Organic Farmer April / May 2021

April/May 2021
How Much Nitrogen Can You Expect
from Organic Fertilizers and Compost?
Understanding the Economics
of Organic Seed Production
How to Help Endangered Pollinators
Biosolarization and Cover Crop
Impact on Weeds and Soilborne Pathogens
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2 Organic Farmer April/May 2021
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IN THIS ISSUE
PUBLISHER: Jason Scott
Email: jason@jcsmarketinginc.com
EDITOR: Marni Katz
ASSOCIATE EDITOR: Cecilia Parsons
Email: article@jcsmarketinginc.com
PRODUCTION: design@jcsmarketinginc.com
Phone: 559.352.4456
Fax: 559.472.3113
Web: www.organicfarmingmag.com
4
10
14
20
24
How Much Nitrogen Can You
Expect from Organic Fertilizers
and Compost?
Understanding the Economics
of Organic Seed Production
Biosolarization and Cover Crop
Impact on Weeds and Soilborne
Pathogens
USDA Passes Final Rules on
Hemp Growing
Research into Alfalfa Crop
Rotation for Organic Tomatoes
14
CONTRIBUTING WRITERS
& INDUSTRY SUPPORT
Danita Cahill
Contributing Writer
Taylor Chalstrom
Assistant Editor
Daniel Geisseler
UCCE Nutrient
Management
Specialist
Sabrina Halvorson
Contributing Writer
Timothy Jacobs
Risk Management
Specialist, USDA
Neal Kinsey
Kinsey Ag Services,
Contributing Writer
Patricia Lazicki
UC Davis PhD
Candidate
Margaret Lloyd
UCCE Small Farms
Advisor
Joji Muramoto
UCCE Organic
Production Specialist
Kiki Hubbard
Organic Seed Alliance
Richard Smith
UCCE Vegetable
Production Specialist
Ashraf M. Tubeileh
Cal Poly, San Luis
Obispo
26
30
36
Food Safety Laws and Standard
Operating Procedures for Urban
Farmers
How to Help Endangered
Pollinators While Also Helping
Your Farm
USDA National Organic Program
Changing Approach to
Organic Oversight in India
26 UC COOPERATIVE EXTENSION
ADVISORY BOARD
Surendra Dara
UCCE Entomology and
Biologicals Advisor, San Luis
Obispo and Santa Barbara
Counties
Kevin Day
County Director/UCCE
Pomology Farm Advisor,
Tulare/Kings Counties
Elizabeth Fichtner
UCCE Farm Advisor,
Tulare County
Katherine Jarvis-Shean
UCCE Area Orchard Systems
Advisor, Sacramento,
Solano and Yolo Counties
Steven Koike
Tri-Cal Diagnostics
Jhalendra Rijal
UCCE Integrated Pest
Management Advisor,
Stanislaus County
Kris Tollerup
UCCE Integrated Pest
Management Advisor,
Parlier
Mohammad Yaghmour
UCCE Area Orchard Systems
Advisor, Kern County
38
Micronutrients: Effective
Measurement and Use of
Manganese
30
The articles, research, industry updates,
company profiles, and advertisements in this
publication are the professional opinions of
writers and advertisers. Organic Farmer does
not assume any responsibility for the opinions
given in the publication.
April/May 2021 www.organicfarmermag.com 3

How Much N Can You Expect from
ORGANIC FERTILIZERS
AND COMPOST?
By MARGARET LLOYD | UCCE Small Farms Advisor
DANIEL GEISSELER | UCCE Nutrient Management Specialist
PATRICIA LAZICKI | UC Davis PhD Candidate
JOJI MURAMOTO | UCCE Organic Production Specialist
and RICHARD SMITH | UCCE Vegetable Production Specialist
Nitrogen (N) is an essential plant
nutrient, providing the building
blocks for plant growth and development.
The N sources on an organic
farm are numerous, including crop
residue, compost, fertilizers, soil organic
matter and irrigation water (Figure 1).
Nitrogen management in organic systems
is challenging because complex organic
forms of N originating from organic
materials need to be mineralized by microbes
to become plant-available mineral
forms of N: ammonium (NH4+) and
nitrate (NO3-). Learning how to predict
and monitor N release from soil amendments
are important skills useful for
selecting amendments and determining
application rates and timing to achieve
optimum plant health and yield.
Soil microbes facilitate N availability in
organic systems through organic matter
decomposition. Microbes use carbon
(C) as their primary energy source. However,
to grow, microbes also require N.
When compost and fertilizers are added
to moist soil, microbes are “fed” and
microbial activity is stimulated. With
this activity, there is rapid turnover
of microbes as well as organic matter
decomposition, which become the two
main sources of available N for plants.
However, as the ratio of C:N in the
amendments approaches 20:1, additional
N is required to facilitate microbial
breakdown. This additional N is taken
Figure 1. An example of N uptake and N supply in an organic tomato field. Field studies
occurred in the Sacramento Valley in a silt loam soil with approx. 1% organic matter content,
growing fresh market tomato cv Brandywine. Cover crop was an oat legume mix with 3% N
that averaged approximately 3 T/A biomass that was incorporated one month before planting.
Granular fertilizer was applied at 700 lb./acre. Irrigation water total estimated 3.6 acre-feet with
a concentration of 1 ppm NO 3
-N (Geisseler et al., unpublished).
Cumulative N release/ uptake
(lbs/acre)
250
200
150
100
50
Irrigation water
Granular fertilizer (4% N)
Poultry manure compost
Cover crop
Soil (0-24 in)
Plant uptake
Apr May Jun Jul Aug Sep
from the pool of plant-available forms
of N in the soil. Because this reduces
the amount of N available to plants, it is
sometimes referred to as “tying up N” or
N immobilization. Because most amendments
available to organic farmers are
bound in complex molecules containing
both C and N, only a portion of the N
becomes available to plants in the short
term. This begs the question, how much
N can you expect from organic fertilizers
and compost?
What to Expect
Composts, manures and organic fertilizers
are all applied to supplement soil N.
The N availability from these materials
differs widely, from 90% to tying up
N. To better understand this, we mixed
common soil amendments with organically-managed
field soil and incubated
them for 84 days in warm and moist soil
(73 degrees F and 60% water holding
capacity.) Figure 2 (see page 5) shows
how quickly N became available from
each material. A negative value indicates
4 Organic Farmer April/May 2021

