Kerry ClarkBradford Research Center, University of Missouri

clarkk@missouri.edu

2013 Soil Health Workshop

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 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 DEFINITION

Soil quality has three main components• Sustained biological productivity

• Environmental quality• Plant and animal health

• Inherent soil quality relates to the natural characteristics of the soil, such as its texture. These qualities are the result of soil-forming 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 deals with both inherent and dynamic soil features.

• 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

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.

Does Soil Quality = Soil Health ?????

2013 The Year of Soil Health for the USDA- NRCS (Natural Resources Conservation Service)

http://www.nrcs.usda.gov/wps/portal/nrcs/main/national/soils/health/

http://www.swcs.org/en/publications/beyond_t/

•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

Why Soil Quality is Important

•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 IndicatorsIndicator Relationship to Soil Health

Soil organic matter (SOM) Soil fertility, structure, stability, nutrient retention; soil erosion

Physical: soil structure, depth of soil, infiltration and bulk density; water holding capacity

Retention and transport of water and nutrients; habitat for microbes; estimate of crop productivity potential; compaction, plow pan, water movement; porosity; workability

Chemical: pH; electrical conductivity; extractable N-P-K

Biological and chemical activity thresholds; plant and microbial activity thresholds; plant available nutrients and potential for N and P loss

Biological: microbial biomass C and N; potentially mineralizable N; soil respiration. 

Microbial catalytic potential and repository for C and N; soil productivity and N supplying potential; 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)

•Awareness and education•Assessment as an adaptive management tool

•Evaluation of alternative practices

•Assessment as a monitoring tool

Why Assess Soil Quality

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 SQIhttp://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

Puget and Lal, 2005

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.

http://soilquality.org/indicators/total_organic_carbon.html

Soil organic matter and its major constituent, organic carbon, can be depleted from soil during tillage

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 poolsActive CarbonActive 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.

Results are read in a spectrometer in lab or field or from a color card

Potassium Permanganate TestKMnO4 oxidizes active carbon. The purple color of the chemical changes to pink the more active carbon there is in a soil sample.

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://vro.dpi.vic.gov.au/dpi/vro/vrosite.nsf/pages/soilhealth_soil_structure

http://ecomerge.blogspot.com/2010/05/what-soil-aggregates-are-and-how-its.html

Aggregate StabilityFungal-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 InfiltrationGood 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 tillageReducing tillage minimizes the loss of organic matter and protects the soil surface with plant residueTillage•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 efficientlySoil buffers and detoxifies chemicals when not overloadedPesticides 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.

ManagementLeave 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-sudangrassLegumes underlined

Bradford Winter Cover Crop Mix: cereal rye, hairy vetch, Austrian winter pea, crimson clover, tillage radish, oatsLegumes underlined