The fact that we harvest more corn silage than any other state in the nation, nearly 15 million tons annually, suggests that while alfalfa may be known as the “queen” of the forages, it is probably safe to proclaim corn silage is indeed “king” for many of our dairy operations.

As recently as 2010, corn silage was being bought and sold for approximately $45 per wet ton; however, the economics of forage have changed dramatically in the two years since.

In August of 2011, prices as high as $78 to $80 per wet ton were verified. The drought during 2012 kept prices in the $80 area all summer long, reinforcing the importance of corn silage to any dairy operation’s bottom line.

These economics make corn silage a very valuable commodity heading into the 2013 growing season, suggesting farmers are going to be looking for ways to increase their yields and efficiency.

Twin-row corn planters place seed 8 inches off-center of the traditional 30-inch rows. Ideally, the planter is also staggering the placement of the seed to maximize growing area and provide for a more uniform spacing between individual plants.

In turn, this should provide a larger area for the roots to develop as the corn plant emerges due to greater total distance between corn plants.

While there had been a lot of research conducted in when it came to twin-row corn production for grain, the question remained whether or not this type of row spacing would result in any substantial increase in corn silage yield or quality.

Evaluating the results
In 2011 and 2012, the Midwest Forage Association (MFA) helped fund a local forage research proposal, in partnership with the Outagamie County Forage Council, that evaluated twin rows versus single rows in an effort to determine if there were indeed yield or quality differences.


Four farms hosted twin-row corn silage research plots in 2011, with three sites being harvested successfully.

In 2012, two farms participated; however, due to the impacts of the drought, we were only able to collect data from one location.

In this project, we not only were comparing single rows to twin rows, but we also tried to answer the question that all producers often ask: “At what population should I be planting my corn?”

The trial examined 30,000, 35,000 and 40,000 planting populations in both twin rows and single rows in 2011 and 2012. Plots were harvested, weighed and samples collected for each replication.

Dry matter (DM) yields were determined and milk per ton (MPT) values calculated using neutral-detergent fiber digestibility (NDFd). The results were interesting and illustrate the importance of multiple replications and multiple sites over multiple years (and growing conditions).

In 2011, the single rows averaged 6.2 tons of DM silage per acre, while the twin rows averaged 6.3 tons of DM – an increase, but not statistically significant.

In terms of MPT, the singles averaged 2,764 pounds MPT, while the twins averaged 2,779 pounds MPT – an increase, but not statistically significant.

Lastly, when it came to milk per acre (MPA), the singles averaged 17,108 pounds MPA, while the twins averaged 17,638 pounds MPA – once again, an increase, but not statistically significant.

In 2012, the single rows averaged 5.9 tons of DM silage per acre, while the twin rows averaged 5.9 tons of DM. In terms of MPT, the singles averaged 3,104 pounds MPT, while the twins averaged 3,081 pounds MPT.

Lastly, the singles averaged 18,164 pounds MPA, while the twins averaged 18,119 pounds MPA.

While we were not able to demonstrate a statistical difference between twin rows and single rows when simply evaluating row spacing (RS), we were able to confirm data from existing studies on plant density (PD).

In this particular study, the lower your PD, the higher the observed MPT. MPT is the quality measurement accounting for NDFd.

Using the mean MPTs for each PD across the sites in 2011, 30,000 (both twin and single) yielded the highest average MPT (2,884 pounds), followed by 35,000 (2,745 pounds) and then 40,000 (2,686 pounds).

The 30,000 PD was statistically higher than both the 35,000 and 40,000 PDs when it came to overall total MPT over the three sites in 2011.

PD MPT numbers for 2012 were slightly different than 2011 but still demonstrated that when it comes to quality, 30,000 and 35,000 planting populations produced higher MPT than 40,000 planting populations – 3,076 pounds MPT (30,000) and 3,145 pounds MPT (35,000) versus 3,055 pounds MPT (40,000).

At the end of the day, what conclusions could we draw from this effort? In this particular study, RS had little effect on corn silage yield and quality.

PD is a major factor in corn silage yield and quality, suggesting producers consider the yield and quality trade-off between MPT and MPA. MPA is DM yield multiplied by MPT.

Producers always want higher yields but need to consider what quality they might lose (MPT) at those ultra-high planting populations.

Last but not least, in this particular study, when both PD x RS interactions were evaluated together instead of independently, few forage yield and quality measurements were detected when the two characteristics (RS and PD) were combined.

It should be noted that studies conducted by other companies and institutions have shown different results. However, the more extensive my literature review became when searching out additional sites, the more I found myself corroborating a conclusion reached by Dr. Joe Lauer, UW-Madison/UW-Extension corn agronomist, back in 2007.

In an interview, Dr. Lauer stated his observations were that “half the time 30-inch rows will beat narrow or twin rows, and the other half of the time twin or narrow rows will beat 30-inch rows.” After looking at this effort over multiple sites, over multiple years, I would tend to agree with him.

If there was a way to sum up the observations of this particular study of twin rows based on the research conducted in east-central Wisconsin, it may be best put this way:

The use of twin rows was not observed to have a substantial impact on corn silage yield or quality – while there were individual replications where increases were observed, when multiple treatments and multiple locations were combined, consistent, statistically significant results demonstrating an increase in either silage yield or silage quality were not observed.

It is important to note that planting corn silage in twin rows does not negatively impact silage yields or quality; we simply did not observe some of the double-digit differences in east-central Wisconsin that have been cited in studies that have been conducted in other locations across the U.S.  FG

For more information about this Midwest Forage Association twin-row corn silage research project.

An example of twin-row corn silage. Photo courtesy of Kevin Jarek.


Kevin Jarek
Crops, Soils and Horticulture Agent
University of Wisconsin