
fields and 100 high tunnels in Minnesota. The y-axis was limited to 1250 ppm,
occluding one outlier (high tunnel, once at the beginning, 2464 ppm) to improve readability of graph.
Box plots indicate the median, 1st, and 3rd quartile for each group.
Sustainability 2025,17, 1192 10 of 22
3.3.2. Inputs
Inputs were similar across high tunnels and fields. Composted manure was the most
frequently used input in both systems, with over half of respondents using it every year or
more than once per year. This was closely followed by “organic supplemental fertilizers like
bone meal, fish meal, blood meal, feather meal, etc.” (Figures 5and 6). Because educators
have noticed confusion about the use of the term “compost”, and the fact that it is often
used interchangeably to describe composted manure and vegetable-based compost, we
asked participants to share where they source their compost, and what type of compost
they most often use. A total of 29% of respondents said they use animal-based compost,
16% said they use plant-based compost, and 54% said they use a mix of the two. Most
compost was generated on the farm. Off-farm compost primarily came from commercial
facilities. Farmer participants were more likely to purchase compost from a cooperative or
input store for use in their high tunnel, whereas, for use in fields, they were more likely to
source it from neighbors (Table 2).
Sustainability 2025, 17, x FOR PEER REVIEW 11 of 25
Figure 5. Input use frequency in fields at 100 Minnesota vegetable farms as reported by farmer par-
ticipants.
Figure 6. Input use frequency in high tunnels at 100 Minnesota vegetable farms as reported by
farmer participants.
Table 2. Survey responses to questions about compost sourcing in both high tunnel and field envi-
ronments at 100 Minnesota vegetable farms. Percentages reflect the percentage of participants who
selected each option on a multiple-choice survey.
High Tunnels Fields
Source of compost (multiple responses allowed)
Generated on farm 62% 62%
Commercial compost facility 35% 41%
Neighbors 10% 15%
County or city delivery program 7% 8%
Agricultural cooperative or input store 9% 4%
Yard waste site 4% 3%
Reasons for adding compost (multiple responses allowed)
0%
25%
50%
75%
100%
Composted
manure
Organic
supplements
Vegetative
compost
Fresh
manure
Synthetic
complete
fertilizers
Synthetic
nitrogen
Frequency of input use in vegetable fields
indicated by % of respondents
More than once per year About once per year Every few years Never
0%
25%
50%
75%
100%
Composted
manure
Organic
supplements
Vegetative
compost
Fresh manure Synthetic
complete
fertilizers
Synthetic
nitrogen
Frequency of input use in high tunnels
indicated by % of respondents
More than once per year About once per year Every few years Never
Figure 5. Input use frequency in fields at 100 Minnesota vegetable farms as reported by farmer participants.
Sustainability 2025, 17, x FOR PEER REVIEW 11 of 25
Figure 5. Input use frequency in fields at 100 Minnesota vegetable farms as reported by farmer par-
ticipants.
Figure 6. Input use frequency in high tunnels at 100 Minnesota vegetable farms as reported by
farmer participants.
Table 2. Survey responses to questions about compost sourcing in both high tunnel and field envi-
ronments at 100 Minnesota vegetable farms. Percentages reflect the percentage of participants who
selected each option on a multiple-choice survey.
High Tunnels Fields
Source of compost (multiple responses allowed)
Generated on farm 62% 62%
Commercial compost facility 35% 41%
Neighbors 10% 15%
County or city delivery program 7% 8%
Agricultural cooperative or input store 9% 4%
Yard waste site 4% 3%
Reasons for adding compost (multiple responses allowed)
0%
25%
50%
75%
100%
Composted
manure
Organic
supplements
Vegetative
compost
Fresh
manure
Synthetic
complete
fertilizers
Synthetic
nitrogen
Frequency of input use in vegetable fields
indicated by % of respondents
More than once per year About once per year Every few years Never
0%
25%
50%
75%
100%
Composted
manure
Organic
supplements
Vegetative
compost
Fresh manure Synthetic
complete
fertilizers
Synthetic
nitrogen
Frequency of input use in high tunnels
indicated by % of respondents
More than once per year About once per year Every few years Never
Figure 6. Input use frequency in high tunnels at 100 Minnesota vegetable farms as reported by
farmer participants.
