C.O.R.N. Newsletter : 2019 - 33

  1. October 2019 - Weather Prediction

    16 - Day Moisture Forecast
    Author(s): Jim Noel

    After another hot week (until late this week), a cool down to normal temperatures is expected starting either Oct. 3 or 4 that will last through Oct. 15. Temperatures are expected to return to above normal (but no where near current levels) from Oct. 15-31.

    Rainfall will be above normal in northern Ohio this week. The week of Oct. 7 will be normal or below normal but confidence is next week's rainfall pattern is low to moderate. Above normal rainfall is in the outlook for the second half of October which could slow harvest after Oct. 15.

    The hot and drier pattern for a good part of September was caused in part by tropical activity. The remnants of Dorian created a big low pressure system not far from Greenland while a typhoon called Lingling in the western Pacific created a big low pressure near Alaska. This resulted in a hot and dry dome of high pressure over the Southeast U.S. and wet weather in the western corn and soybean belt.

    This pattern appears ready to breakdown later this week.

    We are moving into frost and freeze season and overall it still looks like a delayed frost and freeze season. Most see their first freeze by Oct. 10-20.  Currently, it still looks like a normal to later than normal first freeze.

    The November outlook still indicates a warmer than normal month with precipitation not far from normal (but with a lot of uncertainty). We will keep you posted on this.

    Finally, the two week rainfall outlook from OHRFC can be found here:

    https://www.weather.gov/images/ohrfc/dynamic/NAEFS16.apcp.mean.total.png .

    It shows the wettest areas being the western two-thirds of the corn and soybean belt. Rainfall for the next two weeks in Ohio will be 1-2+ inches in northern Ohio but generally 0.10-0.50 inches in southern Ohio. Normal is about 1.5 inches for two weeks.

  2. Fire Safety During Harvest Season

    Combine harvesting soybeans
    Author(s): Dee Jepsen

    Meteorologists would likely correct us if we referred to this year’s summer climate as bipolar. However, the early fall rain patterns seem to be completely different depending on where one stands in the state. It is either rain, and lots of it – or dry, on the verge of drought. So when readers see an article about fire safety for harvest season, it is intended for those encountering dry and windy conditions, whenever these conditions appear.

    October and November are two months where fire is a particular concern. In agricultural areas, fires can break out during unseasonably warm temperatures. Fire risks are particularly a concern around fields with dry crop residues, near woodland areas, or within equipment with heated bearings, belts, and chains. There are several aspects to consider for fire prevention and fire protection during harvest season.

    Preventing Combine Fires

    Combines are at high risk of fire. Work crews should take extra precautions to prevent fires from starting.  

    • Park a hot combine away from out-buildings. Keeping a combine out of barns, shed, and away from other flammables is a common prevention strategy in case a hot spot ignites. Insurance claims can double when equipment fires are responsible for loss of farm structures.
    • Regular maintenance is priority. Check the machine daily for any overheated bearings or damage in the exhaust system. Keep the fittings greased. Maintain proper coolant and oil levels. Repair fuel or oil hoses, including fittings and metal lines, if they appear to leak.
    • Keep dried plant material from accumulating on the equipment. Frequently blow dry chaff, leaves and other crop materials that have accumulated on the equipment with a portable leaf blower or air compressor. Be sure to inspect the engine compartment and other areas where chaff accumulates around bearings, belts and other moving parts.
    • Maintain the electrical system. Pay attention to machine components that draw a heavy electrical load, such as starter motors and heating/cooling systems. Monitor circuits for any overloading, especially if fuses blow regularly. Keep wiring in good condition and replace frayed wiring or worn out connectors. 
    • Refuel a cool engine whenever possible. Never refuel a combine with the engine running. It is recommended to turn off the engine and wait 15 minutes; this helps to reduce the risk of a spill volatilizing and igniting.
    • Prevent static electricity while operating in a dry field. Use a ground chain attached to the combine frame to prevent static charges from igniting dry chaff and harvest residue, letting the chain drag on the ground while in the field.
    • Have 2 fully charged fire extinguishers on the combine.  ABC fire extinguishers are recommended on farm machinery. In a combine, keep a 10-pound unit in the cab and a 20-pound unit mounted at ground level.
    • Have 1 fully charged fire extinguisher in the tractor, grain cart, and pickup truck. ABC fire extinguishers are recommended on farm machinery. These extinguishers are good for fires at incipient phases – meaning at the first sign of smoke or a small flame.