Figure 2. Predicted N release curves from different amendment types when
incorporated into warm, moist soil 2 .
Figure 3. Relationship between potentially available N
and amendment carbon to nitrogen ratio 2 .
Available N
(% amendment N)
100
80
60
40
20
0
0
Guano
Blood & feather meal
Liquids
Granular fertilizer, 4% N
Composted poultry manure
Composted yard trimmings
20 40 60 80
Available N @ 12 weeks
(% amendment N)
Available N @ 12 weeks
(% amendment N)
90
70
50
30
10
0
0
5:1
10:1
Liquids
Blood & feather meal
Granular fertilizers and guano
Manure composts
Yard trimmings composts
Carbon to nitrogen ratio
%N not a good predictor
for mineralization from
liquids
N risks being
immobilized
15:1 20:1
Days after incorporation
0 5 10 15
Nitrogen concentration (%)
N immobilization. Actual N release rates
in the field will depend on soil moisture
and temperature but will follow a similar
pattern.
Our research along with dozens of other
studies has found that the C:N ratio and
% N of an amendment are good predictors
of N availability. The lower the C:N
ratio in the material, the more quickly N
will be released. As the C:N ratio exceeds
15:1, available N moves closer to 0 due to
temporarily tying up N. Such materials
should not be applied too close to planting.
Especially for compost, it is important
to find out the total N and C:N ratio
from the supplier to understand whether
this material will be contributing N or
tying up N in the soil. When C:N ratio
is unavailable, the total N concentration
is closely related to availability. Generally,
as total N increases, availability of N
increases (See Figure 3).
Among the amendments tested, guano
had a very high N content (% N) and a
very low C:N ratio which resulted in high
N availability (80% to 90% of the total N)
and rapid availability—more than 50% of
Continued on Page 6
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Continued from Page 5
the N was available immediately with an
additional 30% to 40% becoming available
over 40 days (Figure 2, see page 5).
On the other hand, composted yard
trimmings had low total N content, less
than 2%, and a high C:N ratio between
13 to 20, which resulted in slight N
immobilization to 4% N release.
Low C:N ratio materials like guano,
feather meal and fish emulsion released
much of their N in the first week, and
almost all their N within three weeks.
This quality makes them good sidedress
materials. They can also be used to
remediate known N deficiency.
Table 1. Potential N availability from different types of organic amendments under warm, moist
conditions. Negative numbers mean the compost tied up soil N2. All % N numbers for solid
amendments are on a dry weight basis. Note: Liquid % N is reported on a fresh weight basis and
isn’t a good indicator of the release rate. *(See Figure 3, page 5)
Municipal yard trimmings
compost
Poultry manure composts
Granular fertilizers
(except guano)
Blood & feather meal
Liquid fertilizers
Guano
Material
Typical
%N
0.5-2
2-5
2-7
13-15
2-4*
12-13
Typical C:N
ratio
13-20
6-8
5-7
3-4
4-6
3-4
N available
after 12 weeks
-3% - 4%
30 - 35%
38 - 60%
65 - 70%
50 - 100%
80 - 90%
Releases in:
Years
Weeks-months
Days-weeks
Days
Days
Days
Poultry manure composts and granular
fertilizers contributed some available N
as soon as they were applied, but released
their N more slowly. When incorporated
into moist soil under warm conditions,
they will release more quickly, though
still over weeks, not days (See Table 1).
High C:N materials like plant-based yard
trimmings and composts released little
to no N. They provide C which supports
microbial communities and, over time,
improves soil physical structure, but
provides little N in the short term. Longterm
soil fertility may be improved.
Plant-based liquid fertilizers ranged
from 48% to 92% N availability whereas
manure-based liquid fertilizers (typically
fish) ranged from 83% to 99% N availability
after four weeks 1,2 . Organic liquid
fertilizers are suspensions and often
include particulate matter with which
8% to 21% of total N content is associated.
Without proper filtration, these
materials increase the risk of clogging
drip emitters. If they are injected before
the filter, a significant amount of the N
can be removed from the suspension.
Regular backflushing may be required to
maintain system flow. New technology in
liquid organic fertilizer is now providing
materials in which N is thoroughly
dissolved and does not have the issues
just discussed. Coupled with the high
cost per unit N, liquid fertilizers are often
viewed as an easy way to supplement
in-season fertility, but too expensive to
provide the bulk of the crop’s N demand.
In all cases, amendment N release is
slower in cool weather or dry conditions
as microbial activity is decreased. Crops
planted in cold temperatures may benefit
from starter fertilizers that contain some
available N initially − those with a higher
amount at day 0 and a steep initial curve
(Figure 2, see page 5). For example, manure-based
composts have roughly 15%
of their total N available at application,
whereas granular fertilizers started with
an average of about 22%, or guano at
more than 50%.
If only a portion of the total N becomes
available, what happens to the rest?
The unmineralized organic N becomes
part of the soil organic matter pool of
N, and will be available in the future as
the material is subject to mineralization
processes.
How Much N and When?
Crop N demand and yield are very closely
linked. The crop N demand includes N
requirements to produce the plant material,
harvested crop and cull produce. Expected
yield is a good starting point for
estimating how much N the crop needs.
Specific crop N demand guidelines can
be found at geisseler.ucdavis.edu/Guidelines/Home.html.
The timing of crop demand depends on
the crop. Figure 4 (see page 8) shows
the N demand curve for broccoli tomato
and strawberry. The steep areas on the
curve indicate high N demand and represent
times when N should be in high
and sufficient supply. The fresh market
tomato curve shows that from full bloom
to early harvest, tomatoes utilize 73%
of the crop’s total N demand. During
this period, N uptake rates averaged 3
to 5 pounds N/A/day. Little N was used
prior to flowering or once harvest was
on-going, in this case of indeterminate
tomatoes. Crops with similar growth and
fruiting habits form similarly shaped N
demand curves, though additional crops
can be found at geisseler.ucdavis.edu/
Guidelines/N_Uptake.html.
To ensure that sufficient N is available
for the period of high N demand, taking
a soil test a couple of weeks prior to that
period is recommended. Samples taken
at this time will reflect current availability
from any number of organic sources
(fertilizers, compost, cover crop residue,
soil organic matter and others). Convert
soil test data to lb./A to determine
whether the supply will meet the demand.
Details on how to take a soil sample can
be found at geisseler.ucdavis.edu/Guidelines/Soil_Sampling_Nitrate.pdf.
Conclusion
Supplying a crop with sufficient N is
essential for optimum health and production.
In organic production, this is
very challenging and requires the ability
to synthesize hard numbers, educated
Continued on Page 8
6 Organic Farmer April/May 2021

Continued from Page 6
guesses, and keen observations.
Here are some tips:
• Establish an N goal for your crop.
• Identify the C:N ratio or total % N of your
amendment to estimate N availability for your
amendment (Table 1, see page 6, Figure 3, see
page 5).
• Familiarize yourself with the N release pattern
from amendments (Figure 2, see page 5).
• Learn the N uptake demand for your crop (Figure
4).
• Monitor N with soil sampling to refine your estimations
and confirm sufficient N for your crop.
Organic N management is challenging, so we hope
this article will help you navigate this important
decision with more confidence and success.
Additional Resources
N dynamics in field-grown organic heirloom tomatoes:
ucanr.edu/sites/SFA/files/343252.pdf
Practical Training on N Planning and Management
in Organic Production: ccsmallfarms.ucanr.edu/
Events_and_trainings/Nitrogen_Planning_and_
Management_in_Organic_Production_of_Annual_Crops_915/
References
1 Hartz, T..K., Smith, R., Gaskell, M., 2010. Nitrogen availability
from liquid organic fertilizers, HortTechnology 20(1),
169-172.
2Lazicki, P., Geisseler, D., Lloyd, M., 2020. Nitrogen mineralization
from organic amendments is variable but predictable.
Journal of Environmental Quality 49, 483-495. Available
at: https://acsess.onlinelibrary.wiley.com/doi/epdf/10.1002/
jeq2.20030
3Hartz, T.K., Cahn, M.D., Smith, R.F., 2017. Efficient nitrogen
fertility and irrigation management of cool-season vegetables
in coastal California. Available at: https://vric.ucdavis.edu/
pdf/fertilization/fertilization_EfficientNitrogenManagementforCoolSeasonvegetable2017.pdf
Comments about this article? We want to hear from
you. Feel free to email us at article@jcsmarketinginc.
com
Crop N uptake (lb N/acre)
Crop N uptake (% of total)
400
300
200
100
Crop N uptake (% of total)
0
0
100
60
40
20
0
0
100
80
60
40
20
0
0
Broccoli
Broccoli seeded in
summer starts
growing and taking
up N quickly. Uptake
starts to slow wjen
the weather cools.
20 40 60
Tomato, fresh market
30
60
Full
bloom
Broccoli seeded in winter
only starts to rapidly
take up N when the
weather warms. N
uptake is high right
through to harvest.
Days after Planting
Green fruit
80 100 120 140
Harvest period
60 90 120
Days after Planting
Harvest
period
0
120 180 240 300 360
Days after Planting
200
150
100
50
0
150
Figure 4. Example of crop N uptake curves of fresh market ‘Brandywine’
tomato and broccoli. Broccoli data is from a conventional field in the Salinas
Valley. Yields were 28,000 and 22,000 lb./acre for summer- and winter-seeded
broccoli, respectively 3 . Tomato data is from a fresh-market organic heirloom
trial in Yolo County. Total yield was 62,000 lb./acre (unpublished data).
160
120
80
40
Crop N uptake (lb N/acre)
Crop N uptake (lb N/acre)
8 Organic Farmer April/May 2021

CONVERTING SOIL TEST DATA TO LB/A
L
Soil test results are often reported as either NO3-N or NO3 and in ppm or mg/kg. NO3-N is reporting
just N whereas NO3 is reporting the whole molecule and needs to be adjusted (See conversion too).
1 mg/kg = 1ppm
If soil test is NO3, convert to NO3-N: ppm / 4.42 =
NO3
ppm
NO3-N
Converting ppm or mg/kg to lb./acre can be calculated by multiplying this number by a factor of
three to four per 12’’ depth of soil, depending on the soil bulk density. If you do not know your soil
bulk density, 3.6 is a good starting place. See the conversion tools for details.
If soil test is in ppm, convert:
ppm x 3.6 =
NO3-N soil bulk density
lb. N/A
NO3-N
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Understanding the
Economics of Organic
Seed Production
By KIKI HUBBARD | Organic Seed Alliance
Organic seed production can be an economic opportunity for organic growers (photo by Broken Banjo Photography.)
Organic seed production is a
developing industry and viable
economic opportunity for organic
growers. To help growers manage the
uncertainties and risks inherent to seed
production, and to help growers earn
more profit, Organic Seed Alliance
(OSA) recently published an online
toolkit to assist organic seed growers
and seed enterprises. The toolkit serves
as the first of its kind to focus on organic
seed production specifically, offering
support in the form of budgeting
spreadsheets, inventory management,
and foundation and stock seed planning.
Seed production can be deeply rewarding
work. However, turning a passion
for seeds into a viable livelihood is a
challenge that even experienced seed
growers struggle to overcome. That’s
why this entire toolkit was developed in
partnership with agricultural economists
at Highland Economics— experienced
professionals who understand
the importance of a farm budget and
production plan.
Tracking Expenses and Budgets
The first tool in the Seed Economics
Toolkit is a spreadsheet that helps growers
track the costs associated with producing
seed crops. Enterprise budgets
provide a snapshot of costs associated
with a crop for a single year and do not
make predictions or forecasts for future
years. However, they can be used to
provide guidance for growers who are
considering investments in new equipment
and scaling up.
Stock and Foundation
Seed Production
Common questions around foundation,
stock and production seed include:
How much foundation seed do I need
to ensure I have enough stock seed?
How much stock seed should I produce
every third year for my production
seed? This second spreadsheet helps
guide decisions around how much and
how often to produce foundation, stock,
and production seed based on your
operation, desired inventory, longevity
of the seed and estimated yield.
Tracking Labor
Tracking on-farm labor can be confusing
and overwhelming, but it is also
extremely important for growers trying
to get a handle on their operation costs.
A third piece of this toolkit is designed
as a guide for tracking your operation
each day, including a form designed
for routine activities over the course of
many days (such as watering in a greenhouse
or screening a large seed lot) for
tracking labor in seed production.
Getting Seed Contracts
Success in seed production contracts
requires careful management of the
grower-buyer relationship and an
understanding of the terms of the contract.
Learning from others’ experience
can save many headaches and ensure
a successful grower-buyer relationship.
Over the years, experienced seed
growers and buyers have shared their
experiences and advice in workshops
and webinars at the Organic Seed
Growers Conference and other online
networking events. Several of these
webinars also offer contact information
Continued on Page 12
10 Organic Farmer April/May 2021