Sustainability 2025,17, 1192 11 of 22
Table 2. Survey responses to questions about compost sourcing in both high tunnel and field
environments at 100 Minnesota vegetable farms. Percentages reflect the percentage of participants
who selected each option on a multiple-choice survey.
High Tunnels Fields
Source of compost (multiple responses allowed)
Generated on farm 62% 62%
Commercial compost facility 35% 41%
Neighbors 10% 15%
County or city delivery program 7% 8%
Agricultural cooperative or input store 9% 4%
Yard waste site 4% 3%
Reasons for adding compost (multiple responses allowed)
To add fertility (nutrients) 83% 81%
To improve soil structure 70% 79%
To add organic matter 72% 76%
To lessen soil compaction 32% 32%
To bury weeds 7% 8%
To fill beds 10% 6%
To remediate contamination 0% 0%
Other 10% 9%
How much compost do you apply each year?
A set amount (e.g., 1 inch per bed) 41% 34%
As much as I can get 24% 34%
Based on soil tests 16% 16%
Enough to bury weeds 3% 4%
Other 16% 12%
The highest-ranked motivation for using compost among survey participants was to
add fertility to the soil, indicating that many farmers do consider compost to be a source of
nutrients. This was closely followed by the desire to improve soil structure and increase
organic matter, with fewer participants using compost for compaction remediation, to
bury weeds, or to fill beds. No one reported using compost to remediate contamination
(Table 2). All of the “Other” responses were related to increasing crop yields, except for one
write-in response from an open field indicating that the producer adds compost to improve
soil biodiversity.
While participants ranked soil tests as their primary motivating factor in making
fertility decisions, soil tests were less important than other factors when it came to deciding
how much compost to apply. According to survey responses, participants were most
likely to apply a set amount of compost each year (41% in tunnels, 34% in fields), or to
apply as much as they could source (24% in tunnels, 34% in fields) (Table 2). In both
tunnels and fields, only 16% of respondents applied compost based on soil test results.
Write-in responses for “Other” included comments about the limited experience and still
figuring out compost applications, amounts based on equipment (e.g., “one spreader full”
or one truckload), purchasing as much as people could afford, and as much compost as is
generated in the respondent’s chicken coop.
3.4. Cover Crop Use
Overall, farmers were significantly more likely to use cover crops in open fields than
in high tunnels (
χ2
= 17.208 p= 0.0006). While 72% of the farmer participants had planted a
cover crop in their fields, only 41.5% had done so in their high tunnel (Table 3).
Sustainability 2025,17, 1192 12 of 22
Table 3. Survey responses to questions about cover crop use in high tunnels and fields at
100 Minnesota
vegetable farms, percentages reflect the percentage of participants who selected
each option on a multiple-choice survey.
