Soil health and howSoil health and how to measure itto measure it

Lori Hoagland

Assistant Professor

Department of Horticulture & L d A hiLandscape Architecture

Purdue University

Outline

Wh t i il h lth d h h ldWhat is soil health and why should we care about it?

What constitutes healthy soil?

How can you build soil health?

H il h lth?How can you measure soil health?

Why should you care y yabout soil health?

Analogy

You’re going on a trip – which tires do you want?

Leaky tires  Fully inflated tires OR

Eric Brennan – USDA‐ARS

Analogy

P il= Poor soil qualityquality

Leaky tiresy

What is soil health?

Definition: The capacity of a living soil to:Definition: The capacity of a living soil to:‐ function within natural or managed

b d iecosystem boundaries ‐ sustain plant and animal productivityp p y‐maintain or enhance water and air

litquality‐ promote plant and animal healthp p

(Doran et al.,1996, 1998)

Why care about soil health?

Alleviate soil compactionAlleviate soil compaction

Increase water infiltration and water‐holding capacity

R d i i i d i hReduce irrigation costs and improve the potential for your soil to withstand drought

R d i d k il i lReduce erosion and keep your soil in place

Consequences of poor soil health

A single inch ofA single inch of topsoil can take 500 

years to form naturally

Erosion in the Palouse

Surface runoff from a farm field in Iowa during a rainstorm

naturally

Columbia River Basin from space Fall 2009

g

Why care about soil health?

Reduce incidence of pest outbreaks andReduce incidence of pest outbreaks and lower pesticide costs

Increase nutrient holding capacity of the 

soil reduce nutrient loss and lowersoil, reduce nutrient loss and lower 

fertilizer costs

Improve crop productivity and quality of your produceyour produce

What constitutes healthy soil?y

Components of soil healthChemical – well understood and applied

Physical – fairly well understood but not

Biological – the least understood andunderstood, but not 

often appliedMoebius, 2004

understood and applied

Relevance of chemical soil health

pH – measure of acidity or alkalinity of the soil

impacts:

‐ nutrient availabilityy

‐ availability of toxic metals

activities of microorganisms‐ activities of microorganisms 

that facilitate nutrient

li d d dicycling and reduce disease 

risk

Relevance of chemical soil health

Salinity – salt content of the soili i i i f ili d‐ in irrigation water, fertilizers, composts and manure

‐ accumulation can degrade soil structure and restrict

vegetable growth

Cation exchange capacity – quantity of cations in the soil‐ cation is a positivly charged ion (ie. Ca2+,Mg2+, NH4+,

Zn2+, Cu2+, Mn2+)

‐ depends on amount of clay and organic matter in the soil 

‐ impacts the soil’s nutrient‐holding capacity

Relevance of physical soil health

Soil texture – proportion of sand, silt and clay particles in the soilparticles in the soil

‐ function of soils parent 

material

‐ virtually unchangeablevirtually unchangeable 

except through erosion

‐ important for soil test 

interpretation

Relevance of physical soil health

Soil structure (or tilth) – arrangement of soil particles into aggregatesinto aggregates‐ can change rapidly in response to management

T th t t d t tTogether texture and structure 

impact:W t d t i t h ldi it‐Water and nutrient holding capacity

‐Water infiltration

‐ Aeration‐ Aeration

‐ Seed germination and root proliferation

‐ Biological activity

Moebius, 2004

g y

‐ Erosion potential

Relevance of biological soil healthIt’s Alive!Megafauna –mice, ants,  

earthworms spiders etcearthworms, spiders, etc.

‐ initiate organic matter 

decompositiondecomposition

‐ aerate the soil

f dMesafauna – nematodes, 

mites, springtails

‐ regulate microbial 

populations

Microfauna – bacteria & fungi

Regulate nutrient cycling

Improve plant health

Rhizosphere – zone of greatest 

Roots support microbesMicrobes aid plants

microbial activityRhizobia

Release signals & 

Fix nitrogen

Solubilize phosphorous

ppp

gnutrients

Enhance root growth Provide protection

Suppress plant pathogens

More benefits of soil biological health

Build soil aggregates‐ secrete biological ‘glue’

Filter and detoxify chemicalsFilter and detoxify chemicals

Make that sweet smellMake that sweet smell ‐ Streptomyces & geosmin

Guides camels‐ Guides camels 

Glomalin production by mycorrhiza

How can you build yhealthy soil?y

Add organic matter

Beneficial impacts on soil properties:

Chemical ‐ higher CEC, pH buffer, ties up metals, interacts with xenobiotics

Physical ‐ stabilizes soil structure, improves water‐holding capacity, reduced compaction, dark color helps warm soilp y, p , p

Biological ‐ supplies energy and body‐building constituents f il i d i k f t i t ( ilfor soil organisms, source and sink for nutrients (soil fertility bank account), ecosystem resilience

(H. Atthowe)

Apply biological amendments

Eric Zakarison demonstrates his “solorpowered tractor”

Plant cover crops

Reduce tillage

No‐till vegetable transplanter

http://www.separcd.org/no‐till_vegetables.htm

Restoring organic matter & soil health

(Brady and Weil, 2002)

