Category Archives: Forages
Nitrates and Grazing Forages: the fact that we haven’t had a hard frost is throwing a wrench into grazing covers. For those with cattle on cover crops, please be aware of the potential for nitrate and/or prussic acid poisoning with the light frosts. Nitrogen moves from the roots up the plant. When a frost occurs, nitrates accumulate in the plant, and, we had lighter frosts for several days in a row. For sorghum species where prussic acid poisoning is also of concern, we say to wait at least 5 days before returning animals back to the field after frost. And, for every light frost, the 5 day window resets until a hard freeze occurs (at 26F or lower). It’s been hard to find any recommendations regarding nitrate accumulations in brassicas after frost…and what happens to the nitrates after a frost. We know weathering in general reduces nitrate levels in plants by spring. Just advising to watch cattle with these light frosts-especially those in seed corn fields that had milo in corners.
A study conducted by Mary Lenz, grad student for Dr. Mary Drewnoski, found brassicas accumulate more nitrate than small grains, millet, sorghum/sudan grasses, or cover crop mixes, and that 48% of the brassica samples submitted to Ward Labs were considered “highly toxic” for nitrate levels compared to 20-28% of other cover crop species. Yet what’s interesting is how often fields in the “highly toxic” level (or with no testing) are grazed with no impacts. Dr. Mary Drewnoski has shared that brassicas and immature grasses are also high in energy and that cattle consuming diets high in energy can handle more nitrates. So, this may be why we thankfully don’t see more issues grazing turnips and radishes high in nitrate. She shared other factors for consideration are that cattle are selective and will graze the upper-most parts of plants first which are lower in nitrates, grazing animals eat more gradually than those receiving hay, and the high moisture forages that are grazed release nitrates at a slower rate than with dry forages like hay. Ways to reduce nitrate concerns when grazing include: turning out cattle full before grazing the covers, using lower risk cattle such as open cows and stockers (as pregnant cows have risk of abortion when fed forages high in nitrate), graze lowest nitrate fields first for adaptation, graze highest nitrate concentration fields lighter so not as much forage is removed, or there’s also the option of not grazing fields that are very high in nitrates.
Corn Nitrogen Calculator: For those desirous to calculate N rates utilizing different sources and prices, the UNL nitrogen calculator has been updated. Before, it didn’t allow for the prices we currently are experiencing and there’s been some updates to the manure credits. The UNL nitrogen equation itself has remained the same, and honestly, I still say it’s conservative. For example, the nitrogen credit from soybeans is 45 lbs/ac in the equation. However, on-farm research conducted in the mid-2000’s in this part of the State found a credit of 1 lb for every bushel up to 60 bu/ac was achievable in irrigated soybean.
To utilize the N calculator, go to: https://cropwatch.unl.edu/soils, scroll down to “Corn Nitrogen Recommendations Calculator” and download the excel spreadsheet. You will want to open the “October 2021” version. They’re currently working on an online calculator for the future.
A few questions I received this week: “How much yield loss should I expect if I reduce N rates?” and “With higher corn prices, how much profit is one giving up with lower yields due to lower N application?”. These are valid questions and ones every operation will have to determine for oneself. That’s where on-farm research is really helpful too.
We have lots of data through the years of comparing a grower base rate +/- 30 lbs. of nitrogen mostly showing no yield differences. Most of this data is from the 1990’s for this part of the State, with data from the past 10 years from other parts of the State. In 2020 and 2021, a grower conducted nitrogen rate studies in York and Hamilton counties using his rate +/- 50 lb N. As I’ve shared the results with growers with the above-mentioned questions, they’ve been surprised at the yields and profits. I’ve summarized the grower’s results at jenreesources.com and also showed the profit based on today’s fertilizer prices. There’s a few ways to approach this data. It shows minimal benefit to yield and profit for increasing nitrogen application above the grower’s rate. Thus, there may be opportunity this year for those who have been over-fertilizing for high yield goals to try cutting back. It also shows that yield is reduced to some extent by reducing N rate 50 lb/ac below what the grower’s rate typically would be; however, with today’s prices, profit may be comparable. We also have several farmers who are already doing a great job with fertilizer rate for their realistic yield goals, so there may not be room to cut back. Appreciate all the farmers conducting on-farm research so we have data to share to help in answering questions!