High Tunnels Fields
Cover crop use frequency
Never 58.50% 28%
Occasionally 19.50% 26%
Every 2–3 years 10% 21%
Every year 12% 26%
Cover crop barriers
Cost 5% 10%
Limited space 15% 15%
Questions about logistics 16% 11%
Limited time 23% 29%
Concern about performance of
next crop 6% 2%
Other 35% 33%
Despite these differences in cover crop adoption between high tunnels and open fields,
barriers were nearly identical across environments (Table 3). In fields, farmer participants
were slightly more likely to cite costs and time constraints as a barriers. In high tunnels,
they were slightly more likely to cite performance about the next crop and questions about
logistics as barriers. The choice most frequently selected by the farmers for both fields and
high tunnels when asked about barriers to cover crop use was “Other”, suggesting that
a key factor (or factors) was missed in the survey questionnaire. There were 52 write-in
responses, some of which included multiple barriers: 28 responses related to a lack of time,
not necessarily in terms of labor, but in terms of being able to fit cover crops into existing
crop rotations. Of these 28 responses, 12 were related to fields, and 16 were related to high
tunnels. Two people mentioned struggles incorporating cover crops into their perennial
plantings, and seven mentioned weather as a barrier, specifically a lack of rainfall at the
right time. Seven people mentioned lacking experience or being unsure of where to find
seed. Two people mentioned labor and cost, and five discussed equipment barriers. Among
the equipment barriers, two felt that the equipment needed to plant and terminate cover
crops was too costly, and the other three shared that cover crops do not work with their
system due to the use of plastic mulch or landscape fabric.
Of the demographic variables surveyed, only organic certification was correlated with
cover crop use (
χ2
= 21.149, p= 0.012). Overall, certified organic farmers were the most
likely group to plant a cover crop every year in both environments, and the least likely
group to have never planted a cover crop (Table 4). In high tunnels, farmers claiming to
use mostly or exclusively organic practices without certification were slightly more likely
to plant a cover crop than farmers who identified as conventional, though, in fields, the
results were more mixed (Table 4).
Table 4. Frequency of cover crop use across environments according to farmer’s organic certification
status based on farmer survey responses at 100 Minnesota vegetable farms. Percentages reflect the
percentage of participants who selected each option on a multiple-choice survey.
Never Occasionally Every 2–3 Years Every Year
High tunnels
Conventional (n = 7) 86% 14% 0% 0%
Using mostly organic practices (n = 17) 71% 6% 24% 0%
Sustainability 2025,17, 1192 13 of 22
Table 4. Cont.
Never Occasionally Every 2–3 Years Every Year
Using exclusively organic practices but not
certified (n = 43) 58% 26% 2% 14%
Certified organic (n = 15) 33% 20% 20% 27%
Fields
Conventional (n = 11) 27% 9% 45% 18%
Using mostly organic practices (n = 17) 35% 18% 18% 29%
Using exclusively organic practices but not
certified (n = 44) 32% 34% 16% 18%
Certified organic (n = 14) 7% 21% 21% 50%
Farmer experience (
χ2
= 5.287, p= 0.5075), land access arrangement (
χ2
= 28.194,
p= 0.2519
), and race (
χ2
= 24.046, p= 0.1535) did not significantly impact cover crop use.
In fields, total acreage was not correlated with cover crop use (χ2= 34.345, p= 0.356).
3.5. Tillage Practices
Overall, tillage intensity, as determined by tillage score (Equation (1)), was slightly
lower in high tunnels than in fields (Figure 7). This difference was borderline significant
according to a chi-square test (χ2= 3.1817, p= 0.0745).
Sustainability 2025, 17, x FOR PEER REVIEW 14 of 25
3.5. Tillage Practices
Overall, tillage intensity, as determined by tillage score (Equation (1)), was slightly
lower in high tunnels than in fields (Figure 7). This difference was borderline significant
according to a chi-square test (χ2 = 3.1817, p = 0.0745)
Figure 7. Tillage score (according to Equation (1)) in 100 fields vs. 100 high tunnels on Minnesota
vegetable farms. Box plots indicate the median, 1st, and 3rd quartile for each group.
Organic certification and land access did not significantly correlate to tillage score (χ2
= 6.5276, p = 0.1631 and, χ2 = 8.9553, p = 0.3461, respectively) but more experience was
significantly correlated with tillage score (χ2 = 8.8471, p = 0.0120). In general, experienced
farmers were more likely to use more intensive tillage than their less experienced coun-
terparts (Figure 8). More experienced farmers did, on average, have larger farms than
those with less experience (Figure 9).
