[Update: 5/24/15] We have recently sprayed our CF and DNS. We have so few weeds in these fields that it is difficult to justify the cost of chemical, but it is to soon to cut these applications. Our agronomist advised against application to the CF, but we couldn't leave the scattered single Downy Brome plants. We put out one short load doing the draws and bordering the CRP.
The DNS has a light infestation of Downy Brome (the bane of our small grains and fallow rotation), and plants from the failed winter canola crop. We hit the crop with a fungicide, broadleaf, and grass herbicide.
When I started direct seeding, years ago, one worry I had, was --chaff rows left by the combine. Combines of any make will drop grain, and in areas, a lot of grain. Our combine is no different then anyone else's. Rains fall, seed germinates, and fields green up, but over the years ours have consistently shown less than most fields. Since 2012 when we bought the stripper head and changed from high disturbance direct seeding to ultra low disturbance direct seeding I have noticed that we have further reduced the weed pressure in our fields.
We have some theories but no validated research to support the claims.
----Leaving the seed bank on the surface hastens its destruction over planting it! For a long time I have felt that the elements (heat, cold, rain, wind, sun) would decompose seed if it were not buried. There is a lot of research stating the number of years that various seeds can remain viable in the ground.
---Seed laying on a blanket of residue germinates, dries, and dies! We think this occurs, even on bare soil. Many seeds on the surface will take up moisture and dry and die before they can get a root anchored to sustain them. It appears that the thicker the residue layer the better.
---There are a lot of critters (granivores) skittering along the ground surface (birds, invertebrates, mammals) that eat seed. The tall stubble may be protection for these granivores.
The purpose of our direct seeding from the start was the lure of saving moisture for use by our crops as mentioned in other posts (label--Moisture). As we have progressed toward that goal, the reduction of weed pressure is a welcome side benefit.
Where do we go from here? With the adoption of the stripper head, and a ULD system in the form of the CrossSlot drill, we have reached a wall (in our thinking). We have been very successful to this point. What further can we do to improve moisture saving and weed reduction techniques. COVER CROPS????
I've wondered about the effectiveness of harrowing fields post harvest to get them to "green up". Harrowing to get them planted in the fall and sprayed out may be effective to a point, but whether its any more effective than just spraying out what comes up and leaving the rest to the critters and elements is something to be pondered. Do you have any issues in your system with an increase in any other weeds, grassy or otherwise?
ReplyDeleteThe two and three year rotations with small grains and fallow is a natural multiplier of downy brome, goat grass, and any other grassy weed. A harrow worsens the condition by spreading seed to non-infected areas. Downy brome is still troublesome (although reduced) and requires an application of grassy weed herbicide in wheat or barley. Lengthening the rotation by adding a pulse and/or brassica crop will reduce the problem over time through two mechanisms. ---ability to use a different, and better grassy herbicide, and, ---a lengthened rotation upsets the growth habit the weed has become accustom too. The other grassy weed we have is rattail fescue. It continually bleeds out of the CRP. We successfully manage this weed by increasing the solution volume, and spreader/sticker to make sure that all leaves are covered. Roundup is our herbicide of choice.
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