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Certified seed
This is high quality seed with important characteristics such as good
germination potential and purity, and is subjected to strict norms and
standards which seed companies guarantee. If producers have prob-
lems with such seed, an investigation is initiated if a claim is lodged.
This kind of seed is available from recognised seed- and agricultural
companies.
Commercial seed
This is seed of acceptable to good quality that complies with cer-
tain requirements of the plant improvement act. The quality require-
ments are not as strict as for certified seed. This kind of seed is also
available from recognised seed- and agricultural companies.
Retained seed
Retained seed is seed of the established crop which is harvested and
retained for planting the next season. This practice is legal, as long
as the seed is not sold. Producers often face production and storage
risks when retained seed is used.
Problems experienced include:
Low quality seed due to incorrect seed harvesting periods and
techniques.
Weed contaminated seed lots.
Mould on seed when seed is stored when damp.
Poor germination potential when stored in warm conditions.
Germination and purity tests must be conducted before estab-
lishment and seed needs to be treated with a registered pesticide
against seed-borne diseases.
Taking all the aforementioned factors into account, the use of certi-
fied and commercial seed remains a lower risk and possibly a more
economically viable option in some cases. Grain SA’s viewpoint with
regards to retained seed, is that they are completely against the il-
legal sale of retained seed (which is only intended for own use).
They too acknowledge that seed is being retained as a result of the
current economic climate. It is imperative for producers to be aware
of the fact that, when a producer retains seed it restricts the develop-
ment of newer cultivars over the long term. Grain SA will continue to
find ways to address the aforementioned issues.
To highlight the complexity of the practices and processes of seed
production, the following factors are discussed.
Planting practices for seed production
Only healthy seed, from a producer’s own source, which should be
free of weeds and seed-borne diseases, should be used for planting
in a uniform, level seedbed, and not planted to the same crop as the
previous two years.
To avoid cross-pollination from nearby plots of the same species,
ensure that the seed plot is isolated either through spatial isolation
or planting time. Wind can carry pollen more than 300 m and it is
imperative to take this factor into account when selecting seed plots.
It is important that information be obtained regarding the mode of
reproduction of the crop from which you wish to produce seed. For
example, many temperate forage grasses and legumes are cross-
pollinators, tropical forage legumes are often self-pollinators and
many tropical and subtropical grasses are apomictic (a-sexual repro-
duction). To make access easier, especially when inspecting the seed
plots for diseases and off types, prostrate species should be planted
in rows and for twining species broadcasting is recommended.
Similar fertilisation rates as for grain production is required for
seed production. Too much nitrogen, however, promotes vegeta-
tive growth rather than flowering and should thus not be excessive.
Phosphorus and potassium stimulate flowering and ensure higher
seed yields therefore fertiliser rates should be based on reliable
soil analyses. Day length is the main factor that controls flowering
in many plants: In day-neutral plants, flowering is unaffected by
day length (e.g.
Stylosanthes spp
.); in short-day plants, flowering is
stimulated if the day length is shorter than the critical length (e.g.
Glycine max
) and in long-day plants flowering is stimulated if the day
length is longer than the critical length (e.g.
Avena sativa
(oats) and
Raphanus sativus
: fodder radish).
Moisture stress after flowering will affect seed yields negatively and
if possible should be irrigated during this stress period. Regular field
inspections are evidently an important aspect to remove undesirable
plants, weeds, and diseased plants to safeguard against harvesting
seed of inferior quality and increased processing costs.
Harvesting seed
Time of harvest is crucial in ensuring optimum and healthy seed
yields. Because the seed harvested has a high moisture content it
must be placed in a seed dryer or spread thinly over a concrete floor
and turned regularly by raking until adequately dry.
Harvesting too late will result in more diseased, insect damaged,
shattered and brittle seed. In general, grass seeds should be har-
vested when the bulk of the seed is not far from shedding.
For legumes with determinate growth (flowering falls within a short
period) seed can be inspected regularly and harvested when seeds
are mature.
On-farm cover crop seed production
FOCUS
Seed
Special
“
On-farm production of cover crop
seed is a viable option for the
advancement of CA systems in
South Africa. However, seed
production is a complex and
intricate process and requires
adherence to fairly
strict guidelines.
“