Soil Microbiological Activities in Vegetative Buffer Strips and Their Association with Herbicide Degradation

By

C.H. Lin, R.N. Lerch, R.J. Kremer, H.E. Garrett, U. Ranjithand M.F. George

Recent Studies Regarding Herbicides and Health,

Ecological and Social & Economic Impacts • Public Heath ImpactThe men living in the Mid Missouri, as compared to other U.S. urban areas, tend to have poorer

sperm quality and lower sperm counts. (Dr. Swan et al. 2003)The lower sperm quality and counts strongly associated with the higher herbicides residue

levels (alachlor, atrazine) in their urine samples. (Dr. Swan et al. 2003; Center for Disease Control and Prevention 2003)

(None of the men in the study worked at or lived next to farms)

• Ecological ImpactFrogs exposed to atrazine in the reservoir near Midwest states developed reproductive

deformity (hemaphroditic; mixtures of ovaries and testes) (Dr. Hayes et al. 2003).

• Social & Economic ImpactTo comply drink water regulation, St. Louis County estimated the costs of compliance for their

five drinking water treatment plants by the installation of granular activated carbon at a capital cost of $164 million, with operation and maintenance costs of $7 million per year.

Our Mission

• To optimize the riparian buffer designs in agroforestry systems to reduce the herbicide transport from nearby agricultural lands before they reach the reservoirs or drinking water sources

• To develop the recommendations (species selection and biodegradation agents) and cost-effective management plans to enhanced the degradation of trapped herbicides within buffers

Effectiveness of Grass Buffer Designs in Reducing

Herbicides Transport in Surface Runoff

(University of Missouri Bradford Research Center)

Atrazine Transport in Surface Runoff

0

20

40

60

80

100

120

-2 0 2 4 6 8 10

Distance from Source Area (m)

Rel

ativ

e A

traz

ine

Loa

d (%

)

Fallow_Control

Tall Fescue

Hedge+TallFescue

Hedge+Native

Metolachlor Transport in Surface Runoff

0

20

40

60

80

100

120

-2 0 2 4 6 8 10

Distance from Source Area (m)

Rel

ativ

e M

etol

achl

or L

oad

(%) Fallow_Control

Tall Fescue

Hedge+TallFescue

Hedge+Native

Glyphosate Transport in Surface Runoff

0

20

40

60

80

100

120

140

-2 0 2 4 6 8 10

Distance from Source Area (m)

Rel

ativ

e G

lyph

osat

e L

oad

(%) Fallow_Control

Tall Fescue

Hedge+Native

Further Consideration

A robust buffer design needs to rapidly degrade the deposited & intercepted herbicides before they have a chance to be released to surface and subsurface flow.

Site of Lysimeter Project at University of MissouriSite of Lysimeter Project at University of Missouri

Percent of Atrazine Degradation Products in Soil

0

10

20

30

40

50

60

70

80

90

Bare ORCH TALL TIMO SMOO SWITGrass Treatm ents

% o

f Atra

zine

Deg

rada

tion

Prod

ucts

DIHA

DEHA

HA

DIA

DEA

40

50

60

70

80

90

100

0 100 200 300

Microbial Biomass C (gC/g Soil)

Deg

rada

tion

(%)

%Degradation Correlation Coefficient = 0.58 p = 0.015

Microbial Biomass C vs. Atrazine Degradation in Soils

Contour Buffers Watershed Project

Control-traditional corn-soybean rotation

Grass Contour Buffer-redtop, brome grass and birdfoot trefoil

Agroforestry Contour Buffer- pin oak, white oak, bur oak and same mixture of grasses

Objectives (Phase I)

• *To evaluate the effect of vegetation buffers and topographic factors on soil enzymatic activities and their association with herbicides degradation

• To evaluate the effects of the contour buffers on herbicides transport and transformations in sub-surface flow.

NH

N N

N

Cl

NH

NH

N N

N

OH

NH

NH

N N

N

Cl

NH2

NH

N N

N

OH

NH2

NH2

N N

N

OH

NH

NH2

N N

N

Cl

NH

NH2

N N

N

Cl

NH2

NH2

N N

N

OH

NH2

Atrazine Degradation Pathways

Atrazine

Deethylatrazine

Deisopropylatrazine

Didealkylatrazine

Ammeline

Hydroxyatrazine

Deethylhydroxyatrazine

Deisopropylhydroxyatrazine

N-Dealkylation

Chemical orPhotochemical Hydrolysis

(ATR)

(DEA)

(DIA)

(HA)

(DEHA)

(DIHA)

Measured Enzymatic Activities

1. Fluorescein Diacetate Hydrolytic (FDA) Activity (proteases, lipases, and esterases)

2. Dehydrogenase Activity (dehalogenation, biological oxidation)

3. -Glucosidase Activity (carbon utilization efficiency)

Contour Buffers Watershed Project

Control-traditional corn-soybean rotation

Grass Contour Buffer-redtop, brome grass and birdfoot trefoil

Agroforestry Contour Buffer- pin oak, white oak, bur oak and same mixture of grasses

E1, E2: summitE3: shoulder slopeE4: back slope E5: foot slopeE6: toe slope

Control

Grass Buffer Agroforestry

E1, E2: summitE3: shoulder slopeE4: back slope E5: foot slopeE6: toe slope

0

50

100

150

200

250

300

E1 E2 E3 E4 E5 E6

Control (A)Agroforestry (B)Grass (C)

Microbial Enzymatic Potential for Herbicides Degradation[Fluorescein Diacetate Hydrolytic Activity (FDA; mole g-1 h-1)]

E1, E2: summitE3: shoulder slopeE4: back slope E5: foot slopeE6: toe slope

0

2

4

6

8

10

12

14

16

E1 E2 E3 E4 E5 E6

Control (A)Agroforestry (B)Grass (C)

Dehydrogenase Activity (mole g-1 h-1)

E1, E2: summitE3: shoulder slopeE4: back slope E5: foot slopeE6: toe slope

0

0.5

1

1.5

2

2.5

3

3.5

4

E1 E2 E3 E4 E5 E6

Control (A)Agroforestry (B)Grass (C)

-Glucosidase Activity (mole g-1 h-1)

E1, E2: summitE3: shoulder slopeE4: back slope E5: foot slopeE6: toe slope

14CO2 Trap

HPLC-FSA

Microbial Mineralization Rates of Atrazine vs. Microbial Enzymatic Activity

0

1

2

3

4

5

6

7

8

9

10

Mic

robi

al M

iner

aliz

atio

n R

ates

(%

app

lied

14C

))

0

1

2

3

4

5

6

7

8

9

10

Mic

robi

al E

nzym

atic

Act

ivity

14CO2 Evolution

FDA (0.494)*

dehydrogenase (0.763)

B-Glucosidase (0.857)

* correlation coefficient

• Contour vegetative buffer across the landscape showed significantly increased soil enzyme activities compared to cropped control treatment.

• Soils collected from grass buffers showed the highest microbial enzymatic activities and herbicide degradation potential.

• Topographic positions did not significantly affect soil microbial enzymes activities in this study.

• The preliminary results from growth chamber study suggested dehydrogenase and -Glucosidase activities showed promise as useful tools for evaluating the overall herbicide bioremediation potential of various vetetative buffer designs.

Conclusions

Current Efforts

Glyphosate and Its Metabolite

P NHOHO

HO O

O-

P NH2OHO

HO

Glyphosate

Aminomethylphosphonic acid (AMPA)

Turbo-Ion Spray LC-MS/MS