reducing herbicide and veterinary antibiotic losses from agroecosystems using vegetative...

Reducing Herbicide and Veterinary Antibiotic Losses from Agroecosystems

Using Vegetative Buffers

R. N. Lerch1, C. H. Lin2, K. W. Goyne3, and H. E. Garrett2

1USDA-ARS, Cropping Systems and Water Quality Research Unit, Columbia, MO2 Center for Agroforestry, University of Missouri

3Department of Soil, Environmental and Atmospheric Sciences, University of Missouri

Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

Rationale and Objectives• Rationale:

– The ability of vegetative buffer strips (VBS) to reduce the transport of herbicides and veterinary antibiotics (VAs) has not been evaluated for high runoff potential soils such as those in the Central Claypan Region of northeastern Missouri.

– Data to needed to support design criteria for implementation relative to contaminant of interest, choice of grass species, and buffer width

• Objectives: – 1) To compare the effectiveness of three grass buffer treatments in

reducing herbicide and VA loads in surface runoff from a claypan soil– 2) To establish design criteria, relative to grass buffer widths, for estimating

compound-specific load reductions using regression relationships.– 3) Evaluate the effect of season (spring, summer, fall) on VBS performance


• Plot Layout– Mexico silt loam, 5% slope, eroded– Twelve 1.5 m by 16 m plots (4 treatments

replicated 3 times)– Grass treatments:

1) Tall fescue (TF); 2) Tall fescue with a switchgrass hedge (Hedge

+ TF)3) Native warm-season grasses (mainly eastern

gamagrass and switchgrass) (Native)4) Continuous cultivated fallow (Control)

– Buffer width Runoff collectors at: -1 m; 1 m, 4m, and 8m

• Herbicides and VAs (rate, kg/ha)– Atrazine (2.2), glyphosate (1.5), and

metolachlor (1.7)– Tylosin (4.65) and sulfamethazine (4.29), and

Enrofloxacin (4.65)

Materials and MethodsExperimental Design

8 m

1.0 m

4 m

Slope(4.9%)

Fescue

Runoff sampling troughs

Fescue

T1

Native

T2 T3 T4

TilledArea

Switchgrass hedge width is 0.7 m

8 m

TilledArea

TilledArea

TilledArea

TilledArea

1.5 m

Materials and MethodsExperimental Design – Grass Treatments

1 M

4 M

Source Area-1 M

8 M


• Plot Preparation– 1.5 m by 8 m area above the VBS was roto-tilled to ~10 cm

(source area)– Plots brought to saturation 24 hours before runoff collection– Herbicides and VAs broadcast with a backpack sprayer 16

hours before runoff collection (not incorporated)• Runoff Collection

– Runoff generated by a rainfall simulator at a rate of ~5 cm/hr– Samples collected beginning with initiation of flow at the 8 m

sampler– Collected every 10 minutes for 60 minutes; composited to

create one sample for each buffer width (i.e, -1, 1, 4, and 8 m)• Sample Analysis

– Herbicides: water and sediment analyzed– VAs: only water analyzed

• Experiments conducted from 2004 to 2010; pooled data from the summers of 2004 and 2006 are presented (VAs in 2006 only).

Materials and MethodsExperimental Design


• Relative Load– Load = concentration (C) X flow (Q) for

each buffer width. – Normalized Load = contaminant mass at

each sampling position normalized to the total mass at the -1m samplers (input)

• Statistics– 2-way ANOVA

Factors – grass species and buffer width Significance level, α = 0.10 F-LSD0.1 for mean comparisons

– Correlated relative load reduction to buffer width General form of the 1st-order decay

equation: y = a + be-kx

Materials and MethodsComputations and Statistics

-1m(Input)

1m 4m 8m

X X X XC1 C2 C3 C4

M1 M2 M3 M4M1/M1 M2/M1 M3/M1 M4/M1

( N o r m a l i z e d t o I n p u t )

Q1 Q2 Q3 Q4


y = relative load reduction; x = buffer width; a,b, and k – model coefficients

Herbicide Properties

70

147

Antibiotic Properties

Relative Load Reduction - AtrazineR

elat

ive

Atr

azin

e Lo

ad (%

)

0

20

40

60

80

100

-1 0 1 2 3 4 5 6 7 80

20

40

60

80

100

ObservedPredicted

Hedge + Fescue

y = 44.6 + 23.6e(-0.855x)

r2 = 0.635 (p < 0.001)

Tall Fescue

y = 36.1 + 37.1e(-0.545x)

r2 = 0.640 (p < 0.001)

y = 85.52 + 9.37e(-0.451x)

r2 = 0.041(p = 0.68)

Control

Buffer Width (m)-1 0 1 2 3 4 5 6 7 8

Native

y = 31.8 + 34.9e(-0.670x)

r2 = 0.748 (p < 0.001)

Error bars are 95% Confidence Interval


Relative Load Reduction - Glyphosate

0

20

40

60

80

100

Buffer Length (m)-1 0 1 2 3 4 5 6 7 8-1 0 1 2 3 4 5 6 7 8

Rel

ativ

e G

lyph

osat

e Lo

ad (%

)

0

20

40

60

80

100

ObservedPredicted

NativeHedge + Fescue

y = 17.9 + 54.2e(-0.414x)

r2 = 0.803 (p < 0.001)y = 34.6 + 33.3e(-0.677x)

r2 = 0.616 (p < 0.001)

Tall Fescue

y = 19.3 + 58.7e(-0.315x)

r2 = 0.863 (p < 0.001)

Control

y = 81.2 + 14.5e(-0.171x)

r2 = 0.053 (p = 0.632)

Error bars are 95% Confidence Intervals



ResultsDissolved-Phase and

Sediment Bound Transport

Native Treatment

0

20

40

60

80

100

120

-1 1 4 8

Atrazine

0

20

40

60

80

100

120

-1 1 4 8

0

20

40

60

80

100

120

-1 1 4 8

Metolachlor Sediment Bound

Dissolved

Glyphosate

Atrazine and metolachlor were predominantly transported in the dissolved-phase (i.e., 95-98% was dissolved in the runoff water).

