Standard Operating Procedure (SOP)
Science Advisory Council for Exposure (ExpoSAC)
Health Effects Division (HED)
Office of Pesticide Programs (OPP)
Policy Number: 15.2
Regarding: Standard Values for Amount of Seed Treated and/or Planted Per Day
Date: January 2022
Contacts: Matthew Crowley, Brian VanDeusen, Jeff Dawson, Kelly Lowe
Executive Summary
This revision of Policy 15 ensures that consistent standard values are used to calculate the
amount of seed treated and the amount of seed planted per day for commercial and on-farm seed
treatment scenarios. The standard values in this SOP are based on information obtained from
OPP's Biological and Economic Analysis Division (BEAD) and the Agricultural Handler
Exposure Task Force (AHETF). If refinements are needed, these values may be modified by
chemical-specific information. Such refinements require consultation with the appropriate staff
from BEAD.
In general, HED uses the term handlers to describe those individuals who are involved in the
pesticide application process, and the term post-application to describe exposures that occur
when individuals are present in an environment that has been previously treated with a pesticide
(also referred to as re-entry exposure). HED believes that there are distinct job functions or tasks
related to pesticide applications, and exposures can vary depending on the specifics of each task.
For seed treatment assessment, HED considers both the treatment of seed and the planting of
treated seed to be handler scenarios (primary and secondary handlers, respectively) and thus
subject to any applicable pesticide 'handler' regulations. Both activities are part of the pesticide
application process for seed treatment. The potential for post-application exposures following
the planting of treated seeds is unlikely because sustained levels of contact with treated seed after
it has been placed in the soil or other planting media would not be expected because no routine
cultural practice required for the production of agricultural commodities involves such an
activity, as defined in the no/low contact criteria in the Worker Protection Standard (WPS).
This SOP is divided into the following sections:
1. Amount of Seed Treated
2. Amount of Seed Planted
3. Planting Transplants Grown from Treated Seed
4. Glossary
Note: Glossary terms are identified throughout the document via hyperlinks to the glossary
section.
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Table of Contents
1.0 Introduction 3
2.0 Amount of Seed Treated (AST) 7
2.1 Commercial Seed Treatment 7
2.2 On-Farm Seed Treatment 14
3.0 Amount of Seed Planted (ASP) 15
4.0 Planting Transplants Grown from Treated Seed 18
Glossary 19
Appendix A. Small and Large Seeded Vegetable Assignments for Seed Treatment 22
Attachment 1: Documentation of Revisions 23
Page 2 of23
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1.0 Introduction
This revision of Policy 15 ensures that consistent standard values are used to calculate the
amount of seed treated and the amount of seed planted per day for commercial and on-farm seed
treatment scenarios.
Historically, high volume seeding practices were used to compensate for crop field mortality.
Now, farmers seek methods to cut costs while still obtaining high yields. As agricultural
practices advance, seed treatment is a viable and cost-effective option for crop protection. Seed
treatment prevents the spread of pests and soilborne pathogens, protecting the seed from initial
infections, thereby systemically protecting the entire plant.
There are multiple venues for treating seeds, including large commercial companies, smaller
downstream companies, and local on-farm businesses. Commercial seed treatment companies
are seed producers that own or license their own seed lines, and provide seed enhancement
services in addition to seed treatment. Downstream seed treatment companies obtain cleaned
and ready-for-planting processed seed from other sources such as seed producers, seed breeders,
and growers. These companies include retailers, distributors, and agricultural cooperatives. On-
farm businesses treat batches locally on a per order basis. For additional clarification and
definitions of the various terminologies used in seed treatment practices, see the glossary in
Appendix A.
Commercial seed treatment can involve three different seed treater types:
1. Continuous flow treaters which treat a steady flow of untreated seed with the seed
treatment product (photos copied from AHETF 20141);
Continuous Flow Seed - Seed
Treatment Application and Mixing
Atomizer for initial seed Mixing systems for secondary mixing
treatment application to seed
Sprar Nozzle Atomization Auger/Mixing Finger mixing; Drum mixing
1 Agricultural Handler Exposure Scenario Monograph for Commercial Seed Treatment Scenarios. Report Number AHE1008.
March 2014.
Spinning disc Atomization
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2. Batch treaters which treat a single batch (or given amount of seed) at a time (photos
copied from AHETF 20141); or
Batch Treaters
"UH Trough batch mixer
Simple batch mixers Seed holding bins
V J
3. Continuous batch treaters which are a combination of a continuous flow and a batch
treater, utilizing seed from a steady flow of untreated seed, and treating the seed in
batches until the seed source is depleted or a predetermined number of batches are treated
(photos copied from AHETF 20141).
- .
Continuous Batch Treating Systems
Tvpical CB treater Niklas & Gustafson CB Treater
In commercial seed treatment facilities, seed is professionally treated and packaged in small
bags, mini-bulk containers (e.g., bins or large bags), or loose bulk containers (e.g., seed wagons
or trucks), and then delivered later to growers (photos copied from AHETF 20142).
2 Agricultural Handler Exposure Scenario Monograph for Commercial Seed Treatment Scenarios. Report Number AHE1008.
March 2014.
"¦LT'Trough batch mixer
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Exa mple of Bagged Seed
Examples of BulkSeed Boxes arid Bags
Loose B ulk Storage Containers a nd conveying systems
Bins with Elevator Leg Bins with auger 1 Ton Bulk Bag & Box
Bucket Elevator
SeedTruck
Seed Wagon
Downstream facilities process much of their seed as loose bulk, where treated seed is conveyed
into a grower's truck or wagon directly from the treater. This is distinctly different from on-farm
seed treating where seed is treated more locally (e.g., at a specific farm), and planted without
bagging. All on-farm seed treatment systems have a method to transfer and treat clean untreated
seed from bulk storage to a seed wagon or truck, or from a truck or wagon to the planter.
