atrazine incorporation and soil erosion – balancing competing water quality concerns for claypan...

Atrazine Incorporation and Soil Erosion – Balancing Competing Water Quality Concerns for Claypan and

Restrictive Layer Soils

R. N. Lerch, C. M. Harbourt, R. R. Broz, and T. J. Thevary

ARS Field 1 near Centralia, MO

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

Background - Claypan SoilsCentral Claypan Areaso Major Land Resource Area 113

o Encompasses 33,000 km2 in MO and IL

Claypan Characteristicso Smectitic mineralogy (high shrink-

swell potential)

• 40-60% clay content

o Near surface feature (0-60 cm)

o Ksat <1 mm/s

o Claypan is an extreme form of an argillic horizon

Vulnerable to contaminant transport in surface runoff • Soil-applied herbicides

• Soil erosion


Rationale A major challenge associated with claypan soils is the

need to develop cropping systems that concurrently facilitate incorporation of herbicides to reduce their transport in surface runoff, but maintain sufficient crop residue cover to control soil erosion (Lerch et al., 2008).

Conflicting Goalso No-till precludes the incorporation of herbicides. o Incorporation increases soil erosion

Conflicting goals require a balanced approach rather than managing for one problem at the expense of anothero Herbicide application methods must be found that can

incorporate soil-applied herbicides and maintain greater residue cover than commonly used reduced tillage systems, such as disc harrow or field cultivator.

No-Till Treatment; Simulation #3


Objective Compare the effect of 3 tillage systems on sediment

and atrazine transport in surface runoffo Tillage treatments

• Phillips Harrow (Harrow)• No-Till• Field Cultivator (Minimum-Till)

o Data Collected• Hydrologic

Time to initiation of runoff, instantaneous discharge, and total volume

• Water Quality Suspended sediment (SS) concentration and load Atrazine concentration (by ELISA) and load

• Agronomic Residue cover, weed cover, corn yield


Phillips Harrow• Roller harrow

• Seedbed preparation

• Maintains greater residue cover than disc harrows or field cultivators

• Incorporate herbicides (or fertilizer) to ~5cm depth

• Working speeds up to 12 mph

• Low horsepower requirements (90-130 hp)

• High working capacity - >40 ac/hr for the 45’ wide implement

• One-pass spraying and incorporation - can be equipped with spray nozzles and tanks


Experimental DesignSite Description

Site located at the University of Missouri, Bradford Research and Extension Center

Soil Serieso Leonard Silt Loam, ~2% slopeo Common backslope claypan

soilo Managed as no-till corn-

soybean rotation for last 15 years (soybean in 2010).

Experiment conducted from 6/6 – 6/10/2011o No natural rainfall occurred!


Experimental DesignPlot Layout

Each treatment was replicated six times in two sets of three plots.

S

N



S

N

Experimental DesignTillage Treatments

Phillips Harrowo Tilled with a disc harrow to 10 cm depth one week prior to

experiment• Intended to represent the expected residue cover from a

conventionally managed corn-soybean rotationo Atrazine applied at 2 lbs/ac, then incorporated with 2-passes to 3-5

cm depth.o Operating speed was 8-9 mph (13-15 km/h).

No-Tillo Atrazine applied at 2 lbs/ac

Field Cultivatoro Disc harrow one week prior to experimento Atrazine applied at 2 lbs/ac, then incorporated with 2-passes to 10

cm depth.

All treatmentso Whole plot areas sprayed with Bicep (2 lbs/ac atrazine; 1.6 lbs/ac

metolachlor) following rainfall simulationso Corn planted on June 16, 2011


Experimental DesignPlot Set-up

Site selection within the bulk plot based on minimizing side slope

0.25% or less Slopes

o Harrow – 2.1%o No-Till – 2.6%o Minimum-Till – 2.3%

Border steel installed to ~15 cm depth after herbicide spraying

Down slope section constructed with a diversion wall and metal gutter

Gutter attached to a PVC pipe to divert runoff to the sample bucket

Diversion wall

Gutter5 cm PVC pipe


Runoff was generated using the HMWRS-001 rainfall simulator, designed by Waterborne Environmental, Inc. o Rainfall rate target for runoff collection was 27 mm/hro Rained on three sub-plots at a timeo Field operations were performed in the following sequence:

• Plots brought to saturation 48 hours before runoff collection• Plots sprayed 24-28 hours before runoff collection

Experimental DesignRainfall Simulation

Photo courtesy of Waterborne Environmental, Inc. Photo courtesy of Waterborne Environmental, Inc.


Experimental DesignRunoff Collection

Instantaneous discharge o Determined by recording the

time to fill a 15-L bucketo Buckets composited in a 500-L

plastic barrel• Provided total runoff volume and

composite samples for atrazine and suspended sediment

Runoff Samples o Collected at 1, 5, 10, 15, 20, 30,

50, 70, and 90 minutes following the initiation of runoff.

o Samples analyzed for SS and atrazine concentration

Photo courtesy of Waterborne Environmental, Inc.


