Grateful for a nice week for harvesting and for the good yields being reported! It’s also good to see cattle being turned into cornstalks. A reminder to read herbicide labels to understand if there’s any grazing restrictions from corn and soybean herbicides applied in-season.
It’s also important to look for any grazing restrictions on fall-applied herbicides to control marestail and other germinating weeds. These restrictions can also be found in the Forage Feed Grazing Restrictions in the UNL Guide for Weed Management. The forage, feed, and grazing restriction only applies to the crop for which the herbicide was applied. When it comes to grazing cover crops planted into these residues, one must use the replant/rotation restriction guidelines found on the herbicide label and in the UNL Weed Guide: Replant Options Rotation Restrictions-long. I apologize as these scanned blurry; hopefully you can zoom in ok to read what you need.
If the label doesn’t specify any restrictions, then it should be ok. If you want to be on the safe side, a rule of thumb is to use the pre-harvest interval for the amount of time to wait before grazing stalks. Some labels will say that residue should not be grazed or baled and fed to livestock. Sometimes studies were actually conducted to know there is a safety concern. In other cases, the chemical company may not choose to conduct all the studies the Environmental Protection Agency (EPA) required for labeling due to high costs. If that’s the case, the EPA requires the strongest restrictive language be placed on the label. Regardless, if it says there’s a grazing restriction on the label, the label needs to be followed as it is a legal document and the law.
As you plan for next year’s herbicide program, if you’re thinking about fall cover crops, the following NebGuide may be of benefit to you as it goes through the grazing restrictions of various herbicides.
Many stalks in Nebraska are left ungrazed for various reasons. One reason I’ve heard is the potential impact of increased compaction and reduced yield of the next crop. Nebraska Extension has long-term research addressing this concern…in fact, 16 years of research conducted at the Ag Research and Development Center near Mead. There’s various components to this study and you can view the full report at: http://go.unl.edu/8mp6.
In this study, cattle were allowed to graze corn residue in the spring (February to mid-April) or the fall (November through January) and these treatments were compared to an area not grazed. Corn and soybeans were planted the spring after grazing the residue for 16 years to determine the effect of grazing on the subsequent crop yield.
In the fall grazing treatments, the corn and soybeans were planted no-till. For corn or soybeans planted into the spring grazing treatments, three tillage treatments were also implemented for nine years: no-till, ridge-till, and spring conventional till, after which all treatments were converted to no-till. This result of the tillage by spring grazing treatments for either corn or soybean yield over nine years showed no interaction and suggested the same effect on yield regardless of tillage treatment used after spring grazing.
Spring grazing across all tillage treatments did increase soybean yields statistically (58.5 bu/ac for spring grazed vs. 57.0 bu/ac for ungrazed) and had no effect on corn yields. The results were similar looking at 16 years of grazing vs. not grazing under no-till for both corn and soybeans in the spring; there was no yield effect found for corn and the soybeans showed a slight yield increase with grazing.
Looking at a 10 year period of no-till management for both spring and fall grazed corn residue and subsequent corn and soybean crops, fall grazing statistically improved soybean yields over both spring grazing and no grazing (65.5 bu/ac vs. 63.5 bu/ac and 62.1 bu/ac respectively). No grazing effects were observed on corn yields in either season. All statistics were at the 95% confidence level meaning the researchers were 95% confident any yield differences were due to the treatments themselves vs. random chance.
Regarding compaction, in the fall, the field was typically frozen and the researchers felt any mud and compaction associated with grazing cattle was minimized; highest subsequent soybean yields were achieved with fall grazing. The spring treatment was designed to look more at potential compaction and muddy conditions after spring thaw till right before planting-thus the implementation of different tillage treatments as well. They used a stocking rate consistent with UNL grazing recommendations resulting in removal of half the husks and leaves produced (8 lbs of leaf and husk per bushel of corn grain produced). Results of this study indicate that even with muddy conditions in the spring, grazing increased subsequent soybean yields compared to not grazing regardless of tillage system used and that corn yields were not different between grazing vs. not grazing and regardless of tillage system used in the spring. This study was conducted in Eastern Nebraska in a rainfed environment with yields ranging from 186-253 bu/ac with a 16 year median yield of 203 bu/ac.
