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C.O.R.N. Newsletter: 2020-28
Making Corn Silage in Dry ConditionsAuthor(s): Bill Weiss
The primary goal of making corn silage is to preserve as many nutrients in the corn plant as possible, to produce a feed that is acceptable to cows, and to minimize any risks associated with feeding the silage. The following are important considerations for making corn silage when growing conditions have been dry.
Chop at the correct dry matter concentration (Editor’s note: see accompanying article “Corn Silage Harvest Timing”). Drought-stressed corn plants are often much wetter than they appear, even if the lower plant leaves are brown and dried up. Before starting chopping, sample some plants (cut at the same height as they will be with the harvester) and either analyze DM using a Koster tester or microwave or send to a commercial lab (turn-around time may be a few days if you send it to a lab). If the plants are too wet, delay chopping until the desired plant DM is reached. The plant may continue to accumulate DM (increase yield), and you will not suffer increased fermentation losses caused by ensiling corn that is too wet.
Use a proven inoculant. When silage is worth upwards of $80/ton (35% DM) reducing shrink by 2 percentage units has a value of about $2/ton. Homolactic inoculants (these are the ‘standard silage inoculants’) produce lactic acid which reduces fermentation losses but sometimes can increase spoilage during feedout. The buchneri inoculants increase acetic acid which slightly increases fermentation losses but greatly reduce spoilage during feedout. Severely drought-stressed corn can have a high concentration of sugars because the plant is not depositing starch into the kernels. High sugar concentrations can increase spoilage at feed out because it is food source for yeasts and molds. Use of a good (from a reputable company with research showing efficacy) buchneri inoculant may be especially cost-effective with drought-stressed corn.
Check for nitrates. Drought-stressed corn plants can accumulate nitrates which are toxic (as in fatal) to ruminants. Silage from drought-stressed fields should be tested before it is fed. Ideally, corn plants should be sampled and assayed for nitrates prior to chopping (most labs offer very rapid turn-around times for a nitrate assay). If values are high, raising the cutting height will reduce nitrate concentrations in the silage because the bottom of the stalk usually has the highest nitrate concentrations. Because forage likely will be very limited this coming year, do not raise the cutting height unless necessary to reduce nitrate concentrations. Nitrate concentrations are often reduced during silage fermentation so that high nitrates in fresh corn plants may end up as acceptable concentrations in the fermented corn silage. Silage with more than 1.5% nitrate (0.35% nitrate-N) has a high risk of causing nitrate toxicity in cattle. See the following University of Wisconsin-Extension fact sheet for more details on nitrate toxicity: https://fyi.extension.wisc.edu/forage/nitrate-poisoning-in-cattle-sheep-and-goats/
Chop at correct particle length. Do not chop too finely so that the effective fiber concentration of corn silage is reduced. If the corn plants have limited ear development, fine chopping is not needed for good starch digestibility. Generally, a theoretical length of cut (TLC) of about ½ inch is acceptable (longer with kernel processing and BMR silage) but this varies greatly between choppers and crop moisture concentration. If using a Penn State particle size sieve, aim for 5 to 10% on the top screen.
Use a kernel processor. Kernel processed corn silage tends to pack more densely than unprocessed corn silage which may help increase aerobic stability. Kernel processing will also increase starch digestibility by breaking the kernel. Poor starch digestibility is a major problem with dry, mature corn silage.
Reduce Shrink. Fill quickly, pack adequately, cover, and seal the silo as soon as you are done filling. Practicing good silage-making techniques can reduce shrink by more than 5 percentage units, which can be worth more than $4/ton of corn silage (35% DM).
Corn Silage Harvest Timing
Silage harvest has begun in some parts of Ohio. Proper harvest timing is critical because it ensures the proper dry matter (DM) concentration required for high quality preservation, which in turn results in good animal performance and lower feed costs. The proper DM concentration is the same whether it is a beautiful, record breaking corn crop or a severely drought stressed field with short plants containing no ears.
The recommended ranges for silage DM are:
Bunker: 30 to 35%
Upright: 32 to 38%
Sealed upright 35 to 40%
Bag: 32 to 40%
Chopping corn silage at the wrong DM concentration will increase fermentation losses and reduce the nutrient value of the silage. Harvesting corn too wet (low DM concentration) results in souring, seepage, and storage losses of the silage with reduced animal intake. Harvesting too dry (high DM concentration) promotes mold because the silage cannot be adequately packed to exclude oxygen. Harvesting too dry also results in lower energy concentrations and reduced protein digestibility.
