Roadside Revegetation

IMPLEMENTATION GUIDES
seed data is unavailable at this point in planning. The information that
is needed includes an estimate of the following factors:
◾◾
Pure live seeds per pound
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Field survival
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Target seedling density
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Target species composition
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Area to seed
Bulk
Seed
Purity
Test
Germination
Test
12 seeds 5% debris
2 dead
79% PLS
95% Purity 83% Germination
Pure Live
Seed
Pure Live Seeds Per Pound (PLS/lb) – The quality of seedlots can
vary greatly. One method to assess seed quality is to calculate percent
pure live seed (PLS). This value represents the percent of the gross seed
weight composed of viable seeds. For example, if a seed producer
did not clean the harvested seed of a seedlot very thoroughly, the
PLS would be low because there would be a lot of additional weight
associated with non-seed debris. Seedlots that were cleaned well, on the other hand, would
have a higher PLS because the debris weight would have been removed. Seedlots that have
higher germination rates also have higher PLS. These two factors, percent purity and percent
germination, when multiplied together and divided by 100, give the PLS of a seedlot. The
concept of PLS is illustrated in Figure 10-65. In this example, purity of a grass seedlot is 95
percent and germination is 83 percent which results in a PLS of 79 percent.
Another example of calculating PLS/lb is shown in Figure 10-66 for western pearly everlasting
(Anaphalis margaritacea). For this seedlot the estimated purity is 60 percent which indicates
that over half of the gross weight of seed is actually viable seed and the remaining part is either
debris or non-viable seed. Multiplying this value by the percent of seeds per pound and by
the percent of germination will yield the number of viable seeds per pound. In this example,
the number of seeds in a pound of a western pearly everlasting seedlot is tested at 8,000,000.
Multiplied by 60 percent purity and 85 percent germination gives a value of approximately
4,080,000 PLS per pound of bulk seed. This value can be used in sowing calculations as shown
in the example. Keep in mind that for each additional seedlot in a mix, similar calculations will
have to be made. Estimates for purity, germination, and seeds per pound can be obtained
from Table 10-14, seed inventories, or seed extractory managers.
Figure 10-65 | Pure live seed
Pure live seed (PLS) is the percent of the
bulk seed weight that is composed of
viable seed. In this example 95 percent
of the bulk weight is composed of seed
and of this seed 83 percent was found to
germinate from seed tests. Multiplying
percent purity by percent germination
gives percent pure live seed.
A Number of seeds/lb: 8,000,000 seeds/lb From Table 10.14 or other sources
B Purity: 60 % From Table 10.14 or other sources
C Germination: 85 % From Table 10.14 or other sources
D A * B / 100 * C /100 = 4,080,000 PLS/lb Pure Live Seeds (PLS) per bulk pound of seed
E Field survival: 3 %
Estimate of the pure live seeds that become
seedlings (as low as 3% for harsh sites and
up to 25% for excellent sites)
F 25 seedlings/ft 2 Target seedling density:
foot — all species (10 to 30 for grasses
Desired number of seedlings per square
and forbs)
G Target composition 10 % Percent of total plants composed of ANMA
H (F / E) * G = 83 PLS/ft 2 PLS of ANMA to sow per ft 2
Figure 10-66 | Determine
amount of seed needed
Determining the quantity of seed that will
be needed for a revegetation project can
be made by completing this spreadsheet for
each species. The estimated pounds of seed
determined for each species can be the basis
for ordering seed through a seed increase
contract. This example calculates the quantity
of western pearly everlasting (Anaphalis margaritacea
[ANMA]) seeds needed for a project.
I 43,560 * H / D 0.9 lbs/acre Pounds of ANMA to sow on a per acre basis
J Area to seed: 25 acres Total area for seed mix
K I * J = 22 lbs Total ANMA needed
Roadside Revegetation: An Integrated Approach to Establishing Native Plants and Pollinator Habitat
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