Figure 7. Tillage score (according to Equation (1)) in 100 fields vs. 100 high tunnels on Minnesota
vegetable farms. Box plots indicate the median, 1st, and 3rd quartile for each group.
Organic certification and land access did not significantly correlate to tillage score
(
χ2= 6.5276
,p= 0.1631 and,
χ2
= 8.9553, p= 0.3461, respectively) but more experience was
significantly correlated with tillage score (
χ2
= 8.8471, p= 0.0120). In general, experienced
farmers were more likely to use more intensive tillage than their less experienced counter-
parts (Figure 8). More experienced farmers did, on average, have larger farms than those
with less experience (Figure 9).
Sustainability 2025,17, 1192 14 of 22
Sustainability 2025, 17, x FOR PEER REVIEW 15 of 25
Figure 8. Tillage score (according to Equation (1)) in 100 fields and 100 high tunnels (data aggregated
across sites) based on farmer experience level. Box plots indicate the median, 1st, and 3rd quartile
for each group.
Figure 9. Farm size (acres in production) vs. farmer experience at 100 Minnesota vegetable farms.
Box plots indicate the median, 1st, and 3rd quartile for each group.
Figure 8. Tillage score (according to Equation (1)) in 100 fields and 100 high tunnels (data aggregated
across sites) based on farmer experience level. Box plots indicate the median, 1st, and 3rd quartile for
each group.
Sustainability 2025, 17, x FOR PEER REVIEW 15 of 25
Figure 8. Tillage score (according to Equation (1)) in 100 fields and 100 high tunnels (data aggregated
across sites) based on farmer experience level. Box plots indicate the median, 1st, and 3rd quartile
for each group.
Figure 9. Farm size (acres in production) vs. farmer experience at 100 Minnesota vegetable farms.
Box plots indicate the median, 1st, and 3rd quartile for each group.
Figure 9. Farm size (acres in production) vs. farmer experience at 100 Minnesota vegetable farms.
Box plots indicate the median, 1st, and 3rd quartile for each group.
Sustainability 2025,17, 1192 15 of 22
When we looked at types of tillage rather than the overall tillage score, we saw
differences between farms of different scales. The smallest farms used less frequent deep
tillage (rototillers or moldboard plows) and less shallow tillage (harrows, tilthers) than
larger farms, but used manual tillage techniques like broadforks much more frequently.
Farmers with 1–3 acres were more likely to use shallow tillage techniques, whereas farmers
with more than 3 acres were more likely to use more deep tillage techniques. Tillage
techniques in high tunnels fell somewhere in the middle (Figure 10).
Sustainability 2025, 17, x FOR PEER REVIEW 16 of 25
When we looked at types of tillage rather than the overall tillage score, we saw dif-
ferences between farms of different scales. The smallest farms used less frequent deep
tillage (rototillers or moldboard plows) and less shallow tillage (harrows, tilthers) than
larger farms, but used manual tillage techniques like broadforks much more frequently.
Farmers with 1–3 acres were more likely to use shallow tillage techniques, whereas farm-
ers with more than 3 acres were more likely to use more deep tillage techniques. Tillage
techniques in high tunnels fell somewhere in the middle (Figure 10).
Figure 10. Types of tillage and frequency of tillage passes at 100 Minnesota vegetable farms based
on farm size and production environment (high tunnel vs. field). Tillage score is the cumulative
tillage intensity based on Equation (1). Bars represent means, error bars represent standard error.
There was no significant association between cover crop use and tillage (χ
2
= 0.1795,
p = 0.9808).
4. Discussion
4.1. Nutrient Management Decision-Making
More experienced farmers and certified organic farmers in our study were more
likely to utilize soil testing than their less experienced or non-certified organic peers. The
National Organic Program requires that certified organic producers manage inputs in a
manner that does not contribute to contamination of crops, soil, or water by plant nutri-
ents[39]. Rule §205.601(j) prevents farmers from adding micronutrients to their soil with-
out first documenting a deficiency by testing the soil[39]. These rules, along with support
provided by certifiers likely contribute to the higher rates of soil testing among certified
organic farmers. While there is limited research exploring the links between organic cer-
tification and soil testing, organic certification has been linked to improved soil health in
a variety of studies and contexts [40–42].
