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Re: soil seed bank
It has been my experience that by not tilling the soil, initially there
is an increase in weed pressure. I farm 175 acres and have some
fields(15 acres) that were not tilled for over 30 years. However I've
noticed that I can reduce my herbicide rates significantly after
no-tilling for about 5 years. I think by tilling the soil you are in
effect "planting" some weed seeds that will then germinate when
conditions are favorable for that species. By leaving the seeds on the
soil surface they are exposed to the elements and germination survival
rate is diminised.(This is only my theory from my experience and
observation) I don't believe I can just credit no-till for lowering my
weed pressure though. Cover crops have also been impressive in there
effect of controlling weeds. In 1996 I split a field with one side
having a vetch/rye mix while the other side had no over wintering cover.
You could see the diference the following year with very few weeds in
the vetch/rye side while the other side had lots of pigweed and other
weeds.
Row spacing also plays a role in lowering the weed seed bank. Closer row
spacings hinder late season weed viability due to earlier crop canopy
closure. 15" field corn has shown a noticable difference in late season
grass pressure and in the following year the emergence of foxtail was
reduced. I 've even started planting my no-till tomatoes in 44" rows and
brocolli in 30" rows to take advantage of this effect.
We of coure can't forget crop rotation and its desirable advantages of
reducing weed pressure also. I'm convinced that it is the key on my farm
in not having a perenial weed problem.
I think the whole question of the weed seed bank and it's relationship
to cropping systems is something that should be further researched but
needs to go beyond tillage issues.
--
"New Generation Cropping Systems": the cutting edge of sustainable
agriculture
http://www2.epix.net/~cmfarm/
Steve Groff
Cedar Meadow Farm
679 Hilldale Rd
Holtwood PA 17532 USA
Ph. 717-284-5152
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