®
IMAGINATION
INNOVATION
SCIENCE IN ACTION

Continued from Page 10
and guidance on how to reach out to
seed companies when seeking contracts
(all of these webinars are provided as
part of the Seed Economics Toolkit at
the link at the end of the article.)
The best time to contact seed companies to
inquire about contract opportunities is between
September and January when companies are
‘preparing for the following year’s production.
Growing seed on contract for a seed
company takes some of the sales-related
risks out of seed production, but
finding the opportunity to grow on
contract can also be a hurdle as it is not
always clear how to connect with a seed
company to acquire contracts. Seed
companies and growers alike report
that they most often make new relationships
by networking at conferences,
such as the Organic Seed Growers
Conference, and other regional events.
Many seed growers also cold call
companies to see if they’re looking to
contract with new growers.
As an organization that strives to create
networking opportunities for seed
growers, OSA developed an online registry
called the Organic Seed Producers
Directory to connect seed growers with
seed companies. It includes a user profile
that shares each grower’s location,
scale and crop expertise. In this way,
the directory can be searched by seed
companies seeking new growers and for
producers to connect with one another
as well.
If you are an organic seed grower who
would like to join this directory, create
a profile today to start connecting with
seed companies and other growers at:
seedalliance.org/directory/.
Seed Company Advice
Prices for wholesale production vary
widely by crop, variety and scale as
well as terms of the contract. The roles
and expectations of the producer also
influence the pricing in a production
contract and understanding the expectations
of the seed company is very
important as it significantly influences
the risks and costs of production.
While prices vary widely from company
to company and depend on a multitude
of factors, it is also helpful to have
some ballpark idea of average wholesale
prices to help in negotiating contracts
and using the enterprise budgeting tool
to project profit potential.
OSA surveyed nine seed companies to
solicit feedback on best practices for
engaging in contract seed production
and to inquire about average contract
prices for specific crops to help growers
develop production plans (these prices
are listed in the online toolkit at the
link at the end of the article.) Contract
prices often varied widely between
companies and within a given crop
by each company. Commonly mentioned
determinants of prices included
production scale; variety type (high or
low yielding, ease of production); roles
of producer, such as need for rogueing
or finished quality seed cleaning; seed
quality, such as germination rate and
disease testing; and whether the crop is
an open-pollinated or hybrid variety.
Below is a summary of best practices
shared by seed companies:
The best time to contact seed companies
to inquire about contract opportunities
is between September and
January when companies are preparing
for the following year’s production.
Communication is critical to maintaining
a good contract relationship. Most
companies request an update on the
crop status two to three times throughout
the growing season. Photos of the
crop and updates on any off types are
very helpful.
Timely delivery of clean seed is important
as it helps the company prepare for
the following year’s sales.
If you are new to contract production,
start small and try crops that you are
familiar with growing. Try a test plot
the first year if it is a new crop you are
unfamiliar with so you can determine
if you can grow it in your location. Also,
plan for how you will harvest and handle
the finished seed crop.
Keep good records on your costs of
production, including your time, so
that you are able to engage in informed
negotiations on price.
Share your production information
with the company and ask them to
share what they know about the crop.
Seed companies want to learn from
your experience and also help you
succeed. It takes an open exchange of
information to ensure everyone’s success.
If you need help, ask!
To access the Seed Economics Toolkit,
visit seedalliance.org/publications/
seed-economics-toolkit/.
Comments about this article? We want
to hear from you. Feel free to email us at
article@jcsmarketinginc.com
’
12 Organic Farmer April/May 2021

Strawberries in May (peak production period for San Luis Obispo) of non-solarized (left) and solarized plots (right) (all photos courtesy A.M. Tubeileh.)
Biosolarization and
Cover Crop Impact on
Weeds and Soilborne
Pathogens
By TIMOTHY JACOBS | Risk Management Specialist, USDA
and ASHRAF M. TUBEILEH | Cal Poly, San Luis Obispo
Soils contain a lot of good things, but they are also
reservoirs for weeds, pathogens and nematodes, which,
if left uncontrolled, can devastate crop yields. If soilborne
pests rise to economically damaging levels, it becomes
necessary for growers to use soil disinfestation techniques to
kill soilborne organisms.
Most conventional growers use fumigants for soil disinfestation.
Fumigation is unavailable to organic growers leaving
organic growers few options for controlling soilborne
pests. However, over the past couple of decades, there has
been substantial research into organic soil disinfestation
techniques due to increasing regulations for conventional
fumigants. Researchers at California Polytechnic State University,
San Luis Obispo recently conducted research on soil
solarization and biosolarization, two organic soil disinfestation
techniques, on organic strawberry production at the
Cal Poly Organic Farm in San Luis Obispo, Calif.
Strawberry beds undergoing solarization during August.
Soil Solarization
Solarization involves placing clear, thin (25 to 50μm),
low-density polyethylene tarps over irrigated soil to increase
soil temperatures to lethal levels for pathogens, pests and
weeds. In general, temperatures generated during soil solarization
range from 104 to 158 degrees F. The tarp is left on
the soil for four to eight weeks, depending on the soil temperatures
generated during solarization. The efficacy of solarization
is primarily based on ambient air/soil temperatures
and intensity of solar radiation. In most cases, solarization
should raise the ambient soil temperature between 10 and 20
degrees C (18 to 36 degrees F) in the top six inches of the soil.
14 Organic Farmer April/May 2021

Germination (% )
100
90
80
70
60
50
40
30
20
10
species
annual sowthistle
bristly oxtongue
common lambsquarters
common purslane
little mallow
pigweed
0
0 40 80 120 160 200 240 280 320
Hours
Figure 1. Logistic regression models showing how germination rate of different weed species is affected by the duration of exposure to 122
degrees F under laboratory conditions simulating solarization.
Solarization is most effective when used during the summer
when solar radiation is high in sunny, warm climates. Costs
of solarization vary depending on plastic prices, but in general,
the plastic costs in between $150 to $300 per acre. The
best plastics are clear/transparent, one to three millimeters
thick and UV-inhibited to prevent breakdown in sunlight.
Biosolarization, which combines the use of organic soil
amendments and soil solarization, has been proven to
enhance the results of solarization in numerous field experiments.
Organic amendments commonly used are plant
residues, animal manure, compost and other high-nitrogen
organic materials such as blood meal. Biosolarization is a relatively
new area of research and can reduce the time needed
for solarization as well as increase solarization’s effectiveness
in areas with marginal conditions for solarization. For
example, in San Luis Obispo, we are about five miles from
the coast, experience frequent, foggy mornings and rarely
have temperatures above 90 degrees F. We included biosolarization
of cover crop residues in our experiment to see if it
would increase the efficacy of solarization in our climate.
The rest of this article will focus on the results from our
research. For more information on solarization and biosolarization,
including application techniques, please see our
previous Organic Farmer article from April/May 2019 or UC
extension’s webpage on solarization ipm.ucanr.edu/PMG/
PESTNOTES/pn74145.html.
Solarization Research
As part of our research, we conducted lab experiments under
simulated solarization conditions assessing the time needed
to kill weed seeds at five different temperatures (104, 113, 122,
131 and 140 degrees F). Seeds tested included little mallow,
redstem filaree, bristly oxtongue, annual sow thistle, common
purslane, common lambsquarters and redroot pigweed.
Efficacy of solarization temperatures differed between
different species. In general, cool-season annuals annual
sow thistle and bristly oxtongue were more susceptible to
heat treatments than warm-season annuals such as redroot
pigweed. Additionally, hard seeded (thick seed coats) seed
were relatively unaffected by heat treatments taking long
duration to kill. Time and percent mortality of weed seeds
were used to create thermal death models for weed seeds
at each temperature (Figure 1). Additionally, models were
Continued on Page 16
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used to estimate the amount of time
needed to kill 90% of seeds for all species
tested (Figure 2). Redstem filaree
germination rates were unaffected by
heat treatments. Additionally, common
purslane was unaffected by heat
treatments below 113 degrees F or lower
and redroot pigweed was unaffected by
temperatures of 104 degrees F or below.
Results indicated daily temperatures
above 122 degrees F are needed for
four to eight weeks to achieve adequate
weed management via solarization.
Time (hours)
700
600
500
400
300
200
100
0
Time needed to achieve 90% mortality
45° C
50° C
55° C
40° C
40° C
45° C
50° C
55° C
50° C
Little mallow
Bristly
oxtongue
55° C
60° C
Common
purslane
40° C
45° C
50° C
55° C
60° C
Common
lambsquarters
45° C
50° C
55° C
Redroot
pigweed
60° C
40° C
45° C
50° C
55° C
Annual
sowthistle
We also conducted field experiments on
solarization of sudangrass residues in
organic strawberry production.
The objectives of our field experiment
were:
Species
Figure 2. Time needed to reduce germination rates by 90% for six different species at
five different temperatures (40°C=104°F, 45°C=113°F, 50°C =122°F, 55°C=131°F, 60°C=140°F )
according to logistic regression models.
• To determine if soil solarization
can reduce weed and pathogen
pressures and improve plant health
and strawberry yields in San Luis
Obispo County,
• To determine if the effect of sudangrass
cover crop residues will
increase the effects of soil solarization,
and
• To compare the effects of sudangrass
residue mulching vs. incorporation
on weed populations, pathogen
populations and strawberry health
and yields.
The experiment was designed so that
we had three cover crop treatments:
A control, one where sudangrass was
left as a surface mulch after mowing,
and the other where sudangrass was
incorporated into the soil after mowing.
Within each cover crop treatment, we
solarized half and left the other half
non-solarized.
‘Piper’ sudangrass was planted in mid-
May using a seed drill. In mid-July,
sudangrass was chopped and shredded
with a tractor-drawn flail mower and
incorporated into the soil in our incorporated
treatment. After incorporation,
beds were created in all plots except
mulched plots. In mulched treatments,
sudangrass residue was left on the
soil surface and no beds were created.
On July 26, solarization plastic was
hand-applied onto solarized plots. After
applying plastic, fields were irrigated
for 72 hours using one line of drip tape
till fields reached field capacity. Tarps
were left on for five weeks and removed
on August 31, 2018. Strawberries were
planted in October after doing weed
population assessments in our various
treatments.
Results
Maximum soil temperatures in solarized
plots were 118 degrees F at a soil
depth of two inches and 42 degrees C
at a soil depth of 6 inches. On average,
temperatures in cover crop mulched
plots were 4 to 6 degrees F lower than
other solarized plots. Temperatures in
all solarized plots were 18 to 30 degrees
F higher than non-solarized plots. In
initial weed biomass assessments taken
six weeks after tarp removal, non-solarized
incorporated plots reduced weed
biomass by 24.4% compared to the
control. Non-solarized mulched plots
reduced weed biomass by 95.6% compared
to the control. All solarized plots
resulted in similar reduction in weed
biomass compared to the control with
an average reduction of 97.1% ± 0.6%.
Efficacy of solarization treatments
decreased with time. In final weed
biomass assessments taken 15 weeks
after tarp removal, the only solarization
treatment providing a significant
reduction in weed biomass compared
to the control was incorporated plots
with solarization resulting in 67% lower
biomass than the control. Mulched
plots without solarization also provided
significant control, reducing weed biomass
to 84.1% of the control. However,
in non-solarized mulched treatments,
the sudangrass re-grew after mowing
and did not die until the winter.
Continued on Page 18
16 Organic Farmer April/May 2021