This finding suggests a need for more outreach and education targeted to beginning
farmers about how to correctly collect soil samples for soil testing and also how to
Figure 10. Types of tillage and frequency of tillage passes at 100 Minnesota vegetable farms based on
farm size and production environment (high tunnel vs. field). Tillage score is the cumulative tillage
intensity based on Equation (1). Bars represent means, error bars represent standard error.
There was no significant association between cover crop use and tillage (
χ2
= 0.1795,
p= 0.9808).
4. Discussion
4.1. Nutrient Management Decision-Making
More experienced farmers and certified organic farmers in our study were more likely
to utilize soil testing than their less experienced or non-certified organic peers. The National
Organic Program requires that certified organic producers manage inputs in a manner
that does not contribute to contamination of crops, soil, or water by plant nutrients [
39
].
Rule §205.601(j) prevents farmers from adding micronutrients to their soil without first
documenting a deficiency by testing the soil [
39
]. These rules, along with support provided
by certifiers likely contribute to the higher rates of soil testing among certified organic
farmers. While there is limited research exploring the links between organic certification
and soil testing, organic certification has been linked to improved soil health in a variety of
studies and contexts [40–42].
This finding suggests a need for more outreach and education targeted to beginning
farmers about how to correctly collect soil samples for soil testing and also how to interpret
laboratory soil test results, particularly for farmers who are not certified organic or pursuing
certification. Extension agents have been identified as crucial for promoting organic farming
Sustainability 2025,17, 1192 16 of 22
practices and other agroecological practices [
42
]. As such, Extension programs should
invest in promoting soil testing and soil test interpretation with this audience and also
consider promoting organic certification to connect farmers with additional support for
sustainable nutrient management practices.
Even when farmer participants tested their soil regularly, this did not translate to
meaningful differences in soil nutrient concentrations, and most fields and high tunnels in
the study had excessive soil phosphorus. Excess phosphorus in agricultural soils is corre-
lated with runoff and leaching, resulting in eutrophication of freshwater ecosystems [
43
,
44
].
A 2022 soil health-related needs assessment of emerging and beginning farmers in Min-
nesota identified that even when farmers test their soil, they often struggle to interpret
soil test results and make nutrient management decisions accordingly [
32
]. These results
support the finding that soil testing does not always translate into nutrient management
decision-making and further emphasizes the need for additional education about soil test
interpretation among small-scale vegetable farmers. This is consistent with farmers in
both Michigan and Ghana, whose observations of physical and biological attributes of soil
generally aligned well with soil health assays, but whose perceptions of chemical properties
of soil did not consistently align with soil test results [45,46].
The farmers in our study based fertility decisions more on their own observations
of previous crop performance and other farmers’ recommendations than on consultant
or Extension recommendations. This is consistent with findings from studies on farmer
decision-making across the region and the world, in which farmers prefer to learn from one
another versus seeking advice from agricultural professionals [
26
,
47
–
49
]. By leaning into
this finding and using train-the-trainer models, peer learning cohorts, and other methods
to engage communities of farmers in learning together, educators can have more impact
when sharing best practices for soil health and nutrient management.
4.2. Compost Confusion
This study highlights a particular need for compost-specific and composted-manure-
specific education among diversified vegetable farmers. Composted manure was the most
commonly used input among farmers in the study. They applied it primarily to add
fertility and yet treated it very differently from other nutrient sources. They tended to
apply as much as possible or a set amount each year rather than calculating compost and
composted manure inputs based on soil test values. A previous qualitative study identified
similar issues among beginning and emerging farmers in Minnesota, specifically, over-
application of composts including composted manure, and conceptualizing composted
products separately from nutrient sources [
32
]. Our findings here show that these challenges
do not just apply to emerging farmers and that even experienced diversified vegetable
farmers struggle to apply nutrient management principles to the use of composted manure
and vegetative compost.
