Ag Expo 2004

Greg Schwab and Lloyd MurdockExtension Soil Specialists

UK Department of Agronomy

Soil Management for Higher Yields

Nitrogen Deficiency

Low Soil pHLow Soil pH

Idealized Kentucky Soil Idealized Kentucky Soil

Air 25% Soil Minerals

(Silt loam)47%

Water 25%

Organic Matter 3%

Compacted KY Soil Compacted KY Soil

Air5%

Soil Minerals(Silt loam)

72%

Water 20%

Organic Matter 3%

Macropores are Macropores are compressed compressed soil oxygen soil oxygen decreased decreased dramatically dramatically

EffectsEffectsPoor Drainage Poor Drainage Slow Root Slow Root Growth Growth

(Tire pressure remained at 12 psi for all tire sizes) (Tire size 11 x 28, load 1,650 lbs, pressure 12 psi)

Depth of compaction as (6) axle load and (7) soil moisture increases

8 10 12 14 16 18 20 228 10 12 14 16 18 20 22

Po

ten

tial

Co

mp

acti

on

Po

ten

tial

Co

mp

acti

on

Soil Moisture Content (%)Soil Moisture Content (%)

Optimum M.C.=14.3% for a silt loam

Proctor Compaction Curve

More tires will spread weight …BUT allows operations in wetter conditions and compacts a greater soil volume.

Sometimes we Sometimes we need to admit …need to admit …

There really are days we shouldn’t be in the field ! (Even if equipment lets you)

Compaction SurveyCompaction Survey Murdock and County Agents

1992-1993

• Categories– Little or None – Less than 30% of

penetrometer readings in field were 300 psi or greater

– Slight – 30 to 50% of the penetrometer readings were 300 psi or greater

– Moderate – 50-75% of the penetrometer readings were 300 psi or greater

– Severe – 75 to 100% of the penetrometer readings were 300 or higher

Stunting, uneven stands are often the first symptoms

Compaction SurveyCompaction Survey Murdock and County Agents

1992-1993

• Results– Little or None – 46%– Slight – 18%– Moderate – 18%– Severe – 18%

• By Drainage Class– 77% of poorly drained fields had

moderate to severe compaction– 20 % of well drained fields had

moderate to severe compaction

169 Fields

Compaction SurveyCompaction Survey Murdock and County Agents

1992-1993

Tillage Tillage Amount of CompactionAmount of Compaction

HistoryHistory FieldField LittleLittle SlightSlight ModMod SevereSevere

No.No. %% --------------- % ------------------------------ % ---------------

No-tillNo-till 3232 1919 5050 2222 1515 1313

DiscDisc 3737 2222 2727 33 2424 4646

ConventionalConventional 9494 5656 4545 2525 1717 1313

SubsoiledSubsoiled 66 44 6767 00 1616 1717

TotalTotal 169169 100100

Higher Higher Yield Yield Potential?Potential?

Effects of Compaction on Crop Yield

• Corn and Tobacco– Extreme 30-50% Yield Reduction– Severe 10-20% Yield Reduction– Moderate 5-10% Yield Reduction

• Soybean and Wheat – Extreme 15-25% Yield Reduction– Severe 5-10% Yield Reduction – Moderate <5% Reduction

Soil Compaction Questions

•How much will it decrease yields?

•Will deep tillage restore all of yield

potential?

•How long will compaction last?

•Are penetrometers a good measure?

Methods

•Zanesville silt loam

•Tilled and no-tilled areas

• Treatments

•Compacted

•Compacted &

Subsoiled

•Uncompacted

•Multiple passes of 10

ton equipment

•12 inches in depth

• Tilled 6 in. each year

Soil Compaction Effects on Corn and SoybeansLloyd Murdock and John James, Princeton, KY

Tillage Yield (Bu/Ac)

Till Comp. ‘97 ‘98 ‘99 ‘00 ‘01 ’02

Corn Soyb Corn Corn Soyb Corn

Till Yes 76 31 148 114 76 103

Till Yes 82 31 138 123* 74* 98*

Till No 98 40 174 135 84 135

NT Yes 2 36 158 109 82 116

NT Yes 2 33 163 130* 81* 134*

NT No 104 42 180 117 89 130

Effect of Soil Compaction on Corn and Soybean Yields With and Without Compaction and Subsoiling

*Treatment subsoiled only in fall of 1999

Tillage Yield (Bu/Ac)

Till Comp. ‘97 ‘98 ‘99 ‘00 ‘01 ’02

Corn Soyb Corn Corn Soyb Corn

Till Yes 76 31 148 114 76 103

Till Yes 82 31 138 123* 74* 98*

Till No 98 40 174 135 84 135

NT Yes 2 36 158 109 82 116

NT Yes 2 33 163 130* 81* 134*

NT No 104 42 180 117 89 130

Effect of Soil Compaction on Corn and Soybean Yields With and Without Compaction and Subsoiling

*Treatment subsoiled only in fall of 1999

Tillage Yield (Bu/Ac)

Till Comp. ‘97 ‘98 ‘99 ‘00 ‘01 ’02

Corn Soyb Corn Corn Soyb Corn

Till Yes 76 31 148 114 76 103

Till Yes 82 31 138 123* 74* 98*

Till No 98 40 174 135 84 135

NT Yes 2 36 158 109 82 116

NT Yes 2 33 163 130* 81* 134*

NT No 104 42 180 117 89 130

Effect of Soil Compaction on Corn and Soybean Yields With and Without Compaction and Subsoiling

*Treatment subsoiled only in fall of 1999

Results•Tilled compacted yields were 75% of check and improved to almost 90%.

•No-tilled compacted yields were 2% of check and improved to 90% rapidly

•Recovery beyond 90% will probably be very slow

•Rapid no-till recovery is probably due to high rate of biological activity

Soil Compaction?

QUANTIFYING COMPACTION• Crop and Soil Symptoms• Penetration Resistance

–Moisture Dependent–No Absolute Value–Note Depth and Relative Force–Compare Good and Bad Areas

• Bulk Density–Mass per Volume–Calculate Porosity–Texture Dependent

Effect of Time on the Percentage of Soil Penetrometer Readings Over 300 psi in

Compacted Tilled and No-Tilled Treatments.

Treatment

No-Till

Tilled

1997

100

94

1998

100

94

1999

88

94

2000

75

100

2001

88

100

2002

88

100

Percent Readings

COMPACTION AFFECTSNUTRIENT UPTAKE

Potassium Affected Most• Compaction Reduces Porosity• Lowers Soil Oxygen

• O2 Needed for Root Respiration and Active Uptake

y = -0.2244x + 2.0377

r2 = 0.92

1.4

1.45

1.5

1.55

1.6

1.65

1.7

1.75

1.8

1.85

1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6

Organic matter (%)

Max

imu

m B

ulk

Den

sity

(g

/cc)

Organic Matter and

Soil Compaction

Conclusion

DETERMINE THE NEED FOR SUBSOILING

• Evaluate Depth and Severity of Compaction

• Check with Penetrometer, Probe, Shovel

• Dig Plants to Examine Roots

• Leave Untreated Strips for Comparison