Corn silage that is too dry is almost always worse than corn silage that is slightly too wet. So if you are uncertain about the DM content, it is usually better to err on chopping a little early rather than a little late. Follow the guidelines below to be more confident in your moisture assessment.
Kernel stage not a reliable guide for timing silage harvest
Dry matter content of whole plant corn varies with maturity. Research has shown that the position of the kernel milk-line is NOT a reliable indicator alone for determining harvest timing. Geographic location, planting date, hybrid selection, and weather conditions affect the relationship between kernel milk-line position and whole plant DM content. In a Wisconsin study, 82% of the hybrids tested exhibited a poor relationship between kernel milk-line stage and whole-plant % DM. In Ohio we have seen considerable variation in plant DM content within a given kernel milk-line stage.
Appearance of the kernels should only be used as a guide of when to begin sampling for DM content, see section below When to Begin Field Sampling.
Determining silage moisture
The only reliable method of determining the optimal time to harvest corn silage is to sample and directly measure the % DM of whole plants. This information combined with average whole plant dry-down rates can be used to roughly predict the proper time to chop corn silage.
How to sample fields
Collect about 5 representative plants from the entire field, from areas with representative plant population and not from edge rows. Collect separate samples from areas that may have different dry down rates, such as swales, knolls. The moisture concentrations of plants can vary within a field (plants will be wetter in low lying area and drier on knolls) and this should be considered when collecting your sample plants.
As soon as the plants are collected, chop them uniformly (using a cleaver, machete, chipper shredder, or silage chopper) and mix thoroughly to obtain a sample with representative grain to stover ratios for DM determination. Put representative sample in a plastic bag and keep it cool (refrigerate if possible) until determining the DM concentration. Some farmers prefer sampling only 2 or 3 plants without any additional sub-sampling to reduce the chances of a non-representative grain to stover ratio that can affect the results. In this case, choosing representative plants is even more critical.
Determine the DM by drying the plant material using a Koster oven tester, microwave, convection oven, a vortex dryer (https://extension.psu.edu/a-vortex-forage-and-biomass-sample-dryer), or taking to a lab.
From our work, on-farm measurement of DM is probably only accurate to +/- 2 units. So if you measure a DM of 30% it could easily be 28-32%. Keep this in mind as you plan harvest timing.
When to begin field sampling
We know that kernel milk stage is NOT reliable for determining the actual harvest date, but its appearance is a useful indicator of when to begin sampling fields to measure plant DM content.
Corn in Ohio should be first sampled to measure DM at full dent stage (100% milk, no kernel milk-line) for conventional tower or bunker silos. Full dent stage happens about 40 days after silk in Ohio. For sealed (oxygen-limited) tower silos begin sampling when the milk-line is one-fourth down the kernel (75% milk remaining). It is important to begin sampling early as a precaution against variation in dry down.
The milk-line of on these ears is about one-fourth to one-third down the kernel. This stage might be about right for oxygen limited silos but could be too late for conventional tower or bunker silos.
Predicting the harvest date
Once whole-plant % DM is determined, use an average dry down rate of 0.5% unit per day to estimate days until the optimal harvest moisture is reached. For example, if a given field measures 30% DM at the first sampling date, and the target DM is 35% for harvest, then the field must gain an additional 5% units of DM, thus requiring an estimated 10 days (5% units divided by 0.5 unit change per day).
This procedure provides only a rough estimate for the harvest date. Many factors affect dry down rate, such as hybrid, planting date, general health of the crop, landscape position, soil type, and weather conditions. Early planted fields and hot and dry conditions can accelerate dry down rates to 0.8 to 1.0 % unit per day. Fields should be monitored closely and more frequently under those conditions. As mentioned above, corn silage that is slightly too dry is usually worse than corn silage that is slightly too wet. Harvesting a little early is usually better than waiting too long.
Potential for Nitrate Problems in Drought Stressed Corn
Have very dry soil conditions increase the potential for toxic levels of nitrates in corn harvested for silage? Nitrates absorbed from the soil by plant roots are normally incorporated into plant tissue as amino acids, proteins, and other nitrogenous compounds. Thus, the concentration of nitrate in the plant is usually low. The primary site for converting nitrates to these products is in the growing leaves. Under unfavorable growing conditions, especially drought, this conversion process is slowed, causing nitrate to accumulate in the stalks, stems, and other conductive tissue. The highest concentration of nitrates is in the lower part of the stalk or stem. For example, the bulk of the nitrate in a drought-stricken corn plant can be found in the bottom third of the stalk. If moisture conditions improve, the conversion process accelerates and within a few days, nitrate levels in the plant return to normal.