Compost applications can enhance the sustainability of a farm by improving root
growth and nutrient uptake, improving crop yields and quality, and improving soil charac-
teristics including porosity, aggregate stability, moisture and nutrient contents, and organic
matter [
50
]. Mismanagement of synthetic fertilizers and pesticides has led to pollution and
the degradation of soil on a global scale [
51
], and supplementing fertility programs with
compost can mitigate some of these challenges. The use of compost to improve soil condi-
tions has implications for the ability of a farm to remain sustainable, including the ability to
withstand unpredictable weather conditions, manage pathogens, reduce soil erosion and
nutrient runoff, and reduce the need for chemical fertilizers and irrigation [
50
]. Composting
also improves the sustainability of global waste management and phosphorus management.
A significant portion of human municipal waste is compostable, with estimates of 50% in
Sustainability 2025,17, 1192 17 of 22
Europe [
52
], and 40–70% globally [
53
]. This is particularly true in urban environments [
54
].
By diverting this waste from landfills and recycling it into high-quality compost, there are
sustainability implications for greenhouse gas reductions and soil organic matter improve-
ment at a global scale [
52
,
53
]. A 2011 analysis of the Minnesota Twin Cities Capitol Region
Watershed estimated that food consumed and wasted by humans was the largest source of
phosphorus inputs to the watershed and that diverting food and yard waste from landfills
would reduce the storage of phosphorus in the watershed landscape by 66% [55].
Using compost to supplement soil fertility programs contributes to improving the
sustainability of agriculture by improving nutrient use efficiency and productivity [
56
].
However, to promote more informed use of composts and mitigate externalities, there is
a need for more research to develop accurate recommendations about the right volumes
and types of compost needed for substituting commercial or synthetic fertilizers across
different soils, crops, and growing conditions [
53
,
56
]. Compost is a highly variable product,
referring to any organic matter that has been derived from plants, animals, or people and
decomposed under aerobic conditions [
50
]. The final product depends on composting
temperature, moisture, carbon-to-nitrogen ratio, source, and particle size of the feedstock,
the presence of microorganisms, and the amount of oxygen and aeration available during
the process [50].
If farmers are not using soil tests to determine compost application rates, but using
compost and composted manure as primary fertility sources, soil tests have limited utility.
This, combined with the excessively high soil nutrient concentrations on the farms in
our study, represents a need for more targeted education about how to translate soil test
results for farming systems primarily relying on composted vegetable scraps and manure
for fertility.
4.3. Cover Crops
The majority of farmers in this study (72%) used cover crops at least occasionally in
their fields, while the majority (58.5%) had never done so in their high tunnels. Adoption
of cover crops was significantly higher in this group overall compared to estimates of
the average Minnesota farmer. According to the 2022 Census of Agriculture, only 9% of
Minnesota farms that participated in the census planted cover crops, representing about
3% of farmland represented in the census [
6
]. Of the demographic variables studied, only
organic certification was significantly correlated with higher cover crop adoption. Farm
size, experience, race, or land access were not significantly correlated with cover crop use.
Other studies of small-scale vegetable farmers have identified that this group of farmers
tends to be very conservation-minded, prioritizing soil health practices as a core motivation
behind their approach to farming [
10
,
13
]. While a study of 541 organic fruit and vegetable
farmers in the United States found that smaller farmers (<40 acres) were more likely to use
cover crops and other conservation practices than their larger counterparts, almost all of
the farmers in our study fell into the “small” farm category [41].