On-farm seed treatment generally involves workers that operate any on-farm seed treating
equipment, including mixing, loading and application of a pesticide to untreated seed, and any
associated tasks such as maintaining the treating equipment and planting the treated seed. This
scenario applies to any seed type labeled for on-farm seed treatment. Treating equipment for this
scenario includes both open and closed systems. On-farm seed treating equipment typically
involves some type of mechanical conveying or augering system that accommodates treatment as
the seed is moved into equipment such as a seed truck (such as for transport to the field), onto a
conveyor (such as for transport into temporary storage), or directly into a planter. All on-farm
seed treaters are continuous flow treaters, meaning the seed treatment process continues until the
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seed supply is depleted. On-farm systems are manual in design and require an operator to stop
and start the seed treating process (photos copied from AHETF 20143).
M ixing Seed Treatment with Seed
Hand Mixing
Auger Mixing
The Small Grain Transfer Auger
giBfl
The potential for exposure from seed treatment can be divided into two main categories: treating
seed and planting seed. Within the treating seed category, potential exposure scenarios can
include mixing, loading, applying formulations; bagging treated seed (for commercial seed
treatment only); sewing bags (for commercial seed treatment only); and other activities, such as
cleaning and calibrating treatment equipment. Within the planting seed category, potential
exposure only includes the planting of treated seed. Typically, planting treated seed consists of
the farmer purchasing treated seed, placing treated seed in a hopper, and applying treated seed to
fields.
3 Agricultural Handler Exposure Scenario Monograph for Commercial Seed Treatment Scenarios. Report Number AHE1008.
March 2014.
Page 6 of 23
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For commercial seed treatment, depending on seed type, exposure duration may vary between
short-, and intermediateterm. For on-farm seed treatment, the exposure duration is anticipated
to be short-term only.
For both commercial and on-farm seed treatment, handler exposure can be calculated with the
following equation:
Dose =
UE x AR x AST
BW
Where:
UE = Unit Exposure (mg/lb ai), task-specific (see ExpoSAC Policy #14)
AR = Application Rate (lb ai/lb seed)
AST = Amount of Seed Treated per Day (lb seed/day)
BW = Body Weight (kg)
For planting of treated seed, handler exposure can be calculated with the following equation:
UExARxASP
Dose =
BW
Where:
UE = Unit Exposure (mg/lb ai)
AR = Application Rate (lb ai/lb seed)
ASP = Amount of Seed Planted per Day (lb seed/day)
BW = Body Weight (kg)
Note: If Application Rate is provided in mg ai/seed, the following equation can be used to
convert the application rate to lb ai/lb seed.
ARlbai/ =ARmgai/ X SC X CF
'lb seed 'seed
Where:
ARib ai/seed = Application Rate (lb ai/lb seed)
ARmg ai/seed = Application Rate (mg ai/seed)
SC = Seed Count (# seeds/lb seed)
CF = Conversion Factor (1 lb ai = 454,000 mg ai)
Seed count information (# seeds/lb seed) can be found in the BEAD memo "Acres Planted Per Day and
Seeding Rates of Crops Grown in the United States" (J. Becker, March 2011).
The unit exposure (UE) inputs for the exposure calculations are provided in ExpoSAC Policy 14.
The amount of seed treated (AST) and amount of seed planted (ASP) are provided in this
document.
2.0 Amount of Seed Treated (AST)
2.1 Commercial Seed Treatment
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For most seed types that are treated commercially, the AST per day is primarily driven by
equipment capacity. In this approach, the AST is determined by assuming that the equipment is
operated at full capacity continuously during an 8-hour workday. The primary source of
information on the amount of seed treated commercially per day is provided by the AHETF4.
The information was collected from surveys which provide daily seed treatment throughput data
along with information on seed treating equipment and worker activities. These surveys were
reviewed and the methods were found to be acceptable (D3433755).
In the first phase of the survey, data were collected for the following five major crops: (1)
canola, (2) corn, (3) rice, (4) soybean, and (5) wheat. The second phase collected data for the
following three additional crops: (1) cotton, (2) peanut, and (3) sunflower.
The AHETF surveys were conducted in the United States and Canada in both commercial and
downstream facilities. The AHETF surveys also include information about seed treatment
duration, both in number of hours worked per day and number of days worked per year. The
design and data collection of the surveys dictate how the resulting data can be utilized.
All else equal, because the surveys indicate commercial seed treatment facilities have higher
throughput than downstream treatment facilities, HED assumes that the commercial seed
treatment risk assessment is protective of downstream seed treatment. Thus, a separate risk
assessment is not required for the downstream facilities.
Information in the survey is provided for both normal production periods and peak periods of
seed treatment. A normal production period is defined as the period when the treatment line(s)
of the facility are fully operational and operating at a normal or typical level. This period does
not include peak periods or the beginning or ending of the season (i.e., the start-up or wind-down
time). The peak production period is defined as the period when the treatment line(s) of the
facility are operating at a maximum level - for example, when there are maximum orders and the
operation needs to run up to 24 hours a day. Peak production throughput is about two times
higher than normal production throughput for most facility and seed types.
Short- and intermediate-term exposures are expected for seed treatment. Long-term exposures
are not anticipated. While the AHETF survey provided information on the length of the seed
treatment season, the duration of treating that was captured represents the total number of days
the facilities treated seed. It does not represent the total number of days that a specific active
ingredient may be used nor does it represent the actual number of days that a worker may be
involved in the seed treatment during that season. It is not considered likely that one active
ingredient would be used every day for the entire treating season. For these reasons, long-term
exposure is not anticipated for seed treatment and is not assessed.
Exposures resulting from seed treatment activities (e.g., loading/applying) <30 days are
considered short-term exposures for which the 75th percentile values of the typical throughput
4 MRID 49185401. Survey Results of Commercial and Downstream Seed Treating Facilities. Study Number
AHE149. My 23, 2013. Agricultural Handler Exposure Task Force.
5 Memo, D343375, Seed Treatment - Review of "Survey Results of Commercial and Downstream Seed Treating
Facilities".
Page 8 of 23
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days during peak season are recommended to provide an appropriately health-protective short-
term exposure estimate.
Exposures lasting 30 to 180 days are considered intermediate-term exposures, for which the 75th
percentile values of the typical throughput days during normal season are recommended to
provide an appropriately health-protective intermediate-term exposure estimate.