    When a fire appears, it is important to put worker protection before saving equipment.   

    • Have an emergency plan in place and be sure all employees know the plan. Combine fires happen fast – be sure all employees know what to do if smoke or fire appears.
    • Turn off the engine. If in the combine cab, turn off the engine and exit the machine.
    • Call 911 before using the fire extinguishers. If the fire is in the cab, only use the 10-pound fire extinguisher from the outside of the cab – on the exterior platform. If the fire is on the ground, use caution when opening the engine compartment or other hatches as small fires can flare with extra air. Stay a safe distance away from the fire.   
    • Use a shovel on small field debris fires. Throwing dirt over burning field residue can stop a fire from spreading. However, stay back if the fire takes off.
  3. Late-season Frost Effects on Corn: Grain Production (Adapted from Dr. J. Lauer, Univ. of Wisconsin)

    Author(s): Peter Thomison

    The following is information on the effects of late-season frost injury to corn from an article by Dr. Joe Lauer, Corn Extension Specialist at the University of Wisconsin (http://corn.agronomy.wisc.edu/Management/L041.aspx).  

    Freezing temperatures before physiological maturity will damage corn. Maturity in corn occurs when kernels form a black layer at the kernel tip, grain will be at approximately 30 to 35 percent moisture. After maturity, no additional dry matter will be accumulated in the seed. In addition to creating quality problems, premature frost will reduce the yield of dry grain.

    Temperatures required to kill corn plants

    Corn is killed when temperatures are near 32 F for a few hours, and when temperatures are near 28 F for a few minutes (Carter and Hesterman, 1990). A damaging frost can occur when temperatures are slightly above 32 F and conditions are optimum for rapid heat loss from the leaves to the atmosphere, i.e. clear skies, low humidity, no wind. At temperatures between 32 to 40 F, damage may be quite variable and strongly influenced by small variations in slope or terrain that affect air drainage and thermal radiation, creating small frost pockets. Field edges, low lying areas, and the top leaves on the plant are at greatest risk. Greener corn has more frost resistance than yellowing corn.

    Symptoms of frost damage will start to show up about 1 to 2 days after a frost. Frost symptoms are water soaked leaves that eventually turn brown. Because it is difficult to distinguish living from dead tissue immediately after a frost event, the assessment should be delayed 5 to 7 days.

    Grain quality impact

    Late season frost damage can affect grain quality and is directly proportional to the stage of maturity and leaf tissue killed. Severe impacts on grain quality can occur at mid-dough, while moderate impacts are seen at the dent stage. By the time, the kernel has reached half milk line only minor impacts will occur to grain quality. Differences among hybrids, overall plant vigor at the time of frost and subsequent temperatures will all affect final grain quality.

    Other considerations

    Growers should monitor stalk rot of severely defoliated plants, which have a good-sized ear. Photosynthate will be mobilized towards the ear rather than the stalk. This could weaken the stalk and encourage stalk rot development. These fields may need to be harvested early to avoid standability problems.

    Table 4. Potential grain yield losses after frost.

    Corn development

     Killing frost
    (Leaves and stalk)

    Light frost
    (Leaves only)


     percent yield loss

    R4 (Soft dough)



    R5 (Dent)



    R5.5 (50% kernel milk)



    R6 (Black layer)



    derived from Afuakwa and Crookston (1984)

    Yield impact on frost-damaged corn grain

    Yield losses are negligible if frost occurs when grain moisture is below 35 percent. Yield loss is directly proportional to the stage of maturity and the amount of leaf tissue killed. Those who will be advising growers about the likelihood of frost damage and its impact on yield should get ready by consulting the National Corn Handbook NCH-1 "Assessing Hail Damage to Corn" (Vorst, 1990). This publication has charts used by the National Crop Insurance Association for assessing yield loss due to defoliation. Knowing how to recognize frost damage and assess probable loss is important for decision making. An abbreviated version of the loss chart is shown in Table 7. For example, corn that was defoliated 20% at the milk stage would have 3% yield loss.

    Table 7. Estimated percent corn yield loss due to defoliation occurring at various stages of growth.

      Stage of growth

    Percent leaf area destroyed








     Yield loss (%)





































    Black layer






    derived from Vorst (1990)

    The stem on a corn plant is a temporary storage organ for material that eventually moves into the kernels (Afuakwa and Crookston, 1984). Grain yield will continue to increase about 7 to 20% after a light frost that only kills the leaves as long as the stem is not killed (Table 4).

