pesticide downward movement in a bermudagrass system compared with movement in a fallow system h.d....

Pesticide Downward Pesticide Downward Movement in a Bermudagrass Movement in a Bermudagrass

System Compared with System Compared with

Movement in a Fallow SystemMovement in a Fallow System H.D. Cummings*, J.B. Weber, R.B. Leidy, F.H. Yelverton,

and R.L. Brandenburg

NCSU, Raleigh, NC

NC State University

Introduction• Previous studies have characterized

the downward movement of pesticides in conventional till systems.

• If regulatory issues of pesticides are based on downward movement of pesticides in traditional agricultural systems, they may not be appropriate for turf systems.

Introduction

• In turf, pesticides are rarely applied to bare soil.

• In turf, a lower fraction of pesticides reaches soil.

• In turf, some pesticides are absorbed and metabolized by plants (biological degradation).

• Compared to agriculture, knowledge is generally lacking on pesticide fate in actively growing and dormant turf.

Introduction• Managed bermudagrass systems are

stratified by pH. • Thatch layers have high levels of organic

matter.• Organic matter and pH can influence some

movement of pesticides.• Thatch layers contain diverse

microorganism populations.• Nutrients and irrigation are applied at

regular intervals to turf.

ObjectiveObjective

• To compare the downward movement of pesticides in a bermudagrass system to movement in a fallow system.

Materials and Methods• ‘Tifway’ hybrid bermudagrass

maintained at 1.9 cm at the Sandhills Research Station near Pinehurst, NC

• Native soil (Candor sand) (sandy siliceous, thermic, Arenic Paleudult) (83% sand, 11% silt, 4% clay, 2% OM) (High potential for leaching)

Materials and Methods (continued)(continued)

• In early May 2001, half of the bermudagrass area (580 m2) was sprayed with glyphosate; two weeks later, it was removed with a sod cutter.


• The area was tilled once.

• On May 25, 2001, the tilled ground was fumigated setting up a split plot design (Turf Vs Fallow Ground).


• In June and August of 2001 and May 2002, a total of 40 soil column lysimeters (91 cm long x 15 cm in diameter) were installed in both turf and fallow soil.


• Four herbicides

• One insecticide

• Two replications

• Applied in July when turf was actively growing and in November when turf was dormant in 2001 and 2002

Plot size:2.3 m2

470 L/ha

Insecticide applied with shaker can

Irrigatedwith 1 cm of water

Six weeks after initialfumigation

Treatments

Common Trade RateWater

Solubility Koc

Name Name (kg ai/ha) (mg/L) (mL/g)

Simazine Princep 2.2 3.5 140

Imazaquin Image 0.56 60 20

Pronamide Kerb 1.7 15 800

Prodiamine Barricade 0.56 0.013 13,000

FipronilChipco Choice 0.014 1.9 – 22 749

Pesticide ClassificationSimazine Triazine Weak base. Cationic

at low pH, binds to clay and OM

Imazaquin Imidazolinone Carboxy acid. Anionic at high pH, binds to OM at low pH

Pronamide Amide Nonionic. Binds weakly to OM independent of pH

Prodiamine Dinitroaniline Nonionic. Binds strongly to soil

Fipronil Phenylpyrazol Nonionic. Binds to soil

Materials and Methods (Continued)

• After 140 days, the soil column lysimeters were harvested.

• The soil in the lysimeters was divided into 8 depth increments.

• Turf tissue was collected by depth.

0 – 2 cm

2 – 4 cm

4 – 8 cm

8 – 15 cm

15 – 30 cm

30 – 45 cm

45 – 60 cm

60 – 91 cm

(Deeper increments may not have been analyzed)(Turf tissue data not presented )


Sonication removes adsorbed compounds from soil (10 g soil).

Rotoevaporator concentrates extract.


Gas chromatograph (GC) separates the compounds and determines the concentration of the compound of interest (TSD detector).