*Please overlook my formatting issues below. There are no links even though some of the wording keeps appearing in blue instead of black.
2020 York County Spring Anhydrous Nitrogen Rate on Corn
This study essentially showed what the previous studies had: that less nitrogen can be applied without hurting yield or net return. 50 lb/ac N above the grower rate resulted in reduced profit. Field yields were impacted by the July 9, 2020 wind storm. This study is sponsored in part by the UBBNRD.
|Pre-Plant||In-season||lbs N/bu grain||Yield||Marginal Net Return|
|110 lb N/ac spring NH3 (March)||25 lb N/ac as UAN May||0.73 C||184 A||$599.14 A ($849.30)|
|160 lb N/ac spring NH3 (March)||25 lb N/ac as UAN May||0.98 B||189 A||$600.38 A ($837.80)|
|210 lb N/ac spring NH3 (March)||25 lb N/ac as UAN May||1.23 A||191 A||$594.88 A ($810.70)|
*Values with the same letter are not statistically different at a 90% confidence level. Marginal net return based on $3.51/bu corn, $8/ac for the anhydrous application cost, $0.28/lb N as anhydrous, and $0.35/lb N as UAN. (Updated marginal net return using $5.20/bu corn, $0.75/lb N as anhydrous and $1/lb N as UAN.)
2020 Hamilton County Evaluating Nitrogen Rate and Timing on Corn
This study showed no difference in nitrogen timing nor rate on yield and showed less nitrogen can be applied without impacting yield. Yields were impacted by the July 9, 2020 windstorm. This study is sponsored in part by the UBBNRD.
|Pre-Plant||In-season||lbs N/bu grain||Yield||Marginal Net Return|
|180 lb N/ac Fall NH3||25 lb N/ac as UAN May||1.03 B||199 A||$629.85 A ($866.80)|
|230 lb N/ac Fall NH3||25 lb N/ac as UAN May||1.27 A||201 A||$625.49 A ($839.70)|
|180 lb N/ac Spring NH3||25 lb N/ac as UAN May||1.02 B||201 A||$638.30 A ($877.20)|
|230 lb N/ac Spring NH3||25 lb N/ac as UAN May||1.24 A||206 A||$641.70 A ($865.70)|
|120 lb/ac N Spring NH3||25 lb N/ac as UAN May|
60 lb N/ac side-dress V8
|1.00 B||205 A||$645.69 A ($880.00)|
|170 lb/ac N Spring NH3||25 lb N/ac as UAN May|
60 lb N/ac side-dress V8
|1.24 A||206 A||$633.50 A ($847.70)|
Values with the same letter are not significantly different at a 90% confidence level. Marginal net return based on $3.51 bu corn, $0.28/lb N as anhydrous ammonia, $8.00/ac for anhydrous application, $0.35/lb for UAN applied with herbicide or as a sidedress, and $3/ac for sidedress UAN application. (Updated marginal net return using $5.20/bu corn, $0.75/lb N as anhydrous, $8/ac for anhydrous application, $1/lb for UAN applied with herbicide or as sidedress, and $3/ac for sidedress UAN application.)
