Did the 2025 Drought Impact Soil Test Results?

In short, yes—for those areas that experienced a D3 drought. For much of the region, D3 drought conditions developed partway through the fall harvest of 2025 and extended through the spring of 2026. Over the past few years, areas impacted by D3 drought have shown consistent effects on soil samples. Observations suggest that late D2 into D3 droughts can significantly influence soil test results.

Below are previous blog posts with additional information on how drought impacts soil samples:

• algreatlakes.com/blogs/news/impacts-of-the-dry-2024-fall
• algreatlakes.com/blogs/news/soil-testing-after-a-drought-originally-posted-2012

How can you tell if your data is impacted?
The clearest indicator is areas within fields showing very high soil pH. While not ideal to manage, these locations are best suited to assess drought impact. These areas typically have a soil pH of 8.1 to 8.2 and are often associated with free calcium carbonate in the soil—meaning there are more carbonates (lime) present than can chemically react.

High soil pH is usually accompanied by very high calcium (ppm) levels and calcium cation saturation of 80% or greater in mineral soils with a CEC of 10–20, and over 90% in sandy soils.

This situation is unique because the acid-neutralization reaction stalls when soil pH reaches 8.1 to 8.2 and cannot increase further. At that point, unreacted carbonates (lime) remain in the soil, available to neutralize future acid inputs. This reserve capacity keeps soil pH elevated for the foreseeable future. These conditions can result from excessive lime applications or naturally occurring carbonates.

However, in areas with free or excessive carbonates that are severely impacted by drought, soil pH may drop below 8.0. In parts of northwest Indiana and northwest Ohio from fall 2025 through early spring 2026, soil pH values of 7.5 to 7.6 were observed in areas that historically tested between 8.0 and 8.2 - representing an approximate 0.5-unit decrease.

Soil test potassium (K) declines are less predictable but tend to occur under similar conditions. Reports indicate estimated declines of 15–30% in soil test K levels compared to recent historical values. While soil pH typically recovers quickly with increased rainfall, potassium levels may remain depressed for several months.

Some notable phosphorus (P) declines have also been reported. However, these may be influenced by reduced phosphorus application rates over the past few years.