The highest levels of nitrate accumulate when drought occurs after a period of heavy nitrate uptake by the corn plant. Heavy nitrate uptake begins at the V6 growth stage and continues through the silking stage. Therefore, a drought during or immediately after pollination is often associated with the highest accumulation of nitrates. Extended drought prior to pollination is not necessarily a prelude to high accumulations of nitrate. The resumption of normal plant growth from heavy rainfall will reduce nitrate accumulation in corn plants, and harvest should be delayed for at least 1 to 2 weeks after the rainfall. Not all drought conditions cause high nitrate levels in plant. If the soil nitrate supply is low in the dry soil surface, plant roots will not absorb nitrates. Some soil moisture is necessary for absorption and accumulation of the nitrates.
If growers want to salvage part of their drought damaged corn crop as silage, it’s best to delay harvest to maximize grain filling, if ears have formed. Even though leaves may be dying, the stalk and ear often have enough extra water for good keep. Kernels will continue to fill and the increases in dry matter will more than compensate for leaf loss unless plants are actually dying or dead. Moreover, if nitrate levels are high or questionable, they will decrease as the plant gets older and nitrates are converted to proteins in the ear.
Preharvest Herbicide TreatmentsAuthor(s): Mark Loux
Information on preharvest herbicide treatments for field corn and soybeans can be found in the “Weed Control Guide for Ohio, Indiana, and Illinois”, at the end of these crop sections (pages 72 and 143 of the 2020 edition). Products listed for corn include Aim, glyphosate, and paraquat, and for soybeans include Aim, paraquat, glyphosate, and Sharpen. Some dicamba products are also approved for preharvest use in soybeans, and some 2,4-D products are approved for use in corn, and these are not listed in the guide. The basic information for these follows:
Dicamba - soybeans: Apply 8 - 32 oz/A (4 lb/gal products) as a broadcast or spot treatment after soybean pods have reached mature brown color and at least 75% leaf drop has occurred; soybeans may be harvested 14 days or more after a pre-harvest application; do not use preharvest-treated soybean for seed unless a germination test is performed on the seed with an acceptable result of 95% germination or better; do not feed soybean fodder or hay following a preharvest application of this product.
2,4-D - corn: Labels vary with regard to types of corn that can be treated (some indicate no sweet corn) and based on whether crop is being grown for seed. Apply after the hard dough (or dent) stage when silks have turned brown. Weed seed production can be suppressed if applied prior to the flowering stage. Allow 14 days between application and grain harvest. Do not forage or feed corn fodder for 7 days after application.
Preharvest herbicide treatments are primarily intended to suppress/kill and dessicate weeds that can make harvest more difficult. Products with contact activity will cause faster dessication and leaf drop of weeds, but may be less effective at killing weeds compared with systemic products. Effective dessication with contact herbicides may still require a wait of a week or more following application, and this can can vary by weed. The maximum paraquat rate is well below the rate required to actually kill large weeds, but it is still probably most effective for dessication of morninglory. Glyphosate is not likely to be effective on marestail and waterhemp, and many giant ragweed populations, whereas dicamba or 2,4-D may with enough time between application and harvest. The first frost will usually provide results similar to herbicides, so in a situation where crop maturity is delayed or the infested field can be harvested later in fall, consider whether a herbicide treatment is actually needed. Preharvest treatments can also be effective for control of warm season perennials, and the systemic herbicides will be most effective where this is the goal. Keep in mind also that for weeds with fruits that can contaminate harvest, such as black nightshade, the preharvest treatment can dessicate the foliage but will not affect the fruits, except that dessication of weeds may result in fruits closer to the soil.
Preharvest treatments are not intended to be used to speed up crop maturity, and largely do not accomplish this. The restrictions on preharvest treatments that specify how mature the crop must be at time of application are designed to minimize any effect of herbicides on crop maturation. Applying earlier than specified could interfere with that process. The residue tolerances for this use are also based on a certain application timing, and failure to follow label guidelines could result in illegal herbicide residues in grain. For crops being grown for seed, and for sweet corn and popcorn, be sure to check with the seed company/processor for approval prior to using any preharvest treatments.
Late Season Forage Harvest ManagementAuthor(s): Mark Sulc
The best time to take a last harvest of alfalfa and other legumes is sometime in early September in Ohio, for the least risk to the long-term health of the stand. These forages need a fall period of rest to replenish carbohydrate and protein reserves in the taproots that are used for winter survival and regrowth next spring.
Many forage producers around the state have been cutting this past week and are continuing into this week. It will be ideal if this is indeed the last harvest of the season. But some growers might try to squeeze out another late cutting, and others have fields that are not quite ready for harvest right now. Like most farming decisions, there are trade-offs and risk factors to consider when making a fall harvest of forage legumes after the first week of September. This article reviews best management practices and risk factors affecting fall cutting management.
