sensors for mapping soil ph

Sensors for Mapping Soil pH

Eric Lund, Veris Technologies, Salina, KS

Sensors for Crop Management ConferenceStillwater OK January 17, 2008

• How does it work?

• How accurate is on-the-go pH mapping?

• Does managing pH pay?

On-the-go pH mapping

On-the-go pH mapping is here...

HERE’S HOW IT WORKS:

A sampler shank is lowered into the soil

A soil core flows through the sampler trough

The soil core is raised

against two pH

electrodes

The geo-referenced pH and EC data are recorded

The entire process is automated

Automated pH Mapping How Does It Work?

How accurate is on-the-go pH mapping from Veris Technologies?

• Statistical analysis

• Visual comparisons

• Repeatability

Statistical analysis2002-2004 Field Trials: 328 validation samples...15 fields...4 states...

r2 = 0.81

3.0

4.0

5.0

6.0

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8.0

9.0

3.0 4.0 5.0 6.0 7.0 8.0 9.0

328 Lab Samples

On

-th

e-G

o p

H M

app

ing

Lab vs. Veris pHOSU lime trials--Enid R2 = 0.9051

4

4.5

5

5.5

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6.5

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7.5

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9

4 4.5 5 5.5 6 6.5 7 7.5 8 8.5

Lab pH

Ver

is p

H

Statistical analysis

Visual comparisons

Lab samples overlaid on Veris pH sensor data

Visual comparisons

Lab samples overlaid on Veris pH sensor data

Visual comparisons

Repeatability

Significantly more accurate liming than other methods.

How do the results compare? 2.5 acre grids, zones, blanket rate

Improvement over blanket rate lime

0

500

1000

1500

2000

2500

2.5 acre grids soil type Veris sensors

lim

e (

lbs

/ac

re)

Does managing pH pay?

Does managing pH pay?

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7.5

8

Enid fields

lab

pH

Does managing pH pay?

Does managing pH pay?

Does managing pH pay?

Cumulative gross income

Cumulative net income

Cumulative expense (7 yr proration)

Soybean yield increase

Corn yield increase

1995 0 -6.29 6.29 01996 5.5 -7.08 12.58 11997 13.5 -5.37 18.87 41998 57.5 32.34 25.16 81999 65.5 34.05 31.45 42000 98.5 60.76 37.74 62001 102.5 58.47 44.03 22002 141 96.97 44.03 72003 163 118.97 44.03 112004 185 140.97 44.03 42005 189 144.97 44.03 22006 211 166.97 44.03 4

Does managing pH pay?

University of Nebraska studyLime vs. no limeCorn-bean rotation7 yr study (but data still being collected)Corn $2/bu Soybeans $5.50/bu

Soil EC zones

Soil EC zones

Take-home messages• pH varies widely within most fields• On-the-go pH sensing can accurately map pH

variability• Soil EC zones are another alternative—not as

precise as on-the-go sensing, but typically better than blanket rate

• Lime economics vary by field, but:-low pH levels in OK fields call for lime-since many fields have areas that need zero or a reduced lime amount, precision lime should pay