Purpose of workshop is to provide
background and resource material
on soil health
• Soil biology
• Rhizosphere interactions
• Soil, landscape and
watershed features and
interactions
• Soil erosion
• Improvement through
management practices
Present soil health research and
results that are occurring in Missouri
• Forest soils
• Agricultural soils
Provide information on methods of
soil health assessment
• MU Soil Health Lab
• Field assessments
• Farmer self-assessments
Provide material and information for
developing soil health presentations
and demonstrations for producers
• Water infiltration
• Water Quality
• Soil quality indicator tests
• Active carbon
• Bulk density
• Aggregate stability
SOIL QUALITY DEFINITION
Soil quality is the capacity of a specific kind of soil to
function within natural or managed ecosystem
boundaries, to sustain plant and animal productivity,
maintain or enhance water and air quality, and
support human health and habitation.
(Karlen et al., 1997)
Soil quality has three main
components
•
Sustained biological productivity
• Environmental quality
• Plant and animal health
Soil quality deals with both
inherent and dynamic soil features.
•
Inherent soil quality relates to the natural characteristics of the
soil, such as its texture. These qualities are the result of soilforming factors and processes and cannot be changed easily.
•
Dynamic soil quality components -- such as organic matter, soil
structure, infiltration rate, bulk density, and water and nutrient
holding capacity -- are readily affected by management practices.
The dynamic component is of most interest to growers because
good management allows the soil to come to its full potential.
Inherent and dynamic soil quality components interact with each other.
Some soils are much more susceptible to degradation and unforgiving
of poor management than others.
http://soilquality.org/basics/inherent_dynamic.html
• Soil quality is the integration of
biological with chemical and
physical measures of soil quality
that affect farmers' profits and
the environment.
This definition reflects the
living and dynamic nature of
soil
Does Soil Quality = Soil Health
?????
In USA, SSSA Ad Hoc Committee on Soil Quality
recommended a separation between the two terms, with soil
quality being a more analytical and quantitative term (Karlen
et al., 1997)
Terms are now used interchangeably in both scientific
literature and the media. Soil health generally refers to the
condition of a soil as a result of management while soil
quality refers to both the condition of the soil and its inherent
properties.
2013
The Year of Soil
Health for the USDANRCS (Natural
Resources
Conservation
Service)
http://www.swcs.org/en/p
ublications/beyond_t/
http://www.nrcs.usda.gov/wps/portal/nrcs/main/national/soils/health/
Why Soil Quality is Important
•Soil degradation is a major world-wide
problem
•The vast majority of agricultural land in the
US already has depleted levels of SOM
•Poor soil health can lead to reduced yields
and reduced profits
•Nutrients are lost
through leaching
and soil erosion
in degraded soil
•A healthy stable soil
absorbs and holds
water better and leads
to better water
infiltration and erosion
control
What Healthy Soil Does
• Gives us clean air and water
• Productive crops and forests
• Productive grazing lands
• Diverse wildlife and landscapes.
Soil does all this by performing four
essential agricultural functions:
• Regulating water
• Sustaining plant and animal life
• Filtering potential pollutants
• Cycling nutrients
• Soil quality cannot be measured directly, so
we evaluate indicators.
• Indicators are measurable properties of soil
or plants that provide clues about how well
the soil can function.
• Indicators can be physical, chemical, and
biological properties, processes, or
characteristics of soils.
• They can also be morphological or visual
features of plants.
Useful indicators:
• are easy to measure,
• measure changes in soil functions
• encompass chemical, biological, and
physical properties
• are accessible to many users and
applicable to field conditions
• are sensitive to variations in climate
and management.
Soil Quality Indicators
Indicator
Soil organic matter (SOM)
Relationship to Soil Health
Soil fertility, structure, stability,
nutrient retention; soil erosion
Physical: soil structure, depth Retention and transport of water and
of soil, infiltration and bulk
nutrients; habitat for microbes;
density; water holding
estimate of crop productivity potential;
capacity
compaction, plow pan, water
movement; porosity; workability
Chemical: pH; electrical
Biological and chemical activity
conductivity; extractable N-P- thresholds; plant and microbial activity
K
thresholds; plant available nutrients
and potential for N and P loss
Biological: microbial biomass Microbial catalytic potential and
C and N; potentially
repository for C and N; soil
mineralizable N; soil
productivity and N supplying potential;
respiration.
microbial activity measure
Although soil characteristics are indicators of soil
quality, soil quality must be identified by how soil
performs its functions.
The ultimate purpose of assessing soil quality is not to
achieve high aggregate stability, biological activity, or
some other soil property
The purpose of soil quality improvement is to protect
and improve long-term agricultural productivity, water
quality, and the habitats of all organisms, including
people.
NRCS soil health website
Soil quality assessments require measuring
the current state of an indicator and
comparing the results to known or desired
values (Karlen et al., 1997)
Why Assess Soil Quality
• Awareness and education
• Assessment as an adaptive
management tool
• Evaluation of alternative practices
• Assessment as a monitoring tool
Types of Soil Quality Assessment Tools
•Qualitative Scorecards – Farmer driven with NRCS
•Field Test Kits – NRCS or commercially available
•Lab-based assessments
•Soil Management Assessment Framework
•Cornell Soil Health Assessment
•Practice Predictors - use research outcomes to predict the
effects of management practices on soil quality.
•NRCS Soil and Water Eligibility Tool (SWET)
•Conservation Measurement Tool (CMT)
•Landscape-level assessments - use satellite and remote
sensing technology to assess resource quality at large spatial
scales.
