The Science of Soil Health and Value of Soil Stewardship Francisco J. Arriaga, PhD Soil Management State Specialist Dept. of Soil Science & UW-Extension [email protected] 608-263-3913 SWCS Conference, Greensboro NC July 28, 2015
Aug 17, 2015
The Science of Soil Health andValue of Soil Stewardship
Francisco J. Arriaga, PhDSoil Management State Specialist
Dept. of Soil Science & [email protected]
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
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)
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.
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
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
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: [email protected]: 608-263-3913