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9/12/2011 - 9/18/2011

Does Corn Lose Drymatter After Physiological Maturity? No

By Roger Elmore, Department of Agronomy

Iowa’s corn this year reached dent (R5) development stage on pace with that of 2010, but well ahead of normal (see NASS report).  Some combines are rolling across Iowa’s 14 million plus acres of corn; others will roll soon. Harvest begins. Fall approaches.

It seems like every year at this time – just like the onset of harvest and changing of the seasons – the question poised in the title of this article resurfaces; it doesn’t change. Neither does the answer.

Several years ago, 1995 to be exact, widely circulated reports in popular farm press suggested that corn dry matter decreases after R6 (physiological maturity) during drydown. That work was never published in scientific literature.

A colleague and I in Nebraska compared several hybrids in three years with different drying environments each year and with different harvesting techniques. Grain weights, i.e. dry matter, were stable in all environments following maturity. It was clear: grain does not lose drymatter during in-field drydown. For more information on this, see the extension publication, "Corn grain yield and kernel weight stability after black layer," referenced below.

As grain dries in fields after reaching black layer, monitor individual fields and hybrids for grain moisture, stalk quality and ear retention. You can lose yield to ear drop and kernels shelled out onto the soil during harvest. Schedule harvest based on these variables.

Regarding drymatter stability: “Corn grain yield and kernel weight stability after black layer” on ISU corn web page.

Additional related references:



Roger Elmore is a professor of agronomy with research and extension responsibilities in corn production. He can be contacted by email at or (515) 294-6655.

New Publication Helps Farmers Manage Energy Used for Corn Drying

By Mark Hanna, Department of Agricultural and Biosystems Engineering

When corn harvesting conditions allow optimal time for in-field drying, taking full advantage can reduce on-farm energy consumption. A new publication from Iowa State University Extension and Outreach explains the basic principles of energy management for grain drying.

“Improving Corn Drying Efficiency” (PM 2089Q) explains corn moisture content, plant physiology and the fundamental principles of drying corn following harvest. Topics include in-field drying, considerations for selecting earlier maturing hybrids and recommendations for holding corn “wet and cold” through the winter. When conditions allow, implementing some or all of these techniques can help growers reduce fuel bills for grain drying.

Both over-drying and under-drying corn can lead to wasted energy and lost grain quality. Consider options to reduce your drying needs and manage your drying system closely during changing weather and grain conditions to reduce energy use and maintain grain quality.

For more tips on energy efficiency around the farmstead, visit or follow @ISU_Farm_Energy on Twitter.

The Farm Energy publications are part of a series of farm energy conservation and efficiency educational materials being developed through the ISU Farm Energy Initiative. The purpose is to increase farmers’ awareness of opportunities for improving efficient use of farm energy. The initiative also will help farmers and utility providers to explore opportunities to reduce farm energy demand and to improve overall profitability in a rapidly changing energy environment.


Mark Hanna is an extension agricultural engineer in agricultural and biosystems engineering with responsibilities in field machinery. Hanna can be reached at or (515) 294-0468.

Harvest Update – It’s that Time Again

Charles Hurburgh, Department of Agricultural and Biosystems Engineering

It hardly seems like a year has passed since the last grain harvest and quality briefing. Last year we had very dry grain, thanks to warm dry weather after a summer of warm nights and accelerated plant development. In 2011, the weather just could not make up its mind – wet, moderate, hot but humid, moderate and dry, and then rain and storms. The net result is that average exists as a mathematical term but probably not on anyone’s farm.


Until July, conditions looked great with high yields of heavy corn in the offing.  However, the extreme heat in July accelerated plant growth; example – denting very early, fewer kernels per ear , lighter kernels and eventually tipping back. From a grain quality perspective, the potential for high test weights (57-60 lbs/bu) was reduced. The subsequent shift in August to cooler nighttime temperatures limited the chances for field mold and toxin development.  The forecast for the next 10 days is very conducive to field drydown and low grain moisture at harvest. 