    Frost damaged grain drying rates

    Freezing air temperatures sometimes occur in early autumn before grain is physiologically mature (“black layer). Grain drying rates can range from 0.83 to 1.16% moisture less/day (Hicks et al., 1976). Drying rates of grain following leaf blade defoliation or moderate to severe cold treatments are not different from the drying rate of normally maturing maize grain. Husk condition does not affect grain drying rates. Defoliation and freezing before physiological maturity (R6) causes grain moisture levels to be 2 to 6 percentage points greater than that of grain from control plants when grain from control plants was in the 22 to 30% harvest range. Grain frozen before R6 required 4 to 9 additional days of field drying to reach the 22 to 30% moisture range. Defoliation and cold treatments have little effect on the drying rates of cobs and ears, but moisture levels are greater than those of the control. Loose husks cause faster cob and ear drying compared to normal husks.

    Characteristics of frost-damaged corn grain (http://www.extension.iastate.edu/publications/PM1635.pdf).

    • Small, misshapen, soft kernels
    • Undeveloped starch structure; pithy kernels
    • Test weights progressively below 52 lb./bu., depending on maturity (in 1993, some corn was less than 40 lb./bu.)
    • Average protein (7.5 to 8.0 percent) in corn heavier than 45 lb./bu., lower protein in corn lighter than 45 lb./bu.
    • High breakage susceptibility; many fines generated in handling
    • Lower digestibility compared with normal corn, especially for test weights below 45 lb./bu.
    • Little or no increase in test weight after drying
    • Variable amino acid levels
    • Moisture meters generally read low in immature corn. Surface drying of kernels, giving deceptively low (by 1 to 2 percent) moisture readings on dried corn

    Recognize that these effects are progressive, with least impact on corn closer to maturity.

    Uses for frost-damaged corn

    Animal feed is the best use for frost-damaged corn. Low test weight corn used for large animal feed is only slightly less valuable (2 to 5 percent) than normal corn on a per-pound basis. Poultry, however, with limited volumetric capacity, may be more sensitive to frost-damaged corn than larger livestock.

    Before feeding, test light corn for protein level, amino acid level, and mycotoxins (especially fumonisin and vomitoxin). Composition will vary. Be aware that fungi invade stressed corn more readily than they do normal corn.

    Wet, dry milling, and dry grind ethanol operations will not want frost-damaged corn. Using frost-damaged corn in wet milling causes low starch yields, and the separation of starch and protein cannot be clean. In dry milling, frost damaged corn sharply reduces yields of dry mill grits. Processors will discount light corn more heavily than its reduction in feed value. Fermentation will be more variable in ethanol production, with lower yields and less predictable distillers grain quality.

    Handling and storage of frost damaged grain

    Immature and frost-damaged corn will have marginal quality, so it's important to manage equipment carefully to minimize further quality degradation. Set combines carefully, to balance the need to get small kernels with kernel damage. Manage the fines and chaff, which can increase mold problems in storage. Dry grain to uniform moisture levels, a tricky business because harvest moisture is likely to be somewhat uneven after a cold, short growing season. Dry frost-damaged corn at reduced air temperatures (below 160 °F) and store at 14 percent (or lower) moisture. Dry corn as gently as possible, even if it is tempting to crank it up for higher dryer capacity. Also, use slow cooling methods after gas-fired drying to minimize quality problems. If possible, aerate stored grain to cool it to 20 to 30F for winter storage (in the upper Midwest).

    Frost-damaged corn breaks easily and goes out of condition quickly, even at low moisture levels. Expect storage life to be about half as long as that of normal corn. Do not harvest through low-lying frost damaged areas. The mixture will be a high storage risk. Harvest and handle them separately.

    Because immature corn kernels dry on the surface, expect the moisture level of stored corn to be higher than test results. Expect to aerate the stored corn frequently. Move immature corn to market before summer. Store only clean corn and pull out the fines-laden center core of grain in bins.


    Afuakwa, J. J. and R. K. Crookston. 1984.  Using the kernel milk line to visually monitor grain maturity in maize. Crop Sci. 24:687-691.

    Carter, P.R., and O.B. Hesterman. 1990. Handling corn damaged by autumn frost. Available at: https://www.extension.purdue.edu/extmedia/NCH/NCH-57.html

    Hicks, D.R., G.L. Geadelmann, and R.H. Peterson. 1976. Drying Rates of Frosted Maturing Maize. Agron. J. 68:452-455.