The decision of when to take the last harvest with the least risk to the stand can be boiled down to two choices: 1) cut early enough in the fall (generally early September) to permit alfalfa to regrow and replenish carbohydrate root reserves, or 2) cut late enough so that alfalfa does not regrow and use up root reserves prior to winter dormancy. Cutting in between those times (mid-September to mid-October) means more risk to the stand. Factors such as previous cutting management, age of stand, soil fertility, variety, and soil moisture affect the level of that risk.
For those who are risk adverse, following the last cutting date recommendations offers the highest probability of promoting good winter survival and vigorous growth next spring. The recommendation in the 15th edition of the Ohio Agronomy Guide is to complete the last regular harvest of alfalfa by September 7 in northern Ohio, September 12 in central Ohio and by September 15 in southern Ohio. The corollary is to delay final harvest until a killing frost (25F for several hours) has occurred.
Another approach to fall harvest management uses growing degree-days (GDD) rather than calendar dates. Research conducted in Canada showed that alfalfa needs 500 GDD (based on degrees Celsius and base 5 C for alfalfa growth) between the last cutting and a killing frost to generate sufficient regrowth to provide good winter survival and yield potential the following year. Dan Undersander, University of Wisconsin Extension retired forage specialist, wrote in a 2012 article “…we do not need to wait for a killing frost to take the last cutting. We must only wait until it is so cool that little or no regrowth will occur. Thus, harvesting in late fall, when less than 200 GDD will accumulate, minimizes winter injury.”
The period between an accumulation of 200 to less than 500 GDD is a no-cut period (GDD calculated from degrees Celsius scale with base 5C). This GDD approach provides more exact timing for the date of last harvest, but it involves more risk because the grower must predict or consider the probability of either accumulating enough GDD for energy replishment or GDD not accumulating to enough to trigger regrowth that uses up energy reserves. Historic weather data, like that available from the OSU weather stations (http://www.oardc.ohio-state.edu/weather1/), is useful to calculate those probabilities.
Based on this GDD approach, we studied 5 years (2013-2017) of weather data at Wooster, OH. The date of a killing frost (25 F for several hours) ranged from November 3 to 22. The no cut zone of 500 to 200 GDD prior to the killing frost was September 17 to October 13 for three of the five years, but September 4 to 30 in 2014 and September 10 to October 4 in 2013.
So, the period of most risk for cutting alfalfa based on this GDD criterion agrees well with past recommendations to not cut alfalfa from early September to mid-October. Therefore, cutting in late October prior to a true killing frost of forage legumes, is likely to result in little to no regrowth and no significant depletion of root reserves. However, there is still the risk of frost heaving with the late removal of forage cover (discussed more below).
Previous harvest management should be a part of the risk assessment for fall cutting. The cutting frequency during the growing season affects the energy status of the plant going into the fall. Frequent cutting (30-day intervals or less) results in the plant never reaching full energy reserve status during the growing season. A short regrowth period just prior to the fall harvest can be especially risky, if that fall harvest occurs between mid-September and early October, because the regrowth uses root reserves and there won’t be enough growing weather remaining for the plants to restore a high level of root reserves before cold weather shuts down the plants. This lower root reserve status may limit winter survival and spring regrowth, depending on the winter and early spring growing conditions.
Variety selection may also affect the fall cutting risk assessment. Today’s top varieties have genetics selected to better withstand intensive cutting schedules. Alfalfa varieties with high disease resistance and good levels of winter hardiness will be more tolerant of a fall cutting. Adequate fertility, especially soil potassium, and a soil pH near 6.8 will improve plant health and increase tolerance to fall cutting. Stands under 3 years of age are generally more tolerant of fall cuttings than older stands where root and crown diseases are setting in. However, you have more productive stand life to lose if younger stands are harmed by fall cutting.
Soil drainage and soil moisture affect the risk of fall cutting. High soil moisture slows down the cold hardening process, increasing the risk of winter injury. Alfalfa on well-drained soils tolerates late fall cuttings better than on moderately or poorly drained soils. But a word of CAUTION - Removing the top growth of alfalfa plants going into the winter on heavy soils and poorly drained soils increases the risk of spring frost heaving. Heaving is a significant risk on many Ohio soils with higher clay content. This would be a concern when cutting very late after the 200 GDD threshold date.
Finally, consider the economics of a fall harvest. Often the height of the alfalfa is deceptive as an indicator of tonnage. The resulting windrow after cutting is often sparse. Thus, the cost of mechanical harvesting is high on a per ton basis.
