1

An Integrated System for Mapping An Integrated System for Mapping Soil Physical Properties OnSoil Physical Properties On--thethe--GoGo

(the Mechanical Sensing Component)(the Mechanical Sensing Component)

Viacheslav AdamchukViacheslav AdamchukPhilip ChristensonPhilip Christenson

Biological Systems EngineeringBiological Systems EngineeringUniversity of Nebraska University of Nebraska -- LincolnLincoln

Presentation OutlinePresentation Outline• Background

– Problem statement and history of sensor development

– Overview of integrated mapping of soil physical attributes

• Materials and Methods– Vertical blade with an array of strain gage bridges– Ling-term tillage plots experiment

• Results and Discussion– Comparison of tillage practices using on-the-go

measurements of soil mechanical resistance– Field mapping– Overview of the latest prototype system– Summary

Problem Statement Problem Statement

• The assessment of soil variability is one of the most important steps in site-specific management

• Conventional means to attain soil variability data are incapable of accurately identifying spatial inconsistency within a production field at an economically feasible cost

• There is a need to develop equipment for mapping soil attributes on-the-go

• On-the-go sensing technology must be reliable, rapid, simple, inexpensive, repeatable

OnOn--thethe--go Soil Sensorsgo Soil Sensors

Electrical and Electromagnetic

Acoustic

Mechanical Electrochemical

H+

H+ H+H+

H+

Pneumatic

Optical and Radiometric

Applicability of OnApplicability of On--thethe--Go Soil SensorsGo Soil Sensors

OKSomeSomeResidual nitrate (total nitrogen)

OKOKCEC (other buffer indicators)

OKSomeOther nutrients (potassium)

GoodSomeSoil pH

SomeOKSomeDepth variability (hard pan)

SomeGoodSoil compaction (bulk density)

SomeOKSoil salinity (sodium)

GoodGoodSoil water (moisture)

GoodSomeSoil organic matter or total carbon

SomeOKGoodSoil texture (clay, silt and sand)

Soil property H+

H+ H+H+

H+

Integrated Mapping ApproachIntegrated Mapping Approach• Instrumented blade

– Compacted field areas– Soil mechanical resistance profile– Blade with an array of strain gage bridges– Sensing depth down to 30 cm– Minimum soil disturbance

• Capacitor-type sensor– Volumetric water content– Dielectric soil properties measurement

• Optical sensor– Organic matter content– Soil reflectance at 470 and 660 nm– Direct soil contact through a sapphire window

2

Vertical Blade Mapping ApproachVertical Blade Mapping Approach

Strain Gages

Tool Bar

Travel Direction

Purdue University (West Lafayette, Indiana)

1998

< 2.892.89 – 3.113.11 – 3.333.33 – 3.55> 3.55

Soil Mechanical Resistance, kN

1998 Farm Progress Show Site

Corn Yield

20 cm __20 cm __

Vertical Smooth Blade with an Array Vertical Smooth Blade with an Array of Strain Gagesof Strain Gages

Purdue University (West Lafayette, Indiana) – UNL

(Lincoln, Nebraska)1999 - 2001

Strain Gage Array

Three Independent Blade SystemThree Independent Blade System

UNL (Lincoln, Nebraska) –University of Sao Paulo

(Piracicaba, Brazil)2002 - 2004

Three blades• 0 – 10 cm• 10 – 20 cm• 20 – 30 cm

Soil-metal friction compensation

sensor

Soil Mechanical Resistance (Three Blade System)Soil Mechanical Resistance (Three Blade System)

Soil Mechanical Resistance (Three Blade System)Soil Mechanical Resistance (Three Blade System)

Soil Mechanical Resistance, MPa

ARDC (Mead, Nebraska)

Field 1.10December 2002

0 – 10 cm depth 10 – 20 cm depth

20 – 30 cm depth

Example of Spatial Resemblance Example of Spatial Resemblance between Different Data Layersbetween Different Data Layers

bu./acre

Soybean Yield, 2000

Soil Mechanical Resistance, 20-30 cm

Soybean Yield, 2002

Soil Electrical Conductivity, 0-30 cm

bu./acre

MPa

mS/m

3

Integrated Soil Physical Properties Integrated Soil Physical Properties Mapping System (ISPPMS)Mapping System (ISPPMS)

Two wavelengths soil reflectance sensor

Soil mechanical resistance profiler with an array of

strain gage bridgesCapacitor-based

sensor

UNL (Lincoln, Nebraska) 2004

““Organic Matter” SensorOrganic Matter” Sensor

Shank

Cross-sectionof the sensor

660 nm LEDs

Photodiode

Purdue University (West Lafayette, Indiana)

1988 - 1992

UNL (Nebraska, Lincoln)

2004 - 2005

CapacitorCapacitor--Based SensorBased SensorUNL (Lincoln, Nebraska) –

Retrokool (Berkeley, California)2001-2003

• Silty clay loam soil• Triple replicates• Two tests

2.0

2.2

2.4

2.6

2.8

3.0

3.2

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35

Gravimetric Soil Moisture, g/g

Sens

or O

utpu

t, V

Test 1Test 2Average

Instrumented Blade with a Instrumented Blade with a HalfHalf--Split Cutting EdgeSplit Cutting Edge

