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Rain, Runoff, and Sediment Loss in

Normal and Abnormal Weather Years

in an Agricultural Landscape

in Southeastern U.S.

A 10-yr Dataset

69th SWCS International Annual ConferenceLombard-IL

July 27-30,2014

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69th SWCS International Annual ConferenceLombard-IL

July 27-30,2014

Dinku Endale

David Bosch

Tom Potter

Tim Strickland

USDA-ARS-SEWRL Tifton-GA

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THE SOUTHEAST

136

153

152134

135133

Tifton

Background

MLRAs, NRCS

Cropland in the SoutheastUSDA-NRCS, 2006

MLRA Name Km2 % MLRA133 Southern Coastal Plain 46885 17134 Southern Mississippi Valley Loess 24727 36135 AL and MS Blackland Prairie 2640 16136 Southern Piedmont 15010 9152 Eastern Gulf Coast Flatwoods 332 1.3153 Atlantic Coast Flatwoods 11158 15

Total 100,753 km2 (10 million ha)

GA, AL, SC, NC, TN, MS 7.2 million ha planted (CTIC 2008 CRMS)40% no-till; 41% conventional tillageUS harvested cropland 127.5 million ha (2012 Census of Agriculture) 31% no-till;24 conservation tillage other than no-till; 34% conventional tillage

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Background

Benefits of conservation tillage:• Reduce runoff, erosion and soil loss

(Credited for 43% reduction in soil loss from U.S. cropland 1982-2007; NRCS-2010)

• Improve soil health and water quality• Improve soil water availability

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In the Southeast, benefits of conservation

tillage being threatened by:

• Shifts in weather

• Shifts in cropping practices

o Removal of crop residue from fields

o Increased herbicide resistance of weeds

Background

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Background

Fig. 2.11

Ingram, K., K. Dow, L. Carter, J. Anderson, eds. 2013. Climate of the Southeast United States: Variability, change, impacts, and vulnerability. Washington D.C.: Island Press.

Fig. 2.8

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Background

Shifts in cropping practices that could increase soil erosion:• Removal of crop residues from croplands in

response to renewable energy initiatives.

• Challenges with herbicide-resistance weeds (pigweed; glyphosate-resistant Palmer amaranth) as some growers choose to revert to conventional tillage methods in response.

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Challenge

Long-term research and data are critical in

generating scientifically-based information on

environmental risks associated with cropping

practices in response to shifting weather, national

initiatives, weed pressure, market forces, etc.

Society needs to make wise management decisions

to sustain the natural resource base.

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Objective

Present summarized runoff and sediment loss

data from three fields managed under

conventional tillage, and three under strip

tillage, in a Southern Coastal Plain landscape,

during ten years (2000-2009) of rotational

cotton-peanut cropping with rye as a winter

cover crop.

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Methods

SITE• Six 0.2-ha fields near

Tifton, GA• CT – conventional tillage,

block 1, fields 1, 3, 5• ST –strip tillage, block 2,

fields 2, 4,6• 1.5 ft H-flumes per field

to measure & sample runoff

Slope 3 to 4%

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Methods

SITE - soil• Upper landscape position:

Carnegie sandy loam(... Plinthic Kandiudult)

Ap sandy loam; Bt sandy clay loam / sandy clay

• Middle: Tifton loamy sand (…Plinthic Kandiudult)Ap loamy sand; Bt sandy clay loam

• Lower: Fuquay loamy sand (…Arenic Plinthic Kandiudult)Ap sand Bt sandy loam / sandy clay loam

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Methods

Cropping

Cotton Peanuts2000 2002

2001 2004

2003 2006

2005 2008

2007

2009

Management per UGA Extension recommendations

Irrigationwhen needed

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MethodsMonthly rain + irrigation versus long‐term monthly mean rainfall# of months rain + irrigation is percent of year

YEAR < Normal Normal > Normal < Normal Normal > Normal2000 7 2 3 58 17 252001 6 2 4 50 17 332002 3 5 4 25 42 332003 5 3 4 42 25 332004 6 1 5 50 8 422005 4 2 6 33 17 502006 5 2 5 42 17 422007 7 1 4 58 8 332008 4 3 5 33 25 422009 4 2 6 33 17 50Total 51 23 46 43 19 38

120Monthly rainfall < (Long-term mean < 95% Confidence Level)Monthly rainfall = (Long-term mean +- 95% Confidence Level)Monthly rainfall > (Long-term mean + 95% Confidence Level)

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Result Highlights

RESULT SUMMARYParameter Stat Unit CT ST CT/ST

Runoff 10-yr total mm 8,059 4,731 1.710-yr total mean mm/field 2,686 1,577 1.7Year total range mm/yr 43 (2007) 6 (2007)

(tillage mean) 507 (2003) 315 (2002)

Normailized Mean annual % 20.5 12.0 1.7runoff Range % 4 (2007) 1 (2007)

40 (2003) 24 (2002)CT - conventinal tillage ST - strip tillage

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Result Highlights

Monthly runoff amount by status of monthly rain+irrigation inputCT Field 1 ST Field 6

% of % of Status mm 10-yr total mm 10-yr total

Below normal 252 7 60 5

Normal 441 13 204 16

Above normal 2712 80 983 79

SUM 3405 100 1247 100

Below normal: Monthly rainfall+irrigation < (long-term monthly mean runoff - 95% confidence limit)Normal: Monthly rainfall+irrigation = (long-term monthly mean runoff +- 95% confidence limit 0Above normal: Monthly rainfall+irrigation > (long-term monthly mean runoff + 95% confidence limit)

