The Science of Soil Health andValue of Soil Stewardship

Francisco J. Arriaga, PhDSoil Management State Specialist

Dept. of Soil Science & UW-ExtensionFrancisco.arriaga@wisc.edu

608-263-3913

SWCS Conference, Greensboro NCJuly 28, 2015

What is Soil Health?

• “The capacity of a soil to function within ecosystem boundaries to sustain biological productivity, maintain environmental quality, and promote plant and animal health.”

(Doran and Parkin, 1994)

• Abbreviated version: Ability of a soil to function in a way that benefits both humans and the environment.

[Note this assumes there is a baseline (i.e. maximum potential) for different soils]

Soil Health Indicators(or Soil Properties that Influence Productivity)

Physical Chemical

Biological

•density•infiltration•water retention•aggregation

•nutrient availability•pH•CEC

•organic matter•biological activity•roots•organisms

Soil Health

Proposed Basic Soil Health Indicators

(Doran and Parkin, 1994)

Soil Quality Indicators & Their Impact

Measurement Process Affected

Organic matter Nutrient cycling, pesticide and water retention, soil structure

Infiltration Runoff and leaching potential, plant water use efficiency, erosion potential

Aggregation Soil structure, erosion resistance, crop emergence, infiltration

pH Nutrient availability, pesticide absorption and mobility

Microbial biomass Biological activity, nutrient cycling, capacity to degrade pesticides

Forms of N Availability to plants, leaching potential, mineralization and immobilization rates

Bulk density Root penetration, water/air filled pores, biological activity

Topsoil depth Rooting volume, water and nutrient availability

Available nutrients Capacity to support plant growth, environmental hazard

(Karlen et al. SSSAJ , 1997)

(Lado, Paz and Ben-Hur, 2004)

Aggregate Formation/Stability Concept

(Six et al. SSSAJ, 1999)

Energy in the organic matter “wasted” to re-form aggregates

Assessing Soil Health

1. QUALITATIVE:– Soil Health?– Smell, feel, look, taste?– Soil Quality Rating

2. QUANTITATIVE:– Chemical

• pH, O.M., nutrients– Physical

• Structure, bulk density– Biological

• Respiration, microbial biomass

– Integrate factors into an index

Soil Health Score Card Example

soil test showed needfor potassium

1. add potassium fertilizer2. ?????

Soil Health Score Card Example (cont.)

wheat2013somewhere in Wisconsin

Sept 25, 2014 X

X

X

X

X

X

X

X

X

not applicable

cover crop planted; slightly denser soil layer detected between 6-8” of depth.

Field Based Assessments (Visual)

photos: Roger Schmidt, NPM Program

Quantitative Assessments

• Often require for soil samples be taken and sent to a laboratory

• Attempt to measure chemical, biological and physical properties

• A score is given to the soil based on the properties measured

Proposed Basic Soil Health Indicators

(Doran and Parkin, 1994)

Biological Indicators

(Moebius-Clune et al.,2008 )

OM- Soil organic matter PMN – Potentially mineralizable NNemParasitic – Parasitic nematodes EEG – Easily extractable glomalin conc.NemBeneficial – Parasitic nematodes TG – Total glomalin concentrationDecomp – Cellulose decomposition rate

Continuous Corn System with Residue Harvest (32 years)

• Most sensitive indicators were: Db, AWC, OM, Decomp and TG• Tillage had a lager positive impact on improving indicators than

returning corn residue to soil

0

500

1000

1500

2000

2500

0 10 20 30 40 50 60 70 80

Time Since Plowing (days)

Cu

mu

lati

ve C

O2 (

kg C

/ha)

Moldboard No Till

Microbial Respiration

Plowed July 23, 1997

(Rochette and Angers, 1999)

Time (days)

Property SH Assessment SH Rank State Based State Based Recom.

pH 6.5 ok 7.3 ok

Phosphorus (ppm) 6.7 ok 34 High (ok)

Potassium (ppm) 153.9 ok 90 Very low/low (ADD)

OM (%) 3.4 ok 4.2

Score YES NO, but gives nutrient recommendations

based on field trials (CALIBRATION WITH

CROP RESPONSE)

The Potential Issue with Some SH Assessments

The “New” Frontier

• Microbiological assessments (e.g. metagenomics)

• Linking soil quality indicators to crop performance

• New statistical approaches to develop a robust SH/SQ Index

(Stine & Weil, 2002)

Tillage:conventionalreducedno-till

Corn Yield &Soil HealthIndicators

The “New” Frontier

• Microbiological assessments (e.g. metagenomics)

• Linking soil quality indicators to crop performance; new statistical approaches

(Dorr de Quadros et al., 2012)

Closing Remarks

• The science of SH/SQ assessment has been moving slowly from qualitative to quantitative, as new knowledge is developed by scientists and implemented by practitioners.

• Care should be taken not to “over sell” a specific SH metric or procedure, as this can turn the end-user away.

• Microbial community composition and function assessments, and linking soil indicators to crop and environmental performance is the current focus and next “frontier”.

Photo: F. Arriaga, 2012 Workshop Brown Co. Land & Water Conservation

Soil Management Matters

E-mail: francisco.arriaga@wisc.eduPhone: 608-263-3913