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Intro to nutrient management

Soil pH modification

Nitrogen as a plant nutrient

Introduction to nutrient management

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There are 18 nutrients essential for plant growth and reproduction.

Oxygen Carbon Hydrogen

Nitrogen Potassium Phosphorus

Calcium Magnesium Sulfur

Chloride Boron Zinc

Iron Copper Manganese

Molybdenum Cobalt Nickel

Element SymbolTypical leaf concentration

(dry weight basis)Form(s) taken up from

soil

Nitrogen N 2-5% NO3-, NH4

+

Phosphorus P 0.2-0.6% HPO42-, H2PO4

-

Potassium K 2-5% K+

Calcium Ca 0.5-4.0% Ca2+

Magnesium Mg 0.4-1.0% Mg2+

Sulfur S 0.25-1.0% SO42-

Chlorine Cl 0.3-1.5% Cl-

Iron Fe 50-250 PPM Fe2+, Fe3+

Manganese Mn 30-250 PPM Mn2+

Boron B 20-80 PPM H3BO30

Zinc Zn 20-70 PPM Zn2+

Copper Co 5-20 PPM Cu2+

Molybdenum Mo < 1 PPM MoO42-

Cobalt Co < 1 PPM Co2+

Nickel Ni < 5 PPM Ni2+

Essential elements for plant growth and development.

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ElementAbsorbed

form

Relative mobility

in soil

Relative mobility

in plants

Nitrogen NO3-, NH4

+ high, moderate high, high

Phosphorus HPO42-, H2PO4

- low moderate

Potassium K+ moderate high

Calcium Ca2+ low low

Magnesium Mg2+ low moderate

Sulfur SO42- high low

Chlorine Cl- high high

Iron Fe2+, Fe3+ low low

Manganese Mn2+ low low

Boron H3BO30 high Low to high*

Zinc Zn2+ low low

Copper Cu2+ low low

Molybdenum MoO42- low low

Cobalt Co2+ moderate low

Nickel Ni2+ moderate high

Relative mobility of essential elements in soil and in plants.

Plants absorb nutrients from the soil solution.

http://www.extension.umn.edu/distribution/horticulture/m1193.html

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Soil solution nutrients are in equilibrium with those on the exchange phase

http://www.extension.umn.edu/distribution/cropsystems/DC6437.html

Different soils have differing capacity to hold nutrients and resist depletion based on mineral and or organic matter content.

ReservesReserves

Availible

Availible

Singer and Munns, Soils: An Introduction. 2002, page 191

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Desired pH change

Pounds of CaCO3 equivalent per acre

(6” depth) sandsandy loam

loamsilt

loamclay loam

4.0 to 6.5 2,600 5,000 7,000 8,400 10,000

4.5 to 6.5 2,200 4,200 5,800 7,000 8,400

5.0 to 6.5 1,800 3,400 4,600 5,600 6,600

5.5 to 6.5 1,200 2,600 3,400 4,000 4,600

6.0 to 6.5 600 1,400 1,800 2,200 2,400

Estimated lime application to adjust soil pH.

Here is an example of the relationship between buffering and soil texture.

Overview of nutrient pools in soils.

http://www.extension.umn.edu/distribution/horticulture/m1193.html

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Dissolved nutrients arrive at root surfaces by one of three processes.

• Root interception

• Diffusion

• Mass flow

NutrientAmount (lb/a)needed for 150 bu/a corn crop

Root interception

Mass Flow Diffusion

Nitrogen 170 1 99 0

Phosphorus 35 3 6 94

Potassium 175 2 20 78

Calcium 35 171 429 0

Magnesium 40 38 250 0

Sulfur 20 5 95 0

Copper 0.1 10 400 0

Iron 1.9 11 53 37

Zinc 0.2 33 33 33

Manganese 0.3 33 133 0

Boron 0.2 10 350 0

Molybdenum 0.01 10 200 0Havelin, et al, 1999, pg 28; originally from Barber, Soil Bionutrient Availability, 1984

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A balanced approach to

nutrient management is

the most effective.

http://www.thinksoil.com/pages/Liebigs.aspx

Modifying soil pH

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What causes soil pH to change?

