Tag: testing

What the Haney Test Revealed: Biological Benefits of Cover Crops in Action

Over the past few weeks, I’ve written about what cover crops like Sunn Hemp, Tepary Bean, and Cowpea leave behind in the soil and how their nutrient contributions stack up in standard soil tests. But it wasn’t until we looked at the Haney Soil Test results from March 2025 that we could truly see the biological influence each of these summer cover crops had on the soil. In this post, I’m sharing new insights drawn from those results and why I believe every grower should consider this test when evaluating cover crop performance.

Why the Haney Test?

Unlike standard chemical soil tests that only measure nutrient availability, the Haney Test adds a biological lens. It measures microbial respiration (CO₂-C), available organic nitrogen (Haney N), and gives an overall Soil Health Score. These indicators help us understand how biologically active the soil is and how much of the nutrients are likely to cycle into plant-available forms.

For organic and sustainable systems, this is vital. We’re not just feeding the crop—we’re feeding the soil.

All Plots Started Equal

Just to set the stage: all test plots had a rye cover crop terminated in early spring 2024 and were kept bare and weed-free through summer. The only difference among plots came when Sunn Hemp, Tepary Bean, or Cowpea was planted in August 2024. The check plot remained bare.

The Biological Winners and Stragglers

Here’s what the Haney Test results (click here to see reports) show:

  • Sunn Hemp had the highest CO₂-C (43.21 ppm), strong Haney N (74.74 lbs/ac), and the highest Soil Health Score (9.41). It fed the microbes and left behind a soil system ready to cycle nutrients. If you’re planting a high-demand crop like corn or grain sorghum, Sunn Hemp sets the table biologically.
  • Cowpea followed closely with a CO₂-C of 32.08 ppm, Haney N of 71.50 lbs/ac, and a Soil Health Score of 7.80. Reliable, balanced, and consistent—it’s a solid choice for improving soil function while conserving moisture and nutrients.
  • Tepary Bean, despite good forage quality and tissue N content (3.02%), showed low microbial activity (CO₂-C of 13.75 ppm) and the lowest Soil Health Score (6.43). It may decompose slower or produce compounds less favored by microbes. That’s not necessarily bad—it might serve longer-term fertility, but it’s not the best option for short-term nutrient release.
  • Check Plot (bare fallow) showed high mineral N (83.73 lbs/ac) and decent CO₂-C (37.14 ppm), but that’s misleading. There was no cover crop to feed soil life or cycle nutrients—just unutilized residuals from last year. Long term, this approach does not build soil health.
  • Click here to read a summary report – Summary of Soil Samples

What This Means for Growers

The biological boost from a cover crop can be measured and managed. Without the Haney Test, we’d only be guessing how much nitrogen or biological activity remains from cover cropping. We tell growers: don’t plant blind—use this test to make more informed fertility and management decisions.

Sunn Hemp again proved why it’s a leading summer cover crop for southern systems. Cowpea is a great second choice when water is limited or biological stimulation is still desired. Tepary Bean may have a role in longer rotations but isn’t the best for quick turnover systems.

Final Thought

We use cover crops for more than just erosion control. They’re engines of soil biology, nutrient cycling, and resilience. The Haney Test gives us a dashboard to read those engines.

If you’re not already using it, this is your sign: test for biology, not just chemistry.

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