Despite the lower adoption of cover crops in high tunnels, we did not identify any
barriers that were more significant in high tunnels than in open fields. Overall, the most
significant barriers for cover crop use were a lack of time, and not being able to fit cover
crops into crop rotations. This is consistent with the characterization that small-scale
vegetable farms tend to plant very intensively, using season extension and succession
planting to efficiently produce high yields on a small scale, leaving limited windows for
cover crops and fallow periods [19].
The cost was one of the least significant barriers to cover crop adoption. This is
important, as many of the conservation payment programs that incentivize cover crop use
cover the cost of seed, but not of farmers’ time. A 3-year study on economic tradeoffs for
Sustainability 2025,17, 1192 18 of 22
high tunnel cover crops in Minnesota, Kansas, and Kentucky found that seed made up
only 1% or less of the cost of planting cover crops, and that labor accounted for the vast
majority of the cost [
57
]. Our results support the finding that incentive programs may be
more effective if they can offset the costs of labor related to planting cover crops versus
simply covering the cost of seed [57].
Only 16% of high tunnel participants and 11% of field participants identified edu-
cational barriers (questions about logistics). This suggests that the primary barriers to
cover crop use on small-scale vegetable farms are not educational in nature. Nonetheless,
targeted educational outreach could still be beneficial for improving cover crop adoption
among the farmers who identified it as a barrier.
4.4. Tillage
More experienced farmers in our study were more likely to use more intensive tillage
than their less experienced counterparts. While we do not have enough data to investigate
the reasons behind this trend, this finding is consistent with a study of 96 organic (including
those using organic practices but not certified) field crop and vegetable producers in
Michigan. The survey found that farmers with fewer years of experience were more likely
to be interested in reduced tillage methods and that vegetable farmers were more likely
to be interested in reduced tillage methods than field crop farmers [
58
]. While this study
did not report on why, they cited that smaller, newer farms generally have less capital
to invest in equipment like reduced tillage machinery and that the return on investment
for equipment may be lower on highly diversified vegetable farms where equipment may
only be suitable for a subset of the crops grown. Small beginning farmers are also likely
to be debt-averse [
10
]. Thus, smaller vegetable farms may be more motivated to find
alternatives [
58
]. Our breakdown of tillage types among different farm scales supports this
hypothesis. Our results also show that while reduced tillage methods are common among
the smallest-scale vegetable farmers (1 acre or less), there is a need for education, as well as
research into methods for reducing tillage at the 3–50-acre scale. This is especially important
for organic systems; conventional no-till approaches rely heavily on herbicides [59–61].
While organic certification was significantly correlated with soil testing and cover crop
use, it was not significantly correlated with tillage score.
Finally, a commonly cited tradeoff of using cover crops, particularly in systems that
do not use herbicides, is that tillage is typically required to terminate them [
62
]. We did
not find a correlation between the frequency of cover crop use and tillage score to support
this. This may be partially explained by the fact that if well timed, the weed suppression
benefits of cover crops may offset additional tillage passes for weed management [62].
4.5. Limitations and Future Research
Because of the number of participants in our study and the complexity of their agri-
cultural systems (i.e., many crops per farm), our analysis lacks a detailed accounting of
inputs. While our general categorization of input frequency (e.g., number of times per
year participants applied a variety of inputs), the lack of quantification limits our ability
to draw detailed conclusions about nutrient management practices. We can infer that
the use of compost, particularly composted manure, is contributing to excessive nutrient
accumulation based on soil nutrient levels and qualitative survey data, but without a full
cost accounting of inputs, these conclusions are speculative in nature.
We also acknowledge the limited soil data presented in this paper. Due to the volume
of data produced in this project, a follow-up paper will document more detailed soil
test data from the 100 farms. Future research should address both agronomic challenges
addressed here, including the development of better guidance for using compost products
Sustainability 2025,17, 1192 19 of 22
for fertility in a diversified agricultural system, as well as the social dynamics of how to
effectively communicate soil health practices to farmers.
