|
Every year you spray pre-emergent weed killer on your
field crops and rogue out any weeds that come through. Every
year…there are no weeds in the field. You would think that over the
years the supply of viable weed seed in a particular field would
eventually diminish into non-existence.
Yeah right…..the one year that one of your sprayer
nozzles clog, when spraying that pre-emergence weed killer, you get
to see all the weed seeds just waiting for you to slip up and
immediately germinate and grow in the one row that you missed.
Why do all those weed seeds stay viable over such a
long period of time when the seed from commercial seed lots, even
when stored in the most ideal conditions, seem to lose vigor and
viability faster than we’d like?
Dormancy is the answer.
Certain plant species have survived over the
centuries because they have developed mechanisms to germinate over a
long period of time, or only under certain environmental
conditions. This increases the species probability that at least
some of the seeds will germinate at the time when conditions are
ideal for plant growth and reproduction. Here are a couple of
dormancy types that enable seeds to survive naturally in the soil,
and also the ways that seedsman have devised to break that
dormancy…opening the physiological door.
|
Dormancy Type |
Seedsmens way to break
dormancy |
|
Seed Coat-Imposed |
|
Seedcoat too hard or impermeable
|
Scarification – Chemical (sulphric acid) or mechanical
(abrasion) treatment breaking down seedcoats |
Chemical inhibitors in seedcoat
|
Soaking in
water and then rinsing to remove inhibitors from seedcoat |
|
Seed Embryo-Imposed |
|
Freshly harvested seed and/or a seed metabolic requirement
|
Moisten
seed and store at low temperatures (stratification),
or moisten with dilute KNO3, or apply light to moisten seed,
or any combination of the above. |
|
That’s it for this time. Next time we’ll talk about
“Seed Shelf Life – Things are Happening Inside that Seed Sitting on
the Shelf.” See you then.
Keith |