    Hurburgh, C.R., R. Elmore and P. Pedersen. 2007. Frost Damage to Corn and Soybean. PM 1635. Available at: http://www.extension.iastate.edu/publications/PM1635.pdf.

    Lauer, J.G. 2014.Frost. University of Wisconsin Extension. Available at: http://corn.agronomy.wisc.edu/Management/L041.aspx


    Further Reading on handling frost damaged corn:

    Early Fall Frost (Extension Specialists, Univ. of Minnesota)


    Corn Drying and Storage Tips for 2011 (K. Hellevang, North Dakota State University)


    Post-Harvest Tips for Late Maturing Corn (K. Hellevang, North Dakota State University)


  4. Fall Herbicide Treatments – Even More Important This Year?

    Winter annuals
    Author(s): Mark Loux

    If you have never applied herbicide in fall to burn down winter annuals, or done it only infrequently, this might be the year to make an investment in fall herbicides.  Fall treatments are an integral component of marestail management programs.  They also prevent problems with dense mats of winter annuals in the spring, which can prevent soil from drying out and warming up, interfere with tillage and planting, and harbor insects and soybean cyst nematode.  2019 was a generally tough year for weed control, leading to higher end of season weed populations in some fields.  A number of acres were never planted, and growers got to experience the difficulty in obtaining season-long control in the absence of a crop.  Reminds us all how important the crop canopy and shading of the soil is during the second half of the season.  Bottom line - there was substantial production of weed seed in some fields, and a replenishment of the soil seedbank by both winter annual and summer annual weeds.  The seed of winter annuals and marestail lacks dormancy so above-average weed seed production can lead to an immediate increase in fall-emerging weeds.  Applying herbicides this fall can compensate for increased weed populations and make life easier in the spring. 

    We have published information on fall herbicides fairly frequently, and our suggestions for fall treatments have not really changed much.  There is plenty of information on fall herbicide treatments in the C.O.R.N. newsletter archive and on other university websites.  Our philosophy on this has not changed much over the past decade.  A few brief reminders follow:

    1.  When to spray?  Anytime between now and Thanksgiving will work, and possibly later.  We have applied into late December and still eventually controlled the weeds present at time of application.  Once hard freezes start to occur, there is usually a substantial change in the condition of certain weeds, such as dandelion and thistle, that renders them less sensitive to herbicides.  We discourage applications during periods of very cold weather which can occur starting about Thanksgiving, and also (obviously) when the ground is snow-covered.  The generally dry conditions we are experiencing have limited weed emergence so far this fall.  We anticipate that rain occurring now that leads to some sustained soil moisture near the surface will likely result in germination and emergence of the weeds that have been missing until now.  Our recommendation is to wait for rain and the additional weed emergence before applying any herbicide this fall.  The risk in this is that the weather turns wet, making it difficult to apply herbicide.  So it’s also possible to apply now and include a residual component to help with later fall emergence (which is the exception to the “no residual” recommendation in #4 below), such as simazine, a low rate of metribuzin or Canopy, or a Sharpen rate higher than 1 oz.

    2.  What about all of the crop residue on the ground after harvest - won’t that cause problems?  We have not worried about this, and the herbicides seem to work regardless.  Most agronomists I have asked have the same impression.  On the other hand, it probably wouldn’t hurt to wait a while after harvest to let the residue settle down, and the weeds to poke through.  Dense crop residue usually prevents marestail from emerging anyway.

    3.  Don’t make it too complicated or pricey.  Keep in mind that the primary goal is control of weeds that have already emerged.  This is hard to accomplish with a single herbicide, but there are a number of relatively low-cost two-way mixtures that easily achieve this goal.  Our philosophy has generally been to start with 2,4-D, and then add another herbicide that results in more comprehensive control.  Herbicides that make the most sense to add to 2,4-D based on our research:  glyphosate, dicamba, metribuzin, simazine, Basis (and generic equivalents), Express (and generic equivalents), or Canopy/Cloak DF or EX.  These allow either corn or soybeans to be planted the following year with these exceptions:  simazine - corn next year; Canopy/Cloak - soybeans next year; Basis - possibly restricted to corn based on rate and geography.  We do not see the need for three-way mixtures, although a case can be made to add a low rate of glyphosate to a two-way mix to control grass or improve activity on perennials.  A two-way mixture of glyphosate and Sharpen could also be used, but we believe Sharpen has more utility in marestail control programs when used in the spring.