There are some caveats to letting the corn dry down in the field the next 15-21 days. If you determine that particular fields have stalk rot, which is prevalent this year, harvest those fields early and dry the corn. At current corn prices, drying is preferable to grain loss. At $2 per gallon for propane, the drying cost in an average dryer (2000 btu/lb water) for one point of moisture is equal to about 0.25 percent field loss, with $7 corn. Dryers vary and propane costs change but in general, very little field loss can be accepted before early harvest and drying is a better choice.

Corn diseases have been prevalent this year, especially Goss’s Wilt, normally a western Corn Belt problem. This  bacterial disease  has caused premature death in many fields. We do not know the total impact of Goss’s Wilt on grain quality, but premature death normally reduces kernel weight and test weight. We are doing a study this fall of fields with Goss’s Wilt  to determine if this disease affects quality beyond low kernel and test weights.

Use test weight as a storage decision criterion. In general, corn below 52 lb/bu (dry) will be a high storage risk; market it first. There will be variations by hybrid and area; know the test weight of each one to make good decisions. The test weight readings from elevator moisture meters are adequate to make these decisions assuming the elevator has periodically checked against a USDA grader to adjust the machine. There will be large variations in test weight this year. Feed value (protein) is likely to be good. Lower yields and fewer nitrogen-removing heavy rains favor increased corn protein, which is good for livestock feed, but which reduces ethanol yield per bushel.

There is a transgenic (GMO) issue this year – you may have heard of the Agrisure Viptera™ 3110 and Agrisure Viptera™ 3111 problem.  Viptera is an insect prevention biotech trait developed by Syngenta to address insect resistance and other issues especially in continuous corn. This is the first year of commercial planting. There are approximately 70  hybrids from Syngenta companies and licensees with this trait.  Estimates are about 2 percent of U.S. corn acres concentrated in the Central Corn Belt have this trait. This transgenic event is approved in all major world markets except China. The Chinese approval process is well structured and organized but requires at least one export nation to approve it before their two- year field tests begin. The Chinese process will conclude in March or April 2012; until then, corn or corn products (e.g. dried distillers grains with solubles for ethanol) containing this transgenic event cannot be imported. If you planted corn hybrids with this trait, please hold the corn for marketing in 2012 rather than at harvest, unless you know the buyer does not sell corn or corn products into market chains that could include China. Also notify the buyer if there is a chance your deliveries could contain this trait. In the next week or so, we will release a more in-depth discussion of the Viptera 3110 and 3111 issue and response options for producers and grain buyers. 

It appears that both corn and soybeans will be harvested in hot weather this year. The most important initial action in grain storage is to cool the grain. You may have to add one to two more aeration cycles this year. Dry air (low dew points) will cool grain by evaporative cooling. The high value of grain puts a premium on cooling but not over drying.  After harvest, we will do a series or newsletter articles on inventory management for quality control and weight preservation.


Many soybean fields benefitted from late- season rains. The result will be mixed maturity in the same field – dry and wet beans together. This will be a challenge for combine setting, but from a storage perspective, mixtures will respond in storage like the wetter fraction. Therefore, the common practice of putting beans in unaerated bins will not work well; aerate them to cool and equalize moisture, then transfer to other bins if needed.

Moisture meters will read 1-2 percentage points low on mixed moisture soybeans, especially in the first week of harvest. This is a storage issue, and also an inventory management issue. One percent moisture in $14 beans is about 16 cents per bushel. There is a much greater premium for accuracy in all grain testing and inventory monitoring.

Frost is forecast in far northern Iowa later this week. Corn is likely out of risk, but some soybean fields will be green. Green soybeans contain chlorophyll which enters the oil requiring additional refining. Green soybeans also do not extract as efficiently, causing a loss of oil into the soybean meal. Greenness will subside somewhat over time. The best plan is put these beans in an aerated storage and wait two to four weeks before delivering them. If there are green soybeans, buyers will need to refresh themselves on the “line” (intensity) of greenness required to be classed as Damage in the Grades. Always use an Official federally-licensed grain inspection agency to determine this line, and as a referee in borderline cases.

Protein will probably be average to above average – late season growth favors protein.


Grain quality this year should be good, but not exceptional. Stresses will cause variability; use test weight in corn as a storage criterion. Grain will be warm coming out of the field; both corn and beans will need to be cooled immediately after harvest. Mixed moisture soybeans will create storage issues that can be avoided by good aeration immediately after harvest.


