Golden Harvest Agronomists Evaluate This Season’s Tar Spot Pressure, Soil pH And Yield Data


As corn and soybean harvests wind down across the Corn Belt, it is important for farmers to evaluate their past season’s performance. With the challenges Midwest farmers experienced this year, the post-harvest season offers the opportunity to address existing issues in the field and adapt approaches for 2022. The Golden Harvest agronomy team provides insight on how to improve field conditions and plan for the upcoming season.

Golden Harvest agronomists recommend farmers add the following items to their post-harvest to-do list: manage tar spot in corn, optimize soil pH and analyze 2021 yield data to pick the right corn hybrids and soybean varieties for 2022.

Mitigate tar spot in corn ahead of next year
While tar spot is still a relatively new disease to the U.S., it has become a pressing issue in farmers’ cornfields across the eastern Corn Belt.

“Tar spot is going to continue to be the No. 1 topic of conversation this winter,” said Charles Scovill, Golden Harvest agronomist for Michigan. “We need to be thinking toward next year and how we’re going to alleviate the problem, but luckily there are a couple of things corn farmers can do.”

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While crop rotation and tillage may be beneficial in managing some diseases that overwinter in fields, Scovill noted that these methods are far less effective in preventing tar spot as the fungus travels easily by wind. Scovill suggests farmers evaluate hybrids used in their operations this season to assess how resistant they were to tar spot and to begin making hybrid selections from there. Golden Harvest corn hybrids G10D21 and G13P84 both offer strong tar spot tolerance in addition to delivering good seedling vigor and root strength.

“When you are looking for tar spot severity in your fields, you should look for plant integrity and how much green material is left on the plant,” Scovill said. “By this time of year, affected fields will have foliage that has progressed from being covered in black dots to turning yellow and then brown. These signs, in addition to stalk lodging issues, indicate that those hybrids are suffering greatly from tar spot.”

Scovill also recommends that farmers prepare to use a strong fungicide, such as Miravis Neo fungicide, during the 2022 growing season.

“Different hybrids handle diseases differently, and we’ve seen this year that Golden Harvest corn hybrids have handled tar spot relatively well,” Scovill said. “We can’t guarantee that we’ll see tar spot pressure at the same level next year, but we’ve got to be prepared by making the best hybrid selections and including strong fungicide choices in our plans.”

Manage soil pH levels
Soil pH levels are directly related to soil productivity, and the off-season is a great time for farmers to understand and improve their fields’ soil health.

“Acidic soils limit crops’ uptake of nutrients, primarily nitrogen, phosphorus, potassium and sulfur,” said Mitch Montgomery, Golden Harvest agronomist for northwest Iowa. “Managing these nutrients and the overall soil pH is imperative for maintaining yield uniformity and maximizing productivity potential.”

Lime applications post-harvest can remedy acidic soils. In tillage operations, that liming material gets mixed through the soil and neutralizes a larger area. But in no-till fields, Montgomery suggests that “instead of applying a corrective amount of lime in the first year, it’s better to break that into smaller rates and apply over multiple years. Or, before transitioning to a no-till or strip-till system, apply a full rate of lime, till, then continue transitioning.”

While acidic soil is more common, there are soils that can be too alkaline. Amending alkaline soils can be more difficult depending on how they were formed, so Montgomery recommends farmers with alkaline soils choose to plant hybrids and varieties tolerant to these soils.

Understanding a field’s pH level through soil sampling will allow farmers to make the proper amendments for next year. Montgomery suggests farmers test their soil every three to four years as soil pH does change over time. For instance, manure, nitrogen, sulfur and other fertilizer applications can all acidify soil.

“If you never measure it, you can’t manage it,” he said. “Soil testing is the start to developing your own personal management plan.”

Interpret yield data to choose the right hybrids and varieties
It’s extremely important to evaluate yield data when selecting hybrids and varieties for the following year.

“The biggest thing to consider when looking at yield data is the environment in which the products were planted, because environment plays a huge role in determining yield,” said Josh Lamecker, Golden Harvest agronomist for northern Minnesota. “This year was extremely variable, and every year has its challenges, so farmers have to take into consideration the stresses their crops endured when evaluating performance.”

In addition to looking at environmental stressors, farmers should also examine the crop protection or fertilizer products that they used and even look at historic yield data to set benchmarks for performance. Lamecker also suggests looking at local yield trials from universities or seed companies, since these sources generally have consistent and reliable testing protocols.

Lamecker emphasized the importance of digital ag tools in assessing yield data and selecting next year’s hybrids and varieties. For instance, the E-Luminate digital agronomy platform can analyze a field’s soil type and product performance and accompany that with regional data.

“It allows you to map your acres and create a product plan, which will help identify hybrids and varieties that are potential good fits for your fields,” Lamecker said.

Data insights drive informed decision-making, which is why it’s important to evaluate multiple data points to plan effectively for next season.