No-till corn production has struggled to be successful
in the Midwestern United States. No-till
farmers say it takes 7–9 years to transition from
conventional farming to long-term no-till. Using
a cover crop with continuous long-term no-till
shortens the time period to 2–4 years. No-till corn
yields are typically reduced 10–20% during those
This occurs for several reasons. First, initially
fewer nutrients are being released from the residues
deposited on the soil surface. Tillage allows surface
residues to decompose faster, releasing nutrients,
but it also destroys organic matter, resulting in less
storage of soil nutrients.
Second, in biologically active soils, the microbial
biomass is increasing in size and population, accumulating
N as amino acids and proteins and P as
DNA in microbes. This initially deprives no-till corn
of nitrogen and soil nutrients until the soil system
Third, the soil is building humus organic matter,
which requires N to decompose and stabilize the
organic molecule. Every 1% SOM requires 1,000
pounds of N, so if the N is being tied up and N is
not available, the soil microbes will utilize N before
the corn. Fourth, soil compaction from the previous
tillage causes denitrification from saturated/
water-logged fields, losing 40–60% of the available
N in the soil.
So to reverse this process, first cover crops
are grown to reduce soil compaction and improve
the recycling of C and N in the soil. Second, as the
microbial and humus organic matter levels build
up, N and P are more efficiently recycled in the
soil to the corn and no-till corn yields increase,
outperforming conventional tilled soils. Third, as
water infiltration increases and soils are better
aerated, denitrification and N losses decrease,
increasing the storage and recycling of N in crop
residues and organic matter (humus) and resulting
in more soil nutrients (N, P, and S) for the corn crop.
See OSU Extension fact sheet Understanding Soil
Ecology and Nutrient Recycling.
Reasons Why No-till Corn Struggles
1. Surface residue ties up nutrients and slows
down decomposition and release of nutrients.
2. Soil microbes tie up soil nutrients, especially N.
3. Long-term soil organic matter ties up nutrients,
4. Compaction and poor drainage causes denitrification
and loss of N.
5. Cold wet soils limit germination and planting.
Successful No-till Plus Cover Crops
1. Reduces soil compaction.
2. Improves C, N, P recycling.
3. Reduced N Losses from denitrification.
4. Increased nutrient storage in soil from increased