Glyphosate was transported in the dissolved-phase and as sediment-bound compound

• Note that at -1 and 1 m ~60% was transported as sediment-bound.

• At 4 and 8 m a large proportion of the sediment was deposited in the buffers and more glyphosate was in the dissolved-phase (~60%).

Distance from source (m)

Grass Buffer DesignAnticipated Field-Scale Results


Buffer Width (m)

-1 0 1 2 3 4 5 6 7 8 90

20

40

60

80

100Rel

ativ

e M

etol

achl

or L

oad

(%)

0

20

40

60

80

1000

20

40

60

80

100

ObservedPredicted

Native(Warm Season)

Switchgrass Hedge + Fescue

Tall Fescue

Metolachlor

Drainage to Buffer Area Ratio8:1 2:1 1:18:0

ResultsSummary of Statistical Differences - Herbicides

• All grass treatments significantly reduced transport of all 3 herbicides– Similar load reductions for dissolved-phase and sediment-bound transport

Atrazine, ↓57-68% ; Metolachlor, ↓66-72%; Glyphosate, ↓77-81% (8m data)

• Atrazine and metolachlor transport– Buffer width: 4m = 8m; both > 1m– Species:

Atrazine – no significant differences among grasses Metolachlor – Native > TF or Hedge+TF

• Glyphosate transport– Buffer width: 8m > 4m > 1m– Species: no significant differences among grasses

• Reduction in herbicide loads as a function of buffer width followed 1st-order exponential decay model for all herbicides


Relative Load Reduction - Sulfamethazine

Buffer Length (m)-1 0 1 2 3 4 5 6 7 8-1 0 1 2 3 4 5 6 7 8

Rel

ativ

e S

ulfa

met

hazi

ne L

oad

(%)

0

20

40

60

80

1000

20

40

60

80

100

ObservedPredicted

y = 1.94 + 91.1e(-0.072x)

r2 = 0.841 (p < 0.001)

y = 11.5 + 66.8e(-0.286x)

r2 = 0.911 (p < 0.001)y = 1.12 + 79.1e(-0.236x)

r2 = 0.843 (p < 0.001)

Control

Hedge + Fescue Native

Tall Fescue

y = -11.2 + 94.0e(-0.198x)

r2 = 0.732 (p < 0.001)

Error bars are 95% Confidence Intervals Dissolved-phase transport only


Relative Load Reduction - Tylosin

Buffer Length (m)

-1 0 1 2 3 4 5 6 7 8-1 0 1 2 3 4 5 6 7 8

Rel

ativ

e Ty

losi

n Lo

ad (%

)

0

20

40

60

80

100

0

20

40

60

80

100

ObservedPredicted

y = 79.7 + 11.3e(-0.600x)

r2 = 0.24 (p < 0.001)

y = 110 -9.20e(-0.036x)

r2 = 0.006 (p = 0.97)y = 75.1 -1.22e(-0.00x)

r2 = 0.00(p = 1)

Control

Hedge + Fescue

Native

Tall Fescue

y =25.5 + 51.9e(-0.382x)

r2 = 0.910 (p < 0.001)

Error bars are 95% Confidence IntervalsDissolved-phase transport only


ResultsSummary of Statistical Differences - Antibiotics

• Sulfamethazine – All grass treatments significantly reduced transport

Load reductions: 81-89% (8m data)– Buffer width: 4m = 8m > 1m– Species: no significant differences among grasses– Reduction in loads as a function of buffer width followed

1st-order exponential decay model• Tylosin and Enrofloxacin

– Dissolved-phase transport trends were not well described by 1st-order exponential decay model <0.2% of applied transported in the dissolved-phase

– Mainly sediment-bound transportTranslating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

ResultsMechanisms for Reducing Transport

• Infiltration– Runoff volume reductions:

43% for TF 42% for Hedge+TF 56% for Native

• Sediment Trapping– Sediment load reduced by:

80% for Native and Hedge+TF 47% for TF

• Enhanced rhizosphere degradation and sorption– Increased microbial activity in VBS soils increases atrazine

degradation (Lin et al. 2003, 2004, 2008, 2011)– Increased VA sorption in VBS soils compared to row cropped soils

indicated less contaminant mobility in VBS soils (Chu et al., 2010).Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

Summary and Conclusions• Effect of Grass Species

– All grass treatments significantly reduced transport of herbicides and VAs Load reductions in the range of 60-90% for 4-8 m of VBS For tylosin and enrofloxacin, only the TF treatment reduced transport

• Effect of Buffer Width– Reduction in loads as a function of buffer width followed 1st-order

exponential decay model Expected field-scale results (20:1): 15-40% reductions

• VBS effective on high runoff potential soils• Buffer Design

– Regression equations account for the contaminant, drainage-to-buffer area ratio, and grass species Provide simple, practical design criteria for land management agencies Potentially achieve desired reductions with less land taken out of

production C3 grasses can be an effective alternative to C4 species


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