NREM 301Forest Ecology & Soils Nutrient Cycling

Day 27November 18, 2008

Uganda Study Abroad Information Meeting5 pm 118 Horticulture - TodayChina - Nov 19 – noon - 9 CurtissMore Info – Ag Study Abroad Office 111 Curtiss

Individual Quiz

Diagram the General Nutrient CycleClearly identify the sub-cycles:

BiochemicalBiogeochemical

Geochemical

Geochemical

Biogeochemical

Biochemical

General NutrientCycle

Group Activity

Now

Diagram the N CycleIn the

Agricultural landscape of Central IowaInclude each of the words (phrases) on the diagram

1. Decomposition2. Nitrification3. Nitrobactor4. Assimilation5. Ammonification6. Drainage Loss 7. Denitrification8. Nitrogen Fixation9. Anaerobic10. Fertilization

11. Nitrate12. Nitrosomanos13. Ammonia14. Nitrite15. Organic N16. N2 gas17. Mineralization18. Anaerobic19. Tiles20. Surface runoff

Surface Runoff

Fertilization

Group ActivityLeaching & tiles

Be prepared to describe each of the words (phrases) on the diagram

1. Decomposition2. Ammonification3. Nitrification4. Assimilation5. Drainage Loss 6. Denitrification7. Nitrogen Fixation

Are there any processes that are missing – especially in agricultural landscapes?

Nitrogen Cycle

NitrosomonasBacteria

NitrobacterBacteria

Mineralization

Uptake

Let’s look in detail at the N cycle

Anaerobic

Free Living BacteriaSymbiotic N-fixersRhizobiumFrankia

Acid soils – few bacteria & actinomycetes – slower decomposition – most available N for plant uptake is NH4

Basic soils – most diverse – faster decomposition – more NO3 – taken up

Neutral

How does pH influence the Nitrogen Cycle?

What happens to Bacteria at low pH?

Acid

Surface Runoff

Fertilization

Leaching & tiles

Be prepared to describe each of the words (phrases) on the diagram

1. Decomposition2. Ammonification3. Nitrification4. Assimilation5. Drainage Loss 6. Denitrification7. Nitrogen Fixation

Are there any processes that are missing – especially in agricultural landscapes?

Nitrogen Cycle

NitrosomonasBacteria

NitrobacterBacteria

Mineralization

Uptake

Let’s look in detail at the N cycle

Anaerobic

How does soil pH Affect microbial activity

&Nutrient availability?

Many nutrients limited by low pH –some micros - not

High pH also limits availability of some – note especially P and micro-nutrients

Decomposition slowed at low pH –fewer bacteria

Surface Runoff

Fertilization

Group Activity

Uptake

Leaching & tiles

No N from Weathering/All from Atmosphere

Geochemical = 16%

Biogeochemical = 45%

Biochemical = 39%

Identify components of the

sub-cycles as annual sources

What Happens to the N Cycle When -Prairie/forest are replaced by corn and soybeans?

Do the following increase, decrease or stay the same?• Fixation• Plant loss• OM added to soil• Decomposition rate• Ammonification• Nitrification• Denitrification• Leaching• Plant uptake

Surface Runoff

Fertilization

Uptake

Leaching No N from Weathering/All from Atmosphere

What happens to N Cycle when

going from prairie to corn?

• Fixation• Plant loss• OM added to soil• Decomposition rate• Ammonification• Nitrification• Denitrification• Leaching• Plant uptake

downup

downup

upup

Down (tile)

upup

What Happens to N Cycle When -

Land is Drained?

Results of Drainage

Nitrate Loads to Mississippi River

Surface Runoff

No N from Weathering/All from Atmosphere

How does fire impact the N Cycle?

• Plant loss -• OM FF -• Decomposition of left over OM -

• Ash -• pH -• Ammonification –• Nitrification –• Plant uptake –

• Leaching loss –• Fixation -• Denitrification -• Surface runoff –

Up but rapid replacementLost – N volatilized

Increases

Left behind – lots of cationsIncreases – CEC - cations

UpUp especially in conifers

Down – shifts to understory

Up – a short timeUp – symbiotic & free

Up if less TrUp a short time

How does the Phosphorus Cycle differ from the N Cycle?

Minor compared to N

Major Loss

Not much atmospheric input

Mining Phosphate Rocks

Detergents Includes animal waste