Fall Soil Fertility Testing: Post-Harvest Testing Benefits

It’s never too early to prepare for a strong growing season. You don’t have to wait until spring to test your soil quality.
Fall soil fertility testing to determine residual nutrients and soil conditions after harvest can help growers make informed decisions to enhance productivity for the next season and years to come.

Fall soil fertility testing versus spring soil testing

There are five key advantages of conducting fall soil fertility testing versus waiting until spring:

• Cost savings: When you test soil fertility in the fall, you can quickly pivot to purchasing inputs. Fertilizer is often cheaper in the fall than at other times of year. You might even pick up a few tax benefits.
• Logistics improvements: By applying fertilizer in the fall, you can simplify spring planting operations and focus on getting the new crop established.
• Weather perks: Fall weather is often more agreeable than spring weather for getting into the field and collecting the soil samples you need to assess fertility.
• Lab advantages: Many soil testing labs have greater capacity to process samples in the fall. Take advantage of your good timing.
• Decision-making gains: You probably have more time for thoughtful decision-making in the fall compared to the spring planting chaos.¹

Now that you know the benefits of fall soil fertility testing, let’s look at the nuts and bolts of how use to post-harvest testing results.

Put post-harvest fall soil fertility testing results to work

You know this better than anyone: Every hour (and dollar) spent on your farm needs a purpose. Making the most of soil testing in fall once harvest has wrapped up is key to managing your time and building a strong fertility management plan. Here are the benefits of fall soil fertility testing and how you can take action to ensure next season’s crops have access to exactly the right nutrients, when and where they need them.

More cost-efficient fertilizer applications

If your farm’s finances don’t pencil out at the end of the day, nothing else matters. That’s why fall is so important: It provides a chance to dig around like a detective and make sure you only invest in exactly the inputs you need.
Post-harvest sleuthing like this is important because you can:

• Tailor new fertilizer applications to account for existing (residual) nutrient levels already in the field
• Limit unnecessary input expenses while still optimizing crop yields
• Avoid applying too much or too little fertilizer²

A good place to start is to evaluate possible application of dry fertilizers paired with tillage. That gets nutrients below the soil surface and reduces the risk of runoff. Phosphorus (P) and potassium (K) can be just as effective when applied at fall compared to spring application, assuming your soils have optimum fertility.

Improved soil amendment opportunities

Lime and other amendments can be applied to your soil to adjust pH levels as needed during the fall. By applying lime in fall, you’re providing plenty of time to neutralize acidity in your soil while improving available nutrients through the winter period.³

More efficient nitrogen management

Once harvest has wrapped up, head to the field and evaluate residual nitrate levels. If levels are high after harvest, it likely signals you’ve overapplied nitrogen in the past. This could lead to leaching of nitrates into groundwater, especially on sandy soils or in areas where excess rain has occurred.
There’s not much you can do in the near term to reduce leaching next season, though. Ultimately, rainfall and soil conditions will determine the behavior of nitrates already present in the field.
Keep in mind that while fall nitrogen testing helps you take stock of past seasons’ nitrogen applications, spring nitrogen testing is preferred for optimal in-season nitrogen management. Several free nitrogen rate tools can help you make these decisions.^4,5

Experts are available to help you make your fall fertility decisions. Reach out to your retailer, a nearby extension office agent, or a professional like your regional BASF representative.

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Endnotes

1. Jeranyama, Panhandle. “Why Soil Test in the Fall?” Michigan State University Extension, 27 Oct. 2016, https://www.canr.msu.edu/news/why_soil_test_in_the_fall. Accessed 4 June 2025.
2. Oberholster, Mary. “Getting the Dirt on Soil Testing.” UC ANR Blogs: Over the Fence – Alameda County, University of California Agriculture and Natural Resources, 22 Mar. 2024, https://ucanr.edu/blog/over-fence-alameda-county/article/getting-dirt-soil-testing. Accessed 4 June 2025.
3. Cox, William, et al. Soil Acidity and Liming: Basic Information for Farmers and Gardeners. North Carolina State Extension Publications, 1 Apr. 2020, https://content.ces.ncsu.edu/soil-acidity-and-liming-basic-information-for-farmers-and-gardeners. Accessed 4 June 2025.
4. Shapiro, Charles A., and Bijesh Maharjan. Nebraska Nitrogen Calculator. University of Nebraska–Lincoln Extension, 2024, https://cropwatch.unl.edu/nitrogen-tool/. Accessed 4 June 2025.
5. Sawyer, John, and Daniel Barker. “Corn Nitrogen Rate Calculator Update.” Iowa State University Extension and Outreach: Integrated Crop Management News, 10 June 2013, https://crops.extension.iastate.edu/cropnews/2013/06/corn-nitrogen-rate-calculator-update. Accessed 4 June 2025.