Transcript Slide 1

Organic Nitrogen
Inputs and the
Soil Food Web
What is the Soil Food Web?
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Interaction and combination of all the organisms
in the soil.
Made up of an incredible diversity of organisms.
They range in size from the tiniest one-celled
bacteria, to small vertebrates, and plants.
Fueled by Carbon, Nitrogen, minerals, water
and Oxygen.
Major components are the Nitrogen Cycle and the
Carbon Cycle.
Organic Nitrogen Inputs and the Soil Food
Web, Tim Stemwedel, COFI
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Who eats Who
The Soil Biology Primer (Chapter 2): By Elaine R. Ingham
Organic Nitrogen Inputs and the Soil Food
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What do Food Web Organisms Do?
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Break down plant residues
Release nutrients through microbial decomposition.
Microbes add stabilized nutrients to both the Active and
Stable fraction of the soil.
Fix nitrogen from the atmosphere for the plant’s use.
Fix Carbon and release CO2
www.soilfoodweb.com
Organic Nitrogen Inputs and the Soil Food
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Why is a diversity of organisms
important?
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Decomposition of Organic Matter requires diversity.
In this interaction, one organism will break down an organic
compound in the soil making the surplus by-products available
as nutrients for other organisms.
These organisms will in turn do the same thing and continue the
cycle, eventually making the nutrients available to plants
and animals.
The microbial concentration and diversity impacts the speed
and extent of nutrient cycling.
The Soil Biology Primer (Chapter 2): By Elaine R. Ingham
Organic Nitrogen Inputs and the Soil Food
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The Food Web in Short
Organic Matter
Organic Nitrogen Inputs and the Soil Food
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What are the requirements for an active
Soil Food Web?
Water
 Air
 Nitrogen (protein and other Nitrogen compounds)
 Carbon ( carbohydrates, i.e. - fuel) – Organic Matter
 Stable C:N ratio of below 15:1 - a higher number will
cause a deficit of available Nitrogen. (Soil C:N is 12)
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The Soil Biology Primer (Chapter 2): By Elaine R. Ingham
Organic Nitrogen Inputs and the Soil Food
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Carbon is in the form of
Organic Matter
Organic matter is the vast array of carbon
compounds in soil. Originally created by plants,
microbes, and other organisms, these compounds play
a variety of roles in nutrient, water and biological cycles.
 Organic matter can be divided into two major
categories:
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Active fraction
 Stabilized organic matter
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The Active fraction is divided into
living organisms
 fresh organic residue
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Organic Nitrogen Inputs and the Soil Food
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Carbon Cycle
Carbon is the Energy that Fuels the Microbes
Stabilized Carbon (humus)
Organic Nitrogen Inputs and the Soil Food
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Components of Soil Organic Matter
Soils with high organic matter content are the most productive,
store more water and contribute to a better environment.
Organic Nitrogen Inputs and the Soil Food
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Active Fraction
Used by living plants, animals and microbes for food.
 Most of the Cycling of Nitrogen and Carbon
Occurs here.
 The Active Fraction” is the “Short Term Bank”
where Nitrogen and Carbon are deposited and
released quickly.
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Organic Nitrogen Inputs and the Soil Food
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Stabilized Organic Matter
After years of decompostion, what remains are large,
complex compounds that few microbes can degrade.
(Humus)
 These hard-to-decompose, or stabilized, substances make up
a third to a half of soil organic matter.
The Stabilized Organic Matter is the “Long Term Bank”
where Carbon and Nitrogen are in a very Stable Form and are
released very slowly by microbial digestion.
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Organic Nitrogen Inputs and the Soil Food
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Increasing Microbial Activity
Organic Nitrogen Inputs and the Soil Food
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The Nitrogen Cycle
Organic Nitrogen Inputs and the Soil Food
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The Organic Nitrogen
Fertilizer Input Cycle
Organic Nitrogen Input is applied to the soil.
 Macro-organisms start the breakdown. (fungi,
protozoa)
 The result of this macrobial action is amines and
ammonia compounds. (plant food)
 A portion of the Nitrogen is bound into insoluble
organic matter called Humus
 Humus is a ligno-protein residue of microbial tissue.
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Organic Nitrogen Inputs and the Soil Food
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The Nitrogen Fertilizer Input Cycle
Bacteria (Microbes vs Macrobes) further break down
amines & ammonia compounds into nitrites. (some
loss to denitrification)
 Plants cannot use this form of nitrogen, so it is further
broken down by bacteria into nitrates.
 Plants can then absorb this form of nitrogen but this