April/May 2021 www.organicfarmermag.com 17

Non-solarized (left) and solarized (right) beds of strawberries during June.
Sudangrass Effect
Mulched
Incorporated
None
Yields per 30
plants (g)
8820 a
7501 a
6480 a
Solarization effect
Solarized
Non-Solarized
Yields per 30
plants (g)
11,595 a
3,609 b
Table 1. The yield in grams per 30 plants from solarized treatments (n=12) and sudangrass
treatments (n=8) from March through June.
Continued from Page 16
the effect of solarization. Cover crop
treatments did not have a significant
effect on verticillium populations or
yields. Mulched treatments did reduce
weed population and had lower disease
severity than other treatments.
Solarization effectively killed mowed
sudangrass, preventing it from regrowing.
Solarization of mowed cover crops
provides a potential mechanism for
killing cover crops for organic growers
wishing to perform no-till production.
However, more research is needed into
this topic.
This led to poor strawberry establishment,
although the strawberries later
recovered.
plant mortality was significantly higher
in non-solarized plots with 35.5%
mortality compared to 16.0 % mortality
in solarized plots. Additionally, solarized
plots had much higher yield than
non-solarized plots. The different cover
crop treatments did not have a clear
effect on reducing verticillium wilt
population, disease severity or increasing
yields.
The effectiveness of solarization depends
not only on the temperatures
you can achieve, but on the disease
and weed species present in a field as
well. Particularly in areas with cooler
climates or frequent foggy/cloudy
days during the summer, knowing the
temperature thresholds required to kill
the pests in your field can be important
in determining whether solarization
is a viable solution. This is another
area where more research can be done.
First, develop models to help growers
estimate the temperatures they can
achieve during solarization. Secondly,
Solarization reduced verticillium wilt
populations by 80.7% compared to
non-solarized plots. Solarized plots had
much lower disease incidence throughout
the growing season. Non-solarized
plots started to experience disease
symptoms in April and were not producing
fruit by May. Solarized plots
experienced almost no disease pressure
till late May/June when temperatures
warmed. Solarized plants experienced
disease pressure from Charcoal Rot,
Macrophomina phaesolina, a warm-sea-
Key Takeaways
Solarization provided effective weed
Biosolarization and
management for 3.5 months after tarp
removal, reduced verticillium wilt populations,
reduced
models can be used to determine the
Cover Crop
disease severity
Impact
and susceptibility of different
on
pest species to
increased yield compared to non-solarized
plots.
Comments about this article? We want
solarization.
son pathogen which we theorize was
not reduced to the same degree
Weeds
as verticillium
wilt populations were. Total Cover crop treatments did not enhance article@jcsmarketinginc.com
and Soilborne
to hear from you. Feel free to email us at
Pathogens
18 Organic Farmer April/May 2021

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USDA Passes Final Rules
on Hemp Growing
Agency Makes Changes Based on Grower
Input and Experiences
By DANITA CAHILL | Contributing Writer
Open-pollinated field of hemp plants in Nicolaus, Calif. (all photos courtesy J. Eve.)
Hemp flowers.
Just when you thought you knew
all the rules and laws that regulated
legal hemp growing in the U.S.
at the federal level, the United States
Department of Agriculture (USDA)
went and made changes to those rules.
They didn’t do it to cause headaches, but
rather because they listened to what
the public had to say and what growers
learned during the 2020 growing season.
The regulations that first came out after
the 2018 Farm Bill passed into law was
Justin Eve believes rules for hemp are being rushed.
an interim final rule. The interim regulations
were published on October 31,
2019 and laid out guidelines for hemp
growers to legally register, test their
plants to stay within the THC limitations
and generally stay out of trouble
with the law.
On January 15, 2021, the USDA published
a final rule. Those updated hemp
regulations took effect on March 22,
2021. Below is a general overview of the
final federal regulations.
Since the law
may vary from state
to state and within
tribal land, be sure to
check the regulations
within your own state
or jurisdiction.
Violation for Too
Much THC
As was law before,
plants that test too
high in tetrahydrocannabinol
(THC), a
cannabinoid, must be
destroyed. The final
rule raises the amount
from 0.5% to 1%. If
plants test at or below
the 1% threshold, there
is no “negligent violation.”
A grower can
only receive one such
violation in any given growing season.
Scientists estimate there are more than
100 different cannabinoids in hemp.
More studies are currently underway.
Of those cannabinoids, two are the
most well-known. The first is THC.
It’s the hallucinogenic, or recreational
component in cannabis (marijuana).
THC is also found in hemp, but generally
in much smaller amounts. The
second most recognized is Cannabidiol
(CBD), the popular medical cannabinoid
in hemp. CBD is also found in
cannabis.
Plants over the 1% THC threshold can
be destroyed in more ways than before.
No longer will a grower be required to
use only law enforcement or a Drug
Enforcement Administration (DEA)
reverse distributor, which is a person
or company that reclaims outdated or
otherwise unusable drugs and destroys
them. Reverse distributors are registered
with the DEA.
According to reports submitted by
states and tribes in 2020, growers planted
6,166 acres under the 2018 Farm
Bill hemp plans and about 730 acres of
those had to be destroyed for noncompliance.
Plant Testing
Since there aren’t enough labs regis-
20 Organic Farmer April/May 2021

Strengthen cell
walls and lessen
the impact of
abiotic stress.
A 2019 midwestern hemp crop.
tered with the DEA for the amount of
hemp production expected in 2021, the
DEA is allowing non-DEA registered
labs to test hemp. This is an extension
only until January 1, 2022. In the
meantime, the DEA is trying to quickly
process lab applications to get more
testing labs registered.
The timing of plant sample collection
has been extended. The interim regulations
gave only a 15-day window from
testing to harvest. That time frame has
been raised to 30 days.
Growers asked for a change in the
sampling method. They requested that
larger samples be taken from each plant
sampled, or that the whole plant be
sampled. They also asked that samples
be taken from fewer plants.
The final regulations let individual
states and tribes set their own policies
using a performance-based approach to
sampling. These policies must be written
into a plan and sent to the USDA
for approval. The plan may consider the
state’s seed certification programs, the
history of grower compliance and other
factors as determined by tribe or state.
Tribal Regulations
The rules were a little fuzzy about tribal
jurisdiction in the interim regulations.
Those initial rules didn’t specifically
discuss if a tribe with an approved
USDA plan had primary rule of law
over hemp production across its entire
territory, or only over land in which it
had inherent jurisdiction.
Since tribes rule themselves as quasi-sovereign
nations, the USDA decided
in the final regulations that a tribe may
exercise jurisdiction, and therefore regulatory
authority, over hemp production
in all of its territory no matter the
extent of the tribe’s inherent regulatory
authority (generally, tribes can’t exercise
criminal or civil jurisdiction over
non-tribe members.)
A Hemp Researcher’s Perspective
So how do hemp researchers and growers
feel about the hemp final regulations?
And how do these regulations
affect them?
“Working with hemp as a researcher
poses unique challenges because of the
regulatory factor,” said Sarah Light,
UCCE agronomy advisor in Sutter,
Yuba and Colusa Counties. “It’s just the
nature of working with the crop.”
Light sees the final rule as a positive
rather than a negative. “Now that we
have the final ruling, we can move
ahead. Now we know,” she said. “We’re
Continued on Page 22
Call to learn more:
208-678-2610
April/May 2021 www.organicfarmermag.com 21

