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Ohio State University Extension


C.O.R.N. Newsletter 2009-29

Dates Covered: 
August 31, 2009 - September 7, 2009
Andy Kleinschmidt

Estimating Preharvest Silage Yields

Authors: Peter Thomison

Although rainfall during recent weeks has been adequate to plentiful throughout much of Ohio, some localized areas, especially in NW Ohio, have experienced significant rainfall deficits and are, for the most part, very dry. In a recent C.O.R.N. article (August 17-24, 2009), widely used procedures for estimating corn grain yields prior to harvest were described . Grain producers who are considering the costs of harvesting mosture stressed corn as grain vs. silage need to assess yield potential in order to evaluate grain and silage marketing options. Two “quick and dirty” methods for evaluating yield of corn silage are as follows:

Grain yield method for estimating silage yield
For moisture-stressed corn, about 1 ton of silage per acre can be obtained for each 5 bushels of grain per acre. For example, if you expect a grain yield of 50 bushels per acre, you will get about 10 tons/acre of 30% dry matter silage (3 tons/acre dry matter yield). For corn yielding more than 100 bushels per acre, about 1 ton of silage per acre can be expected for each 6 to 7 bushels of grain per acre. For example, corn yielding 125 bushels of grain per acre, corn silage yields will be 18 to 20 tons per acre at 30% dry matter (5 to 6 tons per acre dry matter yield).

Plant height method for estimating silage yield
If little or no grain is expected, a rough estimate of yield can be made assuming that 1 ton of 30% dry matter silage can be obtained for each foot of plant height (excluding the tassel). For example, corn at 3 to 4 feet will produce about 3 to 4 tons per acre of silage at 30% dry matter (about 1 ton per acre of dry matter).

Adapted from: Lauer, Joe. 2006. Concerns about Drought as Corn Pollination Begins
University of Wisconsin. Field Crops 28.493 – 42.

For additional information check:
Weiss, Bill. 2007. Pricing Drought-Stressed Corn Silage C.O.R.N. article (July 30, 2007 - August 6, 2007) []

Utilizing Drought-Damaged Corn (NCH-58)

Corn Silage Harvest

Authors: Bill Weiss

Because of high feed costs and low milk prices, maximizing the nutritional quality of your corn silage and minimizing shrink are more important than ever. At this time in the growing cycle, the most important manageable factor that will influence the nutritional value of this year’s corn silage is maturity at chopping. Harvesting corn silage too early (i.e., silage with less than about 30% dry matter) usually results in a lower starch concentration in the silage, which means more corn grain may need to be supplemented. Corn silage is usually among the least expensive ingredients in a diet and high inclusion rates will reduce feed costs. However, because wet silage can reduce feed intake by dairy cows, dietary inclusions rates for wet silage are usually less than for normal silage which can increase overall feed costs.

Over mature corn silage (silage with more than about 38% dry matter) also has less nutritional value than normal corn silage because of lower fiber and starch digestibility. Kernel processing partially reduces some of the negative effects of maturity on starch digestibility and is strongly recommended for mature corn silage, but it will not make mature corn silage equal to corn silage harvested at the optimal dry matter concentration (30 to 38% dry matter).

A portion of the crop that is harvested will be lost during fermentation and storage. That loss is considered shrink. Factors that affect shrink include:

1. Type of silo structure: (bags and sealed silos usually lowest, conventional upright silos intermediate and bunkers usually have greatest shrink).

2. Moisture concentration at filling. Wet silage can have high shrink because of excessive fermentation and seepage. Dry silage can have high shrink because of spoilage (for example, mold) during storage and feed out.

3. Chop length. Chopping too coarsely increases the amount of air trapped in the silage mass and reduces compaction. Chop just coarse enough to provide enough ‘chewable matter’ for the cows. Approximately 5% of the material on the top screen of the Penn State shaker box is usually adequate.

4. Rate of filling. Slow filling reduces the rate of fermentation so that pH stays high for a longer period of time which increases shrink. The faster you fill and pack (filling faster than you can pack will increase shrink), the less shrink.

5. Air trapped in the silage mass and air infiltration into the mass promotes yeast and mold growth causing shrink. Pack, pack, pack, and when you think you have packed enough, pack some more.

