Nutrient Cycling. Day 27 November 18, NREM 301 Forest Ecology & Soils

Transcription

1 NREM 301 Forest Ecology & Soils Day 27 November 18, 2008 Nutrient Cycling Uganda Study Abroad Information Meeting 5 pm 118 Horticulture - Today China - Nov 19 noon - 9 Curtiss More Info Ag Study Abroad Office 111 Curtiss

2 Individual Quiz Diagram the General Nutrient Cycle Clearly identify the sub-cycles: Biochemical Biogeochemical Geochemical

3 Biochemical General Nutrient Cycle Geochemical Biogeochemical

4 Group Activity Now Diagram the N Cycle In the Agricultural landscape of Central Iowa Include each of the words (phrases) on the diagram 1. Decomposition 2. Nitrification 3. Nitrobactor 4. Assimilation 5. Ammonification 6. Drainage Loss 7. Denitrification 8. Nitrogen Fixation 9. Anaerobic 10. Fertilization 11. Nitrate 12. Nitrosomanos 13. Ammonia 14. Nitrite 15. Organic N 16. N 2 gas 17. Mineralization 18. Anaerobic 19. Tiles 20. Surface runoff

5 Nitrogen Cycle Fertilization Free Living Bacteria Symbiotic N-fixers Rhizobium Frankia Let s look in detail at the N cycle Be prepared to describe each of the words (phrases) on the diagram Nitrobacter Bacteria Anaerobic Leaching & tiles Uptake Nitrosomonas Bacteria Surface Runoff Mineralization 1. Decomposition 2. Ammonification 3. Nitrification 4. Assimilation 5. Drainage Loss 6. Denitrification 7. Nitrogen Fixation Are there any processes that are missing especially in agricultural landscapes? Group Activity

6 Acid Neutral How does ph influence the Nitrogen Cycle? What happens to Bacteria at low ph? Acid soils few bacteria & actinomycetes slower decomposition most available N for plant uptake is NH 4 Basic soils most diverse faster decomposition more NO 3 taken up

7 Nitrogen Cycle Let s look in detail at the N cycle Fertilization Anaerobic Surface Runoff Be prepared to describe each of the words (phrases) on the diagram 1. Decomposition 2. Ammonification 3. Nitrification 4. Assimilation 5. Drainage Loss 6. Denitrification 7. Nitrogen Fixation Nitrobacter Bacteria Uptake Are there any processes that are missing especially in agricultural landscapes? Leaching & tiles Nitrosomonas Bacteria Mineralization

8 How does soil ph Affect microbial activity & Nutrient availability? Decomposition slowed at low ph fewer bacteria High ph also limits availability of some note especially P and micro-nutrients Many nutrients limited by low ph some micros - not

9 No N from Weathering/All from Atmosphere Fertilization Geochemical = 16% Biogeochemical = 45% Surface Runoff Biochemical = 39% Uptake Identify components of the sub-cycles as annual sources Leaching & tiles Group Activity

10 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

11 Fertilization What happens to N Cycle when going from prairie to corn? Uptake Surface Runoff Fixation down Plant loss up OM added to soil down Decomposition rate up Ammonification up Nitrification up Denitrification Down (tile) Leaching up Plant uptake up Leaching No N from Weathering/All from Atmosphere

12 What Happens to N Cycle When - Land is Drained?

13 Results of Drainage

14 Nitrate Loads to Mississippi River

15 How does fire impact the N Cycle? No N from Weathering/All from Atmosphere Surface Runoff Plant loss - Up but rapid replacement OM FF - Lost N volatilized Decomposition of left over OM - Increases Ash - Left behind lots of cations ph - Increases CEC - cations Ammonification Up Nitrification Up especially in conifers Plant uptake Down shifts to understory Leaching loss Up a short time Fixation - Up symbiotic & free Denitrification - Up if less Tr Surface runoff Up a short time

16 How does the Phosphorus Cycle differ from the N Cycle? Detergents Includes animal waste Not much atmospheric input Mining Phosphate Rocks Major Loss Minor compared to