An indoor canopy of hemp plants.
In addition to hemp, Eve also grows moringa and sweet potatoes
on 20 acres north of Sacramento, Cal. His background
is in bioenergy, plant sciences and soil chemistry. He sees a
high level of importance in getting viable hemp genetics that
hemp farmers can grow, harvest and make some money on
while staying within the legal boundaries of the regulations.
Hemp growers like Eve are banding together to form the
Hemp Farmers Guild. The guild is working with the DEA
and the USDA to help them understand the growing challenges
of hemp from a farmer’s perspective.
So, are the federal agencies listening to hemp growers?
“They are,” Eve said, but added a caveat about the USDA,
“They’re not really farmers. They’re not granting us a buffer to
make some mistakes as we go along.”
Justin Eve stands next to one of his hemp plants
Continued from Page 21
excited to keep doing research for our growers. We’ll just
continue to be in compliance.”
A Hemp Grower’s Perspective
Justin Eve, owner of 7 Generations Producers, is a USDA-certified
organic grower. He has a different take on the regulations.
“They’re classifying it and approaching it like some sort of
drug,” he said. “It’s a little upsetting to me.
This is an agricultural crop. We already have those regulations
in place. We don’t need to recreate the wheel.”
Eve is frustrated with how the USDA and the DEA focus
on THC levels within hemp. “It’s such a miniscule aspect to
what this crop can be,” he said. “America made its way with
hemp.” (The early drafts of the Declaration of Independence
and the Bill of Rights were written on hemp paper).
The way the regulations are written makes Eve believe there’s
not a lot of wiggle room. “It’s limiting a farmer to harvesting
within 30 days. It’s unconstitutional. We just want to grow
a good crop and not get arrested for what we thought was
legal. “The limitation on THC is low. The way they’re testing
is skewed,” Eve said. If the plants test too high in THC, they
must be destroyed; there’s no other path. Eve mentioned a
hemp grower in the Merced area that had to destroy a 200-
acre, $2 million crop. “It can bankrupt farmers.”
Big companies are hesitant to get involved with the business,
according to Eve. But for the industry to flourish, it will take
large companies investing in expensive processing facilities.
“The major companies are afraid of backlash from the USDA,
the FDA and the DEA,” Eve said.
As for the timing of the final rule, Eve thinks it was rushed.
“We should have two more years to figure out a final rule,” he
said. He believes that state departments and local ag departments
don’t fully understand the USDA regulations. “The
head doesn’t know what the tail is doing.
“I think the USDA is heading in the right direction, but up to
this point, it’s been too hard,” Eve said.
Comments about this article? We want to hear from you.
Feel free to email us at article@jcsmarketinginc.com
22 Organic Farmer April/May 2021

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Research into
Alfalfa Crop
Rotation for
Organic
Tomatoes
By SABRINA HALVORSON | Contributing Writer
The practice of rotating alfalfa
with tomatoes was once more
popular than it is today, but recent
research suggests it offers soil health
benefits in organic tomato crops.
Researchers Nicole Tautges, Emily
Woodward and Dan Putnam tested a
three-year rotation of tomatoes, corn
and alfalfa at the UC Davis Russell
Ranch Sustainable Agriculture Facility.
According to their research, alfalfa benefited
tomato yields when in rotation,
with fruit yields between 10% to 26%
greater following three-year alfalfa as
compared to following corn in a twoyear
tomato-corn rotation.
anecdotal or observational
evidence
that growers reported
seeing on the ground
in their crop rotation,”
said Tautges,
now a researcher
with Michael Fields
Agricultural Institute
in East Troy, Wisc. “A
lot of growers would say that they have
better soil health and the soil was more
workable following alfalfa compared to
following other annual crops. They’re
seeing yield boosts. They’re seeing
decreases in disease and pathogen pressure
in the following vegetable crop.”
Alfalfa grows on test plots at the UC Davis Russell Ranch Sustainable
Agriculture Facility. Researchers tested the use of alfalfa in crop rotations
versus corn when growing organic tomatoes (photo
courtesy N. Tautges.)
at the end of each rotation crop with
the objective of seeing how the differences
persisted in time throughout the
rotation. They planted tomatoes after
both crops and measured the same
indicators in the tomatoes to see how
they compared to the findings from the
previous crop.
“This research was motivated by a lot of
"
“There was a real
visual difference
in the vine health
among the systems,
and I think that
contributed to the
stronger yields also."
− Nicole Tautges, UC Davis
Tautges said there has been limited research
into forages and what exactly the
biological and chemical mechanisms
were that were driving those comments
from growers.
“It’s all qualitative at this point. So, I
wanted to take a stab at doing that
research,” she said.
Tautges explained they measured a
suite of soil health indicators – biological,
chemical and physical – in
the soil at the end of the alfalfa crop
compared to the corn as their annual
control. They compared the indicators
In addition to monitoring the various
indicators in the soil, they kept track of
yields from the tomato crops and found
an increase in tomatoes that followed
alfalfa.
“We saw about a 3- to 5-ton-per-acre
increase in tomato fruit yields. At times,
we did see even up to 10 tons per acre,”
she said. She said while there were
some individual cases of higher yields,
the increase was generally around 10%
minimum.
She said they also noticed some other
results visually. The plants were greener,
24 Organic Farmer April/May 2021

ushier and bigger. “There was a real
visual difference in the vine health
among the systems, and I think that
contributed to the stronger yields also.”
Their research findings broke down
findings in terms of soil health. The
research showed alfalfa enhanced soil
microbial biomarkers and the nitrogen
uptake of the soil microbial pool after
three years compared to the corn. The
alfalfa also showed higher levels of
mycorrhizal fungi in the soil. The mycorrhizal
fungi biomarkers were 45%
higher in alfalfa soil than in corn soil.
There were differences in nutrients as
well. The research states total dissolved
nitrogen in the soil solution was more
than two times greater following corn
than following alfalfa. That dissolved
nitrogen represents a pool of potentially
leachable nitrogen, the research
explains. It also states greater potentially
leachable nitrate in the fall lead
to greater measured nitrate leaching
losses over the winter. According to the
research, nitrate leached with winter
precipitation was lower following alfalfa
compared to conventional corn.
When it comes to nitrogen, Tautges said
things get more complicated.
“There should be nitrogen going into
the microbial community and there
should be nitrogen going into the soil
by all of the organic matter decomposition
that we’re getting from the alfalfa,”
she explained.
Another result from the alfalfa rotation
is a change in soil structure. The
researched showed alfalfa greatly improved
soil aggregation, which Tautges
said is an important indicator of soil
structure.
“We had hypothesized that alfalfa having
a deeper, bigger root system would
be punching more holes in the soil and
aerating the soil more. Fungi that were
being maintained better in the alfalfa
system would be leading to better soil
aggregation through the compounds
fungi secrete,” she explained.
While those factors were leading to
improved soil aggregation, one factor
of growing alfalfa was having a counter
effect. “The haying activities also were
increasing bulk density because you’re
driving equipment across the field a lot
without using any tillage to break it up
again.”
The research did find a couple of issues
with the alfalfa rotation. Findings
indicated the alfalfa tended to deplete
soil cations, which left low levels of
potassium and calcium fertility for
the following tomato crop. However,
overall, researchers determined alfalfa
benefits biological and physical soil
health parameters and tightens nitrogen
cycling.
Comments about this article? We want
to hear from you. Feel free to email us at
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April/May 2021 www.organicfarmermag.com 25

Food Safety Laws and
Standard Operating
Procedures for
Urban Farmers
By TAYLOR CHALSTROM | Assistant Editor
Youth farmers at WOW urban farm in Oakland. Urban farming continues to rise in
popularity as a way for urban communities to tackle food insecurity and promote food
sovereignty (all photos by R. Surls.)
26 Organic Farmer April/May 2021