20% wind damage from July 9, 2021 storm. Updated marginal net return using $5.20/bu corn, $0.75/lb N as anhydrous shows essentially no difference in profit for any yield differences observed:
100 lb-N/ac: $1053.40
150 lb-N/ac: $1052.30
200 lb-N/ac: $1051.20
2021 York County Spring Anhydrous N Rate Study
20% wind damage from July 9, 2021 storm. Updated marginal net return using $5.20/bu corn, $0.75/lb N as anhydrous:
130 lb-N/ac: $900.90
180 lb-N/ac: $969.10
230 lb-N/ac: $924.70
2021 York County Timing by N Rate Study
Spring 140 lb/ac: 110 lb/ac N as anhydrous and 30 lb/ac N with herbicide
Spring 190 lb/ac: 160 lb/ac N as anhydrous and 30 lb/ac N with herbicide
Split 140 lb/ac: 50 lb/ac N as anhydrous, 30 lb/ac N with herbicide, and 60 lb/ac N sidedressed at V8
Split 190 lb/ac: 100 lb/ac N as anhydrous, 30 lb/ac N with herbicide, and 60 lb/ac N sidedressed at V8
This study is sponsored in part by the UBBNRD. Updated marginal net return using $5.20/bu corn, $0.75/lb N as anhydrous, $1/lb N as UAN and $8/ac for the sidedress UAN application:
140 lb/ac spring: $1109.50
190 lb/ac spring: $1077.20
140 lb/ac split: $1096.90
190 lb/ac split: $1054.20
Heat and Pollination: With last week’s heat and anticipated heat later this week, we were receiving questions regarding the impacts of heat and humidity on pollination. You can view the entire article in this week’s CropWatch at https://cropwatch.unl.edu. Key points include: Heat over 95°F depresses pollen production and prolonged periods of heat can reduce pollen production and viability. When soil moisture is sufficient, one day of 95-98°F has little or no impact on yields. After four consecutive days, there can be a 1% loss in yield for each day above that temperature. Greater yield loss potential occurs after the fifth or sixth day. High humidity, without a drop in humidity during the day, can delay pollination or prevent pollen from leaving anther sacs. We’ve been blessed we only had days of extended high heat around pollination, received a break in the heat in addition to weekend moisture.
Insect Pests: From light trap reports, peak western bean cutworm (WBC) flight appears
to have occurred last week, so scout for egg masses and live larvae with a 5-8% treatment threshold. Thistle caterpillars grew rapidly last week. Others are with me in considering spraying closer to 15% (instead of 20% threshold) with stressed fields from flash drought and/or off-target dicamba injury that don’t have canopy cover yet. In CropWatch, check out the articles regarding scouting for grasshoppers in field borders and what to expect for insects depending on crop growth stages yet this year.
Cattle Losses from High Heat: If the recent heat/humidity conditions are determined to be an extreme weather disaster event, then livestock losses would be covered by the Livestock Indemnity Program (LIP). Livestock producers who lost livestock should document losses in the expectation that they may be covered by LIP and contact your local Farm Service Agency (FSA) to report those losses.
South Central Ag Lab Field Day Aug. 1: View current field trials on improving crop production and profitability at UNL’s South Central Ag Lab (SCAL) on August 1 near Harvard. Guests can customize their day to select the tours they’re most interested in. Presentation topics include: Cover crops, pollinators and weed management; European corn borer, corn rootworm, and cover crop insect control; Herbicide-resistant weed management; Assessing injury and management decisions in corn and soybeans; Corn and soybean disease updates; Sensor-based nitrogen management in irrigated corn; Corn stover harvest management and impacts; mobile beef lab and hail machine demonstrations. Registration is at 8:30 a.m. followed by tours through 4 p.m. Lunch and refreshments are included. CCA credits have been applied for. For more info. see the program brochure and register at: https://go.unl.edu/2019scalfieldday.
Silage Webinar Aug. 2: With this year’s challenging weather and the need for forage, there may be more opportunities for harvesting corn for silage. Aimed at feedlot, cow-calf, and dairy producers, a silage webinar on August 2 at Noon CST will focus on moisture at chopping, chop length, inoculants, proper packing, silage covers and more. Pre-registration for the webinar is necessary and can be done at: https://go.unl.edu/vau7.
Trees Losing Leaves: The wet spring and humidity allowed for fungal diseases on leaves of shade trees with flowering pears and crabapples in particular dropping leaves early. I’ve also had a number of questions regarding red maple leaves (Autumn Blaze and Sunset) suddenly turning brown on trees. These symptoms may also be experienced on ash, tuliptree, and other maples. We think it’s environmental stress from having so much cool and wet early to almost a ‘flash drought’ situation in eastern Nebraska prior to this weekend’s rains. Sarah Browning has been recommending watering and mulch as the best ways to reduce stress and to prevent additional root death and tree decline. I’ve been seeing new growth starting to occur on trees so my hope is if your tree is experiencing this, that 10-14 days from now you will also see new growth occurring on your trees.
