Recently, the Rice Soil and Water Conservation District (SWCD) conducted a county-wide visual survey to assess soil residue coverage resulting from various tillage practices. The level of residue—crop material left on the field after harvest—is a key indicator of conservation tillage and an important line of defense against soil erosion, runoff, and organic matter loss.
In 2025, we surveyed 230 miles of crop fields, stopping every half mile to visually estimate soil coverage on both sides of the road. This yielded 920 data points across corn and soybean fields. Surveyors used a calibration method that included physically measuring residue coverage by counting plant residue every six inches over 50 feet.
Understanding Residue Coverage
We classify residue coverage into three categories:
§ Conservation Tillage (≥30% residue) – Includes No-Till, Strip-Till, and Mulch-Till practices.
§ Reduced Tillage (15–30% residue) – Partial residue retention.
§ Conventional Tillage (<15% residue) – Practices like moldboard plowing or disk-ripping that leave the soil largely exposed.
In addition to residue estimates, we documented the use of heavy land rollers and the presence of cover crops. Rolling can help with harvest efficiency but increases topsoil compaction, runoff, and wind erosion risk. Cover crops, on the other hand, are a protective measure that enhances soil health.
Corn Fields: Conservation Setbacks
Historical vs. 2025 Comparison:
§ ≥30% residue: Decreased slightly from 16.3% (1998–2014 avg.) to 15% (2025)
§ Within this group, No-Till/Strip-Till doubled from ~4% to ~8%
§ 15–30% residue: Dropped from 30.5% to 23.9%
§ <15% residue: Increased from 52.4% to 61.1%
These numbers point to a trend in the wrong direction: the majority of corn fields (85%) in 2025 had residue levels below conservation tillage standards. While it’s encouraging to see growth in No-Till and Strip-Till practices, they haven’t been adopted widely enough to offset the increased use of conventional tillage.
Soybean Fields: Mixed Progress
Historical vs. 2025 Comparison:
§ ≥30% residue: Slight decrease from 48.6% to 47.3%
§ No-Till/Strip-Till increased ~4%, while Mulch-Till dropped ~5%
§ 15–30% residue: Increased from 27.7% to 40.4%
§ Most of these were estimated at the lower end of the range (~15%)
§ <15% residue: Decreased from 23% to 12.2%
Soybean fields showed some progress, particularly with reduced use of conventional tillage. However, most fields that shifted from conventional ended up in the 15–30% range—barely above the conservation cutoff. Notably, 38% of soybean fields were also rolled after planting, further reducing soil protection.
Summary: Where We Stand
Overall 2025 Residue Coverage (Corn + Soybeans Combined):
§ ≥30% residue: 30.6%
§ 15–30% residue: 32.0%
§ <15% residue: 37.4%
This means nearly 70% of Rice County’s row crop acres in 2025 had less than 30% surface residue—falling short of conservation tillage benchmarks. While this is disappointing, there are promising signs.
The chart visualizes the changes in soil residue coverage for corn and soybean fields between the 1998–2014 period and 2025 clearly shows:
§ A decrease in high-residue (>30%) corn fields.
§ A drop in low-residue (<15%) soybean fields.
§ A shift of many fields into the mid-range (15–30%) category—especially for soybeans.
We are seeing a slow but steady rise in the adoption of No-Till and Strip-Till, especially by farmers who recognize long-term benefits such as lower input costs and comparable yields. The increased use of cover crops is another encouraging trend.
Crucially, we’re hopeful that financial support will be expanding. Programs like the Minnesota Department of Agriculture’s Soil Health Equipment Grants, the Board of Water and Soil Resources’ watershed-based funding, and the pending USDA/State of Minnesota Soil Health Program will help remove economic barriers to adopting conservation practices.
Looking Ahead
We extend our gratitude to Ryan Lermon of the MN Extension Service for assisting with this year’s survey. The Rice SWCD remains committed to supporting farmers through education, technical assistance, and access to conservation funding. Our soil is one of our most vital natural resources—we all have a role in protecting it for generations to come