As urban farming continues to rise in
popularity as a way for urban communities
to tackle food insecurity and promote
food sovereignty, new laws and standard
operation procedures are being put into place
to ensure food safety of those products. The
California Urban Agriculture Food Safety
Guide, produced in December 2020 by UC
Berkeley, UCCE and Sustainable Economies
Law Center, provides a thorough overview of
what those urban farmers or gardeners may
be subject to.
“For new urban farmers, it outlines relatively
new laws that offer new opportunities for
urban farmers and gardeners to grow and
distribute foods for sale including the Cottage
Food Act and the Community Food Producer
Act,” said Jennifer Sowerwine, UCCE metropolitan
agriculture and food safety specialist
at UC Berkeley and lead author of the guide.
“We tried to take complex regulations and put
them into a format that will be more accessible
for very small-scale growers,” added
Rachel Surls, UCCE sustainable food systems
advisor and co-author.
Radishes for sale at an urban farm
in Ontario, Calif. The 72-page guide
clarifies that all food grown and sold
or donated in urban environments
should be following the CDFA’s Small
Farm Food Safety Guidelines.
Handwashing station
at an urban farm in San
Diego. CDFA’s Small Farm
Food Safety Guidelines
dictate that proper hygiene
should be followed
in every step of the
growing process.
Surls noted that products produced and distributed by
urban farmers have long existed in a “legal gray area” and
that new laws like the ones outlined in the guide are clearing
things up.
Continued on Page 28
The 72-page guide also explains whether or
not urban farmers may be subject to the Food
Safety Modernization Act (FSMA), and clarifies
that all food grown and sold or donated
in urban environments should be following
the CDFA’s Small Farm Food Safety Guidelines,
according to Sowerwine.
DON’T FORGET THE SEASOL...
Solutions for the Earth
“Generally, any farm or organization in
California that grows or distributes produce
offered for public consumption is subject to
these guidelines,” she said. “Therefore, urban
farmers, community gardens and backyard
gardeners should all read and implement
these guidelines before offering food for
public consumption, whether by sale or by
donation.”
Increases Nutrient Uptake Efficiency
Increases Yield for a Bountiful Crop
Decreases Saline Stress
Improves Environment for Soil
Microbial Activity
Conventional and Organic Products Available
Clearing Things Up
The laws and standard operation procedures
in the guide were previously difficult to find
and navigate. Sowerwine said that this guide
provides a “one-stop-shop” for laws that may
affect the urban farm as well as best practices
for safe growing, distribution and storage of
not only fresh produce, but also eggs, chicken
and small livestock. It also provides guidelines
and resources for safe compost production,
application and management.
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earthsol.ag/crops
April/May 2021 www.organicfarmermag.com 27

Vertical urban farm in Los Angeles. Some urban farms, depending on the operation, are
fully or partially exempt from certain laws under the Food Safety Modernization Act.
Continued from Page 27
“[Urban farm produce] was not necessarily
considered an “approved source”
for sale to retail food establishments,”
she said. “Two laws cleared that up.
Now urban growers are considered
“approved source” through a category
called “community food producers”
established by California state laws AB
1990 and AB 234.”
Sowerwine said that the COVID-19
pandemic has contributed to an increase
in household food production
as evidenced by the rapid decline in
seed supplies, and rising demand in
raising chickens in backyards. This has
given more incentive for people to not
only become urban growers but to also
be aware of any laws or acts that may
pertain to them.
“Many are sharing foods with their
neighbors, donating it to food pantries,
aggregating produce into CSA-type
boxes, and some are taking advantage
of the Community Food Producer Act
to sell their products,” Sowerwine said.
Importance of Food Safety
The entire guide is structured around
the necessity for food safety in an urban
environment. Urban farmers need
to adhere to any and all food safety
laws that may apply to their operation,
namely those relating to soil health
and disease prevention in order to
grow and sell products.
“Food safety is very important in the
urban farming sphere, particularly in
relation to urban soils,” Sowerwine
said. “It is important before starting
to farm to assess your urban soils for
any risk of contamination by learning
about the prior site use, and if there is
elevated risk, then getting a soil test.”
The guide outlines testing, remediation
and best management practices for
urban soils.
Another issue is disease prevention.
The guide makes it clear that following
standard operating procedures is
necessary to ensure that every biosecurity
measure is met to reduce any and
all incidence, whether that be between
animals or zoonotic.
“Even one case of E. coli or Salmonella
is too many,” Surls said. “Everyone
who produces food for distribution
wants it to be healthy for whomever is
going to eat it. Growers can face legal
liability if someone gets sick from eating
what they grew, and of course we
want to prevent that from happening.”
Surls said that urban farmers are generally
focused on community health
and food access, so the incentive for
following proper guidelines to keep
food production constant is there.
“Everyone wants to be healthy, and
following the best practices outlined
will help minimize the risk of on-farm
or in-garden contamination.”
On-Farm Assessment
At the end of the guide, Sowerwine
prepared an on-farm food safety
assessment for California urban farms.
According to Sowerwine, the checklist
offers a comprehensive assessment of
potential on-farm food safety risks,
adapted from USDA guidelines and
in compliance with the CDFA Food
Safety Guidelines, yet “tailored to
smaller-scale operations,” she said.
“It covers the five main areas of potential
risk of contamination and how to
assess them, including risk from water,
animals, soils, surfaces and health and
hygiene factors, and best practices to
minimize risk as well sample record
keeping forms to document best practices,”
she said.
Sowerwine noted that even for smaller-scale
operations, it can be helpful
to walk through the assessment and
determine where there may be contamination
issues and how to address
them.
“And for farms that may have community
or student engagement, what
kind of signage and training may be
beneficial,” she added.
A publication of the full guide is available
for free download at anrcatalog.
ucanr.edu/pdf/8660.pdf.
Comments about this article? We want
to hear from you. Feel free to email us at
article@jcsmarketinginc.com
28 Organic Farmer April/May 2021

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HOW TO HELP
ENDANGERED POLLINATORS
WHILE ALSO HELPING YOUR FARM
By DANITA CAHILL | Contributing Writer
No milkweed means no monarch caterpillar food, according to McKibbin (photo courtesy Kitty Bolte, Xerces Society.)
As a result of human activity, the
world has lost about half of its
insect populations in the last 75
years. Those insect declines are due
largely to habitat loss and degradation,
pesticides and climate change, said Jessa
Kay-Cruz of the Xerces Society for Invertebrate
Conservation. Some of those
insects can be important pollinators for
crop production, such as the monarch
butterfly.
“Monarchs across the U.S. are imperiled,
though the Western population is
worse off than the Eastern population,”
said Sarah McKibbin, Restoration
Project Manager of Solano Resource
Conservation District (RCD).
“Monarchs are completely dependent
on milkweed plants,” said McKibbin,
who was a speaker for a recent online
workshop sponsored by Solano.
The butterflies lay their eggs on milkweed
plants. When the eggs hatch, the
caterpillars eat only milkweed.
“The toxins in milkweed helps protect
them from predators,” she said.
Adult monarch on narrow-leaf milkweed, A. fascicuaris . In 2020, the Western Monarch Thanksgiving
Count tallied only 1,914 monarchs (photo courtesy Stephanie McKnight/Xerces Society.)
The milkweed flowers provide a nectar
source, not only for adult monarchs,
but for other pollinators too, such as
native bees. “Milkweed is a relatively
prolific nectar supplier,” McKibbin said
The monarch caterpillars go through
30 Organic Farmer April/May 2021

Monarch caterpillar on woolypod milkweed, A. eriocarpa .There are multiple native milkweed species available for planting
(photo courtesy Brianna Borders/Xerces Society.)
five instar stages (between molts) before
forming a chrysalis and attaching
it to a milkweed stem. The monarch
lifecycle repeats four to five times each
spring through fall. The last batch of
butterflies that emerge are the ones
that migrate from parts of the U.S. and
Canada.
“Western monarchs overwinter along
the California coast in Monterey pines
and eucalyptus trees,” McKibbin said.
“Eastern monarch populations overwinter
in Mexico in Oyamel fir trees.”
Monarch Numbers
In the 1980s, there were an estimated
4.5 million monarchs that overwintered
along the Pacific Coast. In 2019, the
number had dropped to approximately
29,000, and in 2020, the Western Monarch
Thanksgiving Count tallied only
1,914 monarchs.
“Western monarchs have declined by
over 99%,” McKibbin said. “The East-
Continued on Page 32
April/May 2021 www.organicfarmermag.com 31

Incorporating native milkweed species into cover crops can create a habitat for monarchs while reducing the need for
broad-spectrum insecticides.
Continued from Page 31
ern monarchs have ‘only’ declined by
80% in the past 20 years.”
So why are the Western monarchs in
such rapid decline? The reasons are
many, according to Solano RCD:
• Loss of overwintering habitat.
• Development along the Pacific
coastline.
• Decline and aging of pine and eucalyptus
groves without regeneration.
• Breeding habitat loss and degradation.
• Urban sprawl.
• Agricultural practices with extensive
tilling and pesticide use.
• Pesticides used for mosquito control.
• Pesticides used by homeowners and
the nursery trade.
• Widespread pesticide contamination
“ Don’t plant milkweed within
five miles of the coast
because it can interrupt the
monarch’s life cycle.
− Sarah McKibbin, Solano RCD
”
of milkweed.
• Climate change – causing changes
in temperature and rainfall patterns
which affects monarch migration and
milkweed distribution.
• Tropical milkweed, which is not
native and can harbor a parasite
harmful to monarchs.
“Good” vs. “Bad” Milkweed
So, what is the difference between milkweed
that is harmful to monarchs and
milkweed that is beneficial? Tropical or
exotic milkweed, Asclpias curassavica,
is harmful. It grows north to Mexico
but isn’t native to the U.S. or Canada.
It’s an attractive plant and easily grown,
so it is most often the species offered
for sale in nurseries. Tropical milkweed
blooms and grows year-round in mild
climates – except in the case of rare
freeze events. Because of its year-round
availability, tropical milkweed convinces
the monarch to continue breeding
throughout the winter.
Nature didn’t intend for monarchs to
breed year-round, and there are several
risks involved when they do, according
to Monarch Joint Venture (MJV),
University of Minnesota. Risks include
a higher OE infection rate and frigid
temperatures during those rare freezing
events. There is also a chance of food
shortages when caterpillars eat tropical
milkweed to the ground during the
winter and there is no native milkweed
available because of winter dieback.
When gardeners and growers in the
coastal southern U.S. and California
plant non-native tropical milkweed,
there is another potential risk to the
monarch. Milkweed harbors a debilitating
parasite, a protozoan called Ophy-
32 Organic Farmer April/May 2021

