'Yield gap' survey project offered to soybean growers

Ray Mueller

Kimberly — With the yield potential of soybeans shown in the Wisconsin Extension Service's plots during the 2016 growing season, the state's soybean production specialist is promoting a “Yield Gap” survey project designed to boost yields closer to the genetic potential of the soybean varieties suited for growing in the state.

That yield potential was shown by the 10 soybean varieties which produced the equivalent of at least 100 bushels per acre in the Extension Service's 2016 variety trial plots at Platteville, soybean specialist Shawn Conley pointed out at the early 2017 series of agronomy update meetings.

Shawn Conley

Building on a record

While acknowledging that the National Agricultural Statistics Service has estimated the average soybean yield in Wisconsin at a record high average of 55 bushels per acre in 2016, Conley is resolving to help the state's farmers achieve more yields closer to the genetic potential of the soybean varieties they grow.

Impressive yields weren't confined to southernmost Wisconsin in the 2016 plots, Conley emphasized. He cited the year's results at the north central zone plots (Seymour, Valders, Marshfield and Chippewa Falls), where 33 of 82 the Roundup Ready varieties earned a starred rating for their statistically insignificant yield range of 75 to 83 bushels per acre — well above the state's average of 55 bushels.

Nonetheless, Conley described that 55 bushel average yield as “pretty tremendous” and noted  it was a 9 percent increase from the 50.5 bushel record set in 2010. He credited the long growing season and development of large seeds for that major increase in yield.

Another factor supporting higher yields is the breeding change in soybeans which has added as much as seven to 14 days to the reproductive period of the plant, Conley observed.

Wisconsin farmers finally got a good week of advantageous weather to chug through their harvests of soybeans and corn.

'Yield gap' venture

For the “Yield Gap” project, soybean growers in Wisconsin and other North Central states are being invited to share production related data such as soil types, weather conditions, tillage practices, planting dates and fertilization on up to four of their fields.

Conley has sent letters to soybean growers inviting them to take part in the survey that is designed to identify the reason for gaps in the yield between the genetic potential and the actual yields. Letters were sent to 1,500 soybean growers in Illinois, Michigan, Indiana, Ohio and Wisconsin.

Those states are among 10 in the North Central region which account for 80 percent of the soybean production in the United States and 30 percent of the world's total, Conley pointed out. During 2014 and 2015, the survey drew 3,568 responses from soybean growers in those 10 states and the immediate goal is to boost that number to 8,000.

In Wisconsin, a followup to the letter is being conducted at the area soybean meetings being held on Jan. 18 in Fond du Lac, Jan. 19 in Janesville and Jan. 20 in Eau Claire. Soybean growers who attend one of those meetings and supply the information sought for the “Yield Gap” survey will be rewarded with a $10 Culvers' gift card.

Outlook for 2017

As soybean growers prepare for their 2017crop, Conley urges them to be aware of the nutrient removal from the soil on which many of them enjoyed impressive yields in 2016. He said this is most crucial with the availability of potassium, followed by phosphorus.

The removal of soybean stover alone converts to taking as much as 38 pounds of potassium per acre from availability to the next crop, Conley pointed out. Based on its nutrient value, he suggested that soybean growers are not charging enough for the soybean stover that they sell for bedding.

Regarding the large soybean seeds from the 2016 crop and the resulting cracking on some of them, Conley said the only concern with planting them would occur if the soil would be dry at the time and the seed would sprout but then die instead of emerging. He prescribed fungicide seed treatments as a way to reduce the potential for such a problem.

Minimum practices

In addition to being aware of the fertilization needs, Conley strongly recommends that “all soybean acres in Wisconsin” be treated with a pre-emergent herbicide in 2017. Among the weed species that need to be controlled, he is particularly concerned with water hemp.

Although the seed industry strongly endorses seed treatments, Conley pointed out that this creates a conflict with the traditional integrated pest management (IPM) practices. While the hosts and pathogens pertaining to the need for seed treatments can easily be known, it takes the environment to obtain a value from seed treatments in most cases, he explained.

As soybean growers face less than attractive prices for their 2017 crop, they need to be concerned about their input costs and assign the risks of incurring them accordingly, Conley advised. If the concern is with plant populations, he cited numerous studies that show per-acre harvest populations of as much as 40,000 less than the recommended planting of 140,000 on lower quality soils and 100,000 on high quality soils do not result in significant yield decreases.

Tracking plant diseases

The practice of assigning risks applies very directly to the choice of seed treatments, Conley stated. As an example, he cited a supplier's promotion of ILeVO as a control for sudden death syndrome (SDS) in soybeans.

What growers need to realize is that only 7 percent of Wisconsin's soybean fields are infested with the SDS pathogen, Conley indicated. For those fields, the investment of $25 per seed unit or about $12 to $15 per acre for a seed treatment to control SDS is worthy of consideration, he observed.

Conley reported that research with ILeVO was conducted at five of the Wisconsin plots in 2016 — both with and without the presence of the SDS pathogen. At per-acre plant populations of 140,000 and 80,000, there were yield increases with ILeVO compared with seed that was not treated.

But when the entire economic optimum was calculated, the best return at those plots occurred with untreated seed with a per-acre plant harvest population of 110,000 while seeds treated with both the standard commercial base fungicides and ILeVO provided the best return at plant populations of a bit more than 103,000 per acre, Conley reported.

Instead of being overly concerned with SDS at the moment, Conley would like soybean growers to give more attention in their management practices to dealing with the presence of soybean cyst nematode, which has already been identified in 20 to 25 percent of the fields in the state, and to identifying whether it is present in yet more fields. He reminds growers that the Wisconsin Soybean Marketing Board covers the cost of most of the soil samples submitted for SNC testing.

Current connections

Conley invites soybean growers, their crop consultants, seed suppliers and others providing services to use the electronic tools available to them.

One recent addition is the BeanCam app which allows the taking of photos of soybean plant population density when a decision on replanting is pending. One requirement is that weed plants not be included in the image, he stressed.

What BeanCam can provide is the typical first frost date for the location. This then guides the selection of the proper maturity of the variety when replanting, Conley explained. The app also shows the Wisconsin zones for maturity choices of 1.5, 2.0 and 2.5 with a .4 variance for each being acceptable, he added.

Another online source of information is It augments Conley's website.