Soil Organic Matter Profile of Turf and Fallow Soil

525 oC for 16 hours

2.04 1.89 1.69 1.89 1.681.21 1.20 0.99

6.13

7.69

2.08 1.98 1.84

1.04 1.13 0.97

0

2

4

6

8

10

0 - 2 2 - 4 4 - 8 8 - 15 15 - 30 30 - 45 45 - 60 60 - 90

Depth (cm)

Org

anic

mat

ter

(%)

Fallow

Turf

Thatch Layer

Soil pH Profile of Bermudagrass and Fallow Systems

0

1

2

3

4

5

6

7

0 - 2 2 - 4 4 - 8 8 - 15 15 - 30 30 - 45 45 - 60 60 - 90

Depth (cm)

pH

Fallow

Turf

More binding of cations to OM at high pH; however,simazine and imazaquin are more mobile at high pH

Simazine in Soil of Fallow and Turf Systems after 140 Days of Summer

23 11 333

96

0

50

100

150

200

250

300

0 - 2 2 - 4 4 - 8 8 - 15

Depth (cm)

Par

ts p

er B

illio

n (µ

g/kg

)

Fallow yr 1Fallow yr 2Turf yr 1Turf yr 2

Initial Concentration (ppb)

System 0 – 2 cm 2 – 4 cm 4 – 8 cm

Fallow 8,022 70 ND

Turf 7,735 ND ND

ND ND ND ND ND ND ND ND ND ND ND


23 11 333

96

0

50

100

150

200

250

300

0 - 2 2 - 4 4 - 8 8 - 15

Depth (cm)

Par

ts p

er B

illio

n (µ

g/kg

)



(2 days after application)

System 0 – 2 cm 2 – 4 cm 4 – 8 cm

Fallow 8,022 70 ND

Turf 7,735 ND ND



23 11 333

96

0

50

100

150

200

250

300

0 - 2 2 - 4 4 - 8 8 - 15

Depth (cm)

Par

ts p

er B

illio

n (µ

g/kg

)



System 0 – 2 cm 2 – 4 cm 4 – 8 cm

Fallow 8,022 70 ND

Turf 7,735 ND ND


Simazine in Soil of Fallow and Turf Systems after 140 Days of Winter

112 902346

238

5

1198

348

3291 59 104108

189101

0

200

400

600

800

1000

1200

0 - 2 2 - 4 4 - 8 8 - 15 ** 15 - 30Depth (cm)

Par

ts p

er B

illio

n (

µg/

kg)



System 0 – 2 cm 2 – 4 cm 4 – 8 cm

Fallow 9,371 ND ND

Turf 13,369 1,119 ND

ND NDND ND NA

*

* Turf year 1 different from Fallow year 1 at depth 0-2 cm (p<0.05). ** Winter 1 concentrations greater than summer 1 (p<0.05)

Imazaquin in Soil of Fallow and Turf Systems after 140 Days of Summer

83

1918 24

050

100150200250300350400450500

0 - 2 2 - 4 4 - 8 8 -15

Depth (cm)

Par

ts p

er B

illio

n (µ

g/kg

)



System 0 – 2 cm 2 – 4 cm 4 – 8 cm

Fallow 259 148 141

Turf 558 400 26

ND ND ND ND ND ND NDND ND NDND ND

Imazaquin in Soil of Fallow and Turf Systems after 140 Days of Winter

20

453

265

050

100150200250300350400450500

0 - 2 2 - 4 4 - 8 8 -15

Depth (cm)

Par

ts p

er B

illio

n (µ

g/kg

)



System 0 – 2 cm 2 – 4 cm 4 – 8 cm

Fallow 5,166 569 166

Turf 597 571 155

ND ND ND NDND ND ND NDND ND ND NDND

Pronamide in Soil of Fallow and Turf Systems after 140 Days of Summer

96116

135

20

0

50

100

150

200

250

300

350

400

0 - 2 2 - 4 4 - 8 8 -15

Depth (cm)

Par

ts p

er B

illio

n (µ

g/kg

)



System 0 – 2 cm 2 – 4 cm 4 – 8 cm

Fallow 2,047 ND 70

Turf 3,616 199 ND

ND ND ND ND ND ND ND NDND ND ND ND

Pronamide in Soil of Fallow and Turf Systems after 140 Days of Winter

192214 223 218204

20

50

100

150

200

250

300

350

400

0 - 2 2 - 4 4 - 8 8 - 15

Depth (cm)

Par

ts p

er B

illio

n (µ

g/kg

)



System 0 – 2 cm 2 – 4 cm 4 – 8 cm

Fallow 5,570 ND ND

Turf 4,556 441 ND

ND NDND ND ND ND ND ND NDND

* Fallow year 2 different from Turf year 2.