ocystis elektroscirrha (OE). Patches of
tropical milkweed growing year-round
can foster greater transmission of OE,
according to MJV, although another
study shows that tropical milkweed can
lower OE replication. This is because of
elevated levels of cardenolide toxins (a
type of heart-arresting steroid) in the
plant. But less OE replication still may
not be in the monarch’s favor. Instead of
dying quickly, butterflies that are moderately
infected could potentially spread
more disease over a longer life span.
Adult monarchs infected with OE can
harbor thousands, even millions, of
microscopic spores on their bodies.
Infected butterflies scatter the dormant
spores onto eggs or milkweed leaves.
These in turn are ingested by monarch
caterpillars. The spores replicate inside
the larvae and pupae. Heavily infested
monarchs may not emerge completely
from their chrysalis. They either
become stuck or are too weak to fully
open their wings. Monarchs with milder
infections of OE can’t fly as well and
don’t live as long as healthy butterflies.
North America’s native milkweeds
show dieback in the winter, which stops
the winter breeding and resets the population
of OE. If you have any tropical
milkweed, MJV suggests cutting it back
in the fall and winter months and gradually
replacing it with native milkweed
species. The natives include narrow-leaf
milkweed, Asclpias fascicuaris; showy
milkweed, A. speciosa; California
milkweed, A. Californica; heartleaf
milkweed, A. cordifolia; and woolypod
milkweed, A. eriocarpa.
Other milkweed notes: “Don’t plant
milkweed within five miles of the coast
because it can interrupt the monarch’s
life cycle,” McKibbin said.
Continued on Page 34
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Continued from Page 33
The toxin in milkweed concerns ranchers, but it takes a
long ingestion period before it harms cattle. “There are no
recent reported deaths of cattle to USDA from milkweed,”
McKibbin said.
Helping Adult Monarchs and Other Pollinators
Besides native milkweed, there are other plantings that
farmers can grow to attract monarchs as well as native bees
and other pollinators. Plant a variety of nectar sources and
plan your flowering selections so they produce year-round
bloom.
McKibbin suggests practicing the 10-10-10-10-1 rule:
• Plant a 10’ X 10’ area (minimum).
Monarch chrysalis on narrow-leaf milkweed, A. fascicuaris.
Planting milkweed within five miles of the coast can interrupt
the monarch’s life cycle, according to McKibbin (photo courtesy
Stephanie McKnight/Xerces Society.)
• Include at least 10 native milkweed plants of the same
species.
• Plant a total of at least 10 different plant species.
• Plant each species in a block at least one square meter in
size.
• Other ways to help pollinators is to shop mindfully −
buy organic produce and organic nursery stock.
“Avoid products that contain GMO ingredients, especially
corn, wheat, and soy. These are the most common
‘Roundup-ready’ GMO crops that allow farmers to spray
entire fields with roundup to kill all plants except their
crop, including wild milkweed. Milkweed that would have
grown wild in fields and farm edges are collateral damage,
so GMO crops are a large contributor to habitat loss in
agricultural settings – no milkweed means no monarch
caterpillar food,” McKibbin said.
Protect monarch overwintering sites. Volunteer for citizen
science projects. Get involved with the Thanksgiving and
New Year’s monarch counts. Donate to nonprofits that are
helping to protect monarchs and other pollinators. Avoid
pesticides, especially systemic insecticides such as neonicotinoids.
“They are the worst,” McKibbin said. “They can affect plants,
water and soils for months to years.”
Tomato field hedgerow (photo courtesy of Kitty Bolte/Xerces
Society.)
For more information on helping monarchs and other beneficial
insects visit the following websites: Solano Resource
Conservation District: https://www.solano.org, Xerces
Society: https//xerces.org, Monarch Joint Venture: https//
monarchjointventure.org.
Comments about this article? We want to hear from you.
Feel free to email us at article@jcsmarketinginc.com
34 Organic Farmer April/May 2021

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USDA National Organic
Program Changing
Approach to Organic
Oversight in India
By TAYLOR CHALSTROM | Assistant Editor
USDA is increasing its oversight in
the Indian organic market to better
monitor organic products coming
into the United States.
On Jan. 11, 2021, USDA notified India’s
Agricultural and Processed Food Products
Exports Development Authority
(APEDA) that they are ending U.S.-India
Organic Recognition. The decision
comes as USDA deemed India’s organic
control system unable to adequately protect
the integrity of the USDA organic
seal.
The previous agreement between USDA
and APEDA allowed APEDA-accredited
certifiers to provide USDA organic
certification in India, according to the
USDA website (ams.usda.gov/services/
organic-certification/international-trade/India).
USDA is altering the agreement so that
all India organic products/ingredients
across the entire supply chain are to
be certified as USDA organic with
a USDA National Organic Program
(NOP) certificate in order to come to the
U.S. starting July 12, 2022. USDA will
allow a one-and-a-half-year transition
period for India organic suppliers and
U.S. buyers in order to help minimize
market disruption as a result of the
new requirements. During this period,
organic operations previously certified
by APEDA-accredited certifiers will be
allowed to apply for direct certification
to NOP by USDA-accredited certifiers.
The exact timeline of the transition period,
according to USDA, is as follows:
• Jan. 11, 2021: APEDA notified
of an end to U.S.-India Organic
Recognition.
• March 2021: Certifiers are to report
any certification applicants who
are currently certified by APEDA
in India in the Organic Integrity
Database (public data). This will
help U.S. buyers verify that a farm
or business in India has applied for
NOP certification.
• July 12, 2021: Any India organic
business wanting to export to the
U.S. must have applied for USDA/
NOP certification.
• July 12, 2022: To export to the U.S.,
all India organic products/ingredients
across the supply chain must
be certified USDA organic with a
USDA/NOP certificate.
Organic businesses in the U.S. buying
from an India organic supplier certified
by an APEDA-accredited certifier must
communicate with those suppliers about
the need to apply for NOP certification
to a USDA-accredited certifier by July
12, 2021. USDA states that USDA-accredited
certifiers may issue USDA/NOP
certification to any organic business verified
to fully comply with USDA organic
regulations throughout the transition
period.
India organic suppliers cannot continue
business with U.S. buyers after July 12,
2021 if they do not apply for the NOP
certification. The Organic Integrity Database
will need to be used by buyers to
verify existing certification or a pending
application with a USDA-accredited
certifier. The database can be accessed at
organic.ams.usda.gov/Integrity/.
Organic suppliers in India that are certified
by an APEDA-accredited certifier
will need to identify USDA-accredited
certifiers previously approved under
the U.S.-India recognition agreement.
To accomplish this, visit apeda.gov.in/
apedawebsite/organic/NPOP_certification_bodies.pdf
and refer to the “Validity
of Current Accreditation” and “Scope
of Accreditation” columns. Suppliers
that do not apply for certification by July
12, 2021 will be barred from exporting
USDA organic products to the U.S.
India suppliers currently accredited
by APEDA for USDA certification may
apply to the USDA National Organic
Program (NOP) for direct accreditation
at any time.
Comments about this article? We want
to hear from you. Feel free to email us at
article@jcsmarketinginc.com
36 Organic Farmer April/May 2021

The professionals’ top choice
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MICRONUTRIENTS:
Effective Measurement
and Use of Manganese
Part Two: Interpreting Lab Results for Manganese
By NEAL KINSEY | Kinsey Ag Services, Contributing Writer
This article is the second in a two
part series on the micronutrient
manganese. See the February/
March issue of Organic Farmer magazine
for additional information on
manganese.
A close reading of the information
provided in Part 1 of this article series
and elsewhere should make it evident
that testing for manganese levels can be
measured and reported with great variance
from lab to lab. Consequently, the
required numbers can be very different
on other tests than those that are being
discussed here.
The guidelines used below for manganese
needs and recommendations
are based on tests for evaluating soils
analyzed by using the originally established
needs for the Albrecht system.
Some may object and question why one
would report numbers that are not of
universal application. When numbers
vary so greatly, nothing is meaningful
unless it can be based on a foundation
that is solid enough to report what field
testing shows to be actually needed.
Manganese Deficiencies
What should growers look for to help
identify when manganese is deficient
(less than 40 ppm on the true Albrecht
system tests) and limiting for the crop
being grown on such soils? Numbers
reported by other soil laboratories are
not comparable according to those who
have tried to do so. This is just to caution
that pushing up the numbers on
other soil tests to match what is shown
as the measured need for crop examples
used here may result in the overuse
of manganese.
But when this specific test is performed,
40 ppm is the minimum recommended.
Soybeans will begin to show mild
symptoms of manganese deficiency
in mature leaves later in the season at
37 to 38 ppm. Levels of 30 ppm or so
begin to show results of shorter stalks
of corn, though less yield and stalk size
should be expected to result long before
that. This makes manganese deficiency
especially important for attaining the
highest tonnages of corn silage.
38 Organic Farmer April/May 2021