Since the AHETF surveys only include information for eight major field crops, throughput
values for non-surveyed crops are assigned based on consultation with BEAD, including
consideration of similarity of seed size to that of the surveyed crops and general knowledge of
each crop and its production. These extrapolations do not apply for crops that are produced from
"seed pieces" (e.g., potatoes). Information for these crops was collected from open literature and
agricultural extension agents.
Vegetable crops are divided into two groups based on seed size. Based on information from the
AHETF6, there are no exact definitions, but it is generally agreed that vegetables with 10,000 or
more seeds per pound are small seeded vegetables and those with 5,000 or less seeds per pound
are large seeded vegetables. Appendix A provides examples of crops which are considered small
seeded and large seeded vegetables. The 2013 AHETF survey was used to extrapolate the
amount of seed treated for large-seeded vegetables.
The AHETF provided information6 about the treatment of small-seeded vegetables, including a
survey of a limited number of treatment facilities. Essentially, all small-seeded vegetable seeds
receive some sort of treatment or enhancement (e.g., priming or film-coating). Seed treatments
in general are moving away from dusts and slurry treatments, and towards film-coating and other
seed enhancement technologies including encrusting and pelletizing. The goals of these modern
seed treatments are to (1) minimize dust, (2) increase flowability in the seed planter equipment,
and (3) obtain a good visual appearance of the finished product.
Although one or more enhancement processes (priming, film-coating, encrusting, pelleting) are
used on virtually all small seeded vegetable seeds, many seeds are not treated with any chemical
plant protection products. Overall, there are relatively few active ingredients and products being
developed by chemical manufacturers for the treatment of small seeded vegetable seeds.
Two of the most common seed enhancements include film-coating and pelletizing. Film-coating
puts a very thin colored film around the seed, increasing the seed's weight by about 5%, without
changing its original size or shape. Pelletizing turns a lightweight and oddly shaped seed into a
heavier, more uniform, perfectly rounded seed pellet, enabling a more precise and efficient
mechanical seed planting. Depending on seed type and process, the weight of a pelletized seed
can increase from 5-100 times the original seed weight.
Seed treatments vary by region and all small seeded vegetable seeds are custom treated based on
individual customer requests. Because of the relatively small quantity of small seeded vegetable
seed that is coated and treated by each seed treatment company and the wide variety of special
6 Small Seeded Vegetable Use and Usage Report. Report No. AHE189. November 22, 2010. Agricultural Handler
Exposure Task Force.
Page 9 of 23
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enhancements that the coatings must provide, the costs associated with treatment of small seeded
vegetables is much higher than that of other crops. Most individual coating and treating orders
for small seeded vegetable seeds involve very low quantities of seed.
Table 2.1.1 provides the recommended daily seed treatment values for several crops based on
duration of exposure.
Page 10 of 23
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T;il>k' 2.1.1. Ki-i'iimnu-mli-d Y.ilui-s 1'nr Ainiiuiil ol'Si-i-d Tiv;ikd (AST) Pit I);i\: ;iii(l Dow iisliv;im Si-i-d l iviilnunl I'liiililii's.
Surveyed C rops
I ,bs of Seed Treated per 8-hr Work
Shift1
Basis and Comments
Short-Term2
Intermediate-
Temv'
Alfalfa4
125,000
125,000
Daily throughput values are based on surveyed values for canola. Canola was selected to represent alfalfa
because it has the most similar seed size among the surveyed crops. Over 20 million acres of alfalfa is harvested
annually in the United States (USDA 2007). Assuming that this crop is rotated every 3 to 5 years,
approximately 4 to 7 million acres are planted yearly.
Beets, sugar4
3,000
3,000
Sugar beets are not considered vegetables by the USDA, however, limited information is available on sugar beet
seed treatment. Therefore, data available for small seeded vegetables was used as a surrogate. The value
recommended is based on general information collected by the AHETF (2010) from a small number of facilities
(exact number not reported) that film-coat small seeded vegetables.
Canola
125,000
125,000
Treatment facilities for this crop were surveyed (AHETF 2013). Survey indicates that 98% of canola is treated
in commercial facilities (remaining 2% is not treated). The survey reports that commercial facilities in the US
and Canada (data not provided separately for the US) operate 130 days per year (50th percentile; range 72 to 169
days).
Corn (field)
339,500
240,000
Treatment facilities for this crop were surveyed (AHETF 2013). Survey indicates that 98% of field corn is
treated in commercial facilities (remaining 2% is not treated). The survey reports that commercial facilities
operate 195 days per year (50th percentile; range 83 to 247 days).
Cotton
125,000
110,000
Treatment facilities for this crop were surveyed (AHETF 2013). Survey indicates that 98%) of cotton is treated
in commercial facilities (remaining 2%o is not treated). It also indicates that 66%o of the cotton crop is also treated
at downstream facilities. The survey reports that commercial facilities operate 173 days per year (50th
percentile; range 78 to 199 days).
Note: Duration of downstream treatment is reported as 61 days (50th percentile; range 17 to 130 days).
Large Seeded Vegetable4,6
339,500
240,000
Daily throughput values are based on surveyed values for field corn. This crop was selected to represent all large
seeded vegetables because it has the most similar seed size among the surveyed crops.
Peanuts
126,000
105,000
Treatment facilities for this crop were surveyed (AHETF 2013). Survey indicates that 98%o of peanut seeds are
treated in commercial facilities (remaining 2%o is not treated). The survey reports that commercial facilities
operate 65 days per year (50th percentile; range 41 to 104 days).
Page 11 of 23
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T;il>k' 2.1.1. Ki-iomnu-ndi-d Values lor Amount of Seed Trealed (AST) IVr l)a\: Commercial and Downstream Seed Trcalmcnl lai'Milies.
Surveyed C rops
I ,bs of Seed Treated per 8-hr Work
Shift1
Basis and Comments
Short-Term2
Intermediate-
Tenrf'
Daily throughput values from the National Potato Council (2011) are based on information for typical potato
seed piece treatment equipment (Milestone), and are as follows: Average throughput = 3,000 cwt (Milestone
liquid treater 5 cwt per minute * 60 minutes per hour * 10 hours per day). Maximum throughput = 4,800 cwt
(Milestone liquid treater 5 cwt per minute * 60 minutes per hour * 16 hours per day).
