1. El Niño-Southern Oscillation Impact on Nitrogen Leaching in North Florida Dairy Forage Systems Victor E. Cabrera*, Peter E. Hildebrand, and James W. Jones

2. N in water affects human health and ecosystem welfare Increased N levels in Suwannee river basin Dairy farming is thought to be an important factor Evidence indicates forages systems are the main means of N recycle Introduction

4. Improvements in climate forecast can help devise management strategies Data on time-series experiments in Tifton, GA and in North Florida Holstein, Gilchrist, FL Crop models (DSSAT v4.0) were used to experiment N leaching spatially and temporally Introduction

5. Assess the potential N leaching from forage systems under intensive application of dairy manure Capacity of forages to uptake N Risk of N leaching under different: Climate Crop systems Soils Objectives

6. Survey and focus groups Soil series (SSURGO) Climate-ENSO phases Crop systems Manure N application Crop simulations Outputs: data 56-98 Materials and Methods

7. Crop systems Results and Discussion Calibration and validation of DSSAT models Bahia grass – Bermuda grass Corn, sorghum, millet, winter forages

8. Results and Discussion Sorghum

9. Results and Discussion Sensitivity analyses

10. Results and Discussion N leaching by ENSO phase

11. Results and Discussion N leaching by ENSO phase

12. Results and Discussion N leaching by ENSO phase

13. Results and Discussion N leaching by ENSO phase

14. Results and Discussion Precipitation by ENSO phase

15. Results and Discussion Temperature by ENSO phase

16. Results and Discussion Solar Radiation by ENSO phase

17. Results and Discussion N leaching by ENSO phase

18. Results and Discussion N leaching by ENSO phase

19. Results and Discussion Biomass by ENSO phase

20. Results and Discussion Biomass by ENSO phase

21. Results and Discussion N leaching by crop sequences

22. Results and Discussion N leaching by soil types

23. Conclusions Higher (lower) nitrogen leaching (biomass accumulation) is predicted for El Niño years than Neutral years and than La Niña years This is attributed mostly to the rainfall events and their intensity

24. Conclusions An attempt to correlate the leaching with the Japan Meteorological Index, which is used to predict the El Niño Southern Oscillation phases, showed little correlation.

25. Conclusions Winter in general, and January and February in specific, are the critical months for nitrogen leaching at the same time that low biomass accumulation is noticed.

26. Conclusions The best forage systems to prevent nitrogen leaching are those that start in spring with Bermuda or corn; have in summer Bermuda, Bahia or corn; and finish with winter forages. The systems that leach the most are those that include millet and/or sorghum.