This is the second of three articles covering the NDSU Research Extension Crop and Soil Field Day on Wednesday, August 25, 2021, hosted by Abbey Wick, NDSU Extension Soil Health, and Sam Markell, NDSU Extension Broadleaf Crop Pathology. They were joined by professors, researchers, and scientists from NDSU and discussed various topics in a question-and-answer format.
Weed Management: Joe Ikley, NDSU Extension Weed Science, discussed weed management and herbicide carryover. The harvest campaign of small grains is mostly done, though there are some fields to go. There are still 30-60 days or more until a hard frost will kill off whatever is left in the field. Clean up kochia and water hemp now to minimize weed seed production for next year’s crop.
Herbicide carryover depends on the persistence of the herbicide and the selectivity of that herbicide on whatever crop you want to plant next year. Herbicide breakdown will occur over the next couple of weeks and then nothing will occur until spring.
Group 2 herbicides like Pursuit and Raptor can require a 3 to 4-year crop rotation interval until you’re allowed to plant something like sugar beets. Most of our crops have more tolerance and can be planted after 10-12 months. Clopyralid, which is an active ingredient found in Stinger and Widematch, is used a lot in sugar beets and small grains. When you rotate to sunflowers, peas, or beans, there are restrictions as to how much rain you need by a certain date. A lot of areas did not get enough rain to meet those restrictions so you are going to have to look at those herbicide labels this winter and figure out what crops you can actually rotate to. Clopyralid is also more persistent in coarse, textured soil and low organic matter soil, so if you have pockets like that in your field, those pockets may be at a higher risk. Most people are aware of the problematic herbicides that they have applied. It will be important to talk to your agronomist or extension agent this winter and try and figure out what you can rotate to.
If you’ve had no rain, tilling the ground will dilute the herbicide in that profile and decrease your chance of crop injury. Otherwise, tillage does not have much influence on carryover. It’s really more related to soil properties within the soil and the active ingredient. Most people in a corn-soybean rotation are set up well. It’s when you bring in pulse crops, sugar beets, or potatoes that you have to focus on rotation.
Atrazine has a higher risk of carryover. If you use the 3/8 of a pound rate. Ikley is not typically concerned about carryover, especially if your application is made before June 15. Any applications after June 15 gets into a higher risk of Atrazine carryover. If you use the ½ pound rate, then the risk is higher. Ikley typically does not recommend testing for herbicides in your soil because many times no one can tell you what the results mean. However, there is some data on Atrazine. If you have a no detect on Atrazine, you’re probably good to go.
When it comes to herbicide carryover, you have probably heard of bioassays. Soil is taken from a treated field and a non-treated field, seeded in a greenhouse or under grow lights, and checked for growth and injury. The easiest way to conduct your own soil bioassay of a field is to plant check strips about mid-September of the crop you want to plant next year in that field. Ideally, you would plant check strips in another field that did not get the same herbicide to compare it to. Then monitor the growth in both fields and look for injury. If you see injury, remember that there will not be much herbicide degradation until next year.
The best herbicides for burndown before planting a multispecies cover crop for grazing besides Roundup or 2,4-d would be paraquat (Gramoxone), one of the best non-spectrum, kill-what’s-out-there herbicides you can use without any residual activity. Another is glufosinate (Liberty), which is more expensive, and there are many crops that you cannot plant for 120 days. If you’re going broad spectrum, such as 10-20 species, Gramoxone would be your best bet.
If you are going to do soybeans on soybeans, it is important to inspect and test your field’s disease spectrum. Rye is a good cover crop for weed control and weed suppression here. Rye is one of the most tolerant crops when it comes to herbicide carryover. It does not replace a pre-emergent herbicide, but it is a nice complement.
Soil Management: Dave Franzen, NDSU Extension Soil, and Caley Gasch, NDSU Associate Professor Soil Health, discussed soil health and how to preserve what we have left of it. Soil health is the foundation of plant productivity. If the soil isn’t healthy and functioning, catching water, cycling nutrients, regulating pest communities and the beneficial microbial communities, then you don’t have a crop. It is important to feed the soil a diverse, healthy nutritious diet.
Fields that have a manure history seem to yield more and be more resilient. You cannot catch up using chemicals and fertilizers. Soil conservation and soil fertility are interrelated and make a big difference on the bottom line.
A lot of soil biological activity is microscopic and happening at an elemental or chemical level. You can’t see it happening so think of it as two bookends. One bookend is the things supporting the microscopic activity: the food source, habitat, residues, root inputs, plant inputs, and porous soil that allows air and water exchange. If those things are in place, then you have all the parts there to support the microbes, and the upper levels of the food chain, like beetles and earthworms, are going to be thriving as well. This is the other bookend, the organisms that rely on the smaller organisms through the food chain to support them.
Perhaps it helps to know what the soils used to be like to realize how much we’ve lost and the need to protect it. Franzen, a historian by nature, started digging into it about 10 years ago. In 1903, a Cass County survey described some fields as having organic matter of plus 7 percent, 2-3 feet black soil, and the layer underneath would still have organic matter of 4-4.5 percent. These were really deep soils that had not been disturbed for ten-fifteen thousand years. That is what farmers used to farm and why they could grow 40-bushel wheat with adequate moisture, but no fertilizer, crappy equipment, and questionable seed. Now there is 6-8 inches of topsoil. Producers are a generation away from farming subsoil completely.
When an inch of topsoil erodes away, the nitrogen that was in that soil, the E2O5, and the potassium are also lost. Producers don’t want to lose any more soils - they’re valuable, they need them on hilltops, they need them in low parts of the field, and they need the organic matter. Preserving the topsoil has 2 basic approaches: 1) Reducing the tillage, whether by reducing the intensity or the frequency, minimizing the actual footprint of disturbance, strip tilling, doing less tillage, or shallow tillage. There are lots of versions of doing less disturbances, which is good because it leaves residue on the surface and leaves the soil protected to resist water and wind erosion. 2) Maximizing plant productivity. Plants are going to help build, nurture, and protect the soil. Use crop rotations that can maximize that plant growth throughout the year or leave more residue on the surface, and then incorporate cover crops. Roots contribute a lot to organic matter, but you need the residue. If you take all the residue off all the time it will hurt your soil health. If you only do it once in a while, or you leave about half of it in the field, it may be ok.
Think of where you are at right now and what steps you are willing to take. It doesn’t have to be both feet jumping into the pool, but just make a move. Listen to others that are in various stages, or those that have been in it a long time, and try to adapt whatever those ideas are into what you think is possible on your farm, what your family and landlords will stand, and go from there. Commit to long-term soil health management plan and be patient. The no-till in ND originated with farmers, not the USDA or Extension. They have shown that it will work and build soil back. After 40 years of no-till in some parts of the state, the organic matter levels are 7-7.5 percent.
Next week will be the final article with an overview of cover crops, salt tolerant options, and disease trial updates.