Wallaces Farmer

Online tool from Iowa State helps farmers price corn silage, alfalfa and other forages.

Rod Swoboda 1, Editor, Wallaces Farmer

September 8, 2016

5 Min Read

Several farmers Wallaces Farmer spoke with at the Farm Progress Show last week at Boone had questions about pricing corn for silage in the field, when to make the final cutting of alfalfa this year, and when to seed cover crops in the fall.

Iowa State University has a 2008 publication titled “Pricing Forage in the Field” extension.iastate.edu/agdm/crops/pdf/a1-65.pdf  that provides some rough guidelines for pricing standing crop corn silage, alfalfa and other forages. However, this publication is probably due for a revision, says Brian Lang, an Iowa State University Extension field agronomist in northeast Iowa. 

how_price_corn_silage_make_final_alfalfa_cutting_1_636089661408179057.jpg

The University of Wisconsin and University of Minnesota suggest using “7” times the price of corn grain at 65% moisture corn silage. And a recent communication that Lang had with one of our ISU Extension farm management specialists also suggested adjusting the multiplier to “7” instead of “6” which is what is currently used in the “Pricing Forage in the Field” publication from ISU.

Online tools also available to help you price silage
For a more detailed approach to pricing corn silage, Lang says there is an Excel spreadsheet from ISU Extension titled “Corn Silage Pricer.” It is on the ISU Ag Decision Maker website about two-thirds of the way down the page: extension.iastate.edu/agdm/decisionaidscd.html. It will open with the “Drought Model” Excel file. Go to the bottom of the Excel page and click on “Example” to open the file for normal corn silage production. There is also a new mobile app from the University of Wisconsin for pricing corn silage, he says. 

Fall harvest tips for alfalfa—taking the final cutting
Lang says he and his ISU Extension colleagues are also getting questions about alfalfa harvesting management. This time of year, there are always questions regarding when that last cutting of alfalfa hay could be made and still allow enough time to build root food reserves before the first killing frost hits in the fall. The answers to these questions are usually something like… “it’s fine to harvest through the first week of September” and “we recommend harvesting at least six weeks before the killing frost.” 

On average, the alfalfa killing frost (25 degrees F or below) in northeast Iowa occurs in the third week of October. So there is minimal risk harvesting alfalfa through about Sept. 10 in northeast Iowa, notes Lang.

Watch number of growing degree days, not the calendar
While those “good old answers” still work, the more correct answer actually deals with

growing degree days (GDD), not the calendar, says Lang. Researchers now define a risk assessment of fall harvest based on alfalfa GDD. The research basically says as long as the plants accumulate at least 500 GDD from harvest to killing frost, the plants will have stored enough root carbohydrate to survive the winter.

A nice summary of this research is available at the following website. The data from Lancaster and Beloit, Wisc. (southern Wisconsin) would apply quite nicely to northeast Iowa, he says. That website is uwex.edu/ces/forage/pubs/Late-Summer-Cutting-Management-of-Alfalfa.pdf.

The Lancaster & Beloit data suggest alfalfa harvested through the first week of September is very low risk of winter injury, having plenty of time to replenish root carbohydrates going into the winter. A September 15 harvest could start providing some risk, and a September 21 harvest even more risk. “These risks do not mean that you will lose the entire stand, but rather would likely lose a percentage of plants and reduction in first crop yield next season because of winter injury and slowed plant recovery in spring,” says Lang.

What if you chose to harvest “after the killing frost”? 
Growing Degree Day (GDD) research says as long as the plants do not accumulate more than 200 GDD from after harvest to before the killing frost, the plants should still overwinter just fine. “This means that you do not have to wait for the actual killing frost to occur as long as you are close enough to it when you harvest,” says Lang.

For example, October 15 is a good cut-off date in locations if the killing frost has not occurred yet, it likely will soon, and the weather in late October is usually cold enough that 200 GDD will not accumulate in the time remaining in the fall.  A critical issue with harvesting after a killing frost is that little to no regrowth will occur following the harvest, so you want to cut high, leaving a good stubble height (approximately 6 inches) to help trap snow and insulate the plants.

Cover crop time of seeding, does it make a difference?
Lang is also fielding questions from farmers this week regarding cover crops. Aerial seeding of cover crops into standing soybeans usually begins when the mid-canopy leaves start to yellow, he notes. This is around the R6.5 stage of soybean growth.

Some leaf drop begins at this time, and it’s nice to have the cover crop seed under the leaf drop rather than on top of the leaf drop. So, we like to get the seed on the ground before more than 10% of the leaf drop occurs. There are usually ~9 days from beginning R6 stage to R6.5 stage.

For corn, it’s not as clear cut as to when it is best to do what with which cover crops.  The general idea is to wait until the corn canopy would be a week or two away from starting to “open up” and let sunlight in. This suggests anywhere from just past half-milk line to initial black layer. The overriding factor is soil moisture, and not so much whether its half-milk line or black layer. After initial black layer the canopy will start opening up allowing sunlight to penetrate to the germinating/emerging cover crop.

As far as what cover crops and seeding rates, the possible combinations are boundless.  If this management is new to you, start simple. NRCS has a basic publication on cover crops with suggested seeding rates and seeding windows.  Go to nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_005818.pdf   For those looking for more comprehensive information on cover crops, the “catch-all” website is the Midwest Cover Crops Council homepage  mccc.msu.edu/.

About the Author(s)

Rod Swoboda 1

Editor, Wallaces Farmer

Rod, who has been a member of the editorial staff of Wallaces Farmer magazine since 1976, was appointed editor of the magazine in April 2003. He is widely recognized around the state, especially for his articles on crop production and soil conservation topics, and has won several writing awards, in addition to honors from farm, commodity and conservation organizations.

"As only the tenth person to hold the position of Wallaces Farmer editor in the past 100 years, I take seriously my responsibility to provide readers with timely articles useful to them in their farming operations," Rod says.

Raised on a farm that is still owned and operated by his family, Rod enjoys writing and interviewing farmers and others involved in agriculture, as well as planning and editing the magazine. You can also find Rod at other Farm Progress Company activities where he has responsibilities associated with the magazine, including hosting the Farm Progress Show, Farm Progress Hay Expo and the Iowa Master Farmer program.

A University of Illinois grad with a Bachelors of Science degree in agriculture (ag journalism major), Rod joined Wallaces Farmer after working several years in Washington D.C. as a writer for Farm Business Incorporated.

Subscribe to receive top agriculture news
Be informed daily with these free e-newsletters

You May Also Like