Once other obvious deficiencies have
been eliminated, wheat yields tend to
respond well as manganese builds to
the higher levels in any soil. For example,
soils with similar fertility that have
40 ppm manganese will not produce
the yield that those same soils provide
at 80 ppm manganese. In fact, when
manganese is truly the most limiting
factor for high-yielding wheat soils, the
yields will continue to increase on those
soils until 200 to 250 ppm available
manganese is reached when this specific
type of testing is performed. Caution
is extremely necessary here as almost
any textbook will report that 200 ppm
manganese is toxic to growing plants.
Obviously, the tests being used are not
the same as the one advocated here for
determining manganese availability.
Tree crops, especially nut trees, respond
very well to manganese with
best results on soils where manganese
is above 120 ppm. Walnuts are especially
sensitive to manganese deficiency.
Consequently, though normally not
specifically recognized as the problem,
soils that test below 40 ppm using this
particular type of testing for manganese
are generally classified as being
unfit for walnut production.
The guidelines given here for manganese
are specific to this type of testing,
and using them is not advised for any
other laboratory’s manganese test. But
these numbers are being provided here
to show there is a basic foundation to
explain what can be expected when
manganese is properly measured and
applied for crop production.
Anything less than 40 ppm on the test
we use means the full benefits from
adequate manganese will not be realized
for whatever crop. Although on
soils with more than 5% organic matter,
resulting deficiencies may not be as
evident, and optimum results will still
not be attained until any manganese
deficiency is corrected.
In addition, keep in mind that a true
manganese deficiency of below 40 ppm
may be the case, and manganese still
may not give the expected response
when applied and even brought up to
above the deficiency level. That is why
so many “research” plots concerning
manganese use fail to provide any benefits.
If any of the primary or secondary
elements are seriously deficient, correcting
them will take precedence over
the manganese level.
For example, a serious problem with
newly planted almond trees is breakage
during high winds. Some growers
have corrected that problem by adding
sufficient amounts of manganese. Many
others try it without the same satisfactory
results. That is because there
are three elements involved here that
Continued on Page 40
April/May 2021 www.organicfarmermag.com 39

Continued from Page 39
provide for increased wood strength of
which manganese is usually found to be
correctly ranked as the second or third
most important.
Adequate potassium is always of primary
importance for wood strength.
Manganese is second if it is below 40
ppm. Sufficient copper, which will be
considered next in this series, is the
other needed element and is necessary
to help provide strength and resilience
to the limbs.
Without an adequate uptake of manganese,
weaker wood will always be the
result. But soils can have good to excellent
manganese levels and still the trees
or other crops that grow there can be
deficient in manganese. This becomes
a serious problem when soils are too
high in potassium (generally on lighter
soils where too much compost has
been applied) or too high in sodium (a
problem for many soils, especially in
the Western U.S.)
In fact, in any combination where
potassium and sodium added together
exceeds 10% of total soil saturation,
manganese uptake begins to be blocked.
The higher that percentage goes above
10%, the worse this problem becomes
for the growth of any crop.
Note that the soil test may show to have
plenty of manganese, but remember
that, in this case, manganese is still
there and in the correctly available
form. That is because potassium and
sodium do not tie up the manganese.
Between the two when their levels of
soil saturation is too high (10% on
the Albrecht test), then, the uptake of
sufficient manganese is blocked out.
There is so much available potassium or
sodium there that sufficient manganese
just cannot get into the plants.
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Having Sufficient Manganese
Why be concerned about having sufficient
manganese in the soil? What are
the benefits to farmers and growers
when manganese-deficient soil is adequately
corrected?
First, sufficient manganese (above 40
ppm) is necessary for quicker seed
germination. Accordingly, enough
manganese will cause the plants to
grow off faster. Manganese is needed
to determine the number of seed to
be produced and to hold the blooms
and seed or fruit in place. So, adequate
manganese is needed from start to
finish in terms of crop production.
What levels are needed? 40 ppm is the
minimum. 80 ppm is considered as
good. 125 ppm is considered the low
side of excellent and 200 to 250 the
high side, depending on crop sensitivity.
In any case, it is best to build the level
up in increments, even if the cost to do
so is not considered as being a problem.
The guidelines for application rates
on manganese is a maximum of 200
pounds of 28% manganese sulfate per
acre even when severe deficiencies will
not be corrected by that amount.
There is yet another problem that growers
may have in trying to determine
when there is sufficient manganese for
the crop. This has to do with using a
leaf analysis to determine if plants have
sufficient or insufficient manganese.
One good example is when the Albrecht
analysis shows manganese as
even slightly deficient, common scab
can be a problem for potatoes. Yet, in
too many cases, the leaf analysis shows
the level of manganese to be adequate,
even when the soil test still shows manganese
as deficient in the soil. Which
should be believed? The fact that this
problem is never solved until adequate
manganese is present in those soils
should help show which is correct!
Keep in mind that many potato growers
use a metallic manganese based
foliar to treat for disease. This can
40 Organic Farmer April/May 2021

‘
Manganese is needed
to determine the
number of seed to be
produced and to hold
the blooms and seed
or fruit in place. So,
adequate manganese
is needed from start to
finish in terms of crop
production.
’
greatly skew the levels shown from the
leaf test. But this is not the entire story.
Potatoes have been used as an example
here due to their extreme sensitivity to
manganese deficiency. And at times,
even those who have not used a foliar
manganese can have leaf tests that
show manganese as “too high” when, in
actuality, the soils are still too deficient
to correctly supply plant needs.
We find this consistently tends to be the
case with leaf testing for most micronutrients,
not just manganese, as compared
to the levels shown to be required
on the soil test to properly solve each
deficiency. Such deviations can also be
a serious problem when considering
needs for other manganese-sensitive
crops such as wheat, grapes and all
types of trees, but especially English
walnuts and black walnuts.
There is still another precaution that
should be considered when using a leaf
analysis for evaluating available levels
of manganese for crop production.
Even leaving dust on the leaves can
cause manganese levels to appear to be
too high in the plant. A good way to
detect this is when iron and aluminum
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Continued from Page 41
are also shown to be extremely high on
the same analysis. When that happens,
test again with clean plant tissue to be
sure.
Another factor that is essential for
manganese uptake is that a sufficient
supply of calcium must be present in
the soil. This is not determined by the
fact that the soil has an adequate to
high pH. There is only one way to tell
when soils have at least the minimum
level of available calcium to take up
sufficient manganese for the crop: the
soil needs calcium levels to be built up
to and then maintained at between 60%
to 70% base saturation before plants
can most efficiently utilize available
manganese from the soil. (CAUTION:
Some labs may test as much as 4% lower
while others show as much as 12%
higher soil calcium saturation than the
numbers determined by the Albrecht
system testing procedures.)
Perhaps an additional word of caution
should be given here, for even soils that
may initially have an adequate amount
of manganese can develop a deficiency
problem if an excessive amount of unneeded
lime is applied. An excess can
cause manganese to go from adequate
to deficient over the next one to three
cropping seasons.
This can happen when any material
containing a sufficient amount of calcium
is applied on soils that barely have
enough manganese (with even worse
results when the soil is already deficient
in manganese), because when calcium
is applied, as it becomes available over
the next one to three years, it will begin
to tie up plant-available manganese in
that soil. If the soil has enough manganese
to stand the amount of calcium
applied, manganese will not become
a problem there as a result of applying
needed lime.
This is one reason why in some areas
potato growers can apply calcium
limestone and have no problem with
common scab, but in other areas no
one will dare apply it. And due to soils
needing calcium for adequate uptake
of all the other nutrients (including
N-P-K) if the problem is not solved,
crop production will not only suffer
but may even decline in terms of yield
and certainly in terms of food quality.
Yet the issue of adequate manganese in
the soil can be overcome by applying
a sufficient amount of the correct type
of manganese. That needed amount
should be based on a detailed soil
analysis which can accurately determine
the desired level in the soil. The
test should be such that it can accurately
determine how much manganese
is required to overcome any tie-up
from added calcium as well. Whether
already deficient, or for a potential
decrease in manganese due to liming
or other sources of calcium (such as
poultry manure), only the use of true
manganese sulfate should be considered
for adding to the soil to sufficiently
build up the manganese level to solve
that need.
MyAgLife Da
From the tests we use, the need for
manganese will be reflected and solved
based on the use of one pound of actual
manganese for every pound shown to
be lacking. If that does not happen in
the next twelve months after an initial
application, someone is likely providing
the wrong advice or recommending the
wrong product.
Some soils do not even build well using
manganese sulfate. In a very few cases
it has been necessary to apply the needed
amount for two or three years in a
row to reach the desired minimum level.
Because of its physiological make-up,
a crop which can also help to measurably
increase manganese availability in
the soil is rice.
Just keep in mind that the primary
elements, N-P-K, truly are primary in
terms of getting enough nutrients there
to grow the crop. But when any one of
these three are over-applied, providing
more than the soil can tolerate, those
Compacted low-calcium soils reduce manganese
availability for walnuts (photo by N. Kinsey.)
same elements can cause a whole new
set of problems, not just for the crops
mentioned in this article but for all
types of crops and growing plants.
For example, as discussed already in
regard to manganese, potassium or
sodium alone, or any combination of
the two, totaling more than 10% will
begin to block the uptake of manganese.
Normally, available soil boron
will begin to be tied up when potassium
remains above 7.5% saturation in any
soil during the growing season. Excessive
phosphate reduces zinc availability
and uptake in crops. And excessive
nitrogen ties up available copper, which
is the next micronutrient that will be
considered in this series about the need
for trace elements.
Comments about this article? We want
to hear from you. Feel free to email us at
article@jcsmarketinginc.com
42 Organic Farmer April/May 2021

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44 Organic Farmer April/May 2021