Restoring Depleted Soils - Kitchen
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Transcript of Restoring Depleted Soils - Kitchen
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)