This presentation gives an overview of soil health and the role of cover crops. Presented at the WIN field day in Shelby Iowa, June 2014

1. Tim Reinbott and Kerry Clark

2. Soil health has three main
components
• Sustained biological productivity
• Environmental quality
• Plant and animal health

3. 3
Kristen Veum and Robert Kremer

4. SOM is derived from
Plant residue (both
litter and roots)
Animal remains and
excreta
Living soil microbes
(microbial biomass)
Over time fresh
organic material is
transformed into soil
organic matter
Crop
Residues
Bacteria
Fungi
Actinobacteria
SOM
4

5. Loss of Organic
Matter
Soil structure
Soil microbial
biomass
Release of CO2
Soil Erosion
Why Till?
Weed Control

8. 3000
3500
4000
4500
5000
5500
6000
6500
7000
7500
80001900
1910
1920
1930
1940
1950
1960
1970
1980
1990
Year
SoilC(gm-2)
Conventional
Tillage
Reduced
Tillage
53% of 1907
61% of 1907
8

9. 20 – 40% of SOM is lost on cultivation
Management effects on SOM
Tillage (disturbance)
Chemical Fertilization
Manure
Residue Retention
Crop
Crop Rotation
Cover Crop
9
Decline in SOC from Sanborn
Field Plots showing increase
following the return of residues
beginning in 1950

10. 10

11. 58% Carbon
P, S, and other
nutrients
95% of Soil
Nitrogen in SOM

13. Soil Life (macro)
Help create soil structure and
break down larger plant
residues
• Earthworms
• Nematodes
• Beetles
• Ants
• Termites
• Springtails

14. One tablespoon of soil has approximately 1 billion soil
microbes:
• Bacteria: 3,000,000 to 500,000,000
• Actinobacteria: 1,000,000 to 20,000,000
• Fungi: 5,000 to 1,000,000
• Yeast: 1,000 to 1,000,000
• Protozoa: 1,000 to 500,000
• Algae: 1,000 to 500,000
• Nematodes: 10 to 5,000

15. This is the mass
equivalent of two cows per
acre that need to be fed
Soil organisms
are much like
cows, they need
inputs of plant
residues for food
and energy
Specifically, they
need the carbon
that is contained
in plant residue
and soil organic

18. • Natural ‘tillage’ by earthworms
• Burrows enhance water infiltration and soil
aeration. This reduces runoff, and increases soil
water storage for dry spells.
• Worms redistribute organic matter and nutrients
throughout the topsoil layer.
• The soluble nutrient content of worm casts is
considerably higher than that of the original soil.

19. • General saprophytic fungi (i.e.,
decomposers)
• Produce glomalin – glue in aggregation
• Nutrient cycling! Especially hard to
decompose SOM

20. Slake Test
Fungi Hyphae

21. Bacteria bridge short
distances, but fungi
can work over long
distances to explore
and to transport
nutrients thanks to
their fine hyphal
system.
Thus, mycorrhizas
(symbioses between
roots and fungi) have
been very successful
Photo: David Read

22. • Some cause disease
• Can keep bacterial and fungal pathogens in check-
keep balance in microbe world
• Bacterial feeders may dominate in tilled plots,
and herbivorous nematodes may dominate in no-
till (Lenz & Eisenbeis, 2000)
• Bacterial feeders may be stimulated by tillage (Wardle,
1995)
• Tillage may promote a bacterial-dominated
decomposition pathway (vs. fungal), which in turn
supports bacterial feeders.