Gage 1

Gage 2

Gage 3

Gage 4

Boss A

Boss B

Boss C

Vertical location:

Cutting edge

Blade

Discrete reaction forces

Apparent soil surface

Direction of travel

Second order polynomial

model

Actual soil surface

5 – 30 cm measurement depth

Tillage Treatment Experimental PlotsTillage Treatment Experimental Plots

0.25 - 0.290no-till w/o cultivationF0.24 - 0.2513double diskedE0.23 - 0.2630chiselled and diskedD0.24 - 0.275no-till with cultivationC0.24 - 0.2613diskedB0.26 - 0.2820plowed and double diskedA

Gravimetric moisture content, g/g

Maximum depth of tillage, cmTillage treatmentPlot

• Twenty years history• Controlled wheel traffic• Five cone penetrometer profiles• Five on-the-go measurements (1 Hz)

Apparent Soil ProfilesApparent Soil Profiles

Plot B (disked)

0

5

10

15

20

25

-0.8 -0.4 0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8

Soil mechanical resistance, MPa

Rela

tive

dept

h, c

m

ISPPMS - pass 1Cone - pass 1ISPPMS - pass 2Cone - pass 2

Plot D (chiselled and disked)

0

5

10

15

20

25

-0.8 -0.4 0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8

Soil mechanical resistance, MPa

Rela

tive

dept

h, c

m

ISPPMS - pass 1Cone - pass 1ISPPMS - pass 2Cone - pass 2

012

2)( ayayayp ++=

⎥⎥⎥

⎦

⎤

⎢⎢⎢

⎣

⎡

⎥⎥⎥

⎦

⎤

⎢⎢⎢

⎣

⎡

−−−

−=

⎥⎥⎥

⎦

⎤

⎢⎢⎢

⎣

⎡

−−−

−−−

−−−

C

B

A

RRR

aaa

444

656

888

0

1

2

10*65002.110*51320.510*65388.610*67377.610*79098.110*78951.6

10*24800.410*13568.710*68903.1

⎥⎥⎥⎥

⎦

⎤

⎢⎢⎢⎢

⎣

⎡

⎥⎥⎥

⎦

⎤

⎢⎢⎢

⎣

⎡−−−

−=

⎥⎥⎥

⎦

⎤

⎢⎢⎢

⎣

⎡

4

3

2

1

284.150893.1014241.0014025.0104.39587.375969.15727.1

995.25202.53008.19720.18

εεεε

C

B

A

RRR

4

Integrated Load IndicesIntegrated Load Indices

0

2000

4000

6000

8000

-2000 0 2000 4000 6000 8000 10000

Cone penetrometer index estimate, N

ISPP

MS

inde

x es

timat

e, N

Overall integrated loadDifference between lower and upper integrated loadsLower integrated loadUpper integrated load

r2 = 0.24

r2 = 0.56

r2 = 0.55

r2 = 0.03

Overall Integrated Load ComparisonOverall Integrated Load Comparison

1

3

5

7

9

1 1

1 3

0 2000 4000 6000 8000 10000

Overall integrated load (ISPPMS), N

Tilla

ge p

lot

Center rowWheel row

A

F

E

D

C

B

pass

1

2

1

2

1

2

1

2

1

2

1

2

1

3

5

7

9

1 1

1 3

0 2000 4000 6000 8000 10000

Overall integrated load (cone penetrometer), N

Tilla

ge p

lot

Center rowWheel row

A

F

E

D

C

B

pass

1

2

1

2

1

2

1

2

1

2

1

2

Cone PenetrometerInstrumented Blade

double diskedEdiskedBno-till w/o cultivationFno-till with cultivationC

chiselled and diskedDplowed and double diskedATreatmentTillage PlotTreatmentTillage Plot

b) Wheat yield, 2002

a) Total force estimate from instrumented blade, 2004 Overall Resistance Load

Wheat Yield

Mg/kg

N

Maps of Soil Mechanical Resistance Maps of Soil Mechanical Resistance (Instrumented Blade) and Wheat Yield(Instrumented Blade) and Wheat Yield

Rogers Memorial Farm(Eagles, Nebraska) Field R-9, July 2004

Relatively high water holding

capacity

The Latest PrototypeThe Latest Prototype

Replaceable cutting edge

Array of strain gage bridges

SummarySummary• On-the-go mapping of soil mechanical

resistance allows delineation of field areas with relatively hard or soft cultivated layer of soil

• High-order polynomial representation of topsoil profile is not beneficial

• Estimates of soil mechanical resistance attained using cone penetrometer and on-the-go sensing approaches have different nature

• Integration of sensing systems with alternative measurement concepts is critical

• Maps of physical soil properties can be used to prescribe spatially differentiated field management

http://bse.unl.edu/adamchukE:mail: vadamchuk2@.unl.edu