organic nitrogen inputs and the soil food web. 2 what is the soil food web? interaction and...

Organic Nitrogen

Inputs and the Soil Food Web

2

What is the Soil Food Web? 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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The Soil Biology Primer (Chapter 2): By Elaine R. Ingham


Who eats Who

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What do Food Web Organisms Do? 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.comOrganic Nitrogen Inputs and the Soil Food

Web, Tim Stemwedel, COFI

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Why is a diversity of organisms important? 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. InghamOrganic Nitrogen Inputs and the Soil Food


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The Food Web in Short

Organic Matter


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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)

The Soil Biology Primer (Chapter 2): By Elaine R. InghamOrganic 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: Active fraction Stabilized organic matter

The Active fraction is divided into living organisms fresh organic residue


9Organic Nitrogen Inputs and the Soil Food Web, Tim Stemwedel, COFI

Carbon Cycle

Carbon is the Energy that Fuels the Microbes

Stabilized Carbon (humus)

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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.


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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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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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The Nitrogen Cycle


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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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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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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

The Important point is that BIOLOGY and ORGANIC MATTER is REQUIRED!


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Examples:


Organic Nitrogen With No Biology

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Examples:


Organic Nitrogen With Biology

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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.


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Differences in Input Characteristics

Organic Nitrogen Inputs vary dramatically in how they Affect the Soil Food Web and Nutrient Cycling.

They may be Differentiated by the C:N Ratio

C:N Ratio determines how much of the N stays in the Active Fraction and how much goes to the Stable Fraction


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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

In General: The higher the C:N ratio the lower the PAN


Organic Fertilizers


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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.

Higher the C:N Ratio the more N is Immobilized


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How to Calculate PAN Variables:

C: N Ratio of Organic Fertilizer Percent Nitrogen in Organic

FertilizerTotal Pounds to be AppliedMicrobes have 8:1 C:N RationMicrobes use 25% Carbon for

Growth, 75% for Energy


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PAN Calculation 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) Turkey Litter 4% N, 12.5 C:N, 1000

lb/Acre

Calculate for Total N: 1000 x 4% = 40 lbs Calculate for Total C: 40 x 12.5 = 500 Calculate 25% Lb New

Tissue: 500 x 25% = 125


Calculate N

Immobilized, Using Microbe C:N of 8: 125 / 8 = 15.63 Calculate PAN: 40 - 15.63 = 24.37 Calculate In-Season

Efficiency: 24.37 / 40 = 61%

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Examples (PAN) Protein Fertilizer 8% N, 4.0 C:N, 1000 lb/Acre

Calculate for Total N: 1000 x 4% = 80 lbs Calculate for Total C: 80 x 4 = 320 Calculate 25% Lb New

Tissue: 320 x 25% = 80


Calculate N

Immobilized, Using Microbe C:N of 8: 80 / 8 = 10 Calculate PAN: 80 - 10 = 70 Calculate In-Season

Efficiency: 70/ 80 = 87.5%

Fertilizing Material PAN Efficiency Layer Poultry Litter 69% Broiler Poultry Litter 53% Feather Meal 88% Seabird Guano 94% Liquid Fish 92% Corn Steep 88% Molasses Deriv. 81% Liquid Guano 97%

Organic FertilizersPAN EfficiencyPAN Efficiency


Fertilizing Material $/Ton 0r Gal. $/ lb N

Layer Poultry Litter 4% N $250 $4.55 Broiler Poultry Litter 4% N $250 $5.88 Feather Meal 12% N $750 $3.57 Meat & Bone 8% N $600 $4.44 Seabird Guano 12% N $900 $4.00 Liquid Fish 5% N $4.00 $17.37 Liquid Guano 4.5% N $4.00 $18.35

Organic FertilizersCost Analysis Including PANCost Analysis Including PAN


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Other Issues Affecting SFW & Nutrient Cycling

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.

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.


Excess Carbon

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Other Issues……….

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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Crop Demand vs Mineralization

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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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


Organic Fertilizers


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Nitrogen Input Decisions

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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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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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 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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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. 2 what is the soil food web? interaction and...

Documents

soil food web slide

ingham organic nitrogen

cycling of nitrogen

form of nitrogen

half of soil organic

active soil food web

soil microbes

stabilized organic matter