23. • Have cells like bacteria and filaments like fungi –
(were misclassified as fungi)
• Decompose cellulose and chitin & important in
organic matter and nutrient cycling
• Tend to be drought/temp resistant
• Responsible for the “earthy” smell of soil due to
geosmin
• May produce special chemicals when stressed
(e.g., under low P, N, or O2) or secondary
metabolites (e.g., antibiotics), & some are
pathogenic
Photo: Wikipedia

24. Increased aggregate
stability
Increased water
infiltration
Reduced runoff
Increased water
holding capacity
Decreased erosion
Improves aeration
and macroporosity
Avoid this!
Photo: iastate.edu

25. LONG TERM PASTURE
TILLED IN A CORN/SOYBEAN/WHEAT
ROTATION

26. 0
500
1000
1500
2000
2500
3000
Biomass(mg/g)
Cropping Type
PLFA Analysis at Bradford Research Center
Bacteria
Actinomycetes
Fungi
Protozoa
No Protozoa in Corn/Soybean Rotations.
Micro Organism biomass highest in perennial cover
Bradford Research Center, 2012

27. 0
50
100
150
200
250
300
350
400
450
500
Biomass(mg/g)
Cropping System
PLFA Sub-categories at Bradford
Rhizobia
Arbuscular
Mycorrhizal
Saprophytes
Soybean-Conventional-had no Mycorrihizae or Rhizobia

28. Scientists describe 3 pools of soil organic matter
**really is a continuum of decomposition
Passive SOM
500 – 5000 yrs
C/N ratio 7 – 10
Active SOM
1 – 2 yrs
C/N ratio 15 – 30
Slow SOM
15 – 100 yrs
C/N ratio 10 – 25
• Recently deposited organic material
• Rapid decomposition
• 10 – 20% of SOM
• Intermediate age organic material
• Slow decomposition
• 10 – 20% of SOM
• Very stable organic
material
• Extremely slow
decomposition
• 60 – 80% of SOM
28

29. Results are read in a spectrometer in lab or
field or from a color card
Potassium
Permanganate Test
KMnO4 oxidizes active carbon. The
purple color of the chemical
changes to pink the more active
carbon there is in a soil sample.

33. Table 3. PLFA concentrations
Treatment Total Gram+ Gram− Actino Fungi AM Fungi Protozoa
Bare 15.07 DE 4.45 CD 3.94 DE 2.17 BC 0.42 BC 0.58 DE 0.07 B
Black Poly 13.27 E 4.10 D 3.28 E 1.87 C 0.36 C 0.48 E 0.04 B
White Poly 15.49 CDE 4.61 BCD 4.04 DE 2.20 BC 0.45 BC 0.59 CDE 0.08 AB
Rye 19.33 AB 5.48 AB 5.58 AB 2.69 A 0.61 AB 0.85 A 0.18 AB
Rye Roots 18.39 ABC 5.26 ABC 5.16 ABC 2.53 AB 0.60 AB 0.73 ABC 0.14 AB
Rye Shoots 16.72 BCD 4.90 BCD 4.51 CD 2.41 AB 0.44 BC 0.66 BCD 0.11 AB
Vetch 20.38 A 5.82 A 5.76 A 2.71 A 0.73 A 0.81 AB 0.20 AB
Vetch Roots 19.04 AB 5.47 AB 5.36 ABC 2.59 AB 0.54 BC 0.72 ABCD 0.27 A
Vetch Shoots 17.39 BCD 5.05 BC 4.77 BCD 2.46 AB 0.55 ABC 0.71 ABCD 0.13 AB
Plastic Has Much Less Than Cover Crops!!
Buyer, et al, 2010

35. Doug Peterson

36. 140°
F
130°
F
100°
F
70°
F
Soil bacteria die
100% moisture lost through
evaporation & transpiration
15% moisture is used for growth
85% moisture lost through
evaporation & transpiration
100% moisture is used for growth
J.J. McEntre, USDA SCS,
Kerrville, TX, 1956

38. Surface crust impedes infiltration.
Open, granular surface structure
enhances infiltration.
Biopores (earthworm channel)
enhance infiltration.
Conventionally
tilled field
No-till field
38

39. Aggregate Stability-Better Water
Infiltration
Fungal-produced
glomalin helps
bind aggregates
http://ed.fnal.gov/trc_new/pandp/soil_research/soil
_aggregates.html
Wright, et al., 1999

40. From Steve Groff
Cover Crop No Cover Crop

41. No-Till With Cover Crop Took Several Hours For
Water To Run-Off

47. Reinbottt@Missouri.edu
573-884-7945