• Nature

• Human activities

ET > Rainfall = salt accumulation (alkaline forming)

Rainfall > ET = salt loss(acid forming)

Soluble salts move with water.

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In the higher rainfall areas of California, salts are leached and low pH soils are prevalent (blue areas).

In the low rainfall areas of California, where ET > rain, salts accumulate and high pH soils are most common (red areas).

http://casoilresource.lawr.ucdavis.edu/drupal/node/946

Neutral/ alkaline soils have a high base saturation (Ca & Mg, esp. then K & Na)

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Soil Acidification

• Heavy rainfall or irrigation• Long term use of acidifying materials applied for

other purposes (amendments/fertilizer)• Manures, composts (organic materials that undergo

mineralization & nitrification)• Ammonia/ium fertilizers

NH4+ + 2O2 NO3

- + H2O+ 2 H+

-----------------------------------------------------------

• Acidulents added to reduce soil pH (yellow sulfur, sulfuric acid, KTS/ATS, etc.)

How Nitrogen Affects Soil Acidity

• Nitrification - H+ is released during the conversion of NH4

+ to NO3-

• Leaching - NO3- carries basic

ions with it. They are replaced by H+

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Soil Alkalization

• ET > rainfall irrigation

• Long term use of irrigation without leaching/drainage

• Use of lime or alkalizing material on acid soil.

Soil pH problems & corrections.

Soils affected by acidity (low pH)• reduced root growth and microbial activity

• Al, Mn, H+ toxicities

• Lime (e.g. CaCO3, CaO) to neutralize hydrogen ions

CaCO3 + 2H+ Ca2+ + H2O + CO2

Soils affected by alkalinity (high pH)• nutritional problems (Fe, Zn deficient)

• may also be sodic (high in sodium) poor soil structure

• Sulfur (elemental or sulfuric acid) to add hydrogen ions

So + H20 +O2 H2SO4 H+ + SO42-

(+bacteria)

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Common inputs and the direction of soil pH changes.

Input pH change

Lime UpSulfur Down

Ammonium containingfertilizer/

amendment

Down

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Nitrogen as a

plant nutrient

Nitrogen (N) Deficiency

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Nitrogen is the key nutrient input to many agricultural cropping systems.

• Nitrogen is key component of protein, chlorophyll, and nucleic acids.

• Required in large amounts by plants.

• Original source is the air as inert N2.• Can be fixed in useful form by

plants, humans and lightning.

Many crops havehigh nitrogen requirements

Yield N taken up inCrop level total crop, lb

Alfalfa* 8 tons 450Coastal bermudagrass 8 tons 368Corn 160 bu 213Cotton (lint) 1,500 lb 180Oranges 540 cwt 265Almonds 3000 lbs 210Wheat (low protein) 60 bu 113*Legumes get most of their N from the air (biological fixation)

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Symptoms and Consequences of Nitrogen Deficiency Include...

• Yellowing (chlorosis) of older leaves (nitrogen is mobile in the plant).

• Slow growth; stunted plants; fewer leaves or tillers.

• Lower grain protein

• Early maturity, which limits yield potential

• Higher moisture content in corn grain at maturity

Agronomic crops use both nitrate (NO3

-) & ammonium (NH4

+) forms of nitrogen.

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Nitrogen Cycle

• Inputs•Reserves•Pools•Processes• Losses

The Nitrogen Cycle

Atmospheric

fixation

and deposition

Animal

manures

and biosolids

Industrial fixation

(commercial fertilizers)Crop

harvest

Volatilization

Denitrification

Runoff and

erosion

Leaching

Atmospheric

nitrogen

Organic

nitrogen

Ammonium

(NH4)

Nitrate

(NO3)

Plant

residues

Biological

fixation by

legume plants Plant

uptake

Input to soil ComponentLoss from soil

-+

http://www.docstoc.com/docs/98329783/The-Nitrogen-Cycle

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The NITROGEN CYCLE showing relative sizes of N pools.