    4.  Is there an advantage to including residual herbicides?  No, because almost all of them dissipate over the winter and fail to provide any control of spring-emerging weeds.  The primary exception to this is chlorimuron (Canopy/Cloak), which for whatever reason does persist at high enough concentrations to provide some control in spring.  Our research has repeatedly shown that applying other residual herbicides in the fall to get control in spring is a waste of money.  The good news here is that any effective fall herbicide treatment with or without residual will result in a weed-free seedbed in spring, usually into April, so that the spring-applied burndown/residual treatment just has to control small weeds that emerge in the few weeks prior to planting.  That is the goal.

  5. Be Aware of Late-Season Potential Forage Toxicities

    Alfalfa plant
    Author(s): Mark Sulc

    Livestock owners feeding forage need to keep in mind potential for some forage toxicity issues late this season. Nitrate and prussic acid poisoning potential associated with drought stress or frost are the main concerns to be aware of, and these are primarily an issue with annual forages and several weed species, but nitrates can be an issue even in perennial forages when they are drought stressed. A few legumes species have an increased risk of causing bloat when grazed after a frost. Each of these risks is discussed in this article along with precautions to avoid them.

    Nitrate Toxicity

    Drought stressed forages can accumulate toxic levels of nitrates. This can occur in many different forage species, including both annuals and perennials. In particular to Ohio this year, corn, oat and other small grains, sudangrass, and sorghum sudangrass, and many weed species including johnson grass can accumulate toxic levels of nitrates. Even alfalfa can accumulate toxic levels under severe drought stress. An accompanying article in this issue of C.O.R.N. discusses nitrate toxicity potential in corn. Here the other forages will be discussed.

    Before feeding or grazing severely drought stressed forage, the forage should be analyzed for nitrates. Many commercial labs provide this service, and the cost is well worth it against the risk of losing animals.

    See the following references for more details:



    Prussic Acid Toxicity

    Several forage and weed species contain compounds called cyanogenic glucosides that are converted quickly to prussic acid (i.e. hydrogen cyanide) in freeze-damaged plant tissues, or under drought conditions. Several labs provide prussic acid testing of forages. Sampling and shipping guidelines should be carefully followed because prussic acid is a gas and can dissipate during shipping leading to a false sense of security when no prussic acid is found in the sample.


    Drought stress can affect poisoning risk. Drought-stunted plants can contain or produce prussic acid and can possess toxic levels at maturity. Prussic acid poisoning can be associated with new regrowth following a drought-ending rain, which is likely the case in some parts of Ohio now. Rain after drought plus young stages of plant maturity (see below) could combine to cause toxic levels of prussic acid in forage this year.

    Plant age affects toxicity. Young, rapidly growing plants of species that contain cyanogenic glucosides will have the highest levels of prussic acid. Pure stands of indiangrass can have lethal levels of cyanide if they are grazed when the plants are less than 8 inches tall.

    Species with prussic acid poisoning potential. Forage species that can contain prussic acid are listed below in decreasing order of risk of toxicity:

    • Grain sorghum = high to very high toxic potential
    • Indiangrass = high toxic potential
    • Sorghum-sudangrass hybrids and forage sorghums = intermediate to high potential
    • Sudangrass hybrids = intermediate potential
    • Sudangrass varieties = low to intermediate in cyanide poisoning potential
    • Piper sudangrass = low prussic acid poisoning potential
    • Pearl millet and foxtail millet = rarely cause toxicity

    Species not usually planted for agronomic use can also develop toxic levels of prussic acid, including the following:

    • Johnsongrass
    • Shattercane
    • Chokecherry
    • Black cherry
    • Elderberry

    It is always a good idea to check areas where wild cherry trees grow after a storm and pick up and discard any fallen limbs to prevent animals from grazing on the leaves and twigs.

    Frost affects toxicity. Cyanogenic glucosides are converted quickly to prussic acid (i.e. hydrogen cyanide) in freeze-damaged plant tissues. Prussic acid poisoning potential is most commonly associated the first autumn frost. New growth from frosted plants is palatable but can be dangerously high in prussic acid.

    Fertility can affect poisoning risk. Plants growing under high nitrogen levels or in soils deficient in phosphorus or potassium will be more likely to have high prussic acid poisoning potential.

    Fresh forage is more risky. After frost damage, cyanide levels will likely be higher in fresh forage as compared with silage or hay. This is because cyanide is a gas and dissipates as the forage is wilted and dried for making silage or dry hay.