is also the form that is lost to leaching.
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Organic Nitrogen Inputs and the Soil Food
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Understanding the Nitrogen Cycle
Nitrogen Cycling is Dependant on Carbon
 Nitrogen Cycling is Dependant on Microbes
 Nitrogen Cycling feeds the Soil (microbes) which the
Feed the Plant
 This occurs Primarily in the Active Fraction of the Soil
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 The
Important point is that BIOLOGY and
ORGANIC MATTER is REQUIRED!
Organic Nitrogen Inputs and the Soil Food
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Examples:
Organic
Nitrogen
With No
Biology
Organic Nitrogen Inputs and the Soil Food
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Examples:
Organic
Nitrogen
With
Biology
Organic Nitrogen Inputs and the Soil Food
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Organic Fertility Goals
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Increase the Soil Food Web in order to increase the
Activity of the Carbon and Nitrogen Cycles
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Increase the Active Fraction of Organic Matter
(This where the N mineralized)
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Improve the Efficiency of Fertilizer Inputs
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Maintain a C:N Ratio of the Soil Below 15:1 so we
don’t create a Nitrogen sink.
Organic Nitrogen Inputs and the Soil Food
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Differences in Input Characteristics
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Organic Nitrogen Inputs vary dramatically in how
they Affect the Soil Food Web and Nutrient Cycling.
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They may be Differentiated by the C:N Ratio
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C:N Ratio determines how much of the N stays in the
Active Fraction and how much goes to the Stable
Fraction
Organic Nitrogen Inputs and the Soil Food
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Differences in Input Characteristics
Organic Nitrogen Inputs may be Characterized by
their Plant Available Nitrogen ( PAN)
 PAN is the amount of Nitrogen that will be
Available to the Plant during the Growing Season
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In General:
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The higher the C:N ratio the lower the PAN
Organic Nitrogen Inputs and the Soil Food
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Organic Fertilizers
Organic Nitrogen Inputs and the Soil Food
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Plant Available Nitrogen (PAN)
PAN is the quantity of Nitrogen Available
during the growing season after a fertilizer is
applied.
 The amount of Nitrogen Immobilized is
dependant on the C:N Ratio.
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Higher the C:N Ratio the more N is
Immobilized
Organic Nitrogen Inputs and the Soil Food
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How to Calculate PAN
 Variables:
 C:
N Ratio of Organic Fertilizer
 Percent Nitrogen in Organic Fertilizer
 Total Pounds to be Applied
 Microbes have 8:1 C:N Ration
 Microbes use 25% Carbon for Growth, 75% for
Energy
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PAN Calculation
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Total N =
 (Pounds used) x (Percent Nitrogen)
Total Carbon =
 (Total N) x (C:N Ratio)
Carbon used for New Tissue =
 (Total C) x 25% (microbes use 25% of C for new tissue)
Nitrogen Immobilized =
 (New tissue) / C:N Ratio of Microbes (8:1)
PAN =
 (Total Nitrogen) – (Total Immobilized)
In-Season Efficiency
 (PAN) / (Total Nitrogen)
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Examples (PAN)
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Turkey Litter
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4% N, 12.5 C:N, 1000 lb/Acre
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Calculate for Total N:
1000 x 4% = 40 lbs
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Calculate for Total C:
40 x 12.5 = 500
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Calculate N Immobilized,
Using Microbe C:N of 8:
125 / 8 = 15.63
Calculate 25% Lb New Tissue:
500 x 25% = 125
Calculate PAN:
40 - 15.63 = 24.37
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Calculate In-Season Efficiency:
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24.37 / 40 = 61%
Organic Nitrogen Inputs and the Soil Food
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Examples (PAN)
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Protein Fertilizer
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8% N, 4.0 C:N, 1000 lb/Acre
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Calculate for Total N:
1000 x 4% = 80 lbs
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Calculate for Total C:
80 x 4 = 320
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Calculate N Immobilized,
Using Microbe C:N of 8:
80 / 8 = 10
Calculate 25% Lb New Tissue:
320 x 25% = 80
Calculate PAN:
80 - 10 = 70
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Calculate In-Season Efficiency:
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70/ 80 = 87.5%
Organic Nitrogen Inputs and the Soil Food
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PAN Efficiency
 Fertilizing
Material
Organic Fertilizers
PAN Efficiency
Layer Poultry Litter
 Broiler Poultry Litter
 Feather Meal
 Seabird Guano
 Liquid Fish
 Corn Steep
 Molasses Deriv.
 Liquid Guano

