Front Range Seed Analysts
1993 Seed Forum Volume 7 Number 1
Basic Seed Treating for the Laboratory
Part II. Treating seed to comply with a request for a treated seed
germination or a vigor test.
by Russ Elliott, BioTech, USDA/ARS NSSL
Seedsmen and farmers may want to know what benefits they can gain through treating their seed prior to committing their entire seed lot to commercial treatment. Comparisons between treated vs. untreated seed or between different treatments can be made through accurate laboratory treatment of small samples of the seed lot in question, subsequent germination and more importantly, vigor testing (cold tests, growth rate, accelerated aging etc., for example) . The seed analyst's goal is to 1) duplicate what the seedsman/farmer will be applying to his seed lot and 2) use appropriate germination/vigor tests to assess the treatments efficacy and verify that there are no adverse effects on the seed due to treatment.
Equipment
glass beakers (25, 50, 100 ml. sizes)
glass stirring rods
plastic medical (disposable type) syringes (1, 3, 6, 12 cc sizes)
plastic or glass jars to be used as treating containers
(Select sizes which, when filled with the seed to be treated, are approximatiely
1/4 to 1/3 filled with seed. This allows adequate room for the shaking
and rolling action needed to combine seed with the treatment and obtain
an even, uniform coverage)
scale (accurate to 0.01 grams) for weighing wettable powders, etc.
grease pencil
plastic gloves, dust mask, ventilation for safety purposes
Conversion Factors
1 cc. = 1 ml = 1 gram by weight of water
1 fluid ounce (fl. oz.) = 29.574 ml.
1 oz.= 28.35 grams
1 lb.= 453.6 grams
1 cwt. = 100 lbs. (seed)
1 gallon = 128 fl. oz.
Most common commercial seed treatments consist of fungicides/ insecticides in flowable, wettable powder or emulsifiable concentrate forms which may be applied singly or in combination with the addition of water to form a slurry' treatment. The slurry rate is the total volume of chemical plus water together that will be applied to the seed.
Note: The treatments used are for purposes of demonstration only and
do not represent an endorsement of any kind. It is the analyst's responsibility
to obtain the treatments to be used, chemical rates, slurry rates, etc.
from the seedsman/farmer or his chemical sates representative.
Slurry Rates (cwt. = 100 lbs. seeds)
alfalfa = 16 fl. oz/cwt.
barley = 11 fl. oz/cwt.
beans = 8.5 fl. oz/cwt.
cotton = 27 fl. oz/cwt.
field corn = 14.4 fl. oz/cwt.
sweet corn = 19.3 fl. oz/cwt.
canola = 40.6 fl. oz/cwt.
grasses =40.6 fl. oz/cwt.
oats =16 fl. oz/cwt.
lentil/peas =8.5 fl. oz/cwt.
sorghum =14.2 fl. oz/cwt
soybean =8 fl. oz/cwt.
sunflower =16 fl. oz/cwt.
wheat =16 fl. oz/cwt
note: the above slurry rates are approximate and may vary used in a commercial treating situation.
Example: Treat 1/4 lb. wheat with Captan 400 at 2 fl. oz./cwt. + Baytan
30 at
1.25 fl. oz./cwt. using a slurry rate of 16 fl.oz./cwt.
1. The above may be written as follows:
Cp400 @2fl.oz./cwt. + B-30 @1.25fl.oz./cwt. --> 16fl.oz./cwt.
2. Calculate amounts of chemicals plus water to make up a 10 lb. slurry
(enough chemical + water to treat 10 lbs. seed). Note: Although only 1/4
lb. seed will ultimately be treated, it is necessary to make up a larger
amount of slurry due to the limitations of measuring by syringe, etc.,
and to ensure accuracy.