    Toxicity Symptoms

    Animals can die within minutes if they consume forage with high concentrations of prussic acid. Prussic acid interferes with oxygen transfer in the blood stream of the animal, causing it to die of asphyxiation. Before death, symptoms include excess salivation, difficult breathing, staggering, convulsions, and collapse.

    Ruminants are more susceptible to prussic acid poisoning than horses or swine because cud chewing and rumen bacteria help release the cyanide from plant tissue.

    According to a Texas Cooperative Extension Factsheet, “Animals consuming forages with nigh nitrate levels cannot complete the conversion of nitrate to protein, and toxic nitrite levels accumulate. Nitrite is adsorbed directly into the bloodstream through the rumen wall, where it combines with hemoglobin to form methhemoglobin. Hemoglobin carries oxygen in the blood, but methhemoglobin does not. The formation of methhemoglobin can cause an animal to die from asphyxiation, or lack of oxygen. The animal’s blood turns brown instead of the normal bright red. Monogastrics (i.e., hors-es, mules, swine, etc.) are less sensitive to nitrate toxicitythan ruminants. An animal’s conditioning affects its ability to assimilate or tolerate nitrates, so consult your veterinarian before feeding forage that contains nitrates.”
    (see http://forages.tamu.edu/PDF/Nitrate.pdf).

    Grazing Precautions

    The following guidelines will help you avoid danger to your livestock this fall when feeding species with nitrates or prussic acid poisoning potential:

    • Under drought conditions, allow animals to graze only the upper one-third to one-half of the plant or the leaves of coarse-stemmed forages if the nitrate levels in these plant parts is safe. Monitor animals closely and remove them quickly when the upper portion of plants is grazed off.
    • Generally, forage nitrate levels drop significantly 3 to 5 days after sufficient rainfall, but it is always safer to send in a sample for testing before grazing or feeding forage soon after drought stress periods.
    • Making hay does not reduce nitrate levels in the forage, but the hay can be tested and diluted sufficiently with other feeds to make it safe for animals.
    • Ensiling forage converts nitrates to volatile nitrous oxides, or “silo gases”. These gases are highly toxic to humans. Safety practices include removing tarps from a portion of the silo a day or two before removing the silage from the bunker.
    • Do not graze on nights when frost is likely. High levels of toxic prussic acid are produced within hours after a frost, even if it was a light frost.
    • Do not graze after a killing frost until plants are dry, which usually takes 5 to 7 days.
    • After a non-killing frost, do not allow animals to graze for two weeks because the plants usually contain high concentrations of prussic acid.  
    • New growth may appear at the base of the plant after a non-killing frost. If this occurs, wait for a killing freeze, then wait another 10 to 14 days before grazing the new growth.
    • Don’t allow hungry or stressed animals to graze young growth of species with prussic acid potential. To reduce the risk, feed ground cereal grains to animals before turning them out to graze.
    • Use heavy stocking rates (4-6 head of cattle/acre) and rotational grazing to reduce the risk of animals selectively grazing leaves that can contain high levels of prussic acid.
    • Never graze immature growth or short regrowth following a harvest or grazing (at any time of the year). Graze or greenchop sudangrass only after it is 15 to 18 inches tall. Sorghum-sudangrass should be 24 to 30 inches tall before grazing.
    • Do not graze wilted plants or plants with young tillers.


    Green-chopping will not reduce the level of nitrates and is not likely to greatly reduce the level of prussic acid present. However, green-chopping frost-damaged plants will lower the risk compared with grazing directly, because animals are less likely to selectively graze damaged tissue. Stems in the forage dilute the high prussic acid content that can occur in leaves. However, the forage can still be toxic, so feed greenchop with great caution after a frost. If feeding greenchopped forage of species containing cyanogenic glucosides, feed it within a few hours of greenchopping, and don’t leave greenchopped forage in wagons or feedbunks overnight.

    Hay and silage are safer from prussic acid toxicity

    Prussic acid content in the plant decreases dramatically during the hay drying process and the forage should be safe once baled as dry hay. The forage can be mowed anytime after a frost if you are making hay. It is rare for dry hay to contain toxic levels of prussic acid. However, if the hay was not properly cured and dried before baling, it should be tested for prussic acid content before feeding to livestock.

    Forage with prussic acid potential that is stored as silage is generally safe to feed. To be extra cautious, wait 5 to 7 days after a frost before chopping for silage. If the plants appear to be drying down quickly after a killing frost, it is safe to ensile sooner.