Crop Updates: It was nice to see corn greening up and getting some growth this past week! Also on people’s minds is the 45 day post-planting application deadline for RUP dicamba herbicides. The announcement that Risk Management Agency (RMA) adjusted the 2019 final haying and grazing date from Nov. 1 to Sept. 1 for prevented planting this year opened up additional options for our farmers affected by flooding and/or excess rain. An additional option was that “silage, haylage, and bailage should be treated in the same manner as haying and grazing this year. Producers can hay, graze or cut cover crops for silage, haylage or baleage on prevented plant acres on or after September 1 and still maintain eligibility for their full 2019 prevented planting indemnity.”
So how did this change things? Many I talked with, including my family, were originally planning on going with cool season covers like oats planted the first week of August. However, with the ability to harvest a cover crop for forage on Sept. 1, interest increased in utilizing warm season cover crops. For those planning on haying, our forage specialists recommend using millets. The regrowth after haying could then be used for grazing in the late fall/winter. They also said if you’re planning on a mix, don’t add brassicas into whatever you decide to hay as they don’t dry down and tend to create a moldy spot within hay. If you’re looking at grazing only, sudangrass, sorghum sudan, millets, and/or mix with other species are great options. Forage sorghum is a great option for silage.
The other consideration is that some of this ground going into prevent plant already had PRE herbicides applied, making legal options for cover crops that could be grazed or hayed difficult. So Friday was kind of a crazy day for me walking people through options. Honestly, sometimes corn or milo for silage ended up being the most feasible option based on labels. There are also acres of corn and bean fields that were drowned out due to recent flooding and are now considered a “failed crop” by FSA. Herbicides that were applied can make planting covers in those fields difficult too. Some farmers had contracts with seed companies providing free seed for replant. Thus, once again, corn for silage seemed like a feasible and economical option. So, I called Jeff Peterson at Seward Co. FSA to see if this could be an option. He said that it would be a feasible option in 2019 if it was also approved by the person’s crop insurance agent. The first step is to contact your crop insurance agent to discuss your options for prevent plant and/or failed crop. Then go to your FSA office and fill out their form for failed crop and/or prevent plant. Your crop insurance company may require a letter from Extension stating that corn can be used as a forage crop for silage. Again, it will be important to talk with your crop insurance agent and your FSA office about your options for the fields in your counties as I can’t guarantee these are options for every situation.
Tree Problems: The rain and humidity have allowed for numerous fungal diseases on our evergreen and deciduous trees. On deciduous trees, leaves with black/brown spots may be found. We don’t typically recommend fungicides for them and if the diseases get bad enough, the leaves may eventually fall off the trees early. A new flush of leaves typically follows 10-14 days later. On evergreen trees, we’re seeing a number of needle blights and shoot tip blights. We do recommend fungicide applications for them (typically in April or May). However, it is recommended to repeat them every 3-4 weeks when frequent rains occur. Product options for most evergreen diseases include chlorothalonil or a product containing Copper that is labeled for evergreen tree diseases. Bordeaux mixture is often recommended, but I have a hard time finding anyone that carries that.
Also, be checking trees for bagworms. They’re later this year and just forming new bags. In order to see them, what I do is walk up to the trees (especially cedars or spruces) and just watch the branches for any movement occurring on them. If you’ve had a bagworm problem in the past, what you’ll see is tiny, new brown bags moving as the larvae is building a new bag. I have more info and a video to help visualize what to look for: https://jenreesources.com/2015/06/27/bagworms-in-evergreens/. The best time to spray them is when the bags are less than ½ inch in size. More info and products can be found here: https://go.unl.edu/rgju.
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.
With the recent sprouting of grain on the ears and with more producers now learning what percent loss their crop insurance is determining for each field, I felt it would be good to talk about feeding this damaged grain again. This post is written by Dr. Dee Griffin, DVM at UNL’s Great Plains Veterinary Education Center at Clay Center. I appreciate Dee’s willingness to provide this information from a Veterinarian’s perspective.
