Soil Your Undies For Science

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Soil Your Undies Challenge

The Soil Your Undies Challenge is an experiment to find out how healthy your soil is and see the amazing work being done in the soil beneath our feet. Healthy soil gives us clean air and water, bountiful crops and forests, productive grazing lands, diverse wildlife, and beautiful landscapes. The Shiawassee Conservation District conducted their first ever Soil Your Undies Challenge in the summer of 2025. Ten pairs of cotton underwear were “planted”, and nearly all of them were found and “harvested”, showing varying degrees of decomposition. 

Soil is a busy community of life! Soil is filled with billions of microorganisms, working together to break down organic matter, hold water, resist erosion, boost nutrient cycling, and support plant growth. The more active these organisms (including bacteria, fungi, and earthworms) are, the healthier your soil will be. Healthy soil = healthy life!

The Process

Ten pairs of new, 100% cotton underwear were buried in different locations, each with varying land uses and soil conditions. They were buried 3-5 inches deep and placed flat for good soil contact. They were left untouched for 62-79 days. 

The Expectations

Carbon is a common element in all organic compounds – including cotton. When the 100% cotton underwear is buried in the soil, the organisms will see it as food. The healthier the soil, the more microorganisms there will be. The more active they are, the more decomposition of the underwear will occur. 

The Results

Site 1: Corn Field
Site 2: Pumpkin Field
Site 3: Soybean Field with Manure

Site 1: Corn Field

  • Field Data: Crop field operations include crop rotation of corn, soybeans, wheat, and hay; cover crop mix of radish, turnips, and soybeans planted after wheat; 100% no-till for 40+ years.

  • Soil Type: Wawasee Loam 6-12% slope.

  • Underwear “Planted”: 6/23/2025

  • Underwear “Harvested”: 9/5/2025

  • Days Buried: 74

  • Additional notes: As expected, this site had significant breakdown of the cotton material, with only the elastic band and seams remaining. The reason for this is due to the well-established microbial community built up form 40+ years of not tiling the soil. Those finding show that the untilled soil was extremely health and capable of growing crops without disturbance.

Site 2: Pumpkin Field

  • Field Data: crop rotation of corn, soybeans, wheat, hay; cover crop of radish, turnips, soybeans planted after wheat. 100% no-till, until prior to planting 2025 pumpkin crop.

  • Soil Type: Kendallville sandy loam.

  • Underwear “Planted”: 6/23/2025

  • Underwear “Harvested”: 9/5/2025

  • Days Buried: 74

 Site 3: Soybean Field with Manure

  • Field Data: crop rotation of corn, soybeans, wheat; no-till; cow manure surface applied in 2025.

  • Soil Type: Conover loam

  • Underwear “Planted”: 6/23/2025

  • Underwear “Harvested”: 9/10/2025

  • Days Buried: 79 

Site 4: Backyard Garden
Site 5: Plowed Field
Site 6: Warm Season Grass Stand

Site 4: Backyard Garden

  • Field Data: vegetable garden; roto-tilled every 3 years with compost (last tilled 2023); a multi-species cover crop planted Fall 2024.

  • Soil Type: Conover loam

  • Underwear “Planted”: 6/21/2025

  • Underwear “Harvested”: 9/7/2025

  • Days Buried: 78

Site 5: Plowed Field

  • Field Data: field is plowed each year in the spring; sunflowers were planted in 2025 but did not germinate.

  • Soil Type: Conover loam

  • Underwear “Planted”: 7/1/2025

  • Underwear “Harvested”: 9/5/2025

  • Days Buried: 66

 Site 6: Warm Season Grass Stand

  • Field Data: field is well established to native warm season grasses; a prescribed burn is conducted every 5 years for maintenance.

  • Soil Type: Conover loam

  • Underwear “Planted”: 7/1/2025

  • Underwear “Harvested”: 9/5/2025

  • Days Buried: 66

Site 7: Sunflower Field
Site 8: Woodlot
Site 9: Soybean Field

Site 7: Sunflower Field

  • Field Data: crop rotation of corn, soybeans, oats, and sunflower; cover crop of oats and radish; vertical tillage in the spring, tillage of fall inline ripper and occasional chisel plow.

  • Soil Type: Celina loam

  • Underwear “Planted”: 7/2/2025

  • Underwear “Harvested”: 9/10/2025

  • Days Buried: 70

Site 8: Woodlot

  • Field Data: trees managed for production

  • Soil Type: Wawasee loam 6-12% slope

  • Underwear “Planted”: 7/5/2025

  • Underwear “Harvested”: 9/5/2025

  • Days Buried: 62

  • Additional Notes: Underwear was buried on a hill.

Site 9: Soybean Field

  • Field Data: no-till field; no cover crops

  • Soil Type: Wawassee loam 6-12% slope

  • Underwear “Planted”: 8/30/2025

  • Underwear “Harvested”: 9/5/2025

  • Days Buried: 62

  • Additional Notes: Underwear buried in low spot, adjacent to woodlot.

Site 10: Pastureland

  • Field Data: field part of a prescribed grazing plan

  • Underwear “Planted”: 8/22/2025

  • Underwear “Harvested”: Attempted to harvest 9/5/2025. Underwear was not found.

An Unexpected Outcome

Due to the dry weather through the summer and intense rainstorm dropping over 2 inches of rain prior to unearthing, we saw some interesting results at a few of the sites: 

  1. Native grass stand undies were not as decomposed as expected. This is likely due to the slowdown of microbes in the upper layers of the dry soil.

  2. Plowed field undies were very WET! The excessive rain may have added extra decomposition to this pair. Typically, a conventionally plowed field may have a plow pan restricting water infiltration leading to increased microbial activity in the upper layers of soil.

  3. Forest undies were not as broken down as we expected. This is also likely due to the dry weather conditions. Forest soil is highly productive, but the upper layers may not be where microbes are the most active.

Conduct Your Own Soil Your Undies Challenge

It’s easy to conduct your own healthy soil experiment. All you need is a pair of 100% cotton underwear. Bury them 3-5 inches deep, laying them flat for good soil contact, and leave them for 8 weeks. Don’t forget to mark the spot you buried them! 

Do you want to participate in the 2026 Soil Your Undies Challenge with us? Reach out to the Shiawassee Conservation District for more information!




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