Palmer Amaranth: I’ve been speaking a lot this winter on palmer amaranth and a few shared it’s fairly depressing. The positive side of this is we have an opportunity to learn from the research conducted in the Southeastern U.S. regarding palmer management so we don’t get to where they’re at! Their top question for cash renting or purchasing ground is “do you have palmer?”…so we have an opportunity to manage it here now!
In order to do that, though, we need to think of a system’s approach. This approach may not be economical for every year, but a system’s approach looks at the long-term benefits as a whole.
The keys for palmer (or any weed) are to keep it from germinating and then, once germinated, keep it from seed production. Palmer germination has been found to be induced more by natural and red light than soil temperature. Thus, bare soil in the first few weeks of May allow for a good situation for palmer germination and emergence. Management to avoid early germination include: keeping the soil covered with residue, small grain, or cover crop; burndown apps and pre-plant herbicide applications. Palmer can continue to germinate throughout the growing season to mid-September. During the growing season, quicker canopy closure and post-herbicide apps with residual are key.
At harvest, management includes seriously considering not running your combine through palmer patches. We’ve had farmer success stories in 2016 when farmers didn’t harvest their soybean endrows but did harvest the rest of their fields. Instead, some chose to disk down endrows with heavy palmer pressure and planted a wheat or rye cover crop in them. In 2017, they shared it made a big difference in reducing palmer in those fields. I’ve also received farmer testimonials sharing the opposite; they wish they didn’t harvest the endrows or the one patch that had palmer in the field as now they’ve spread it throughout the field. Research has shown 99% of the palmer seed going through the combine is still viable; thus we’re just moving it throughout the field and from field to field.
Fire was not found to be effective to get hot enough to kill the seed when the whole field was burned. Instead, crews carry black trash bags, pull the female palmer plants, and haul them out of the fields burning them in burn barrels.
The University of Georgia found they had to hoe the plants 2” below the soil surface in order to kill them. An average palmer plant can produce 500,000 seeds/plant. The plant on the edge of the field can produce up to 1.8 million seeds. I had a hard time believing the seed production research from the soil surface (22,000 seeds on average) and 1” stem (36,000 seeds on average), until I saw it walking fields last summer. I remember tweeting out the pictures saying #hatethisweed.
A study conducted in Kentucky compared 1-Wheat with double crop soybean 2-Wheat fallow (no herbicides were applied) 3-Full season soybean. They counted palmer plants in 100 square feet in each replicated treatment. No palmer could be found in the wheat other than in the tram lines; the double crop soybean into the wheat stubble only had 5 plants/100 sq. ft. In comparison, the full season soybean
ranged from 18-40 plants/100 sq. ft. while the fallow ground had 80 plants/100 sq. ft. A system’s approach is considering adding a small grain like wheat back into the system. Or, at least consider wheat/rye as a cover crop to help reduce light interception onto the soil surface in early spring.
We’ve also heard more about tillage in the southern states. Palmer is a small seeded plant and the seed can actually germinate within the top two inches of soil. Spring tillage doesn’t appear to significantly reduce palmer germination compared to fall tillage. So the following is all from fall tillage research. Research has found that burying palmer seed at least 2” can reduce densities similar to control with pre- and post-herbicide applications. Research from at least three studies has shown burying palmer seed with a plow to 4” or using inversion tillage reduced palmer germination anywhere from 50-80%. Leaving the seed
buried for three years reduced palmer germination further. So, the suggestion is if you deep till, do it once and then get a small grain cover on the field to knock out the early spring light interception. At least two studies showed that fall inversion tillage followed by cover crop resulted in 85% reduction of palmer the next spring. I share this knowing we can’t afford plowing for soil loss, soil moisture loss, and tillage doesn’t fit some of your systems. It is a management option to consider if other options aren’t working for you. Summary: fall tillage once, get a cover on it, and then leave it alone.
Ultimately, the management keys are to ‘start clean and stay clean’ using burndowns, pre’s, several effective modes of action, keeping the ground covered to reduce light interception, and incorporating a small grain and/or cover crop into your system. Hopefully this helps as we think about managing palmer this coming growing season.
On-Farm Research Updates: One of my favorite winter programs is our Nebraska On-Farm Research Updates because of our growers presenting the research they conducted with us. These are upcoming next week starting Feb. 19 at former ARDC near Mead and Feb. 21 at College Park in Grand Island. Programs most days run from 9 a.m.-4:30 p.m. with registration beginning half an hour before each day’s program. Full details of dates, locations, and RSVP can be found at: https://cropwatch.unl.edu/2018/growers-statewide-share-farm-research-5-sites. Over 80 on-farm research projects will be presented this year including a wide range of topics: cover crops, variable rate seeding, planting populations, multi-hybrid planting, starter fertilizer, etc. Certified Crop Advisor Credits are applied for. Growers take an active role in the on-farm research project sponsored by Nebraska Extension in partnership with the Nebraska Corn Growers Association, the Nebraska Corn Board, the Nebraska Soybean Checkoff, and the Nebraska Dry Bean Commission. To learn more about the Nebraska On-Farm Research Network, visit http://cropwatch.unl.edu/farmresearch. Hope you consider attending!
Crop Insurance, Farm Bill Policy Update: Also reminding you about the final “Farmers and Ranchers College” program for our area this year to be held Feb. 23 in Geneva at the Fairgrounds. This workshop on Crop Insurance, Farm Bill Policy Update and More, will run from 10 a.m.-3 p.m. with registration beginning at 9:45 a.m. You can view the whole agenda and speakers at: https://vandewalleviews.wordpress.com/2018/02/02/crop-insurance-farm-bill-and-more/
Introductory Beekeeping Classes: Was asked to share about upcoming beekeeping classes. There are two course levels: one for beginning beekeeping and one for those who are currently keeping bees and want information on colony health and maintenance. Workshop details can be found at: https://entomology.unl.edu/bee-lab#tab2.
Mixer/Loaders and RUP Dicamba: Mixer/loaders are now required to have RUP dicamba training; however, they may not have a pesticide applicator license. On the RUP dicamba training registration sheets, just put “mixer/loader” instead of a pesticide applicator number. New pesticide applicators who haven’t received their number yet can just put “pending”.
Posted on February 11, 2018, in JenREES Columns and tagged palmer, palmer amaranth, palmer management, palmer pigweed. Bookmark the permalink. Leave a comment.
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