El Niño-Southern Oscillation Impact on Nitrogen Leaching in North Florida Dairy Forage Systems

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

2. Introduction • 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

3. Introduction

4. Introduction • 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

5. Objectives • 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

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

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

8. Sorghum Results and Discussion

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.