Potato5
800,000
(8,000 cwt5)
400,000
(4,000 cwt)
Milestone potato cutters have performance standards of 150 to 550 cwt per hour (1,200 to 4,400 cwt per 8-hr
workday) depending on the equipment model. The most commonly used cutters (Model 60D and 72D) have
average throughput capacities of 400 and 550 cwt per hour. Milestone liquid treaters / dusters have average
throughput capacity of 250 to 1,000 cwt per hour (2,000 to 8,000 cwt per 8-hr workday). Over the last 8 to 10
years, more liquid treatment equipment has been sold. The reported throughput values are based on the
equipment operating normally and this rate can be maintained for an entire workday (Milestone 2010, 2012).
Seed potatoes can be precut and treated and then held for several days to several weeks prior to planting (Bohl
and Johnson, 2010; Milestone 2012). Peak treatment season lasts "a couple of weeks" and typically cutter and
treater equipment operate 12 hours per day (Milestone 2012). This generally agrees with information from the
National Potato Council (2011) that the typical day would be 10 to 12 hours per day for a grower and 12 to 16
hours for a commercial treater.
The selected short-term throughput value is the "typical" hourly output of the largest dust or liquid treater
(Model 42- 1,000 cwt per hour) times 8 hours per workday. The selected intermediate-term throughput value is
the "typical" hourly output of the mid-sized dust or liquid treater (Model 36 - 500 cwt per hour) times 8 hours
per workday.
Rice
302,500
180,000
Treatment facilities for this crop were surveyed (AHETF 2013). Survey indicates that 64% of rice is treated in
commercial facilities and 16% is treated downstream and the remaining 20% is not treated. The survey reports
that commercial facilities operate 35 days per year (50th percentile; range 6 to 86 days).
Small Seeded Vegetables6
Film Coated
3,000
3,000
General information from a small number of facilities (exact number not reported) which film-coat small seeded
vegetables (AHETF 2010).
Small Seeded Vegetables6
Encrusted or Pelleted
225
225
General information from three facilities that encrust or pelletize small seeded vegetables (AHETF 2010).
Page 12 of 23
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T;il>k' 2.1.1. Y.ilui-s lor Amouiil nl'Si-i-il Trviik-(l (AST) Pit I);i\: ( iininu'ixi;il ;ind l)n\\nsliv;im Scwl Tiv;ilnu-nl I'iiiililiis.
Surveyed C rops
I ,bs of Seed Treated per 8-hr Work
Shift1
Basis and Comments
Short-Term2
Intermediate-
Ternf'
Soybeans
281,250
200,000
Treatment facilities for this crop were surveyed (AHETF 2013). Survey indicates that 5% of soybeans is treated
in commercial facilities, 39% is treated downstream, 2% is treated by the grower, and 54% is not treated. The
survey reports that commercial facilities operate 178 days per year (50th percentile; range 1 to 243 days).
Note: Duration of downstream treatment is reported as 42 days (50th percentile; range 4 to 120 days).
Sunflower
80,000
38,500
Treatment facilities for this crop were surveyed (AHETF 2013). Survey indicates that 98%) of sunflower seeds
are treated in commercial facilities (remaining 2%o is not treated). The survey reports that commercial facilities
operate 173 days per year (50th percentile; range 65 to 251 days).
Wheat
360,000
180,000
Treatment facilities for this crop were surveyed (AHETF 2013). Survey indicates that 18%o of wheat is treated in
commercial facilities, 13% is treated downstream, 18%) is treated by the grower and 51% is not treated. The
survey reports that commercial facilities operate 35 days per year (50th percentile; range 1 to 82 days).
1. AHETF Survey (AHETF 2013) shows that work shifts can be longer than 8-hrs per day and that multiple shifts per day occur during the peak treatment season; however, values for an 8-hr
day were chosen as representative of a typical work day. Note that the survey respondents self-determined the categories "typical", "normal", and "peak."
2. The short-term value selected is the 75th percentile of the typical throughput during the peak treatment period as reported in the AHETF survey (AHETF 2013).
3. The intermediate-term value selected is the 75th percentile of the typical throughput during the normal treatment period as reported in the AHETF survey (AHETF 2013).
4. Survey data are not available on the percent of the crop receiving seed treatments, where seed treatments occurs (i.e., commercial, downstream, on-farm), duration of the seasonal seed
treating period, and daily throughput.
5. Cwt = hundred weight or 100 lbs.
6. Small and large seeded vegetables are listed in Appendix A.
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Translation from AHETF Data
Due to the limitations of the AHETF data, crop-specific translations will be necessary to
determine AST. Table 2.1.2 provides examples of possible crop translations for a select number
of crops. Additional translations are possible, but would need to be addressed on a case by case
basis.
T;il>k' 2.1.2. I!\;ini|)k's i>l' Possible ('nip Tmnskilions |};isi-il mi Al II!'IT Simi-\.
Seed Tvpe included in
\lll ll Survey
Translatable Crops
Canola (Rapeseed)
Flax, Lespedeza, Mint, Mustard Seed, Sesame
Corn (field)
Corn (sweet), Corn (pop)
Soybean
Beans, dry
Wheat
Barley, Japanese Millet, Oats, Pearl Millet, Proso Millet, Rye, Safflower, Sorghum, Triticale
2.2 On-Farm Seed Treatment
Currently, with the rapid turnover of seed varieties, farmers have chosen not to store high-value
treated seed that can lose viability or become outmoded in one season, necessitating on-farm
seed treatments prior to planting. For example, farmers may purchase seeds which are
commercially treated with an insecticide and then custom treat the entire or partial amount of
seed with a fungicide on-farm.
In North America, seeds can be treated with a variety of procedures shortly before being planted
at the farm site. This is commonly referred to as "on-farm" seed treatment and can involve the
application of liquid and/or solid products directly onto the seed. Applications can be made
before the seed is put into planting equipment or directly on seed already loaded in planting
equipment (i.e., in the seed hopper box).
