Improving Soil Organic Matter Quality

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Improving Soil Organic Matter Quality
Practical options for vegetable crop production
systems
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SOM
Mineral particles
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SOM is a complex mixture
Living organisms
Biologically active SOM
Recent residues
Humus
Stable SOM
Adapted from Magdoff and Weil (2003)
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HUMUS

• Extreme chemical complexity
• Resistance to further decomposition
• High specific surface and negative charge
• Dark color

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Humus adsorbs ions and molecules
Adapted from Brady and Weil (2002)
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Humus increases buffer capacity
Havlin et al. (2001)
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Humus increases plant available H20
Adapted from Brady and Weil (2002)
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Organic matter functions mainly as it is
decayed and destroyed. Its value lies in its
dynamic nature. W. Albrecht, 1938
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The Soil Stomach
Bacteria Fungi Algae Protozoa Nematodes Microarthr
opods Enchytraeids Earthworms Ants, termites,
spiders Mollusks Others rodents, snakes,
voles, amphibians, etc.
Body size increasing
Microflora
Microfauna
Mesofauna
Macrofauna
Megafauna
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BACTERIA
cocci
bacillus
filamentous
spirilla
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FUNGI
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SOM energizes biologically mediated processes
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The metabolic potential of soil microbial
communities greatly exceeds organic inputs to
soils
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Why does organic matter accumulate in soils ?
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Blechh !!! Tastes Bad !!!!
Biochemical recalcitrance
How do you expect to live off this stuff ???
Mineral protection
I cant get if off, you try !!
Fe
Al
We already are !!!!!!
Yuck !!!!! Sure is gritty !
Physical protection
Theres gotta to be a way inside !!!
Hey !! Theres good stuff in there !!!!
Adapted from Jastrow and Miller (1997)
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How much is enough ??
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Understanding inherent soil variation
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Clay minerals
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Relationship between fine mineral fraction and SOM
Magdoff and Weil (2004)
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Blackland soils of North Carolina
Lily (1981)
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There are many ways to measure SOM
Strek and Weber (1985)
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Permanganate oxidizable C a routine test for
active soil C ??
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Spading machine
http//www.tramsales.com/vp.html
Cool animation !!!
http//www.timmenterprises.com/machines/spader2.ht
m
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What does tillage do to soil ?
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Adapted from House and Parmelee (1985)
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Microbial activity in contrasting tillage systems
Havlin et al. (1999)
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What is tilth ???
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Good Tilth
Poor Tilth
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Aggregate stability is a key component of good
tilth
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Macroaggregates often form around particulate
OM. Processes that impact aggregation impact SOM
dynamics
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SOM reduces bulk density
Magdoff and Weil (2004)
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Soil pore networks
White zones are pores gt 0.1mm
No-till soil
Tilled soil
(Young and Ritz, 2000)
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Managing SOM
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On-farm sources of OM
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Off-farm sources of OM
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The many benefits of organic mulches
Control erosion
Nourish soil fauna
Suppress weeds
Improve soil structure
Increase infiltration
Moderate soil temperature
Supply nutrients
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N and P from long-term applications of compost
Compost nutrient content 1.7 N 1.2 P
Tons of compost to supply 150 lbs of N/acre
Cummulative P build up in lbs/acre
80
3000
60
2000
P in excess of crop removal
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1000
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3 6 9 12
3 6 9 12
YEARS
YEARS
Adapted from Magdoff and Weil (2004)
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Effect of compost maturity on tomato seedlings
Chen et al. (2004)
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Multi-functional cover crops
Cover Crops
Adapted from Magdoff and Weil (2004)
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Erosion Control Practices
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No-till or Minimum Tillage
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The fence post principle
Adapted from Schriefer (1984)
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Understanding organic resource quality
(Giller, 2000)
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Impact of high CN ratio residues on min-N
http//res2.agr.ca/stjean/publication/bulletin/nit
rogen-azote_e.pdf
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Potential for poor synchrony
Available for loss
Adapted from Robertson et al. (1998)
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Seasonal changes in mineralizable N
Adapted from Magdoff and Weil (2004)
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Crop Rotation
High residue crops
Cover crops
Forages
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Plant growth promoting rhizobacteria (PGPR) feast
on root exudates
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Vermicompost contributes to healthy roots
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Decomposition of particulate organic matter (POM)
contributes to disease suppression
Disease Suppression
Damping off
Adapted from Stone et al. (2004)
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Innovative Cover Cropping
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Bailey and Lazarovits (2003)
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