Singer and Munns, Soils: An Introduction. 2002, page 173

Nitrogen Fixation

• Biological - activity of soil bacteria

• Natural oxidation - lightning

• Industrial - the most important process; synthesizes ammonia using hydrogen from natural gas and atmospheric nitrogen

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Most N Used by CropsComes From the Atmosphere

http://www.fertilizer.org/ifa/HomePage/MEDIA/Press-releases-2009/16-March-2009

http://www.extension.org/pages/64401/legume-inoculation-for-organic-farming-systems

Nitrogen can also be fixed by legumes (alfalfa, beans, clover, etc.) and certain other plants via symbiotic relationships with bacteria that live in root nodules.

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Alfalfa 195White clover 105Soybeans 100Cowpeas 90Peanuts 40

Estimated Annual Nitrogen Fixationby Various Legume Crops (Symbiotic)

N fixed,Legume lb/A/yr

http://www.abbotsfordtoday.ca/wp-content/uploads/2010/05/manure-spreader.jpg

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Soil Nitrogen Comes from BothOrganic and Inorganic Sources

• Organic N - part of soil organic matter, unavailable (immediately) to growing plants.

• Inorganic N - readily available to plants

Ammonium N - often ‘fixed’ by clays, slowly available to plants

Ammonium and nitrate ions (soluble), the N which plants use

Mineralization:

The microbial breakdown of soil organic matter, resulting in the release of energy and inorganic nutrients available for plant growth

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Soil N in the organic form must be mineralized before it is plant available.

Bacteria and fungi needed.

http://extension.missouri.edu/publications/DisplayPub.aspx?P=WQ260

Gaskell, M., et al., 2007 UC ANR Pub. No. 7249

Organic

Organic (insoluble,complex) nitrogen must be applied weeks ahead of crop demand to meet that demand.

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Adding an organic N source can initially decrease N availability.

UC ANR

The Length of the Nitrate DepressionPeriod Depends on Several Factors

• C:N ratio of decomposing material

•Quantity of crop residue added to the soil

• Environmental conditions in the soil–Temperature

–Oxygen levels

–Soil pH

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Undisturbed top soil 10:1Alfalfa 13:1Rotted barnyard manure 20:1Corn stalks 60:1Small grain straw 80:1Coal and shale oil 124:1Oak 200:1

Spruce 1000:1

The carbon to nitrogen ratio (C:N) determines the short term plant availability of soil N additions.

Material C:N Ratio

Compost or manure (same original source) provides more or less plant

available N?

Compost N < available than manure N

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Oxygen plus

bacteria

Nitrification

NH4+ NO3

-

Lack of oxygen

bacteriaNO3

- N2O, N2

Denitrification

• Denitrification is a waste of fertilizer.

• Denitrification products (NxOgases) are 300x more powerful as greenhouse gases compared to CO2.

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Improving Fertilizer N Use Efficiency (NUE)

• Four R’s–Right Time

–Right Place

–Right Rate

–Right Material (includes slow release sources and nitrification inhibitors)

Consequences of off-site nitrogen loss:

• Ground water contamination

• Surface water contamination

• Air quality degradation

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http://openchannel.nbcnews.com/_news

10 ppm N-NO3-

45 ppm NO3-

http://nutrients.utah.gov/

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http://online.wsj.com/article/SB125055779852138901.html

Nitrogen Can Be Lost fromthe Soil in Several Ways

• Crop removal

• Volatilization

• Erosion

• Denitrification

• Leaching

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Urea and ammonium-based N fertilizers can be lost from the soil as

ammonia (volatilization).

H20 + NH2CONH2 CO2 + NH3(Urease)

NH3 + H20 NH4+ + OH-

NH4+ NH3 + H+

Conditions that Favor VolatilizationLoss from Soil Applications of Urea

Surface application

Presence of urease enzyme

High temperatures

Moisture

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Incorporate urea or ammonium based fertilizer with water or

cultivation ASAP to avoid loss.

Urea is a soluble, uncharged molecule. It will move with

irrigation water. Don’t put urea out on the front end of irrigation set.

Right Place: Irrigation Rapidly Moves N into SoilSurface applied N Followed by Irrigation (90 minutes)

Courtesy www.IPNI.org

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Right Place: Irrigation Rapidly Moves N into SoilSurface applied N Followed by Irrigation (90 minutes)

Courtesy www.IPNI.org

Right Place: Irrigation Rapidly Moves N into SoilSurface applied N Followed by Irrigation (90 minutes)

Courtesy www.IPNI.org