Charles Hurburgh is a professor of Agricultural and Biosystems Engineering and Professor in Charge of Iowa Grain Quality Initiative. He can be reached at 515-294-8629 or by e-mailing

Fall Cutting Management for Alfalfa

Steve Barnhart, Department of Agronomy

Rainfall throughout the growing season put many alfalfa producers behind several weeks for their first, and correspondingly their second, third, and sometimes forth cuttings. Now in mid-September, producers are trying to decide on their remaining fall harvest options and the possible impact on winter survival of the stands.

The goal is to help keep the forage plants ‘perennial’
During the fall weeks, perennial forage legumes and grasses respond to shortening days and cooling average daily temperatures and progress through their gradual “cold hardening” process. The genetics of the variety determines how cold tolerant the plant crown and taproot can be during the winter months. Most successfully winterhardened alfalfa plants can withstand soil temperatures in the crown area to about 0 to 4 degrees F without crown tissue damage. At lower soil and crown temperatures, varieties and individual plants will vary in the degree of cold damage they may experience.

To acquire their potential for winter survival, alfalfa plants should get 5 to 6 weeks of uninterrupted growth to accumulate root carbohydrates and proteins before going dormant for the winter. A ‘killing freeze’ is about 23-24F for several hours. So it is important to manage fall harvests to give the plants the best chance for strong winter survival.

Fall cutting management strategies

Producer Question: My alfalfa is knee high in mid-Sept, should I cut it now?

Barnhart Answer: My answer will depend on you answer to this question: Will the field be hay next year? 

If you say ‘No,’ I’ll answer saying, ‘Cut anytime.’

But if you plan for the field to be hay next year, my answer will be based on whether you need the hay. If you don’t need the hay, leave the last growth in the field – don’t graze in fall or winter. And if you do need the hay, it is best to wait until at or after the killing freeze (23-24 F) to cut. Then leave a 5-6 inch stubble.

Producer Question: But it is difficult to dry hay in October! (True!!!) What is the risk of cutting in mid-Sept.?

Barnhart Answer: If you cut in mid-Sept. the plant will begin to regrow and begin to use what stored carbohydrates they have. The risk comes if this late growth will leave the plants with a relatively low root level of available root stores when the 23-24 F killing freeze comes. Low levels of winter root stores may lead to a greater susceptibility to winter cold injury and to a delayed spring recovery.

Factors, which improve alfalfa, winter survival

Here is a checklist for you to review to see how your summer and fall management has been relative to alfalfa stand vigor and overwintering potential.

  • 4” or more of winter-long snow cover
  • a winter tolerant variety
  • 2 or 3 summer cut harvest systems with good regrowth between cuttings
  • 5-6 weeks of uninterrupted growth during September and October
  • All of the last growth of the season is left in the field (no cutting or grazing) – if you did take a late fall cut or grazed, you left a 5 to 6 inch stubble.  
  • Management of insects (potato leafhoppers) during the growing season    
  • Good levels of available potassium in the soil
  • Young stands – or older stands with no root or crown disease


Steve Barnhart is a professor of agronomy with extension, teaching, and research responsibilities in forage production and management.

Prussic Acid Poisoning Potential in Frosted Forages

By Steve Barnhart, Department of Agronomy and Grant Dewell, Veterinary Diagnostic and Production Animal Medicine

The first few frosts of the fall bring the potential for prussic acid poisoning when feeding forages. Some forage species, primarily sorghums and closely related species, contain cyanogenic glucosides, which are converted quickly to prussic acid in freeze-damaged plant tissue. Historically in Iowa there are very few documented cases of prussic acid poisoning. However, the risk is present, and good management practices are necessary to minimize the risks.

Prussic acid, or more precisely, hydrocyanic acid, is a cyanide compound that can kill animals within minutes of ingestion under the right circumstances. Cyanide interferes with the oxygen-carrying function in the blood, causing animals to die of asphyxiation. Symptoms include difficult breathing, excess salivation, staggering, convulsions and collapse. Affected animals will have bright cherry red mucous membranes from the cyanide. Ruminants are more susceptible than horses or swine because they consume large amounts of forage quickly and the rumen bacteria contribute to the release of the cyanide from consumed plant tissue.