Fall cutting risk can be reduced but not eliminated. Nature bats last and alfalfa stand health and survival will suffer more from fall cutting when when have early freezes, open and very cold winters, early springs with ice, and/or extreme rainfall and temperature variations. If at all possible, we urge producers to observe the fall rest period for forage legumes. And if you do harvest during the fall rest period, leave some strips of uncut forage to compare to. You might learn something useful!
What is Required Before You Sell Your Field Harvested Seed in OhioAuthor(s): Mark Sulc
This is the time of year we often hear of Ohio producers considering seed harvests of red clover or other crops (e.g. cover crop seed). If the intention is to sell that seed, even if just “across the fence” to a neighbor, it is important to be reminded there is a permitting process that must be followed before any seed can be sold in order to stay legal with state and federal laws related to seed sales and consumer protection.
Before selling any seed, the seed producer must acquire a permit from the Ohio Department of Agriculture. This permit involves an application and testing a sample of the seed for seed purity and germination. The results of the seed test must be disclosed on a label (seed tag) when the seed is sold.
If the Ohio Department of Agriculture finds any restricted weed seeds in the seed sample, this also must be disclosed on the label, and there are limits to how much restricted weed seed can be present in a seed lot for sale. If there are any prohibited seeds found in the sample, the seed permit will be denied and cannot be sold in that condition. The seed would have to be cleaned and then re-tested to prove absence of prohibited seeds before a permit would be issued.
Before considering any seed sales, contact David Simmons at the Ohio Department of Agriculture:
Agri Inspection Administrator
Ohio Department of Agriculture
David will be happy to explain the full details of the seed registration and permitting process. In fact, producers are welcome to submit seed for testing and obtain the results before deciding if they want to move forward with the permitting application. Each producer can obtain free seed testing from Ohio Dept. of Agriculture between June 1 and December 31 (first three tests are free, additional ones charged at cost). Between January 1 and May 31 of each year all seed testing is charged at cost.
Seed can also be tested by Central Ohio Seed Testing, including cover crop seed (614-792-0334).
Keep in mind there are other federal seed laws to consider, such as the Plant Variety Protection Act which provides legal intellectual property rights protection to breeders of new varieties of plants which are sexually reproduced (by seed) or tuber-propagated. So producers need to be aware of what variety they are reproducing and whether it is protected under those laws.
Minimal WBC Reported Across OhioAuthor(s): Amy Raudenbush, Angela Arnold, Mark Badertscher, Jordan Beck, Frank Becker, Lee Beers, CCA, Bruce Clevenger, CCA, Sam Custer, Tom Dehaas, Craig Everett, Allen Gahler, Jason Hartschuh, CCA, Andrew Holden, Stephanie Karhoff, Alan Leininger, Ed Lentz, CCA, Rory Lewandowski, Cecilia Lokai-Minnich, David Marrison, Sarah Noggle, Les Ober, CCA, Eric Richer, CCA, Garth Ruff, Beth Scheckelhoff, Clint Schroeder, Mike Sunderman, Curtis Young, CCA, Chris Zoller, Andy Michel, Kelley Tilmon
Very few Western bean cutworm (WBC) numbers were reported in traps for the week of August 17 – 23. Overall, a total of 26 counties monitored 84 traps, resulting in 30 WBC adults (a statewide average of 0.37 moths per trap) (Figure 1). The low numbers we are observing are expected this time of the year as peak adult flight is now behind us. We would like to thank all the participating Extension Educators that monitored WBC flight this year.
Figure 1. Average Western bean cutworm adult per trap followed by total number of traps in the county in parentheses for week ending August 23, 2020.
Cover Crop Driving TourAuthor(s): Amanda Douridas
Local farmers invite you out to their farms for a Drive-It-Yourself tour of fields with growing cover crops. These three farms are located in Northern Champaign and Logan Counties and are planted to different species of cover crops after wheat. The farmers will be on hand to answer questions and discuss how they adopted cover crops and make it work for their operations.
Cover crops provide many benefits to improving soil health and productivity. Getting started with cover crops can be daunting, especially with limited time and resources in the fall. Through the Cover Crop Champions program in Champaign and Logan Counties, these farmers are committed to helping others become successful. They are here to answer you questions and help you make it work on your individual farms. For additional resources, videos and podcasts about using cover crops, please visit the link at the end of this article.
The tour is slated for September 17, from 5-8pm. Guests are invited to attend in any order at any time within the 3 hours. There is no cost to attend and we appreciate an RSVP. You can view details, the map and RSVP at http://go.osu.edu/CCChampions.
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.
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