Introduction to Soil Health

Russ Higgins, University of Illinois ExtensionJames DeDecker, Michigan State University ExtensionAnthony Bly, South Dakota State University Extension

Overview

• Soil Health Defined

• Minerals & Texture

• Biology & Organic Matter

• Aggregation & Structure

• Porosity & Compaction

• Managing for Soil Health

• The Rainfall Simulator Demo

Why should you care about soil? • “We know more about the movement of celestial bodies than about

the soil underfoot.” - Leonardo Da Vinci, circa 1500’s

• “Essentially, all life depends upon the soil ... There can be no life without soil and no soil without life; they have evolved together.” - Charles E. Kellogg, USDA Yearbook of Agriculture, 1938

• “History is largely a record of human struggle to wrest the land from nature, because man relies for sustenance on the products of the soil. So direct, is the relationship between soil erosion, the productivity of the land, and the prosperity of people, that the history of mankind, to a considerable degree at least, may be interpreted in terms of the soil and what has happened to it as the result of human use.” -Hugh H Bennett

Soil Health• Soil health is defined as the

continued capacity of soil to function as a vital living ecosystem that sustains plants animals and humans.

• Healthy soils sustain plants, animals and humans

– A firm foundation

– Regulating water

– Cycling nutrients

– Filtering, buffering and degrading pollutants

Soil Health Components

• Soil health takes into account integrated physical, chemical and biological components of soil ecosystems

North Dakota State University

Water Quality/Quantity Benefits

• Reductions in erosion, sediment and nutrient delivery to surface waters

• Increased infiltration and soil water holding capacity 2015 Hypoxia Zone, 6474 square miles - (Data: Nancy

Rabalais, LUMCON; R Eugene Turner, LSU. Credit: NOAA)

What Affects Soil Health?

• Environmental factors

– Parent material

– Topography

– Time

– Climate

– Organisms

• Human activities

– Soil disturbance /tillage

– Cropping

– Fertilization

– Manure application

– Animal/wheel traffic

Soil Components

• Soil consists of four major components:

– Mineral material (~45%)

– Organic matter (~5%)

– Water (~25%)

– Air (~25%).

Kleinschmidt and McClure, 2009

Soil Minerals

• The mineral component of soil is the remnants of weathered rocks

• Classified into three categories by particle size:

– Sand

– Silt

– Claycroptechnology unl.edu

Sand (0.2 mm – 2 mm)

• Largest particles

• Feels gritty if rubbed between fingers

• Warms up and dries early in the spring

• Does not hold water or nutrients

Siim Sepp, Wikipedia

Silt (0.002 – 0.05 mm)

• Intermediate size

• Referred to as “rock flour”

– Feels silky or floury

• Can be transported long distances in water or air

rashidfaridi.com

Clay (< 0.002 mm)

• Smallest particle size

• Feels sticky

• Holds nutrients

• Does not drain/dry well

• Slow to warm up

• Difficult to work

• Root growth poor due to small spaces between particles

Finegardening.com

Soil Texture

• The proportion of different mineral particle sizes in a soil determines its texture

• Example: 20% clay, 40% silt, and 40% sand is a loam soil

passel.unl.edu

Soil Texture

• Soil texture is primarily determined by environmental factors, and cannot be easily changed by human activity.

Physicalgeography.net

Soil Texture and Soil Health

• Soil texture is important to soil health as a determinant of surface area and pore space available in a soil for holding nutrients, air and water.

www.ext.colostate.edu

Soil Biology

• Soil dwelling organisms range from bacteria and fungi to vertebrates that coexist in complex food webs.

– Decompose organic matter

– Cycle nutrients

– Create pore space

– Contribute to aggregation

pinterest.com

Soil Organic Matter

• Organic matter is the remnants of plants and animals in various states of decomposition by soil organisms

• A valuable source of plant nutrients

• Adds water holding capacity

• Adds dark color to soil Soil-net.com

Soil Biology and Organic Matter

• Soil life is more abundant in areas with more organic matter

• Near plant roots, surface litter

• Where cover crops and manure are applied Nardi, 2007

Roots following nightcrawler burrow

• Cast material lining the nightcrawler burrow

• Casts are higher in nutrient availability than surrounding soil, because they are a mix of mineral soil and partially decomposed organic materials

Kladivko, Purdue University

Soil Aggregates• The components of soil

stick together in units called aggregates

• Solid (mineral and organic) materials held together by physical and chemical forces.

• Pore space (air and water)

www.waldeneffect.org

Soil Aggregation

• Several natural processes contribute to soil aggregation

–wetting and drying

–freezing and thawing

–microbial activity (glomalinproduced by fungi)

–activity of roots and soil animals (root sugar exudates)

–soil chemical charges

Soilandhealth.org

Soil Structure

• Aggregates vary in their size, shape and stability.

• Patterns of soil aggregation determine soil structure

croptechnology.unl.edu

Soil Aggregation and Health

• Soil aggregation is important to soil health

• Provides pore space for holding air, water and nutrients, soil biology and plant roots– Micropores within and

macropores between aggregatessoilquality.org

Soil Aggregation and Health

Soil Porosity/Compaction

• To maximize plant root growth, a soil should ideally consist of 50% solid (mineral and organic) materials and 50% pore space (air and water)

www.tankonyvtar.hu

Soil Bulk Density

• Soil bulk density is a measure of soil porosity/compaction expressed as soil weight per unit volume (g/cm3).

Bulk Density and Soil Health

• Lower bulk density = loose, porous soil with plenty of room for air, water, biology and roots

• Higher bulk density can limit movement of air and water through soil and restrict root growth

organicsoilsolutions.com

Managing for Soil Health

• Managing for soil health is a matter of improving soil structure and building organic matter to create suitable habitat for soil biology

Managing for Soil Health

Harmful Practices

• Frequent, intense disturbance/tillage

• Plant monocultures

• Excessive fertilizer/chemical use

• Heavy animal/machinery traffic

Beneficial Practices

• Reduced disturbance/tillage

• Diverse crop rotations

• Organic matter maintenance/additions– Crop residue

– Cover crops

– Manure

Building Healthy Soil: cover crops

Building Healthy Soil: compost

Mapping Your Soil

• Web Soil Survey www.websoilsurvey.sc.egov.usda.gov

Reading Your Soil Description

Final Thoughts

Only "living" things can have health, so viewing soil as a living ecosystem reflects a fundamental shift in the way we care for our nation's soils. Soil isn’t an inert growing medium, but rather is teaming with billions of bacteria, fungi, and other microbes that are the foundation of an elegant symbiotic ecosystem.- taken from the NRCS website