Sudangrass varieties are low to intermediate in cyanide poisoning potential, sorghum-sudangrass hybrids and forage sorghums are intermediate to high, and grain sorghum has high to very high poisoning potential. Pearl millet and foxtail millet have very low levels of cyanogenic glucosides. A few other plants also can produce prussic acid, including cherry trees.

Prussic acid does not form in sorghum and sudangrass plants until the leaf tissue is ruptured, as with grazing or chopping. Young, rapidly growing plants will have the highest levels of prussic acid. The cyanide-producing compounds are more concentrated in young leaves. Minimum plant heights of 18 inches are recommended, to avoid using risky, young leaf tissue. Plants growing under high nitrogen levels are more likely to have even higher cyanide potential.

Frost and freezing can cause a rapid change in prussic acid risk in plants of any age or size. With frost, forage tissues rupture, and cyanide gasses form. The cyanide gas can be present in dangerously high concentrations within a short time, and remain in the frosted leaves for several days. Because cyanide is a gas, it gradually dissipates as the frosted/frozen tissues dry. Thus, risks are highest when grazing frosted sorghums and sudangrasses that are still green. New growth of sorghum species following frost can be dangerously high in cyanide due to its young stage of growth. Prussic acid content decreases dramatically during the hay drying process and during ensiling. Frosted foliage contains very little prussic acid after it is completely dry. Sorghum and sudangrass forage that has undergone silage fermentation is generally safe to feed.

Precautions to take to limit risk

When grazing or greenchopping species with prussic acid potential this fall, follow these guidelines:

  • Do not graze on nights when frost is likely. High levels of the toxic compounds are produced within hours after a frost.
  • Immediately after frost, remove the animals until the grass has dried thoroughly. Generally, the forage will be safe to feed after drying five to six days.
  • Do not graze wilted plants or plants with young tillers or new regrowth. If new shoots develop after a frost they will have high poisoning potential, sudangrass should not be grazed until the new growth is at least 18 to 20 inches (24 to 30 inches for sorghum-sudangrass).

Best management is to allow the final, killing freeze to kill the crop, and then wait five to six days before grazing. Other practical managements may be to harvest as hay or silage since. In most cases, adequate growth for safe grazing cannot be obtained after a later, killing freeze occurs.

  • Don’t allow hungry or stressed animals to graze young growth of species with prussic acid potential.

Green-chopping the frost-damaged plants will lower the risk compared with grazing directly, because animals have less ability to selectively graze damaged tissue; however, the forage can still be toxic, so feed with great caution. Feed greenchopped forage within a few hours, and don’t leave greenchopped forage in wagons or feed bunks overnight.

When making hay or silage from sorghum species this fall, consider the following:

  • Frosted/frozen forage should be safe once baled as dry hay. The forage can be mowed any time after a frost. It is very rare for dry hay to contain toxic levels of prussic acid. If the hay was not properly cured, it should be tested for prussic acid content before feeding.
  • Waiting five to seven days after a frost to chop frosted forage for silage will limit prussic acid risks greatly.

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

Other common forages such as alfalfa, clovers and cool-season perennial grasses do NOT produce toxic compounds after a frost and can be fed safely. The only concern is a slightly higher potential for bloat when grazing legumes within a day or two after a killing frost.


Stephen K. Barnhart is the ISU Extension forage agronomist. He can be contacts by phone at 515-24-7835 or by e-mail at Grant Dewell is an assistant professor in Veterinary Diagnostic and Production Animal Medicine and extension beef cattle veterinarian. He can be reached at 515-294-2822 or by e-mail at

Comparing Nematode Management Products on Corn in Strip Trials

By Greg Tylka, Department of Plant Pathology and Microbiology

Plant-parasitic nematodes that feed on corn occur commonly in fields in Iowa and throughout the Midwest. Most nematodes do not reduce corn yields until population densities (numbers) increase to damaging levels and/or other stressful conditions occur in the growing season, like high heat and low moisture.

There are seed-treatment protectants (Avicta® and Votivo™) and a soil-applied nematicide (Counter®) available to manage nematodes that feed on corn. Many growers and agribusiness agronomists are currently testing the effects of these nematode management products on corn yields in strip trials, and some people have inquired about also collecting information on the effects of these management products on nematode population densities.

