Restoring Depleted Soils:

Cover Crops and Soil Health

Newell Kitchen

USDA-ARS Cropping Systems and

Water Quality Research Unit

Columbia, MO

February 18, 2015Cover Crops Iowa Conference, West Des Moines, IA

Consumables

“…. did not so much

collapse as consume

itself.”

How do we get away

from treating soil as a

consumable?

Recent Times

U.S. Piedmont used to be a major agricultural region

Cultivation brought immediate and devastating soil erosion

• In the U.S. Midwest, extensive

flat grasslands were plowed

and put into grain production

about 100 years ago.

• Multiple and damaging large

flood events caused severe

soil erosion and property

damage between 1926-1936.

Grain crop yields for many

fields actually declined when

compared to the previous

century (Bennett, 1939).

More Recently

• A 10-cm rainfall event created

gullies that followed the planter

rows (channeled by the planter

furrow)

• About 5-cm deep x 30-cm wide, of

a 76 cm-row spacing corn crop

• Erosion “consumed” 2 cm of topsoil

• Could be replaced by growing grass for 300-400 years

Few Years Ago

Sheet

Rill Bank

Channel

What is the impact of

past erosion on productivity?

• Average 7” topsoil lost since farming started ~120 yrs ago

• Impact on production today?

• Soybean: 7” x 0.7 bu/in/a/yr x $13/bu = $64/a/yr

• Corn: 7” x 2.9 bu/in/a/yr x $5/bu = $102/a/yr

• C-S rotation: average loss $83/a/yr

“… the slower the emergency, the less

motivated we are to do anything about it.”Dirt, David R. Montgomery

What do we know about

soil health and cover crops today that we

didn’t already know 30 years ago?

Hydrologic Buffer

Food, Biodiversityand Habitat

Nutrient Cycling

Filtering and

Buffering

Physical Stability

and Support

Soil Functions

Dysfunctional Soils

ARS-MU Centralia Field-Research Station

What has been the impact of a decade

of no-till and cover crops?

Long-Term Research Field

1991-2003

Corn-Soybean Mulch-Till

2004-present

Soybean-Wheat (N)

Soybean-Corn (S)

No-Till + Cover Crop

Average Annual Sediment Loss

32% of Watershed

Rate of Soil Formation

350% more @ Field

than Watershed

1991-2003

Mulch-Till

2004-present

No-Till + Cover Crop

Impact of CC and No-till

on Nutrient Loss

1991-2003

2004-present

Downside of Cover Crops

Female meadow voles have a

gestation period of three

weeks, have an average litter

size of five, and produce four

to five litters per year. They

reach sexual maturity at 40

days and have a reproductive

life span of 1 to 2 years

Soil HealthSoil Management Assessment Framework (SMAF)

Physical Score• bulk density

• water-filled pore space

• water-stable

aggregates

Biological Score• organic C

• B-glucosidase

• microbial C

• mineralizable N

Chemical Score• pH

• electrical conductivity

Nutrient Score• extractable P

• extractable K

SMAF Total Score (0-5 cm)

G+CC

Grass/Pasture

NT G

MT G

a

abbc

cc

d

Long-Term Research Field

1991-2003

Corn-Soybean Mulch-Till

2004-present

Soybean-Wheat (N)

Soybean-Corn (S)

No-Till + Cover Crop

~76 ~88

“How might we rethink the

conventional wisdom of

conventional agriculture to

find a way to work with

nature?”

Stop “trying to make soil

adapt to our technology.”

Use technology and innovation to

give us the tools to adapt to how

we manage soils.

Premise: Future agricultural will require innovation and technologies

to achieve a sustainable framework for managing soils.

Questions…..

Physical Score• bulk density

• water-filled pore space

• water-stable

aggregates

Biological Score• organic C

• B-glucosidase

• microbial C

• mineralizable N

Chemical Score• pH

• electrical conductivity

Nutrient Score• extractable P

• extractable K

SMAF Total Score (0-5 cm)