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

Victor E. Cabrera*, Peter E. Hildebrand, and James W. Jones

• 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

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

Introduction

• 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

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

Materials and Methods

• Crop systems

Results and Discussion

MAR APR MAY JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR

PERENNIAL PEANUT* **

FALL - WINTERCORN

BERMUDA GRASSBAHIA GRASS

SORGHUMMILLETCORN

RYEOATS

WHEATSORGHUM*

MILLET*BERMUDA GRASS

BAHIA GRASS

SPRING - SUMMER SUMMER - FALL

RYEGRASSCLOVER**

• Calibration and validation of DSSAT models• Bahia grass – Bermuda grass• Corn, sorghum, millet, winter forages

Results and Discussion

0.00

2.00

4.00

6.00

8.00

10.00

12.00

132 N 174 N 228 N 132 N 174 N 228 N 132 N 174 N 228 N

1996 1996 1996 1997 1997 1997 1998 1998 1998

Mg/

ha Observed

Simulated

Sorghum

Results and Discussion

• Sensitivity analyses

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2.00

4.00

6.00

8.00

10.00

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14.00

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0 70 140 280 420 560 700

MANURE N APPLIED (Kg Ha -1)

BIO

MAS

S (M

g Ha

-1)

0

10

20

30

40

50

60

70

80

N LE

ACHE

D (K

g Ha

-1)

BIOMASS

N LEACHED

CORN

Results and Discussion

• N leaching by ENSO phase All Years La Niña Neutral El Niño N Leach CV N Leach CV N Leach CV N Leach CV DEC 10.59 98% 13.15 93% 7.69 80% 15.64 127% JAN 108.42 32% 83.19a 35% 108.90b 30% 127.35c 21% FEB 78.57 24% 84.22a 9% 79.94ab 29% 71.60b 20% MAR 20.86 49% 23.54 56% 20.55 42% 19.28 45% APR 5.81 97% 4.90 78% 6.42 71% 5.45 70% MAY 12.18 73% 12.39 103% 12.94 59% 10.61 72% JUN 23.22 43% 22.01 45% 25.13 38% 20.69 50% JUL 16.65 44% 18.42 33% 17.09 48% 14.33 37% AUG 17.05 40% 16.99 40% 15.65 38% 19.71 36% SEP 21.22 39% 19.34 44% 20.33 34% 24.50 39% OCT 20.27 33% 19.02 35% 20.79 36% 20.35 21% NOV 7.00 59% 5.11 42% 7.47 58% 7.75 62% YEAR 341.84 322.29 342.90 357.25

Results and Discussion

• N leaching by ENSO phase

0.60

0.70

0.80

0.90

1.00

1.10

1.20

1.30

1.40

1.50

DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV

RE

LAV

IVE

N L

EA

CH

ING

La Niña

Neutral

El Niño

Results and Discussion

• N leaching by ENSO phase

Results and Discussion

• N leaching by ENSO phase

Results and Discussion

• Precipitation by ENSO phase

Results and Discussion

• Temperature by ENSO phase

0

5

10

15

20

25

30

35

274

286

298

310

322

334

346

358 4 16 28 40 52 64 76 88 100

112

124

136

148

160

172

184

196

208

220

232

244

256

268

Day of the Year (DOY)

Tem

pera

ture

(C)

La Niña

El Niño

Neutral

La Niña years: 55,56,64,67,70,71,73,75,88,98

MaximumTemperature

El Niño years: 57,63,65,69,72,76,82,86,87,91,97

MinimumTemperature

Neutral years: 58,59,60,61,62,66,68,74,77,78,79,80,81,83,84,85,89,90,92,93,94,95,96

Results and Discussion

• Solar Radiation by ENSO phase

0

5

10

15

20

25

274

286

298

310

322

334

346

358 4 16 28 40 52 64 76 88 100

112

124

136

148

160

172

184

196

208

220

232

244

256

268

Day of the Year (DOY)

Sola

r Rad

iatio

n (M

J m

-2 d

-1)

La Niña

El Niño

Neutral

Results and Discussion

• N leaching by ENSO phase

Results and Discussion

• N leaching by ENSO phase

Results and Discussion

• Biomass by ENSO phase All Years La Niña Neutral El Niño Biomass CV Biomass CV Biomass CV Biomass CV DEC 86 32% 102 30% 77 28% 92 41% JAN 1,367 17% 1,563a 13% 1,319b 14% 1,301b 22% FEB 2,292 10% 2,343a 11% 2,346a 7% 2,151b 9% MAR 1,439 28% 1,329ab 23% 1,561a 30% 1,297b 14% APR 959 35% 1,094 28% 938 32% 883 27% MAY 4,546 12% 4,691 7% 4,487 16% 4,533 7% JUN 4,908 13% 4,997 9% 4,818 19% 4,997 9% JUL 3,232 13% 3,280 9% 3,173 18% 3,300 8% AUG 1,649 27% 1,660 16% 1,654 20% 1,631 28% SEP 2,784 11% 2,821 10% 2,811 10% 2,704 12% OCT 3,127 12% 3,211 15% 3,060 11% 3,180 9% NOV 811 49% 833 63% 754 51% 899 44% YEAR 27,202 27,924 26,999 26,968

Results and Discussion

• Biomass by ENSO phase

0.80

0.85

0.90

0.95

1.00

1.05

1.10

1.15

1.20

DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV

REL

AVIV

E B

IOM

ASS

La Niña

Neutral

El Niño

Results and Discussion

• N leaching by crop sequences

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0.50

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1.50

2.00

2.50

MAR APR MAY JUN JUL AUG SEP OCT NOV

RE

LATI

VE

N L

EA

CH

BE-BE

CO-SO

MI-CO

SO-CO

MI-SO

SO-MI

CO-CO

CO-MI

CO-BA

CO-BE

BA-BA

Results and Discussion

• N leaching by soil types

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2.50

DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV

RE

LATI

VE

N L

EA

CH SOIL1

SOIL2SOIL3SOIL4SOIL5SOIL6SOIL7SOIL8SOIL9SOIL10

6.04

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

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.

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.

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.