1. Nutrient Cycling Amy Shober, Ph.D. UF/IFAS Gulf Coast REC Advanced Soils & Fertilizers Topics for Master Gardeners 1 of 14 ©2008 University of Florida-IFAS

2. 2 of 14 ©2008 University of Florida-IFAS Figure Credits: Amy Shober, UF-IFAS The Nitrogen Cycle

3. Organic N Sources Plant residues –Ex.: grass clippings, leaf litter Plant Available Soil Bacteria Inorganic N Unavailable Organic N Organic soil amendments –Ex.: compost, manure 3 of 14 ©2008 University of Florida-IFAS Photo Credits: Amy Shober, UF-IFAS

4. Synthetic N Fertilizers Lawn and ornamental fertilizers –Most contain ammonium or nitrate –Some contain urea Quick-release fertilizers Slow- and Controlled- release fertilizers 4 of 14 ©2008 University of Florida-IFAS Photo Credit: Amy Shober, UF-IFAS

5. Atmospheric Nitrogen Adds only a small amount of N Examples: –Legumes –Lightning –Rain deposition 5 of 14 ©2008 University of Florida-IFAS Photo Credits: NOAA (top), UF-CLCE (bottom)

6. How N Behaves in the Soil Mineralization Nitrification Plant Uptake Volatilization Ammonia Gas Denitrification Nitrogen (N 2 ) gas Organic N NH 4 + NO 3 - 6 of 14 ©2008 University of Florida-IFAS Figure Credit: A. Shober

7. Nitrogen Losses Runoff Occurs when Rainfall (or Irrigation) > Infiltration Can transport fertilizers or plant residues to water N Leaching Runoff Leaching Movements of Nitrate through the soil profile Can lead to ground- water contamination 7 of 14 ©2008 University of Florida-IFAS

8. 8 of 14 ©2008 University of Florida-IFAS Figure Credits: Amy Shober, UF-IFAS The Phosphorus Cycle

9. Organic P Sources Plant residues –Ex.: grass clippings, leaf litter Plant Available Soil Bacteria Inorganic P Unavailable Organic P Organic soil amendments –Ex.: compost, manure 9 of 14 ©2008 University of Florida-IFAS Photo Credits: A. Shober

10. Synthetic P Fertilizers Lawn and ornamental fertilizers –Derived from P rich rocks Controlled- release fertilizers 10 of 14 ©2008 University of Florida-IFAS Photo Credits: Rasbak (top), A. Shober (bottom)

11. How P Behaves in the Soil Soil Solution P HPO 4 2- H 2 PO 4 - Plant Uptake Adsorption Weathering H 2 PO 4 - Soil Particle H 2 PO 4 - Desorption Dissolution Precipitation Mineralization 11 of 14 ©2008 University of Florida-IFAS Figure Credit: A. Shober

12. Phosphorous Losses Leaching Runoff/ Erosion P Runoff Transports dissolved P compounds or eroded soil and plant particulate matter containing solid P compounds Leaching Loss of phosphate from the soil as water moves downward 1 of 14 ©2008 University of Florida-IFAS

13. 13 of 14 ©2008 University of Florida-IFAS Figure Credits: IPNI

14. Summary Sources of N and P include organic residues and synthetic fertilizers. Microbes are required to transform organic forms of N and P into plant available forms. Losses of N and P in runoff or leachate can lead to water quality degradation. 14 of 14 ©2008 University of Florida-IFAS