Table 2.2.1 provides a guide for choosing standard values for the amount of seed treated per day
for on-farm seed treatment. The values in this table were derived by using ExpoSAC Policy 9
"Standard Values for Daily Acres Treated in Agriculture" and maximum amount of seed planted
per acre values provided in the BEAD memo "Acres Planted Per Day and Seeding Rates of
Crops Grown in the United States" (J. Becker, March 2011). It should be noted that the list of
crops included in this table is not exhaustive, and if a product label indicates on-farm seed
treatment for a crop not listed, the assessor can estimate the pounds of seed treated per day for
that crop. A value for acres planted per day can be chosen from ExpoSAC Policy 9, and a value
for the maximum seeding rate can be chosen from the 2011 BEAD memo. These two values are
multiplied in order to estimate the pounds of seed treated per day for on-farm treatment.
T.ihli- 2.2.1: Anmuiil nl'Sivil TiViik-d (AST) lYr l);i\ lur On-l-'iirm Si-i-d Tiv;ilnu-nl.
Seed Type
Acres Planted per Day 1
Maximum Seeding Rale
(lbs of seed planted per acre)2
Pounds (lbs) of Seed Treated per 1 )ay
lor On-Farm Seed Treatment'
Barley
200
98
19,600
Corn (field)
200
30
5,910
Cotton
200
19
3,780
Flax
80
50
4,000
Oats
200
90
18,000
Peanuts
80
228
18,300
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T;il>li' 2.2.1: Aiimiiiil ul'Sivd Tivnkd (AST) lYr l);i\ 1'nr Oii-I'iinn Si-i-d Tiv;ilnu-nl.
Seed Type
Acres Planted per Day1
Maximum Seeding Rate
(lbs of seed planted per acre)2
Pounds (lbs) of Seed Treated per Day
forOn-l'arm Seed Treatment'
Potato
61
6,970
425,000
Rice
200
156
31,300
Rye
200
90
18,000
Safflower
80
35
2,800
Sorghum
80
12
960
Soybeans
200
167
33,300
Tomato
80
1.1
87
Triticale
200
109
21,800
Wheat
200
157
31,400
1. Acres planted per day represented by the values for acres sprayed per day from ExpoSAC Policy 9: "Standard Values
for Daily Acres Treated in Agriculture". These assumptions may be further refined if crop-specific seed planting data
are available. The acres planted for potato seed pieces has been refined from ExpoSAC policy 9 since specific
information is available on the maximum number of acres that can be planted in an 8-hr day using a conventional 8-row
potato planter (Table 2 from BEAD memo "Acres Planted Per Day and Seeding Rates of Crops Grown in the United
States" (J. Becker, March 2011).
2. Seeding rates provided by BEAD memo "Acres Planted Per Day and Seeding Rates of Crops Grown in the United
States" (J. Becker, March 2011).
Table 10 provides lb seed/A for barley, oats, rye and safflower. Table 9 provides lb seed/A for sorghum and
triticale.
Corn seeding rate calculated from maximum seeds/A (Table 4, 40,250) and low end seed count (1,361 seeds/lb,
Table B-l).
Cotton seeding rate calculated from maximum seeds/A (Table 6, 85,000) and low end seed count (4,500 seeds/lb,
Table B-l).
Seeding rate for flax: https://www.ag.ndsu.edu/cpr/plant-science/flax-production-4-26-12.
Peanut seeding rate calculated from maximum seeds/A (Table 10, 105,000) and low end seed count (460 seed/lb,
Table B-l).
Rice seeding rate calculated from maximum seed/A (Table 8, 2,438,360) and low end seed count (15,600 seed/lb,
Table B-l).
Soybean seeding rate calculated from maximum seed/A (Table 5, 250,000) and low end seed count (1,500 seed/lb,
Table B-l).
Tomato seeding rate calculated from maximum seed/A (Table 10, 130,680) and low end seed count (120,000
seed/lb, Table B-l).
Wheat seeding rate calculated from maximum seed/A (Table 7, 1,500,000) and low end seed count (9,550 seed/lb,
Table B-l)
3. Derived from multiplying acres treated by maximum pounds of seed planted per acre.
3.0 Amount of Seed Planted (ASP)
Seed planting equipment has become more precise and sophisticated in recent years, which has
allowed growers to better estimate the number of seeds needed for their specific planting rates,
and better determine the cost of planting seeds in their fields. Determining the number of seeds
planted per day (i.e., seeding rate) for a specific seed crop is dependent upon: (1) the desired
number of plants per acre, which depends on the spatial arrangement (within-row or between
row spacing) of the plants; (2) the number of seeds per pound (i.e., seed count); (3) the percent
germination; (4) planting precision; and (5) hours worked per day.
Treated seeds are increasingly sold by count instead of weight. The number of seeds that weigh
one pound is referred to as "seed count." The seed count is a function of the individual seed's
weight and size (i.e., there is a smaller count of larger/heavier seeds in one pound than
smaller/lighter seeds). Because seeds are not uniform in size or weight, even within the same
Page 15 of 23
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type of seed, and can vary depending on environmental factors (weather, soil, etc), storage
conditions and heritable traits, farmers prefer to purchase seed by count rather than weight.
Therefore, the seed treatment industry is increasingly providing seed count information on the
package and is selling seed by count rather than by weight or volume. The American Seed Trade
Association (ASTA) filed a petition to amend Handbook 133 of the National Institute of Science
and Technology (NIST) (which includes procedures for testing packages labeled by weight,
volume, measure and count) to match the standards of the Association of Official Seed Analysts
(AOSA) for testing seeds. The National Conference on Weight and Measures passed a vote to
standardize testing methods and procedures for seed count labeling which became effective
January 1, 2011. This amendment is specific to corn, soybean, field bean and wheat seed.
Different types of planters (including broadcast, drill, precision, or specialized) are classified
based on the number of rows each planter is capable of planting. Different planters account for
the variation in seeding and plant density. Some planters provide a broad placement of seeds
that can reach up to three times the amount needed for a given acreage, whereas other planters
provide precision planting seeding rates that provide the exact number of desired plants
(assuming 100% germination).
