THE LIVING, THE DEAD AND THE VERY DEADFred Magdoff 10/18/2017 2 • Bacteria • Fungi • Protozoa...
Transcript of THE LIVING, THE DEAD AND THE VERY DEADFred Magdoff 10/18/2017 2 • Bacteria • Fungi • Protozoa...
10/18/2017
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THE LIVING, THE DEADAND
THE VERY DEAD
The Role of Soil Organic Matter in the N Cycle
SOIL FORMING PROCESSES LIVING ORGANISMS
• Soil differences related to difference in plant growth over time
• Macroscopic
• Microscopic
• Human
BIOLOGICAL SOIL PROPERTIES
“Soil Organic matter….
The living…The dead….
And the very dead”.
Fred Magdoff
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• Bacteria
• Fungi
• Protozoa
• Nematodes
• Arthropods
• Algae
• Plant roots
• Earthworms, and other larger animals
O.M. represents about 15% of the total soil organic matter.
O.M. represents about 15% of the total soil organic matter.
SOIL ORGANIC MATTERTHE LIVING
SOIL ORGANIC MATTERTHE DEAD
• Crop residue
• Green manure
• Livestock manure
• Sewage sludge
Source of carbon and nutrition for soil microbes.Source of carbon and nutrition for soil microbes.
SOIL ORGANIC MATTERTHE VERY DEAD
Humus
• A product of plant and animal remains.
• More complex than organic matter
• More difficult for other organisms to breakdown.
• Humus can last for many years in the soil.
The “Good Stuff” that makes-up our fertile soils.
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TEMPORARY N LOSSImmobilization-Mineralization
Time
Plant-available
“+” Change
Activity of microorganisms
Add sawdust C:N = 500:1
NITRATES
MICROBES
Sawdust totally degraded
C:N ratio and direction of reaction
• C:N ratios of 20:1 or less (Mineralization)
• C:N ratios of 30:1 or more (Immobilization)
• C:N ratios of 20:1 to 30:1 (No net change)
SOIL ORGANIC MATTERCARBON-to-NITROGEN RATIO (C:N)
OUR C:N Ratio 18/3 = 6:1
SOIL ORGANIC MATTERHUMUS
Stable Organic MatterC:N Ratio = 10:1
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COMMON C:N RATIOS
GREEN MATERIAL C:N Ratio BROWN MATERIAL C:N RatioAged Chicken Manure 7:1 Leaves 70:1Food Scraps 17:1 Straw/Hay 90:1Coffee grounds 25:1 Wood chips 700:1Grass clippings (fresh) 25:1 Shredded newspaper 175:1Fresh weeds 20:1 Nut Shells 35:1Fruit waste 30:1 Pine Needles 80:1Rotted manure 20:1 Corn Stalks 60:1Seaweed 19:1 Wheat Straw 60:1General garden waste 30:1
Maintaining Soil O.M.
100%
50%
Begin permanent sod
25 years after tillage began
Tillage begins
Time
SOIL ORGANIC MATTERMINIMIZING LOSS
• Minimize tillage
• Add residues/green manure
• Maintain environment for good microbes
• Control soil erosion
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7.MINERALIZATION
6.4.
NITRIFICATION5.
1.
FIXATION
Plant Uptake
DENITRIFICATION
VOLATILIZATION
LEACHING
IMMOBILIZATION
7.MINERALIZATION
6.4.
NITRIFICATION5.
1.
FIXATION
DENITRIFICATIONIMMOBILIZATION
LECTURE 4 ASSIGNMENT
• Watch this short Youtube video and offer a comment about what you see.
https://www.youtube.com/watch?v=Mxp1nnrUG0Q
Bioturbation: The reworking of soils and sediments by animals or plants.
Soil Fauna: the organisms of the soil considered as a whole.
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ADDITONAL READING
• Building Soils for Better Crops is a one-of-a-kind, practical guide to ecological soil management, now expanded and in full color. It provides step-by-step information on soil-improving practices as well as in-depth background—from what soil is to the importance of organic matter. A must-read for farmers, educators and students alike.
http://www.sare.org/Learning-Center/Books/Building-Soils-for-Better-Crops-3rd-Edition