6. Not covering the silage in a bunker silo greatly increases shrink. Several studies have shown that covering a bunker with plastic returns around $8 in savings for every $1 invested in plastic and labor needed to cover the silo. For maximum benefit, cover quickly after the silo is filled.

7. Silage inoculants can increase, decrease, or not affect shrink (how is that for a useful statement). The standard silage inoculant (lactic acid bacteria) usually reduces fermentation losses slightly (i.e., reduces shrink) but often slightly increase spoilage losses during feeding. If spoiling during feed-out has been a problem on a specific farm, then use of lactic acid bacteria may increase overall shrink and would not be recommended. If spoilage has not been a problem on a specific farm, then use of lactic acid bacteria should be considered because of the reduction in fermentation losses. If spoilage has been a problem, propionic acid bacteria (Lactobacillus buchneri) is recommended. This inoculant often increases fermentation losses but usually reduces spoilage losses more.


* Maximize nutritional value of corn silage by chopping when corn is between 30 and 38% dry matter.

* Minimize shrink by chopping fine enough (but not too fine), filling rapidly, packing well and sealing the silo with plastic. Lactic acid bacterial inoculants will reduce shrink a bit if spoilage during feedout is not a problem. Lactobacillus buchneri inoculant will reduce spoilage during storage and feedout but will increase fermentation losses slightly.

Timing Harvest of Silage Corn

Authors: Mark Sulc

Determining the proper time to harvest corn for silage is critical because it influences the overall quality of the product that is preserved and stored in the silo. The moisture content critically affects silage fermentation and preservation. Harvesting corn too wet (low dry matter content) results in souring and seepage of the silage and reduction in animal intake. Harvesting too dry (high dry matter content) promotes mold development because the silage cannot be adequately packed to exclude oxygen. Harvesting too dry also results in lower digestibility, protein, and vitamins A and E. Harvesting corn at the proper dry matter content will result in better animal performance and lower feed costs.

Harvest Moisture Guidelines
Corn silage preserved between 30 and 40% dry matter (60 to 70% moisture) generally provides good silage fermentation and animal performance. The optimal dry matter content varies with type of storage structure (see ranges below).

Optimal dry matter contents for different storage structures:
Type of Structure (Optimal % dry matter)
Horizontal bunkers (30 to 35)
Bags (30 to 40)
Upright, top unloading (35 to 40)
Upright, bottom unloading (40 to 45)

Kernel stage not a reliable guide for timing silage harvest
Dry matter content of whole plant corn varies with maturity. Historically, recommendations were to harvest corn silage when kernels were at the black layer stage, but today’s hybrids are too dry at the black layer stage. Through the 1990’s, timing silage harvest based on the kernel milk-line position was widely recommended. But studies have demonstrated that the position of the kernel milk-line, used alone, is not a reliable indicator for determining harvest timing. Geographic location, planting date, hybrid selection, and weather conditions affect the relationship between kernel milk-line position and whole plant dry matter content. In a Wisconsin study, 82% of the hybrids tested exhibited a poor relationship between kernel milk-line stage and whole-plant % dry matter.

Determining Silage Moisture
Predicting when to harvest corn to achieve the proper % dry matter for ensiling is difficult because there is no easily identifiable plant trait that can be used to reliably and accurately estimate the whole plant % dry matter. The only reliable method of determining the optimal time to harvest corn silage is to sample the crop and directly measure the % dry matter of whole plants. The whole plant % dry matter information combined with average whole plant dry-down rates can be used to roughly predict the proper time to harvest silage.

Predicting when to harvest corn to achieve the proper % dry matter for ensiling is difficult because there is no easily identifiable plant trait that can be used to reliably and accurately estimate the whole plant % dry matter. The only reliable method of determining the optimal time to harvest corn silage is to sample the crop and directly measure the % dry matter of whole plants. The whole plant % dry matter information combined with average whole plant dry-down rates can be used to roughly predict the proper time to harvest silage.

How to Sample Fields
Collect 5 to 10 representative plants from the entire field. The plants should be representative, including being from an area with representative plant population. Collect separate samples from areas that may have different dry down rates, such as swales and knolls. Some farmers prefer sampling only 2 or 3 plants to reduce the chances of a non-representative grain to stover ratio. In this case, choosing representative plants is even more critical.

