Rain runoff and sediment loss
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Transcript of Rain runoff and sediment loss
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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