5. Conclusions
Small-scale vegetable farmers face unique challenges related to managing their soils
due to intensive planting windows, labor demands, insufficient access to capital and
equipment, and heavy reliance on inputs like compost and composted manure with hard
to calculate nutrient concentrations.
Extension and other educational programs should develop targeted resources and
education to support farmers with nutrient management in these systems, particularly
related to the application of compost and avoiding over-application of nutrients like
phosphorus as well as soil testing and test interpretation. Farmers in our study used
composted manure and vegetative compost far more often than synthetic fertilizers (58%
of farmers used composted manure at least once per year, 34% used vegetative compost
compared to 18% using synthetic complete fertilizers, and 11% using synthetic nitrogen
at least once per year in fields), and yet the majority (87% of high tunnels and 84% of
fields) had soil phosphorus levels that were “very high”, compromising the sustainability
of these systems. Farmer participants did not treat vegetative compost and composted
manure like other fertility inputs: rather than relying on soil tests to make decisions about
application rates, they tended to apply as much as possible or a set amount each year,
likely contributing to the over-application of phosphorus. More research is needed to
help farmers make informed decisions about organic inputs, and educators may be most
effective by tapping into existing farmer networks and leveraging peer learning.
Cover crops are particularly challenging for this audience due to short planting win-
dows, labor availability, and equipment requirements. Despite this, small-scale vegetable
farmers in this study far surpassed the average Minnesota farmer in their adoption of cover
crops with 72% of farmers in our study using cover crops at least occasionally, compared
to 9% of Minnesota farmers in the 2022 agriculture census. Organic certification was the
only significant driver of cover crop adoption; farm size, farmer experience, race, and land
access were not significantly correlated with cover crop adoption. Conservation incentive
programs that compensate labor in addition to seed costs in combination with more tar-
geted educational outreach may significantly benefit small-scale vegetable farmers and
other farmers.
The use of tillage was related to farm size (or at least land in vegetable production),
with smaller areas (high tunnels and open fields < 1 acre) relying mostly on manual tillage
and larger areas using mechanized tillage. Other demographic variables including organic
certification, farmer experience, race, and land access were not significantly correlated
with tillage score. More investment in reduced tillage practices and methods for small-
scale growers in the 3–50-acre range is critical for reducing tillage among small-scale
vegetable farmers.
Overall, farmers in our study were likely to use practices widely considered sus-
tainable including the use of organic inputs, cover crops, and reduced tillage. How-
ever, they need more targeted information and educational resources to support their
continued sustainability.
Author Contributions: Conceptualization, formal analysis, data curation, writing—original draft
preparation, visualization, project administration, and funding acquisition, N.H.; methodology,
N.H. and P.H.P.; investigation, N.H., S.M.B. and E.L.; writing—review and editing, N.H., S.M.B.,
E.L. and P.H.P.; supervision, P.H.P. All authors have read and agreed to the published version of
the manuscript.
Sustainability 2025,17, 1192 20 of 22
Funding: This research was funded by the University of Minnesota Agricultural Experiment Station
Rapid Response Fund, which is supported by the Minnesota state legislature.
Institutional Review Board Statement: Ethical review and approval were waived for this study by
the University of Minnesota Institutional Review Board because it was determined to be “Not human
research” (study #00018630).
Informed Consent Statement: Informed consent was obtained from all subjects involved in
the study.
Data Availability Statement: The data presented in this study are available on request from the
corresponding author.
Acknowledgments: We are thankful to our team of educators who participated in soil testing for this
project: Anthony Adams, Katie Hagen, Katie Drewitz, Claire LaCanne, Randy Nelson, Jennifer Hahn,
Sarah Waddle, Colleen Carlson, Mercedes Moffet, Troy Salzer, Tarah Young, Kaitlyn Albers, and Erik
Heimark. We are also grateful to Julie Grossman, Adria Fernandez, and Carl Rosen for their input on
survey design and analysis.
Conflicts of Interest: The authors declare no conflicts of interest.
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