The number of acres planted per day is dependent upon a number of variables such as planter
size (number of rows), farm size, and hours worked. The number of hours a day spent planting
seeds can vary depending on the length of the planting window, types of equipment used, and
local conditions (i.e., weather).
Seeding rates are commonly expressed in some measure of volume per acre (e.g., bushels per
acre) or in weight per acre (e.g., pounds per acre). Farmers estimate the proportion of seed that
will actually germinate to determine the pounds of seed needed per acre. Depending on the crop,
the seed germination rate can range anywhere from 70 to 90%. To compensate for less than
100%) germination, farmers typically plant extra seed.
Table 3.1 provides a summary of the default values for the amount of seed planted per day for
several crops.
T;il>li'3.l. Aiimiiiil nl'Si-id Phink-d Pit I);i\.
Crop
Number of
Seeds/lb1
Seeds/A'1
Seeding
Rale (lbs
seed/
acre)*'
Acres Planted
per I )ay"
Amount of Seed
Planted per])av
i lb r
Alfalfa
227,000
3,405,000
15
200
3,000
Asparagus
15,682
156,816
10
80
800
Barley
9,400
921,200
98
200
19,600
Beans, dry
800
130,680
163
200
32,700
Bean, lima
907
95,040
105
200
21,000
Bean, navy
1,814
418,176
231
200
46,100
Bean, snap
1,814
418,176
231
80
18,400
Beets, garden
25,344
633,600
25
80
2,000
Beets, sugar
22,000
435,600
20
200
3,960
Broccoli
80,000
210,845
2.6
80
211
Brussels sprouts
64,000
27,878
0.44
80
35
Cabbage
45,000
98,010
2.2
80
174
Page 16 of 23
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T;il>li'3.l. Aiimiiiil nl'Si-id Phink-d IVr l);i\.
Crop
Number of
Seeds/lb1
Seeds/A'1
Seeding
Rale (lbs
seed/
acre')'1
Acres Planted
per I )a\
Amount of Seed
Planted per ])av
(lb;1
Cabbage, Chinese
45,000
52,272
1.2
80
93
Canola
90,000
740,520
8
200
1,650
Cantaloupe
16,000
13,403
0.84
80
67
Carrot
175,000
2,090,880
12
80
956
Cauliflower
80,000
21,780
0.27
80
22
Celery
1,000,000
69,696
0.070
80
6
Chicory
375,000
2,250,000
6
80
480
Chive
91,200
364,800
4b
80
320
Collards
134,400
537,600
4
80
320
Corn, field
1,361
40,250
30
200
5,910
Corn, pop
1,361
30,000
22
200
4,410
Corn, sweet
1,800
59,739
33
80
2,660
Cotton
4,500
85,000
19
200
3,780
Cowpea / Southern pea
3,200
139,392
44
80
3,480
Cucumber
12,000
139,392
12
80
929
Eggplant
14,520
14,520
1.00c
80
80
Endive
13,068
52,272
4d
80
320
Flax
60,984
3,049,200
50e
80
4,000
Kale
100,000
576,000
6
80
461
Kohlrabi
100,000
58,080
0.6
80
47
Leek
160,000f
149,349
1
80
75
Lentil
7,467
522,720
70
80
5,600
Lespedeza
240,000
8,400,000
35
80
2,800
Lettuce, head
400,000
313,632
0.78
80
63
Lettuce, leaf
400,000
157,000
0.39
80
31
Millet, Japanese
155,000
3,875,000
25
80
2,000
Millet, pearl
85,000
1,700,000
20
80
1,600
Millet, proso
46,667
1,400,000
30
80
2,400
Mint (peppermint, spearmint)
6,670,464«
78,408
0.012
200
2
Muskmelon
16,000
38,848
2
80
194
Mustard
181,000
1,267,000
7
80
560
Oat
13,000
1,170,000
90
200
18,000
Okra
2,904
43,560
15h
80
1,200
Onion, dry bulb
100,000
400,000
4
80
320
Onion, green
100,000
2,500,000
25
80
2,000
Parsley
150,000
6,000,000
40
80
3,200
Parsnip
87,120
435,600
51
80
400
Pea, garden
1,361
560,057
412
80
32,900
Peanut
460
105,000
228
80
18,300
Pepper
50,000
209,088
4
80
335
Potato
5
34,848
6,970
6P
425,000
Pumpkin
1,600
7,260
5
80
363
Radish
32,000
1,045,440
33
80
2,610
Rice
15,600
2,438,360
156
200
31,300
Rutabaga
150,000
300,000
2
80
160
Rye
18,000
1,620,000
90
200
18,000
Safflower
13,608
476,280
35
80
2,800
Sesame
26,400
316,800
12
80
960
Sorghum
8,333
100,000
12
80
960
Soybean
1,500
250,000
167
200
33,300
Spinach
40,000
1,000,000
25
80
2,000
Squash, summer
1,920
11,616
6
80
484
Squash, winter
1,920
7,260
4
80
303
Sunflower
2,000
8,000
4
80
320
Page 17 of 23
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T;il>li'3.l. Aiimiiiil nl'Si-id Phink-d Pit I);i\.
Crop
Number of
Seeds/lb'1
Seeds/A'1
Seeding
Rale (lbs
seed/
acre)*'
Acres Planted
per I )a>
Amount of Seed
Planted per])av
i lb r
Swiss Chard
25,600
204,800
18k
80
640
Tomato
120,000
130,680
1.1
80
87
Triticale
15,000
1,635,000
109
200
21,800
Turnip
167,000
1,045,440
6
80
501
Watermelon
4,800
43,560
9
80
726
Wheat
9,550
1,500,000
157
200
31,400
a. Sources and Calculations:
Number of seeds/lb: low-end seed count from Table B-l from BEAD memo "Acres Planted Per Day and Seeding Rates of Crops
Grown in the United States" (J. Becker, March 2011) or information identified from web search.
Seed/A: high-end seeding/planting rates (seeds/acre) from BEAD memo "Acres Planted Per Day and Seeding Rates of Crops Grown
in the United States" (J. Becker, March 2011).