Collecting nematode data from strip trials is problematic because of the natural variability of nematode populations and their densities in the field. And the effects of management products on nematode numbers will not be season long. As a consequence of limited, early season activity against nematodes, end-of-season nematode numbers on plants treated with management products often are as great as or greater than numbers on untreated plants because nematode populations flourish on healthier, treated plants in the middle and latter parts of the growing season.

Although yield data will be collected from corn strip trials in the upcoming weeks, September is too late in the season for collecting meaningful nematode samples this year.


Tips for comparing nematode management products in strip trials

ISU nematologist Greg Tylka and university nematologist colleagues from Nebraska, Kansas, Wisconsin and Ohio recently published tips on how to design and collect samples from corn strip trials to assess the effects of seed-treatments and soil-applied nematicides on population densities of nematodes that feed on corn. The information will be useful for anyone planning strip trials of nematode management products in the 2012 growing season. The article is titled “Sampling for Plant-parasitic Nematodes in Corn Strip Trials Comparing Nematode Management Products” and is in the online journal Plant Health Progress.

Suggested planting and sampling schemes for assessing effects of management products on nematodes that feed on corn in strip trials. From Tylka et al. 2011.
Sampling for plant-parasitic nematodes in corn strip trials comparing nematode management products. Plant Health Progress doi:10.1094/PHP-2011-0901-01-DG.


The Plant Management Network – a great resource for crop producers and advisers

Plant Health Progress is one of four online journals that are part of the online Plant Management Network (PMN). PMN’s Plant Health Progress and the journal Crop Management contain applied university research articles and diagnostic guides plus industry news and research reviews and briefs related to the production of corn, soybean and other plants. There are special commodity-focused areas in Plant Health Progress, including Focus on Corn and Focus on Soybean, that have narrated webcasts on crop production topics by university faculty. PMN also has journals focused on forages (Forage and Grazinglands) and turf (Applied Turfgrass Science), a searchable database of university extension publications, a searchable image database and much more information related to crop production and protection. A great deal of the content on PMN would be useful to ISU Extension Integrated Crop Management News readers. 

The searchable database of university extension publications on PMN is open to the public, the Focus on Soybean webcasts are available to the public for the first 60 days after publication, and the “Sampling for Plant-parasitic Nematodes in Corn Strip Trials Comparing Nematode Management Products” article will be available to the public through February 2012. Other PMN content is available through subscription. 

Many universities and agribusiness companies are “partners” of PMN and their partnership support allows employees of the organizations access to all content to PMN. Individuals also can purchase subscriptions to PMN. And at the moment, soybean growers and crop advisers can sign up for free, individual one-year subscriptions sponsored by the United Soybean Board by filling out this online form.  


Greg Tylka is a professor of plant pathology with extension and research responsibilities in management of plant-parasitic nematodes.

Soil Management Decisions This Fall

By Mahdi Al-Kaisi, Department of Agronomy

The soil moisture conditions and high temperature across the state during much of July and August may cause an early harvest, which means this is a good time to make soil management decisions for the upcoming season. The main driver of the fast maturity this year most likely is the heat in July coupled with lack of moisture – even though 61 percent of the state’s current top soil is adequate after the last few rain events. The current estimate of corn status in the state that corn is 86 percent dent or beyond, compared to normal of 69 percent. This means combines will start hitting the fields at least by the end of September if not earlier in some areas.

Cover crop

The early harvest will leave soils without crop protection from potential late season rain and the vulnerability to water erosion. One management decision farmers may need to consider is the use of a cover crop when there will be a good window of time to establish cover crop to protect soil – in addition to other benefits associated with cover crop. (See Legume Living Mulches in Corn and Soybeans or  Small Grain Cover Crops for Corn nd Soybeans.)

The decision of tillage

It will be very tempting to do tillage for variety of reasons, especially when there is plenty of time after harvest before winter arrives. However, the decision to till in the fall will be dictated by many factors that are not easy to control. The main factor for tillage in the fall or spring is soil moisture condition. Soil moisture content has significant impact on soil fracturing, tillage depth, clod size and level of soil compaction. Therefore, soil moisture can influence tillage practices, and ultimately yield and soil quality performance in the following season. One thing farmers need to consider before attempting any tillage is whether they need to do any – considering the input cost and potential damage to soil quality and productivity. 