Restoring organic matter & soil health 

S il h lth Silt l Silt L Cl L Cl L

Impact of tillage on soil physical healthSoil health indicator

Silt loamPlow till

Silt LoamNo - till

Clay LoamPlow till

Clay LoamNo – till

Bulk density Not Not 1.21 1.03y(g/cm3) significant significantPores > 30 microns (%)

13 17 12 16

Pores < 30 microns (%)

Not significant

Not significant

29 24

Available water 12 16 Not significant Not significantcapacity (%)

Water stable aggregates

20 41 30 68aggregates 0.25-0.2 mm (%)

(Idowu et al., 2006)

Restoring organic matter and soil health

Impact of orchard floor management on soil health

‐ compost application  coupled with high tillage does not 

positively impact soil health characteristics

‐ cover crops result in dramatic improvement in soil physical,

chemical and biological properties

Restoring organic matter and soil healthRestoring organic matter & soil health 

Impact of wheat cultivation on Fluorescent Pseudomonans

oil

Managing soil‐borne pathogens in apple with wheat cultivation

60

80

100

eudo

mon

as g

‐1so

b

a

ab

a a

0

20

40

Control Pasteurized Wheatgrass Modern Wheat

Organic Wheat

Perennial Wheatof

 Fluorescent ps bc

c

Wheat Wheat Wheat

60

Impact of wheat cultivation on soil‐borne pathogens

# o

s g‐

1 soil

a

2030405060

‐borne

 patho

gens

bb

ccc

010

Control Pasteurized Wheatgrass Modern Wheat

Organic Wheat

Perennial Wheat

# of soil‐

(Hoagland et al., 2010)

Can you add too much organic matter?

Material C:NMicrobial Tissues 6‐12:1

In some cases yesSoil Humus 10‐12:1Animal Manure 13‐25:1Legume Residues/Green Manures 13‐25:1Compost 25 30:1

‐ Nutrient immobilization 

‐Watch the saltCompost   25‐30:1Cereal Residues/Straw 60‐80:1Forest Refuse 150‐500:1

‐ Careful with newly 

incorporated fresh p

residues

Requires careful 5000

6000il

Tukey

PAR

Impact of Brassica seedmeal incorporation on Pythium

Requires careful 

management1000

2000

3000

4000

cfu

pyth

/ g s

oi IRRECHULTHETATT

0Cnt Past. Bj Sa Bn Gm

ATT

Control Pasteurized

(Hoagland et al., 2008)

How can you measure ysoil health?

Standard fertility test at a commercial lab

Recommended every 3‐5 yearsRecommended every 3 5 years 

Generally cost $10‐20

Typically includes: pH, available phosphorous, nitrogen, potassium, calcium, magnesium and organic matter

Collecting the soil sample

Sample at the same time each year to achieve more accurate trendsaccurate trends

Tools: sampling tube or spade, buckets, plastic bags

Collect representative sample 

‐ Soil type, management practices, crop 

growth & yield

‐ Avoid irregular areas

‐ 20‐30 cores per 10‐20 acre field

Collect samples to a depth of  approximately 8”  

Mix and air‐dry

Cornell Soil Health Lab

Basic test ($40) Comprehensive ($65)‐ Standard soil fertility test(pH, OM, P, K, Ca, Mg, Al, Fe, Zn, Mn)     

P ti l i di t ib ti

‐ Basic test 

‐ Potentially mineralizable

i ( )‐ Particle size distribution 

‐Wet aggregate stability 

‐ Available water capacity

nitrogen (PMN)

‐ Root health bioassayAvailable water capacity

‐ Surface hardness

‐ Active carbon

* Samples should be taken in the spring prior to tillage

http://soilhealth.cals.cornell.edu/extension/test.htm

Soil Food Web

Soil food web

http://oregonfoodweb.com/

Measuring soil health on the farm

NRCS Soil Quality Test Kit‐ Electrical conductivity & pH

‐ Soil nitrate 

W t i filt ti & t lit‐Water infiltration & water quality 

‐ Bulk density

‐ Aggregate stabilityAggregate stability

‐ Slake test

‐ Soil respirationp

‐ Earthworms

Measuring soil health on the farm

Soil quality score cards‐ subjective tests based on feel, site and smell

May include characteristics such as:‐ Earthworms

‐ Organic matter color

‐Water‐holding capacity

‐ Drainage/infiltration

‐ Organic matter roots/residues

‐ Subsurface compaction

S il il h/f i bili / ll

‐ Crop condition

‐ pH

N t i t h ldi it‐ Soil tilth/friability/mellowness

‐ Erosion

‐ Nutrient‐holding capacity

Talk to local NRCS office

Interpreting results

Depends on:p

‐ soil type

crops grown‐ crops grown

‐ farm size and management 

Use to evaluate changes in practices over timep

Practice on‐farm experimentation

ResourcesBuilding Soils for Better Crops‐ Fred Magdoff and Harold van EsFred Magdoff and Harold van Es

‐ Sustainable Agriculture Network

http://www.sare.org/publications/soils.htm

Sustainable Soil Management – Soil System Guide‐ ATTRAATTRA

http://attra.ncat.org

Natural Resource Conservation ServiceNatural Resource Conservation Service

Purdue Extension Educators

Lori Hoagland lhoaglan@purdue.edu