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COVER CROPS AND THEIR TOP 10 IMPACTS ON SOIL HEALTH

COVER CROP

TRAINING MODULE

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Developed by

Dr. Rob Myers, University of Missouri and NCR-SARE

Reviewed by

Dr. Abby Wick (North Dakota State University) and Dr. Eileen Kladivko (Purdue University)

Funded by

Walton Family Foundation

These training modules are being made available by free use of other educators through University of Missouri and the Midwest Cover Crops Council, which participated in the WFF project supporting development of these modules and provided many of the technical reviewers.

All photos are by Rob Myers, University of Missouri, unless otherwise noted.

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Photo credit – Edwin Remsburg

What’s happening underneath our feet?

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#1 Cover crops feed the soil food web

Credit: NPR.org

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From NRCS

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When there are no living roots, �soil organisms go short on food

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“Feeding all the soil organisms below ground in one acre is like feeding two African elephants.” Jerry Hatfield, USDA-ARS

Credit: Soil Health Institute, Illustrator: Chelsea Wright

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Can we harvest solar energy with cover crops an extra 7-8 months of the year to feed the soil?

Revitalizationews.com

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#2 Cover crops increase earthworms

Iowa Learning Farms

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Earthworms are soil engineers

Photo credit – Edwin Remsburg

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�WORM TYPES��Nightcrawlers�(anecic)��Red worms�(epigeic)��Pale/gray worms�(endogeic)

http://ecoserv.weebly.com/worms.html

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#3 Cover crops build soil carbon and organic matter

Restoring soil carbon

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From: Weil and Brady. 2017.The Nature and Properties of Soils. 15^th edition. Pearson.

This figure is from the main soils text book used for undergrad soils classes in the U.S., called “The Nature and Property of Soils” by Ray Weil and Nyle Brady.

In short, the diagram depicts how on average, half the soil organic matter has been lost from cultivated soils in the U.S. Of course the amount of soil organic matter loss in individual fields varies, some have lost more and some less.

When tillage of formerly undisturbed prairie and forest soils started, loss of soil organic matter and soil carbon was fast at first in the first few decades, but even with more recent conservation tillage implementation, loss of soil organic matter has continued.

The good news is that soil organic matter can be rebuilt over time, with the active carbon fraction or active organic matter rebounding first when cover crops are implemented. Over time, passive organic matter (the more stabile faction) will gradually start to rise.

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Soil organic matter

wmearthcare.com

Soil water holding capacity
Feeds soil organisms
Supply of crop nutrients
Improves crop rooting

www.smarthacks.tv

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#4 Cover crops help manage soil nutrients

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Nitrogen input – output model

Get a bushel of corn for every pound of nitrogen fertilizer applied

www.farmfutures.com

www.cornandsoybeandigest.com

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Nitrogen impacted by soil microbes

www.integritysoils.co.nz

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Scavenging nutrients

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#5 Cover crops keep the soil covered

Photo credit – Edwin Remsburg

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Cereal rye mulch layer in soybeans

Increasingly, farmers are letting cereal rye grow fairly large ahead of soybeans, sometimes 4-5 feet tall. In some cases the rye is rolled before planting the soybeans. More often, farmers are planting the soybeans directly into the standing rye. The planter will knock down much of the rye. This photo shows rye that has been rolled, either right before or after planting the beans. The rye mulch helps control many weeds, although whereever there are gaps in the rye mulch, some weeds may poke through.

The residue from cover crops can help moderate soil temperatures keeping it cooler, especially until the cash crop leaves (corn, soybeans) shade the row completely. The cooler soil temps help soil microbes function more effectively and reduces stress on the cash crop on hot sunny days.

Cover crop plants and residue can also help trap snow in the winter.

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Prairieview.mustangsps.org

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#6 Cover crops add biodiversity

ABOVE GROUND

and more importantly

\/

BELOW GROUND

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Crimson clover, hairy vetch, and rye

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#7 Cover crops get rain into the soil

Phillips Conservation District

Rainfall simulators have become a common way of illustrating the role of cover crops, no-till and other soil management on rainfall infiltration. In the photo sequence for this slide, cover crops are in the center soil tray and tilled soil immediately to the left of the cover crops. Each metal tray hold about 2 inches of soil and has perforation on the bottom of the tray to allow water to pass through. If the simulated rainfall from an overhead sprinkler (typically an inch of “rainfall” is supplied in these demonstrations) runs off into the front jar (as with the tilled soil in this photo), it’s a sign of poor rainfall infiltration. Where a lot of water goes into the back jar, such as with the cover crop sample, the rainwater is soaking through.

This dynamic is even more apparent when the soil trays are flipped over after applying the simulated rainfall. The tilled soil is in the front, and none of the inch of water has soaked through. This happens because the soil seals up as the rain starts to hit it, and no macropores exist. It seems surprising that a loosely tilled soil can’t soak up the rain, but this is what happens in most silt-loam or clay-loam soils!

The cover crop soil by contrast has let the rainfall soak into the ground, largely because there are macropores created by earthworm tunneling and cover crop roots, plus there is better soil aggregate structure. This greater ability to take up rain water can help fields be planted earlier in wet springs, by avoiding soil ponding after rains, and can really help in dry years by soaking in every bit of rainfall rather than helping it run off.

As rainstorms have gotten more intense, it’s even more important to have resilient soils that can soak up the rainfall.

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#8 Cover crops reduce compaction

Corn and Soybean Digest

Indiana Prairie Farmer

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Soil aggregates = Soil building blocks

From NRCS

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Which is less expensive?

Deere.com

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#9 Cover crops support integration of livestock with row crops

OnPasture.com

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Soils developed with herbivores

Missouri Ruralist

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Cover crops can be very high quality forage

Jim Isermann farm, Illinois – Photo credit: Progressive Forage

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#10 Cover crops help stop erosion

Photo credit: NRCS

Photo credit: Edwin Remsburg

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Cover crop impact on water erosion

Cover crop root channels and earthworm tunnels get rain to infiltrate

USDA-ARS

Living and dead cover crop leaves and stems intercept raindrops

Cover crop roots anchor the soil and residue in place

http://wiki.ubc.ca/LFS:SoilWeb

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Cover crop impact on wind erosion

Photo credit: Bruce MacKellar, Michigan State Univ.

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Erosion connection to soil health

MOST INTENSE BIOLOGICAL ACTIVITY NEAR THE SURFACE

MOST NUTRIENTS AND ORGANIC MATTER NEAR SURFACE

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Photo credit: Edwin Remsburg

BUILDING SOIL HEALTH