* * *

Prodiamine in Soil of Fallow and Turf Systems after 140 Days of Summer

285

16

1158

66

451

64

411

46 5 9230

200

400

600

800

1000

1200

1400

1600

1800

0 - 2 2- 4 4 - 8 8 - 15

Depth (cm)

Par

ts p

er B

illio

n (µ

g/kg

)



System 0 – 2 cm 2 – 4 cm 4 – 8 cm

Fallow 809 ND ND

Turf 2,055 ND ND

ND ND NDND ND

Prodiamine in Soil of Fallow and Turf Systems after 140 Days of Winter

616

13

1083

13414

1614

7

562

71 768109

0

200

400

600

800

1000

1200

1400

1600

1800

0 - 2 2 - 4 4 - 8 8 - 15

Depth (cm)

Par

ts p

er B

illio

n (µ

g/kg

)



System 0 – 2 cm 2 – 4 cm 4 – 8 cm

Fallow 3,424 ND ND

Turf 5,118 199 ND

ND ND ND ND

Fipronil in Soil of Fallow and Turf Systems after 140 Days of Summer

316.8 12 5.9

71

153

162.5 4.2

0

50

100

150

200

250

300

0 - 2 2 - 4 4 - 8 8 - 15

Depth (cm)

Par

ts p

er B

illio

n (µ

g/kg

)



System 0 – 2 cm 2 – 4 cm 4 – 8 cm

Fallow 26 ND ND

Turf 61 ND ND

ND ND ND NDND NDND

Fipronil in Soil of Fallow and Turf Systems after 140 Days of Winter

4019 20 14 311 14 10

0

50

100

150

200

250

300

0 - 2 2 - 4 4 - 8 8 - 15

Depth (cm)

Par

ts p

er B

illio

n (µ

g/kg

)



System 0 – 2 cm 2 – 4 cm 4 – 8 cm

Fallow 33 ND ND

Turf 29 ND ND

NDND ND ND ND ND ND ND

ConclusionConclusion• Initial concentrations (2 days) were greater in

winter except for fipronil in the turf system.

• More movement and higher concentrations tended to occur in winter (140 days) except for fipronil in bermudagrass and imazaquin in fallow systems.

• Simazine and imazaquin were detected at greater concentrations in bermudagrass system (0-4 cm) than the fallow system in winter.

Conclusion Conclusion (continued)(continued)• Simazine and imazaquin were detected at

deeper depths and at greater concentrations in the fallow system than bermudagrass system in summer.

• Pronamide was detected at greater concentrations in the bermudagrass system (0-4 cm) than in the fallow system in summer; however, pronamide was detected at deeper depths and at greater concentrations in the fallow system in winter.

• Prodiamine movement was not influenced by actively growing or dormant turf.

Conclusion Conclusion (continued)(continued)

• Fipronil was detected at greater concentrations in summer in the bermudagrass system (0-4 cm) than the fallow system; however, more fipronil movement occurred in the fallow system in winter.

SummarySummary• Generally, more downward movement and

greater concentrations occurred in winter.• In bermudagrass, pesticides tended to stay

in the thatch layer (0 – 4 cm).• In fallow soil, pesticides tended distribute

more uniformly.• To reduce the potential for leaching, apply

pesticides to actively growing bermudagrass.

Final Conclusions• Generally, more downward

movement and greater pesticide concentrations occurred in winter.

• In bermudagrass, pesticides tended to stay in the thatch layer (0 – 4 cm).

• In fallow soil, pesticides tended distribute more uniformly.

Final Conclusions• Simazine is less likely to move to

groundwater when applied to actively growing bermudagrass.

• Fipronil can provide season-long control (120 day) by causing mortality or avoidance behavior.

Tarleton State University

pesticide downward movement in a bermudagrass system compared with movement in a fallow system h.d....

Documents

soil slide

turf systems

continued materials

leaching slide

fallow soil

dormant turf

turf tissue

initial fumigation slide