Seeding Rate (lb seed/A): Calculated from number of seeds/A -5- seeds/lb or from BEAD memo "Acres Planted Per Day and Seeding
Rates of Crops Grown in the United States" (J. Becker, March 2011) or information identified from web search.
Acres planted per Day: Acres planted per day represented by the values for acres sprayed per day from ExpoSAC Policy 9: "Standard
Values for Daily Acres Treated in Agriculture". These assumptions may be further refined if crop-specific seed planting data are
available.
Amount planted per day: lbs seeds/A * acres/day
b. http://edis.ifas.ufl.edu/pdffiles/CV/CV12800.pdf
C. http://edis.ifas.ufl.edu/pdffiles/cv/cvl2400.pdf
d. http://ufdcimages.uflib.ufl.edu/IR/00/00/34/79/00001/CV12600.pdf
e. https://www.ag.ndsu.edu/cpr/plant-science/flax-production-4-26-12.
f. http://www.ufseeds.com/Leek-Growing-Info.html
g. https://www.groworganic.com/out-rpk-pv-org-mint-peppermint-l-oz.html
h. http://extension. uga.edu/publications/detail. cfm?number=C627
i. https://nevegetable.org/crops/carrot-and-parsnip
j. The acres planted for potato seed pieces has been refined from ExpoSAC policy 9 since specific information is available on the
maximum number of acres that can be planted in an 8-hr day using a conventional 8-row potato planter (Table 2 from BEAD memo
"Acres Planted Per Day and Seeding Rates of Crops Grown in the United States" (J. Becker, March 2011).
k. http://aggie-horticulture.tamu.edu/vegetable/files/2011/10/swisschard.pdf
4.0 Planting Transplants Grown from Treated Seed
Small-seeded vegetable seeds are direct seeded in the field or grown from transplants.
Transplant production has recently replaced direct seeding due to (1) increasingly high cost of
hybrid seeds, (2) early-to-market cost advantages, (3) short growing seasons or a desire to grow
multiple crops per season, (4) crops that are difficult to establish, and/or (5) the fact that planting
transplants uses less seed per acre. Tomato, lettuce, cabbage, broccoli, and Brussels sprouts are
fairly easy to transplant. Celery, onion, pepper, eggplant, and cauliflower are moderately well
adapted to transplanting. Cucurbits can be difficult to grow from transplants due to very slow
root re-development. Root crops such as carrots, beets, radishes, and turnips tend to form
undesirable side roots when grown from transplants; therefore, are not typically grown from
transplants. Small seeded vegetable seeds that are used to produce transplants may be primed,
film-coated, and/or pelletized to improve handling during mechanized planting in greenhouses
and/or in nurseries. There are three types of mechanical planters for transplants: manual, semi-
automatic, and fully automatic. The semi- and fully automatic transplanters have replaced the
manual transplanters for most commercial growers. Handler exposure from transplanting after
treated seeds have been planted is highly unlikely due to the systemic nature of seed treatments.
Thus, exposure during crop transplanting is not represented by the seed treatment scenarios
covered in this policy (i.e., this policy is related to direct seeding scenarios). Exposure to
pesticides while transplanting is better addressed in ExpoSAC Policy 3.
Page 18 of 23
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Glossary
Seed enhancement technologies
Seed enhancement technologies have enabled the vegetable industry to provide uniform crops at
reduced seed cost per acre. Enhancements improve plantability (equal distance between planting
resulting in nicely shaped vegetables) and reduces the amount of pesticide per acre compared to
in furrow or other soil applications.
Priming
Seed priming is a hydration treatment in which dormant seed species are primed with aerated
water under controlled environmental conditions to break dormancy and ensure fast and uniform
germination when planted. Priming solutions can be supplemented with plant hormones or
beneficial microorganisms. Seed priming can result in rapid, uniform and complete seedling
emergence after planting; however, primed seed has a limited storage life compared to non-
primed seed.
Encrusting
Encrusting increases seed weight from 50 to 200% without a significant change in seed shape.
Encrusted seed may appear similar to film-coated seed (but adds more weight to seed) and is
sometimes referred to as mini-pelleting (less weight than pelleting) or coating. Seeds are
encrusted to fill in holes and indentations of seed (primarily carrots and onions). Onions are
commonly encrusted. Encrusted seed has a small quantity of material added to it to minimally
change the shape of the raw seed to enable accurate mechanical seed metering in greenhouse and
field applications.
Film-Coating
Film coating puts a very thin colored film around the seed increasing the weight of the seed by
about 5%, without changing the original size or shape of the seed. The film coat is generally
made up of a water permeable polymer, a plasticizer and a colorant. Three basic reasons to film
coat seeds are 1.) maintains pesticide on the seed for maximum affect (completely enclosed
around seed) and reduces pesticide exposure to handlers; 2.) helps seed flow better in the planter
box and/or metering during loading and planting; and 3.) colorant makes seed easier to pick out
of the soil when checking for seed spacing during planting.
Film coating of small seeded vegetable seeds in the U.S. are typically accomplished using rotary
film coating systems (e.g., Rotostats) and drum coaters such as side vented pan coaters. The
seed is placed in a rotating drum and the film-coating material plus plant protection product (if
desired) is sprayed directly onto the seed. The coated seed is then removed from the drum, dried
and packaged ready for sowing. Although the treating time per batch is fairly short, the drying
step can require several hours and is often the rate limiting step in treatment of small seeded
vegetables.
Pelletizing
Pelletizing turns a seed light in weight and oddly shaped into a pellet which is heavier, more
uniform, perfectly round a possible enabling planter to plant seed/pellet in the most precise
mechanical way possible (precisely planting seed with desired amount of space between each
Page 19 of 23
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seed) resulting in nicely shaped product. Formation of pellet involves powders and adhesives
applied around the seed to form a more or less spherical shaped dispersal unit. The original size,
shape and weight are changed significantly, generally to a size and weight for a particular
planting scheme. The increased weight can be from 1000 to 4000% (10:1 to 40:1 ratio).