In a corn-soybean rotation, and especially for soybean following corn, research showed no advantage for any tillage system for soybean following corn. There are alternatives that are equally as effective as conventional tillage, such as strip-tillage especially in poorly-drained soils, or no-till in well-drained areas. Site specific conditions, soil quality consideration, water quality consideration and economics of tillage need to be included in the decision whether to till.

There are two main considerations for making a tillage decision this fall.

  • One is soil conditions, which include soil drainage, top soil depth, soil texture and soil organic matter. These factors can have significant effect on the success of tillage system (no-till or conventional). 
  • The second is management considerations, which include a set of decisions that are equally important and may include residue management attachments, crop rotation, equipment availability and calibration (i.e., proper setting of planters, combine calibration for proper residue distribution and uniformity, etc.), tile drain availability, fertilizer program and soil test, hybrid selection, etc. These considerations are critically important before attempting to do any tillage operation this fall.



Mahdi Al-Kaisi is an associate professor in agronomy with research and extension responsibilities in soil management and environmental soil science. He can be reached at or (515) 294-8304.

Managing Soil by the Inches

By Mahdi Al-Kaisi, Department of Agronomy

It is eye opening when you work with the best soil formation in the world and see soil with only a few inches of depth, and scratching through it with your hand you find bedrock!

Recently, I was in Guam attending a soil carbon conference organized by the University of Guam. Scientists from the U.S. mainland, China and other Pacific Rim islands attended and presented at the conference. We had a chance to visit several research farms and farmers’ fields on the island. The island is equivalent in size to a small Iowa county: approximately 32 miles long and 17 miles wide. The temperature was a constant 90 F day and night, and humidity was over 50 percent at all times. The conditions reminded me of Iowa weather during the month of July. 

However, a significant difference from Iowa is the absence of well-developed soil. Their soils are only a few inches deep, and sit on volcanic bedrock. They are characterized by a lack of nutrients, high aluminum content and extremely low pH. It reminded me of not only how fortunate we are to have, arguably, the best soil formation in the world, but also how we take our soils here for granted in the way we often manage it. 

The chemical and physical conditions of soil in Guam present significant production and health challenges. Yes, human health challenges for the island’s native inhabitants. The majority of agriculture production is tropical fruits, with a few acres in vegetable production. The side effects of the soil chemical makeup are not only on poor crop yields, but also negative human health effects.

Studies suggested trace metal toxicity, and exposure to these metals from food and water derived from the soil are believed to be the cause of Amyotrophic Lateral Sclerosis-Parkinson Dementia Complex disease in the early 1950s. This neurological disorder was linked to high concentrations of aluminum and manganese in the southern part of the island soil, where certain trees grow, and are utilized by people in that region. The tree is called Cycad, where people used its fruit seeds as part of their diet. The discovery of this disease has lead researchers to link it to high concentration of aluminum in spinal cords of patients who used Cycad seeds as part of their diets. 

The people of Guam developed soil management skills over generations and kept the few inches they have despite the harsh chemical and physical soil conditions that have both negative health and environmental effects.  The magnitude of challenges Guam’s people face are huge in managing their soils. In particular, the soil conditions dramatically affect human survival. The few inches of soil are not suitable to support crop production systems. In some cases you can scratch the soil surface by hand and hit the bedrock!

Our soil is not only a source of survival for the people in our state, but globally. Iowa’s agriculture, completely dependent on our soil, is feeding people across the Pacific and around the world either directly or indirectly. Despite all the weather challenges we face here in Iowa, such as the recent floods and drought in different parts of the state, it is imperative that we double our efforts in promoting soil conservation practices to protect our precious soils and sustain their quality.  

We have great soil resources in Iowa and must manage our soil and keep it in its unique and productive condition. We, too, need to manage it by the inch in order to have healthy, productive people and a safe environment.  


Mahdi Al-Kaisi is an associate professor in agronomy with research and extension responsibilities in soil management and environmental soil science. He can be reached at or (515) 294-8304.

This article was published originally on 9/19/2011 The information contained within the article may or may not be up to date depending on when you are accessing the information.

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