Experimental DesignResidue Cover and Weed Control

Residue cover o Assessed on every runoff plot and 6 randomly chosen

areas within the bulk plots• Digital images acquired on 1 m2 areas using square borders

placed over the soil surface

Weed controlo Six randomly chosen 1 m2 areas within the bulk plot

(runoff plots excluded) were digitally photographed approximately two weeks after Bicep application and corn planting.

Images were analyzed for the fraction of the area covered by residue or weeds


ResultsHydrology

Mean Discharge

Harrow No-Till Minimum-Till

Dis

char

ge (

L/s)

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07 Total Runoff Volume


Vol

ume

(L)

0

100

200

300

400(p = 0.797)(p = 0.797)



ResultsHydrology

ResultsHydrology

Rainfall Normalized Runoff Volume


Run

off V

olum

e (L

/mm

)

0

1

2

3

4

5

6

7(p = 0.005)

LSD0.05

a ab

Time to Initiation of Runoff


Tim

e (m

in)

0

20

40

60

80(p = 0.008)

LSD0.05

a

b

a


ResultsErosion – SS Concentration

Suspended Sediment Concentration*


Sus

pend

ed S

edim

ent (

g/L)

0.00

0.20

0.40

0.60

0.80

Mean Rank of Suspended Sediment Concentrations


Mea

n R

ank

0

20

40

60

80

100

120

140

160(p < 0.0001)

*Median ± average absolute deviation

*CD0.05

a b

c

*Critical difference for


ResultsErosion – SS Loads

Suspended Sediment Load


Se

dim

en

t Lo

ad

(g

)

0

50

100

150

200(p = 0.0002)

LSD0.05

a a

b

Rainfall Normalized SS Load

Harrow No-Till Minimum-TillS

ed

ime

nt L

oa

d (

g/m

m)

0.0

0.5

1.0

1.5

2.0

2.5

3.0(p = 0.0002)

LSD0.05

a

b

a


ResultsAtrazine Concentrations


Atr

azi

ne c

once

ntra

tion

(g

L-1

)

0

500

1000

1500

2000

2500

3000

a

b

c

F-LSD0.05


ResultsAtrazine Concentrations

Time (minutes)

0 10 20 30 40 50 60 70 80 90

Atr

azin

e C

once

ntra

tion

(g/

L)

0

500

1000

1500

2000

2500

3000

3500

4000Minimum-TillNo-Till Harrow


ResultsAtrazine Loads


Atr

azi

ne L

oad

(% o

f A

ppl

ied)

0

5

10

15

20

25

30

a a

b


Rai

nfal

l Nor

mal

ized

A

tra

zine

Loa

d (m

g m

m-1

)0

2

4

6

8

10

12

14

a

b

a

F-LSD0.05F-LSD0.05

A B


Summary and Conclusions Hydrology

o No treatment differences in mean discharge or total runoff volumeo No-till significantly increased normalized runoff volume and

decreased time to initiation of runoff

Erosiono SS concentration: No-till < Harrow < Minimum-Tillo SS load: No-till = Harrow < Minimum-Till

Atrazineo Concentration: Minimum-Till < Harrow < No-Tillo Load: Minimum-Till = Harrow < No-Till

Supported other studies on claypan soils (Ghidey et al., 2005

and 2010): o Effectiveness of incorporation for reducing atrazine transport in runoffo No-till does not reduce runoff volume and greatly increases atrazine

losses on claypan soils

Roller harrow achieved the needed balance by controlling both erosion and atrazine losses


Benefits of Roller Harrows Available tillage implement that is relatively low cost ($20-$40k)

Could readily replace disc harrows or field cultivators commonly used for seedbed preparation in corn production systems within the Central Claypan Areas

Improve sustainability of crop production by controlling erosion

Maintains farmer profitability

Improve the region’s two most persistent water quality problems by simultaneously managing the trade-off between erosion control and atrazine transport in runoff

Can be recommended as an atrazine BMP for claypan and restrictive layer soils!!


Syngenta Corp. for the funding, and proposal review and field work assistance

Waterborne Environmental, Inc. field crew USDA-ARS field crew Kristi Perry and University Extension Todd Hensiek, Kane Holloway, and Tim McClintock

for the research on the roller harrow as part of their ASM capstone class (2009)

Acknowledgments

Minimum-Till Treatment; Simulation #5


atrazine incorporation and soil erosion – balancing competing water quality concerns for claypan...

Documents

o incorporation

o data

mo slide

conflicting goals o

clay content o

thevary ars field

training session

incorporation of herbicides