Depending on seed type and process, the weight of a pelletized seed can increase from 5-100
times the original seed weight. For example, commercial lettuce seed has a raw (commercial)
seed count of 240,000-480,000 seeds per pound while pelleted lettuce seed count varies from
11,500 - 35,000 seeds per pound , a 20X to 13X decrease in seed count.
During the pelleting process raw seed is placed in a rotating drum also referred to as a pan treater
or coating pan. The raw seed is misted with water or other liquids and gradually blended with
fine inert powdered materials. Synthetic plant protection products can be added in either a dry or
liquid form at almost any point during the pelleting process. Each seed becomes the center of an
agglomeration of powder that gradually increases in size. The tumbling action serves to round
and smooth the pellets. Binders and polymers are often added near the end of the pelleting
process to harden the outer layer of the pellet and minimize dust-off for the finished product. At
intervals during the pelleting process, the pellets are removed and mechanically sized on a set of
vibrating screens. Smaller pellets are then returned to the coating pan for additional build up.
The traditional side vent coating pans used for pelleting small seeded vegetable seeds are
single batch open seed treatment systems; either standard flat pans or round pans with open
sides. Regardless of whether the seed is pelleted in a Small Seeded Vegetables - rotary coater or
the more traditional coating pan, the amount of time required to dry the seeds (2-4 hours)
remains unchanged and hence drying is often the rate limiting step in treatment of small seeded
vegetable seeds.
Breeder/producers
Companies that breed and produce small vegetable seeds in-house as much as possible including
priming, film-coating, encrusting and pelleting. These companies will, however, contract with a
seed treatment technology provider for a specific type of pellet or process which they have not
developed internally due to complexity of process, or for which their volume is low enough for a
specific process that it does not warrant developing an internal process. The only major
exception to this rule is the lettuce market. In the lettuce market there are a number of local small
breeder/producers which send all of the seed that they produce to one of the major technology
provider companies for priming, film-coating, encrusting and/or pelleting to meet specific
grower production practices.
Technology providers
Companies which concentrate on the development of seed treatment technology (i.e., prime,
film-coat, encrust and/or pellet seed) to meet specific grower production practices. The major
crops treated by the technology provider companies are leafy vegetables (primarily lettuce) and
onion seeds but tomatoes, peppers and a limited amount of other species are also treated. Note
that the technology providers also treat a significant amount of small seeded flower seeds
(begonias, petunias, etc).
Types of Planters:
Broadcast planters randomly distribute seeds on the soil surface and a separate operation
Page 20 of 23
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is required to cover the seed (e.g., harrowing). Broadcast planters are often used to
establish crops that have very small seeds (e.g., alfalfa) or those that require light to
germinate (e.g., some pasture grasses).
Seed drills are tractor-pulled that have a series of small plows or disks that open furrows
in the soil and randomly drop seed into closely spaced furrows. This type of planter uses
mass flow seed metering and is used to establish crops where there is little incentive to
place seeds equidistant in the row. Almost all small cereal grains (e.g., oats, barley,
wheat) are planted using drill planters.
Precision planters are used to accurately place single seeds or groups of seeds equidistant
in the row. This type of planter can use one of several types of precision metering
devices (e.g., belts, plates) and is used to plant crops that require accurate control of the
plant population. Crops planted with this type of planter include almost all horticultural
crops (e.g., vegetables) and field crops (e.g., sorghum, corn, soybean, sunflower, and
cotton).
Specialized planters are considered here to be those that plant whole plants (e.g.,
seedlings or transplants), plant stems (e.g., sugar cane) or tubers and bulbs (e.g., potatoes
and onions).
Page 21 of 23
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Appendix A. Small and Large Seeded Vegetable Assignments for Seed Treatment
Asparagus
Kohlrabi
Beets, garden
Leek
Beets, sugar
Lentil
Broccoli
Lettuce, head
Brussels sprouts
Lettuce, leaf
Cabbage
Muskmelon
Cabbage, Chinese
Mustard
Cantaloupe
Okra
Carrot
Onion, dry bulb
Cauliflower
Onion, green
Celery
Parsley
Chicory
Parsnip
Chive
Pepper
Collards
Radish
Cucumber
Rutabaga
Eggplant
Swiss Chard
Endive
Tomato
Kale
Turnip
Large Seeded Vegetables
Bean, lima
Pumpkin
Bean, navy
Squash, summer
Bean, snap
Squash, winter
Cowpea / Southern pea
Watermelon
Pea, garden
Page 22 of 23
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Attachment 1: Documentation of Revisions
Diilo
DocuiiH'iiliilion of Ke\ isions
March 2004
Original version
December 2017
Updated amount of seed treated commercially based on AHETF submissions
Updated amount of seed treated on-farm and amount of seed planted using 2011 BEAD
memo which provided updated seeding rates
June 2021
Removed reference to long-term seed treatment exposure duration and provided
justification for excluding this duration from risk assessments
Fixed typographical error: review barcode reference of seed treatment survey review
January 2022
Removed small and large seeded vegetable designations from Table 3.1. Moved
designations to separate table in Appendix A for reference.
Changed footnotes to Table 2.1.1 to point to Appendix list for small and large seeded
vegetables rather than listing out examples.
Removed Lespedeza designation as small seeded vegetable; added it to Table 2.1.2 as
translatable from canola
Removed Proso millet designation as small seeded vegetable; added it to Table 2.1.2 as
translatable from wheat
Removed Japanese millet designation as small seeded vegetable; added it to Table 2.1.2
as translatable from wheat
Removed Pearl millet designation as small seeded vegetable; added it to Table 2.1.2 as
translatable from wheat
Removed mint designation as small seeded vegetable; added it to Table 2.1.2 as
translatable from canola
Fixed typographical error in Table 3.1 for asparagus: seeds/lb changed from 15,862 to
15,682
Deleted footnote "L" from Table 3.1- reference not applicable
Updated swiss chard values for seeds/lb and seeds/A in Table 3.1 to better match with
information from referenced footnote.
Edited Section 4.0 to clarify that exposure during crop transplanting is not represented by
the seed treatment scenarios in this policy; transplanting is addressed in ExpoSAC Policy
3.
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