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Result Highlights

RESULT SUMMARYParameter Stat Unit CT ST CT/ST

Sediment 10-yr total kg/ha 54,682 7,116 7.7

Normalized kg/ha/

mm runoff 6.8 1.5 4.5

10-yr total mean kg/ha/field 18,227 2,372 7.7

Year total range kg/ha/yr 161 (2007) 3 (2007)

(tillage mean) 5914 (2009) 696 (2002)

Tvalue surpassed 2002 None

2240 kg/ha/yr year 2003

2009

CT - conventinal tillage ST - strip tillage

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Result Highlights

0

10

20

30

40

50

60

70

80

0 10 20 30 40 50 60 70 80

Mon

thly ru

noff  coe

fficient (%

)

Exceedance probabaility (%)

Monthly Runoff Coefficicent

CT ST

Y  =  a  + bX  +  cX1.5  +  dX0.5

Y is runoff coeff.  and X is exceedance CT ST

R2  0.996 0.991a 82.45 94.034b 0.376 2.931c 0.024 ‐0.094d ‐14.48 ‐29.28

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Result Highlights

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60 70

Mon

thly sed

imen

t loss  coe

fficient      

(kg/ha/m

m ru

noff)

Exceedance probabaility (%)

Sediment loss coefficient

CT ST

Y  =  a  + bX2  +  c/X0.5  +  de‐XY is sediment coeff.  and X is exceedance 

CT STR2  0.982 0.969a ‐9.788 ‐2.921b 0.0002 0.0001c 75.449 19.032d ‐80.648 42.469

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Result Highlights

Mean sediment loss coefficient by landscape position kg/ha/mm runoff

Period CT ST CT ST CT ST

Monthly 6.0 2.8 4.2 0.8 4.0 0.9*** *** ***

Annual 6.9 2.1 5.7 1.5 5.8 1.6* ** *

*, **, *** Significant difference CT vs ST at 0.05, 0.01, 0.001

probability levels, respectively

10-Yr total 24,160 2,167 14,727 2,676 15,795 2,273kg/ha

Upper Middle Lower

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Result HighlightsMean sediment loss coefficient by landscape position

kg/ha/mm runoffUpper Middle Lower

Season CT ST CT ST CT ST

Fall 2.6 2.7 1.7 0.3 0.7 0.5NS ** NS

Winter 3.3 2.8 3.3 0.7 3.1 1.1* *** ***

Spring 8.8 0.6 3.8 0.8 3.2 1.0*** ** NS

Summer 9.3 5.1 8.1 1.3 8.9 1.1* *** ***

*, **, *** Significant difference CT vs ST at 0.05, 0.01, 0.001probability levels, respectively. NS - not significant.

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Result HighlightsMean sediment loss coefficient by landscape position

kg/ha/mm runoffUpper Middle Lower

Crop CT ST CT ST CT ST

Cotton 6.5 5.1 5.4 1.1 6.7 0.8NS *** ***

Peanuts 5.1 0.8 4.9 0.5 3.5 0.6** ** *

Rye 4.1 3.4 3.5 1.1 2.6 1.1** *** ***

Fallow 8.7 0.6 3.7 0.4 3.4 0.9*** *** NS

*, **, *** Significant difference CT vs ST at 0.05, 0.01, 0.001probability levels, respectively. NS - not significant.

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Result Highlights

Extreme events => 90th pecentileCT ST

Plot 1 Plot 3 Plot 5 Sum Plot 2 Plot 4 Plot 6 SumStat Daily runoff mmSum- all 3405 2352 2302 8,059 1781 1703 1247 4,731Sum- extreme 1979 1323 1273 4,575 1275 1139 832 3,246% extreme 58 56 55 57 72 67 67 69

Daily Sediment Loss kg/haSum- all 24,160 14,726 15,795 54,682 2,167 2,676 2,273 7,116Sum- extreme 14,330 7,603 9,495 31,428 926 1,872 1,437 4,235% extreme 59 52 60 57 43 70 63 60Percent extreme same for monthly summary

All occurring for > normal rainfall (+irrigation) months

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Conclusions

• Runoff and sediment loss will increase in the Coastal Plain if the projected shifts in weather and tillage practices materialize.

In the ten years of research we reported:o Mean normalized runoff was 70% greater

from CT than STo Mean sediment loss was 7.7 time greater

from CT than STo 80% of the runoff amount occurred during

above normal water input months

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Conclusions

• Runoff and sediment loss will increase in the Coastal Plain if the projected shifts in weather and tillage practices materialize.

• We used cover crop in both CT & ST but the typical CT in the SE does not; so the risk is greater.

• In a 1951-1958 study of continuous conventional tillage peanuts with no cover crop, researchers found soil loss of 2758 kg/ha/yr (18 plots,8-m wide and 25-m long close by). There was severe drought in the 1950s.

• In current study loss during 4 yr of Peanuts averaged 1461 kg/ha/yr from CT with cover crop.

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Conclusions

• To consistently reduce soil loss below tolerance levels in the Coastal Plain, producers need to consider combination of best management practices that include cover crops, strip tillage, contour cultivation and reduced slope length.

• Higher landscape positions, where clay rich sub-soils might be near the surface, pose greater risk for runoff and soil loss than those in lower positions that have less clay near the surface. Summer and cotton cropping pose most risk for soil loss at all landscape positions. Producers need to use these facts in designing best management practices.

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Conclusions

• Such long-term research and data are critical in generating scientifically-based information needed to make wise management decisions that sustain the integrity of natural resources.

Many thanks for your attention !!

Research FieldsGoogleearth

3/26/2013

Cover crop fall 2012