Put plants in a plastic bag, keep them cool, and chop as quickly as possible. The plants should be uniformly chopped (using a cleaver, machete, chipper shredder, or silage chopper) and then mixed thoroughly to obtain a sample with representative grain to stover ratios for dry matter determination. Determine the dry matter content by drying the plant material using a Koster oven tester, microwave, convection oven, or taking to a lab. Make sure the sample does not dry down and keep it cool until the dry matter determination is performed.

The accuracy of the % dry matter value obtained will be largely determined by the amount of time and care taken in drying down and weighing the samples. This is especially true for corn silage where whole kernels and cob pieces can be difficult to dry completely without burning the leaf tissue.

When to Begin Field Sampling
Sampling fields to measure whole plant dry matter content should be done well before the anticipated harvest date in case corn is drying down faster than expected. Silking date can be used as a rough indicator of which fields are likely to be the earliest to harvest. The dent stage occurs about 35 to 42 days after silking. The dent stage is when fields should first be checked for kernel milk stage development.

While kernel milk stage cannot be relied upon to gauge optimal harvest dates, it can be a useful indicator of when to begin sampling fields to measure whole plant dry matter. Based on our data and experience in Ohio, corn silage growers in Ohio should first begin sampling corn silage fields to measure dry matter at full dent stage (100% milk, no kernel milkline) for conventional tower or bunker silos, and at 1/4 milkline (milkline one-fourth down the kernel, 75% milk remaining) for sealed (oxygen-limited) tower silos. These stages are slightly earlier than what we most often expect to be the ideal stage for ensiling corn in each type of structure, but it is necessary to begin sampling early because of possible variation in plant dry matter content.

Predicting the Harvest Date
Once the target milk stage is reached and whole-plant % dry matter is determined, an average dry down rate of 0.5% unit per day can be used to estimate the number of days until optimal harvest moisture. For example, if a given field measures 30% dry matter at the early sampling date, and the target harvest dry matter content is 35%, then the field must gain an additional 5% units of dry matter 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 the dry down rate, including hybrid, planting date, general health of the crop, landscape position, soil type, and weather conditions. For example, in early planted fields or under hot and dry conditions, whole plant % dry matter can increase at a rate of 0.8 to 1.0 % unit per day. Fields should be monitored closely and whole plant % dry matter determined again as the predicted harvest date approaches.


Harvest timing is a critical management decision to ensure corn will be ensiled at the proper dry matter content for effective fermentation and storage. The following steps are useful for achieving optimal corn silage harvest timing.
1. Record hybrid maturity and planting date for each silage field.

2. Record the silking date of each hybrid and field to be chopped for silage. Full dent of kernels will typically occur 35 to 42 days after silking.

3. Once the kernel milk-line appears and begins to move (soon after full dent stage), sample and measure the whole plant % dry matter. Use a dry down rate of 0.5% unit per day to roughly predict when the field will be ready for the storage structure used.

4. Sample the field again to determine whole plant % dry matter as the predicted harvest date approaches.

Dodder (Cuscuta spp.) in Western Ohio Red Clover Stands

Authors: Roger Bender

Yellow orange threadlike stems were reported in red clover fields in several western Ohio counties last week. The stems are stringlike, twining, smooth and branching to form dense masses in some fields.

Purdue’s Glen Nice says that dodder is a parasitic plant without any leaves nor any chlorophyll to produce its own food. It lives by attaching to a host with small appendages (called ‘haustoria”) and extracting the host plant’s carbohydrates.

Although neither toxic nor unpalatable to some livestock, dodder can weaken host plants enough to reduce yield, quality, and stand. If infestations are severe enough, dodder may kill host plants. When looking at broadleaf plants, single dodder plants may be missed if you don’t look close enough. They appear as yellow strings winding up the stems or over the leaves of other plants.

Dodders are annuals that spread by seed. Having a hard seed coat, it is suspected that gas and water levels control seed dormancy. Seed may be able to survive in the soil over 20 years. Some have speculated this summer’s cooler conditions have enhanced the growth of dodder. Several control approaches have been investigated. Controlling dodder with herbicides depends on the crop in which you wish to control it. Some herbicides may affect dodder, but also may affect the crop, or not be labeled for use in that crop. Always read and follow herbicide labels.