Calculations:
2 fl.oz CP400 = 0.2 fl. oz. Cp400 = 5.91 cc
Cp400
100 lbs. seed 10 lbs.
seed
10 lbs. seed
1.25 fl.oz. B30 = 0.125 fl.oz. Cp400 = 3.70 cc
B30
100 lbs. seed
10 lbs. seed 10 lbs.
seed
16fl.oz. tot. slurry = 1.6fl.oz. tot. slurry = 47.32cc
tot. slurry
100 lbs. seed
10 lbs. seed 10 lbs.
seed
Therefore, to make up a 10 lb. slurry, the formula may be written as follows:
5.91 cc
3.70 cc
47.32 cc
CP400 @2 fl.oz./cwt + B30 @1.25 fl.oz./cwt ---> 16 fl.oz./cwt
3. Prepare the slurry mixture:
1) Place beaker on scale, tare scale, and add water until scale reads
47.32 grams and use a grease pencil to mark the beaker at this level (1
gram H20 = 1 ml. = 1 cc.)
2) Empty beaker of water (it is advisable to leave some water in the
bottom of the beaker to keep chemicals from adhering to the bottom of the
beaker)
3) Place 5.91 cc Captan 400 into beaker (use Byringe to measure)
4) Place 3.70 cc Baytan 30 into beaker (use a separate clean syringe)
5) Add water until the premarked 47.32 cc. line drawn on the beaker
is reached
6) Stir well with glass stirring rod. The slurry mixture is ready for
application to the seed.
Notes for slurry preparation: Use the smallest syringes, beakers, etc.
you can for the amounts being measured to ensure accuracy. (For example:
use a 6cc syringe to measure out 5.91 cc instead of a 12 cc syringe.) Avoid
air bubbles, etc. in syringe, and be certain that the chemical containers
are well shaken and mixed before measuring out chemicals (there is often
a high degree of settling of chemical within the container).
4. Calculate amount of slurry to apply to 1/4 lb. of wheat seed as follows:
47.32 cc = 4.73 cc =
1.18 cc
10 lbs. seed 1 lb. seed
1/4 lb. seed
1.18 cc of the prepared slurry mixture would treat 1/4 lb. seed but due to the chemical loss to the sides of the treating container, add 2% extra slurry to compensate. Therefore, measure out 1.20 cc with a syringe to treat 1/4 lb. seed.
5. Apply the slurry mixture to 1/4 lb. seed as follows:
1) When using a new, clean treating container, the container should
be 'pretreated' by initially adding an equivalent amount of clean untreated
seed plus an equivalent amount of slurry mixture, treating this seed, and
discarding. This will coat the sides of the treating container with a thin
layer of treatment and avoid future chemical loss when treating. Subsequent
use of the container using the same chemical will not require the pretreatment.
2) Apply 1.2cc of the slurry mixture evenly around the sides of the
jar to be used as the treating container.
3) Add 1/4 lb. of wheat seed, cap jar, and shake/roll seed inside jar
until the seed is evenly treated and there is little or no chemical remaining
visible on the sides of the treating container.
6. Empty the treated seed into a clean paper bag and allow to dry.
A wettable powder product may be used in a slurry mix as well using
the same series of calculations being sure to use the ounce to gram conversion
factor (instead of the fluid ounce to milliliter factor used with flowables).
7. Finally, the addition of dye or colorant may be necessary. Typically these rates are expressed as 1 bottle (a bottle may be 16 or 32 fl.oz.) per 5 gallons of the largest chemical component of a slurry mix (in the example this would be the Captan 400). Therefore, using the example of Captan 400 @ 2fl.oz./cwt. to determine the amount of colorant needed (I bottle colorant = 32 fl.oz.).
colorant/dye calculations:
(1 bottle) 32 fl.oz. colorant = 0.01 fl.oz. (amt.per 10 lb.slurry)
(5 gallons) 640 fl. oz. Cp400 0.2 fl
oz. Cp400 (amt. per 10 lb.slurry)
0.01 fl.oz. = 0.30 cc colorant per 10 lb. slurry
This article has addressed the basic means of duplicating commercial treatments using rates as they are expressed on the sides Of seed treatment containers and reducing both the amounts of chemical and seed to that which manageable in the laboratory.
Often, treating seed for research purposes, field trials, and other small scale uses requires that the rate of application be expressed in other ways than that commonly used in commercial channels. Some examples Of this are PPM (parts per million), oz. AI (active ingredient) per cwt., or milliliters/milligrams per 100 kilograms.