Organic Nitrogen Inputs and the Soil Food
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69%
53%
88%
94%
92%
88%
81%
97%
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Organic Fertilizers
Cost Analysis Including PAN
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Fertilizing Material
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Layer Poultry Litter 4% N
Broiler Poultry Litter 4% N
Feather Meal 12% N
Meat & Bone 8% N
Seabird Guano 12% N
Liquid Fish 5% N
Liquid Guano 4.5% N
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$/Ton 0r Gal. $/ lb N
$250
$250
$750
$600
$900
$4.00
$4.00
Organic Nitrogen Inputs and the Soil Food
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$4.55
$5.88
$3.57
$4.44
$4.00
$17.37
$18.35
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Organic Nitrogen Inputs and the Soil Food
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Other Issues Affecting SFW &
Nutrient Cycling
Excess Carbon
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Excess use of Low PAN Inputs will increase the
Soil C:N Ratio creating a Nitrogen deficit that will
reduce the effectiveness of soil applied Nitrogen.
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This excess Carbon (raw organic matter) is
unstabilized and serves as energy for microbes once
Nitrogen is present resulting in Nitrogen going to
the Stable Fraction.
Organic Nitrogen Inputs and the Soil Food
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Other Issues……….
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What about the mineralization rate of various
Inputs?
Inputs have various rates of mineralization
 Mineralization rate is affected by the Input,
Composition, Temperature, Soil Microbial Activity,
etc.
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Organic Nitrogen Inputs and the Soil Food
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Crop Demand vs Mineralization
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What do we do when the Crop Demand for
Nitrogen is less than the mineralization rate of
the Fertilizer Input?
Apply more fertilizer BUT How?
 What kind of fertilizer?
 When should it be applied?
 Can the cost be minimized?
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Organic Nitrogen Inputs and the Soil Food
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Decision Making Information
Mineralization Rate of Inputs
 PAN of Inputs
 Soil Nitrogen Levels of Nitrate, Ammonia and Total
Nitrogen
 Total Nitrogen from all Sources (fertilizer, soil,
compost, etc.)
 Crop Demand for Nitrogen
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Organic Nitrogen Inputs and the Soil Food
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Organic Fertilizers
Organic Nitrogen Inputs and the Soil Food
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Nitrogen Input Decisions
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Liquid or Dry Fertilizer
Dry Fertilizers have a 6 to 12 week Mineralization Rate
depending on the Product
 Liquid Fertilizers have a 0 to 6 week Mineralization Rate
depending on the Product
 In order to Synchronize Availability with Demand
higher rates of Dry Inputs compared to Liquid Inputs
will be needed due to the Mineralization Rate and
PAN
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Organic Nitrogen Inputs and the Soil Food
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Conclusions
The Food Web is the micro-organisms that
mineralize organic matter and produce humus for
future use and soil stability.
 Soil is comprised of Living/Fresh & Active or
Stable Organic Matter (Living/Fresh and Active is
more available)
 PAN is higher for Low C:N ratio Inputs. High C:N
contributes Nitrogen to the Stable Fraction
(i.e.: not this crop)
 Feed the Soil to Improve the SFW
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Organic Nitrogen Inputs and the Soil Food
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Further Conclusions
PAN affects the true cost of a product.
 Solubility and Availability is important if you need
a fast acting fertilizer.
 Use of very low C: N ratio Nitrogen fertilizers is
better (feed the crop directly) for short season crops
and Peak N demand periods
 Synchronizing applications with crop demand is
critical for success.
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Organic Nitrogen Inputs and the Soil Food
Web, Tim Stemwedel, COFI
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Organic Fertility Goals
Increase the Soil Food Web in order to increase the
Activity of the Carbon and Nitrogen Cycles
 Increase the Active Fraction of Organic Matter
(This where the N mineralized)
 Improve the Efficiency of Fertilizer Inputs
 Maintain a C:N Ratio of the Soil Below 15:1 so we
don’t create a Nitrogen sink.
 Treat short duration deficiencies with low C:N
Ratio Soluble liquids containing MINERALIZED
Nitrogen to increase PAN.
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Organic Nitrogen Inputs and the Soil Food
Web, Tim Stemwedel, COFI
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Thank You!

This presentation will be available at
www.organicag.com

Tim Stemwedel contact information:
7600 N. Ingram, Suite 121
 Fresno, CA 93711
 559-250-1245
 Email: [email protected]

Organic Nitrogen Inputs and the Soil Food
Web, Tim Stemwedel, COFI
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