    Delay feeding silage for 8 weeks after ensiling. If the forage likely contained high levels of cyanide at the time of chopping, hazardous levels of cyanide might remain and the silage should be analyzed before feeding.

    Nitrate accumulation in frost forages

    Freezing damage also slows down metabolism in all plants that might result in nitrate accumulation in plants that are still growing, especially grasses like oats and other small grains, millet, and sudangrass.  This build-up usually isn't hazardous to grazing animals, but green chop or hay cut right after a freeze can be more dangerous. When in doubt, send a forage sample to a forage testing lab for nitrate testing before grazing or feeding it.

    Species That Can Cause Bloat After Frost

    Forage legumes such as alfalfa and clovers have an increased risk of bloat when grazed one or two days after a hard frost. The bloat risk is highest when grazing pure legume stands and least when grazing stands having mostly grass.

    The safest management is to wait a few days after a killing frost before grazing pure legume stands – wait until the forage begins to dry from the frost damage. It is also a good idea to make sure animals have some dry hay before being introduced to lush fall pastures that contain significant amounts of legumes. You can also swath your legume-rich pasture ahead of grazing and let animals graze dry hay in the swath.  Bloat protectants like poloxalene can be fed as blocks or mixed with grain. While this an expensive supplement, it does work well when animals eat a uniform amount each day.

    Frost and Equine Toxicity Problems (source: Bruce Anderson, University of Nebraska)

    Minnesota specialists report that fall pasture, especially frost damaged pasture, can have high concentrations of nonstructural carbohydrates, like sugars.  This can lead to various health problems for horses, such as founder and colic.  They recommend pulling horses off of pasture for about one week following the first killing frost.

    High concentrations of nonstructural carbohydrates are most likely in leafy regrowth of cool-season grasses such as brome, timothy, and bluegrass but native warm-season grasses also may occasionally have similar risks.

    Another unexpected risk can come from dead maple leaves that fall or are blown into horse pastures.  Red blood cells can be damaged in horses that eat 1.5 to 3 pounds of dried maple leaves per one thousand pounds of bodyweight.  This problem apparently does not occur with fresh green leaves or with any other animal type.  Fortunately, the toxicity does not appear to remain in the leaves the following spring.

  6. Dry Matter When Making Summer Annual Silage and How to Measuring Its Dry Matter (or Moisture)

    Author(s): Bill Weiss

    To make good silage from summer annuals such as sorghum, sudangrass, and pearl millet, the dry matter concentration should be between about 30% to 40% (moisture contents of 60 to 70%). Silage made wetter can seep which causes a loss of nutrients and potential environmental damage if the seepage gets into surface water (fish kill). Silage made drier will not pack adequately and may heat during storage. In some situations, heat generation can be great enough to start a fire within the silage mass. The drier the silage, the greater the risk for a silo fire. In addition to DM, chopping length of particle size of the chopped forage affects heating risk. Coarsely chopped silage does not pack as well as finely chopped silage, but silage chopped too finely can cause rumen upsets when fed to cattle. Choppers differ but setting the theoretical length of cut (TLC) at about 3/8 to ½ of inch will usually produce the correct particle size. Chop length needs to be reduced as the DM at chopping increases.

    Measuring Dry Matter

    1. Obtain a good sample. The dry matter of leaves will be much greater than that of the stems and the lower portion of the stem will be wetter than the top. The sample must include the total plant that will be chopped. Go into the field (not outside rows) and hand cut 5 to 10 plants at the same height that the crop will be mowed. Chop all the plants using a wood chipper, forage chopper, or by hand.

    2. Mixed the chopped sample well.

    3. Measure dry matter using one of the methods below.

    Koster Tester (Koster Inc., Brunswick OH)

    Follow manufacturer directions, but basically you need to accurately weigh out about  200 grams (0.5 lbs.) into the drying container. Record the weight. Dry for about 20 minutes and re-weigh and record the weight. Dry another 5 minutes and weigh again. If weight is the same as the 20 minute weight, the sample is dry. If not, repeat drying in 2 or 3 minute intervals until weight is constant.  Calculate DM% as (Starting weight – Ending weight)/Starting weight x100. Moisture = 100 - DM%.