Additional Grazing Study
A five year fall grazing study (December through January) was conducted in an irrigated continuous no-till corn field at Brule, NE to determine the effect of corn residue removal via baling corn residue or fall grazing on subsequent corn yields. That environment receives limited rainfall and residue is deemed important for reducing evaporation of soil moisture in addition for catching/keeping snow on fields. Farmers were questioning the effects of any residue removal on subsequent corn yields and the study was implemented.
Treatments were 1) fall grazing at 1 animal unit month/acre (AUM), 2) fall grazing 2 AUM/ac, 3) baled, or 4) ungrazed. The researchers found that residue removal did not affect corn grain yields from 2009-2013 in the continuous corn rotation. There were no statistical yield differences with 5 year average yields of: 152 bu/ac, 155 bu/ac, 147 bu/ac and 148 bu/ac respectively for the above-mentioned treatments.
With the increasing problem of controlling weeds such as marestail (horseweed), UNL has recommended using fall applied herbicides to help control this in addition to winter annual weeds. This practice usually does help with weed control, but I hadn’t thought about the considerations when grazing corn stalks until I received a recent question on it. The farmer wanted to see if it was safe for his cattle to graze corn stalks after a fall herbicide had been applied. The label wasn’t clear so he gave me a call.
I won’t provide information for the various herbicides that can be applied in the fall, but I will recommend that if you are planning on having your cattle graze stalks, that you check to see if a fall herbicide was applied and check the pesticide label to determine if there are any grazing restrictions with that pesticide.
If the label doesn’t specify any restrictions, then it should be ok. If you want to be on the safe side, a rule of thumb many chemical reps use is to use the pre-harvest interval for the amount of time to wait before grazing stalks. Some labels will say that residue should not be grazed or baled and fed to livestock. Sometimes studies were actually conducted to know there is a safety concern. In other cases, the chemical company may not choose to conduct all the studies the EPA required for labeling due to high costs. If that’s the case, the EPA requires the strongest restrictive language be placed on the label. Regardless, if it says there’s a grazing restriction on the label, the label needs to be followed. Your cattle may not be affected by grazing stalks where a chemical with a grazing restriction is on the label, but there may be other concerns such as problems with the chemical affecting the calf or being retained in the cow’s milk.
I’m still recommending utilizing our corn stalks by grazing and utilizing fall-applied herbicides for weed control. I just also recommend you check the pesticide labels on fields where a fall herbicide has been applied to determine any grazing restrictions or safety concerns.
Numerous calls have come in on the wheat ergot situation. It must have been the perfect environmental conditions for this to happen this year in such a wide area and I need to take some time to figure out why this year during conditions that also favored scab and not a few years ago with similar environmental conditions.
Two main questions have been raised: “Can I save back seed” and “can I bale and graze straw?”. I don’t recommend that you save back seed, yet many seed fields in the area most likely were affected as well. Seed can be sifted on a gravity table to help clean it so that is an option-but most farmers don’t have means for doing this so ultimately I wouldn’t recommend our farmers to save back seed.
In regards to baling straw and grazing, while walking harvested fields, I was noticing some ergot in heads that were too short to go through the combine heads. Ultimately, the few kernels in a large amount of straw would be so dilute, I wouldn’t expect there to be problems with grazing the straw. If you’re concerned about using wheat straw for feeding or bedding, you can always dilute it with alfalfa or another feed to reduce chances of ergotism in livestock even further. I should point out that I’m talking about wheat straw in which the wheat grain has been harvested. I would not recommend feeding wheat straw that was just cut with the ergot contaminated and wheat grain in tact. If you plan to feed straw in that situation, I’d recommend sending samples to a Vet Diagnostic Center for alkaloid testing.
A third question I’ll throw in here is should you plant 2nd year wheat if that is your rotation. While it is not assumed that ergot will happen every year and while the chances of ergot happening a second year are not great, it’s best management practices to go ahead and rotate to be on the safe side as any sclerotia (black fungal ergot fruiting bodies) would be lying on the soil surface and can produce spores that could affect the next wheat crop. Again, this isn’t guaranteed to be a problem again next year (unlike things such as tan spot or septoria that are likely to show up in wheat on wheat fields), but to be on the safe side, I would recommend rotating. Dr. Stephen Wegulo also wrote an article on ergot in wheat at the following site.