University of
Missouri
Soil Health Lab
•Active Carbon
•pH
•Aggregate Stability
•Available P
•Mineralizable N
•PLFA
•Total Carbon
•Infiltration
•SMAF SQI
http://engineering.missouri.edu/soil/soil-health-lab/
Soil Organic Matter is one of
most important soil quality
indicators
• Comprises only a tiny fraction of total
mass of most soils (<3% in MO)
• Exerts a dominant influence on
many soil chemical, physical and
biological properties
• Much of water holding capacity of surface
soils
• Stabilizes soil surface, increases infiltration,
plant available water, decreases erosion
• Majority of cation exchange capacity of
surface soil
• Formation and stabilization of soil
aggregates
• Contains large amounts of plant nutrients
• Supplies energy for soil microorganisms
Why focus on soil organic matter?
• Affects several critical soil functions,
• Can be manipulated by land management practices
• Important in most agricultural settings across the
country
• Enhances water and nutrient holding capacity
• Improves soil structure,
• Managing for soil carbon can enhance productivity and
environmental quality, and can reduce the severity and
costs of natural phenomena, such as drought, flood,
and disease
• Increasing soil organic matter levels can reduce
atmospheric CO2 levels that contribute to climate
change
Soil organic matter and its major constituent,
organic carbon, can be depleted from soil
during tillage
Effect of 10 years of conventional till and
no-till on OC (calculated from SOM data in Edwards
et al., 1999).
Soil profile organic carbon
concentration under plow till, chisel
till, no till, pasture and forest.
Puget and Lal, 2005
http://soilquality.org/indicators/total_organic_carbon.html
Rapid declines in
organic C were seen in
the Morrow and
Sanborn Field plots
after cultivation began.
Sanborn Field removed crop residue until the
1950s, so the decline in SOC was faster there.
SOC increased slightly when residue
management was changed and residue was left
on fields
Soil organic carbon (SOC), which makes
up about half of soil organic matter, can
be divided into active, slow and passive
soil carbon pools
Active Carbon
Active carbon fuels the soil food web and includes
microbial biomass, particulate organic matter, soil
carbohydrates and rapidly mineralizable carbon. The
active carbon pool can be measured and used as an
indicator of differences in management.
Potassium Permanganate
Test
KMnO4 oxidizes active carbon. The
purple color of the chemical changes
to pink the more active carbon there
is in a soil sample.
Results are read in a spectrometer in lab or
field or from a color card
Soil Structure
• Arrangement of soil solids and voids
• Soil structure influences water infiltration and retention,
erosion, crusting, nutrient recycling, root infiltration and crop
yield
• Expressed as degree of aggregate stability
• Aggregation is controlled by SOC, microorganisms, ionic
bridging, clay
http://ecomerge.blogspot.com/2010/05/what-soil-aggregates-are-andhow-its.html
http://vro.dpi.vic.gov.au/dpi/vro/vrosite.nsf/pages/soilhealth_soil_structure
Aggregate
Stability
Fungal-produced glomalin helps bind
aggregates
Measured with wet sieving
http://ed.fnal.gov/trc_new/pandp/soil_research/soil_aggregates.html
Wright, et al., 1999
Tillage reduces aggregate stability and sizes
Chen et al., 2000
Water
Infiltration
Good infiltration
allows for less
runoff and
erosion
Soils with poor aggregate
stability will crust, damaging
emerging seedlings and
increasing runoff
Improving Soil Quality
Different soil types and land
uses call for different
management practices but
general goals are:
Enhance organic matter
• Leave crop residues in the field
• Choose crop rotations that include high
residue plants
• Use optimal nutrient and water management
practices to grow healthy plants with large
amounts of roots and residue
• Grow cover crops
• Apply manure or compost
• Use low or no tillage systems
Avoid excessive tillage
Reducing tillage minimizes the loss of
organic matter and protects the soil surface
with plant residue
Tillage
• Breaks up soil structure
• Speeds the decomposition and loss of
SOM
• Increases erosion
• Destroys the habitat of helpful organisms
• Causes compaction.
Manage pests and nutrients efficiently
Soil buffers and detoxifies chemicals when not overloaded
Pesticides and chemical fertilizers can harm non-target
organisms and pollute water and air if they are
mismanaged.
Nutrients from organic sources also can pollute when
misapplied or over-applied.
Management
• test and monitor soil and pests
• apply only the necessary chemicals, at the right time and
place
• taking advantage of non-chemical approaches to pest
and nutrient management such as crop rotations, cover
crops, and manure management
Prevent soil compaction
Compaction reduces the amount of air, water,
and space available to roots and soil
organisms.
Compaction is caused by repeated traffic,
heavy traffic, or traveling on wet soil.
Deep compaction by heavy equipment is
difficult or impossible to remedy, so prevention
is essential.
Keep the ground covered
• Reduces wind and water erosion and
drying and crusting.
• Protects soil and provides habitats for
larger soil organisms
• Can improve water availability.
Management
Leave crop residue on the surface
Plant cover crops
.
Diversify cropping systems
• Diversity of soil organisms helps control pests
• Diversity of cultural practices can reduce weed
and disease pressures
• Diversity across the landscape can be increased
by using buffer strips, small fields, or contour
strip cropping
• Diversity over time can be increased with long
crop rotations
• Changing vegetation across the landscape or
over time increases the types of insects and
microorganisms
Bradford Summer Cover Crop Mix: millet, sunflower, cowpea,
buckwheat, sunn hemp, sorghum-sudangrass
Legumes underlined
Bradford Winter Cover Crop Mix: cereal rye, hairy vetch,
Austrian winter pea, crimson clover, tillage radish, oats
Legumes underlined