Environmental Engineering Reference
In-Depth Information
Understanding the relationships of germination and purity compared to the unit price of the
species will enable you to determine your best options. Low-unit-priced seed may have very low
purity or germination rates. The result is seed that may cost ten to fifty times the bulk seed weight
price. It is always good to calculate the numbers prior to making decisions. Knowing the bulk seed
cost is important, but it is only the beginning; more critical is knowing the germination and purity
rate of the seed. This will allow you to determine what the actual cost of the seed will be. It is very
enticing to see a bulk pound cost of only two dollars, but after viability is considered, the actual
cost could be as high as one hundred dollars per pound!
An annotated seed mix worksheet (appendix 6) is provided to permit loading into standard
computer spreadsheet software. This will reduce the potential for miscalculations that can occur
when working with several numbers and species. The example in appendix 6 is for applying seed
separately, not as a mix, because different areas of application are identified in column K. Projects
not purchasing seed but collecting their own should attempt to document in some way the quanti-
ties applied, for future reference by others. This information may be qualitative in nature, because
the vegetative component of hay can be highly variable, as is the seed production from year to year.
Seed Quantities
A frequently asked question is how to determine the quantity of each species to put in a seed mix
and how many pounds or ounces should be in a seed mix per measured area. Unfortunately, the
variability between sites, along with numerous other factors, makes it impossible to give a specific
answer. This area of specifying restoration work requires some knowledge and experience working
with each species under similar conditions. Information on how to guide your decisions will come
from different sources.
Inexperienced individuals can get information on quantities and mixes from some suppliers.
However, because environmental conditions significantly influence the outcome of the seeding
efforts, it is important to know the context and circumstances of any anecdotal information to
determine whether your site has similar conditions. Although it requires advance planning, setting
up a few test plots sown with varying mix combinations can prove very helpful. The key to compil-
ing a body of knowledge compatible with site-specific conditions lies in learning as much as you
can from each project, discussing results along the way with other practitioners.
In dry environments, some species do not germinate until the first or second year following
sowing. Without seed pregermination treatment, other species may take several years. Knowing
how a species responds to sowing will directly influence how you develop the evaluation criteria
for the project. Calculating the seeds per area sown will help you evaluate your efforts. Under-
standing how a species develops and matures may influence some potential measurements to be
used as criteria.
Seed application rates are variable. The vegetation community and the composition greatly in-
fluence the quantity and weight applied. Grasslands seed mix (lightweight seeds) will have a much
lower overall weight than a scrubland seed mix (large, dense seeds) with the same number of total
seeds. The site preparation and how the seed is put onto the project site also affect the quantity
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