Also a note, to date we have not found Aspergillus in our hail damaged fields. The grain molds we are seeing are Diplodia and Fusarium. Diplodia does not have the potential to produce mycotoxins. Fusarium has the potential of producing fumonisin, vomitoxin, or DON. You can bring forage samples to Husker Harvest Days this coming week to the IANR building and have them tested that day for nitrates for free if you wish.
Dr. Griffin writes: Any time a growing grain producing plant is damaged there is a potential for changes in the plant or grain on the plant contaminated with fungus/molds to grow. The most common change in stressed plants is the accumulation of nitrates. Aspergillus or Fusarium will be the most likely fungi to be contaminating harvested grain from storm damaged corn in our area.
It is really important to know that most molds are not toxic. Therefore just because mold growth is observed doesn’t mean the feedstuff will harm livestock. Even though a mold may not be toxic it can still cause feed refusal. Not all livestock species are equally sensitive to mold contamination and not all production groups are equally sensitive. For instance pregnant and young animals are more sensitive than mature non-pregnant animals.
Nitrate accumulation in stressed plants can cause be harmless or cause serious harm depending on:
- the level of nitrate in the feed harvested from stressed plants,
- on the life stage of the animal,
- and on the species of animal.
Nitrates accumulate in the forage portion of the plant, so nitrates are not a concern in grain harvested from stressed plants. Additionally, it is important to know nitrate levels will always be highest in the bottom part of the plant and lowest in the top foliage. Nitrate testing is simple and reasonable quick. Your local UNL Extension Educator can help you locate the nearest facility that does forage nitrate testing.
Feed containing nitrate levels less than (<) 1000 parts per million (ppm) seldom are associated with an animal health concern. Feed containing nitrate levels greater than (>) 1000 ppm may be a concern in younger animals and levels >2000 ppm should not be fed to pregnant cattle. Feeder cattle are reasonably resistant to nitrates but feeds containing >4000 ppm should not be fed to any animals.
Molds in corn grain of concern could be either Aspergillus or Fusarium. Your UNL Extension Educator can be a great help in identifying mold growing on ears of your storm damaged corn before the grain is harvested. Both of these fungi are potentially dangerous when found in livestock feed. Toxins produced by molds are extremely stable, therefore if a significant level is found, the level will not decrease over time. Silage produced from damaged plants and grain harvested from mold infested plants is potentially a problem.
Good silage management is critical to lessen the likely hood of continued mold growth after ensiling. Proper packing to remove oxygen and improve fermentation which ensures the pH will be below 4.5 is critical.
You can’t look at harvested grains from storm damaged fields and visually identify mycotoxins. Corn grain from storm damaged fields can … and mostly likely should … be tested for mycotoxins before feeding to livestock. Your local UNL Extension Educator, nutritionist or veterinarian can help with mycotoxin testing.
Proper sampling is crucial to getting reliable results back from the laboratory. A “grab sample” is not adequate. The sample submitted to the lab should be representative of the entire load, bin, pit or pile of feedstuff being evaluated.
The steps are simple
- If sampling a field before harvest, sample at least two dozen ears that appear to have mold growth and submit all the ears to the laboratory for mycotoxin evaluation
- If sampling after harvest, take multiple samples uniformly from throughout the silage or grain in question
- The sample should be taken from what would be used in a single load of feed
- That means, if five loads of feed could be made from a 50,000 lb semi-load of corn, collect not less than five samples from the semi-load of corn
- The sample should be based on sample volume not weight
- For instance, collect “coffee can” size samples
- Mix all the all samples together that were collected from the feed in question
- For instance, if 10 coffee can size samples were collected from across the face of a silage pit, pour all 10 samples onto a plastic sheet and thoroughly mix them together
- Next, collect a single sample from within the 10 mixed samples
- Submit the single sample to the laboratory
The laboratory results usually will provide some recommendations for how the feedstuff can be used. There is an old saying, “Dilution is the solution …” meaning in this consideration, that many feedstuffs that contain higher levels of mycotoxin than would be acceptable, might be usable if a sufficient amount of non-mycotoxin contaminated feedstuff is used to dilute the mycotoxin. Your UNL Extension Educator, nutritionist or veterinarian can help evaluate the possible uses of a damaged feedstuff containing unacceptable levels of a mycotoxin.