    Accurately weigh about 100 grams (0.2 lbs) of chopped forage on a paper plate. Record the weight. Spread it out thinly. Fill a microwave safe mug about half full with water. Put plate and mug into a microwave. Heat on full power for 2 minutes, remove plate, weigh, record the weight and stir the forage. Heat for another 30 seconds, remove, weigh, stir, and record weight. Repeat the 30 second cycle until weight stabilizes. Watch carefully because it can catch fire. It usually takes about 4-6 minutes.  Calculate DM% as (Starting weight – Ending weight)/Starting weight x100. Moisture = 100 – DM%.

  7. Don’t Leave Mycorrhizae Stranded in Your Prevented Planting Acres

    Saturated soil

    What is mycorrhizae, and why should I care?

    Mycorrhizae are beneficial fungi that colonize plant roots. They aid plants in scavenging for soil nutrients, by extending the root system via structures called hyphae. In return, plants provide sugars produced during photosynthesis to the mycorrhizae.

    Mycorrhizae also produce a protein called glomalin, which glues soil aggregates together to increase soil stability. Overall, this may increase soil tilth, drainage, and the soil’s ability to hold onto essential nutrients.

    How has the 2019 season affected mycorrhizae levels?

    Flooding events this spring have caused many acres to go unplanted – stranding the mycorrhizae populations that require a growing crop for survival. High soil moisture levels have also led to anaerobic soil conditions that are not conducive for mycorrhizal colonization. When mycorrhizae populations are reduced, the crops that depend on them for nutrient uptake can suffer.

    What is Fallow Syndrome, and how can I prevent it?

    Fallow Syndrome occurs when a lack of plant growth the previous cropping year drastically reduces mycorrhizae populations. Stunting and phosphorus deficiency (i.e. purple leaves) are common symptoms associated with Fallow Syndrome. These symptoms are exacerbated in cool, wet soils that limit phosphorus availability. Reduced mycorrhizal colonization is also correlated with yield loss in corn.1

    The best way to prevent Fallow Syndrome from occurring in your Prevented Planting acres is to establish a cover crop this summer or fall. When selecting a cover crop, keep in mind that Brassicas, like turnip and radish, are not hosts to mycorrhizae, and need to be mixed with either a legume like clover and soybean, or a grass like cereal rye, winter, and oats.

    If you have not chosen a cover crop yet, click here to access a recent C.O.R.N. article outlining the selection process.


    1Ellis, J.R. 1998. Post Flood Syndrome and Vesicular-Arbuscular Mycorrhizal Fungi. J. of Production Agriculture. 11(2):200-204. doi:10.2134/jpa1998.0200.Center/Books/Managing-Cover-Crops-Profitably-3rd-Edition

Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.


Allen Gahler (Educator, Agriculture and Natural Resources)
Andy Michel (State Specialist, Entomology)
Anne Dorrance (State Specialist, Soybean Diseases)
Clifton Martin, CCA (Educator, Agriculture and Natural Resources)
Elizabeth Hawkins (Field Specialist, Agronomic Systems)
Eric Richer, CCA (Educator, Agriculture and Natural Resources)
Garth Ruff (Educator, Agriculture and Natural Resources)
Glen Arnold, CCA (Field Specialist, Manure Nutrient Management )
Jason Hartschuh, CCA (Educator, Agriculture and Natural Resources)
Jeff Stachler (Educator, Agriculture and Natural Resources)
Jim Noel (National Weather Service)
Les Ober, CCA (Educator, Agriculture and Natural Resources)
Mark Badertscher (Educator, Agriculture and Natural Resources)
Mark Loux (State Specialist, Weed Science)
Mark Sulc (State Specialist, Forage Production)
Mary Griffith (Educator, Agriculture and Natural Resources)
Mike Gastier, CCA (Educator, Agriculture and Natural Resources)
Peter Thomison (State Specialist, Corn Production)
Pierce Paul (State Specialist, Corn and Wheat Diseases)
Sam Custer (Educator, Agriculture and Natural Resources)
Sarah Noggle (Educator, Agriculture and Natural Resources)
Stephanie Karhoff (Educator, Agriculture and Natural Resources)
Steve Culman (State Specialist, Soil Fertility)
Ted Wiseman (Educator, Agriculture and Natural Resources)
Wayne Dellinger (Educator, Agriculture and Natural Resources)


The information presented here, along with any trade names used, is supplied with the understanding that no discrimination is intended and no endorsement is made by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.

CFAES provides research and related educational programs to clientele on a nondiscriminatory basis. For more information, visit cfaesdiversity.osu.edu. For an accessible format of this publication, visit cfaes.osu.edu/accessibility.