In many cases, dodder control may be more effective if herbicide applications are made before the plant attaches to the host. PRE applications of Kerb® have provided good control of dodder in ornamentals and turf (Anonymous). Treflan® and Prowl® have also been reported to suppress dodder germination (Mueller.2006). However, in most cases that Nice has experienced, PRE applications often do not retain enough residual activity to provide control for the rest of the season.

Glyphosate has been reported to control dodder POST and can be applied as a spot treatment of a 1-2 percent solution to alfalfa. However, be aware that the alfalfa will be damaged where glyphosate is applied. Others suggest little or no control with glyphosate.

Raptor® can suppress dodder at 5 fl oz/A when applied after dodder emergence and applied before it is three inches tall. Pursuit DG® also can suppress dodder after emergence, but as soon as dodder attaches to the host plant, suppression drops. The Pursuit® label recommends using it with COC or methylated seed oil to suppress dodder.

For more on dodder, please refer to the following websites and

GVM West Field Day, September 2

Authors: Mike Gastier

Ohio State University Extension will have a strong presence at a Field Day hosted by GVM West in Bellevue, Ohio on Thursday, September 2, 2009. Although GVM sponsors the event chiefly to promote their products, the company graciously supplies OSU Extension with a separate tent to accommodate pesticide training that is open to the public.

From 10:45 to 11:45 a.m., Dr. Dennis Mills, plant pathologist for agronomic crops at Ohio State will speak on the effective use of foliar fungicides on corn and soybeans. The presentation will also include a review of seed treatment options for all grain crops. This session will count for pesticide recertification credits (one hour of 2A commercial or category 1 private).

At 1:00 p.m. Extension Educators Dr. Steve Prochaska of Crawford County and Mike Gastier of Huron County will offer one hour of Core training for both commercial and private applicators. Certified Crop Advisor credits will be available for both sessions in the category of Crop Management.

GVM West is located at 4341 Sandhill Road in Bellevue, Ohio. Their facility is adjacent to US Rt 20 between Bellevue and Monroeville. The actual site of the Field Day is just south of Rt 20 on Sandhill Road. The event begins at 9:00 a.m. and concludes at 4:00 p.m. This is a great opportunity to stay up to date on the latest fertilizer and pesticide application technology and also get recertification credits.

Northern Ohio Farm Management Luncheon September 14, 2009

Authors: Mark Koenig

Please plan to attend the Northern Ohio Farm Management Luncheon September 14, 2009, 11:00am to 2:00pm, Ole Zim’s Wagon Shed, 1375 N. State Route 590, Gibsonburg, Ohio.

The agenda for the Northern Ohio Farm Management Luncheon is “Ohioans for Livestock Care” presented by Sandy Kuhn, Director of Commodity Relations Ohio Farm Bureau, “FSA Farm Storage Loan Program” presented by Todd Warner, Farm Service Agency County Director, plus “Grain Marketing Outlook” presented by Matthew C. Roberts, Assistant Professor in the Agricultural, Environmental, and Development Economics Department at The Ohio State University, and an OSU Extension State Specialist in Grain Marketing

Harvest is just around the corner and what a great opportunity to get the most up-to-date information about this year’s harvest. This meeting will also address the upcoming livestock issue that will face Ohio voters this November.

The cost of the program is $15 and includes lunch and all hand-out material. Reservations are required and can be made by calling 419-334-6340 or by e-mailing koenig.55 Deadline for reservations is September 10, 2009; payment can be made at the door. If you have any questions or need additional information, you can call 419-334-6340. This program is sponsored by Ohio State University Extension Erie Basin.

Archive Issue Contributors: 

State Specialists: Pierce Paul (Plant Pathology), Ron Hammond and Andy Michel, (Entomology), Peter Thomison (Horticulture and Crop Sciences). Extension Educators and Associates: Glen Arnold (Putnam), Roger Bender (Shelby), Tim Fine (Miami), Mike Gastier (Huron), Wes Haun (Logan), Ed Lentz (Seneca), Les Ober (Geauga), Alan Sundermeier (Wood), Harold Watters (Champaign), Mark Koenig (Ottawa/Sandusky), Steve Prochaska (Crawford), Howard Siegrist (Licking), Greg LaBarge (Fulton), Suzanne Mills-Wasniak (Montgomery)

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.