beyond the soil food web: managing soil for diverse ... · managing soil for diverse biological...

YOUTH & FAMILIESAGRICULTURE HEALTH ECONOMY ENVIRONMENT ENERGY COMMUNITIES

Beyond the soil food web:

Managing soil for diverse

biological functions

Doug Collins

Small Farms Extension Specialist

WSU Extension

Outline and Learning Objectives

1. Understand functions

of soil organisms and

mutualistic

relationships

2. Tips to manage for

diverse and synergistic

functions

3. Monitoring soil quality

and function with soil

biological indicators

http://a.espncdn.com/photo/2012/0827/play_jetpack_d1_576.jpg

Important functions of a healthy soil

Magdoff & Van Es, 2009. Building soils for better crops

Supply nutrients from

organic sources.

Allow water & air to

infiltrate easily

Suppress root

diseases

Provide sufficient

water to plants

during dry spells

Develop healthy root

systems

Beneficial organisms

like mycorrhizal fungi

Classical soil food web models focus on predation and

competition.

These classical food web models ignore the

importance of larger soil fauna that encourage

decomposition and “spectacularly fail to

account for these sorts of relationships, or for

habitat modification by larger organisms for

smaller ones” – Wardle, 2002

Groups or guilds of soil organisms and their relative sizes

Body Width (mm)20 2 0.1 0.003 0.001 0.00001

millipedes

earthworms

springtailsprotozoa

nematodes fungi bacteria

primary consumers

secondary and

higher consumers

shredders/litter

transformers

ecosystem engineers

Litter transformers speed decomposition through an

“external rumen.”

Wolters and Ekshmitt, 1997

Earthworms are “ecosystem engineers”; changing their

environment to suit their physiology.

The earthworm’s kidneys; how earthworms answer nature’s call.

Earthworms deal with waste similarly to freshwater organisms

Earthworms increase aggregation in three ways:

1. By physically compacting smaller soil particles

together

2. By creating fecal pellets – which are themselves

durable aggregates

3. By coming to the soil surface to gather organic

matter to take down into their burrows.

Increased aggregation allows water to infiltrate easily during

a down pour and drain afterward to let air in.

Magdoff & Van Es, 2009

Infiltration Runoff

Quality soils supply nutrients from organic sources that

reduce the need for fertilizer

Nitrogen cycles from cover crops and amendments through

the microbial biomass

Isopods

Collembola

earthwormsnematodes

Microbial Biomass

Bacteria Fungi

available N Soil OM

protozoa

atmospheric N2

amendment

legume

C, N

N excreted

Management practices to encourage beneficial soil functions

• Use plant diversity to increase

the diversity in the soil biota

• Keep a living root growing

throughout the year

• Keep the soil covered as

much as possible

• Integrate livestock where

applicable.

• Manage more by disturbing

less

The Daily Worm:

“Mayan calendar predicts tornado, hurricane, and fire”

Larger-bodied organisms are more sensitive to disturbance

Body Width (mm)20 2 0.1 0.003 0.001 0.00001

millipedes

earthworms

springtailsprotozoa

nematodes fungi bacteria

high low

Sensitivity to disturbance

The roller / crimper, flail mower, and strip-tiller provide

opportunities to reduce soil disturbance

Reduced tillage research is underway for organic vegetables

Flail mowed and

strip tilledTilled

Kirsop farm, broccoli planted to flail mowed, strip-tilled common vetch.

8 July 2013, 21 DAT

Biotic indicators are ecological integrators, but not

necessarily easy to understand or inexpensive to measure

Idea soil health indicators should be:

1. Sensitive to variations in management

2. Well-correlated with beneficial soil

functions

3. Elucidate ecosystem processes

4. Understandable and useful to land

managers

5. Easy and inexpensive to measure.

Doran and Zeiss, 2000

Aporcelaimellus-

predator; 1.9 mm

Cephalobidae-

bacterivore;

0.5 mm

Aphlenchoides-

fungivore; 0.3mm

Rhabditidae;

bacterivore

0.1mm

Soil nematodes range in size, function, and sensitivity to

disturbance

stylet

Aphlenchoides;

stylet used to pierce

fungal hyphae

Aporcelaimellus; stylet

(spear) used to pierce

nematodes and protozoa

probolae

Cephalobidae; probolae used

to rasp bacteria from surfaces

Free-living soil nematode feeding strategies and structures

Isotomidae, juvenile

Isotomidae: Isotoma, adult

Entomobridae

OnychiuridaeSminthuridae

Hypogastruridae

Collembola are the most abundant soil microarthopods and

are fungal feeders, and litter transformers.

Earthworms can be coaxed from the soil with a skin irritant,

or physically removed.

Earthworm biomass by burrowing type in three tillage

systems 17 d after tillage, July 2011.

Anecic: p=0.3; Endogeic: p=0.001; n=3

Earthworm isolation from square in organic no-till plot.

Total earthworm biomass by tillage treatment and location

within planting bed, July 2011.

P=0.02 for location, P=0.18 for tillage, n=3

Research at WSU – Puyallup is investigating reduced tillage

frequency as well as amendment type.

Relay plantedLegume (RLY)

Fall-plantedCereal & legume (PH)

Short-term grass-legume Pasture (LEY)

Collembola populations spike in an annual pasture (LEY)

and with relay (RLY) planting that removes fall tillage.

• Dead ass collembola data

May Sep Jan May Sep Jan May Sep

Col

lem

bola

100

cc-1

0

20

60

80

100

120

LEY

PH

RLY

2005 2006 2007

** *** ** ** *

Compost applied in fields at 10 ton / acre or 2 ton/ acre.

Type of amendment did not significantly affect ratio of fungal

to bacterial-feeding nematodesNematode Channel Index

Type of Amendment

CKN OFC

0

1

2

3

4

5

Fungal-feeding nematodes spike in annual pasture (LEY). An

increase in the channel index indicates more fungal-feedersNematode Channel Index

Type of Cropping System

Ley PH Relay

Ch

an

ne

l In

de

x

0

1

2

3

4

5

a

b b

Feed the microfoodweb with plant diversity, but also manage

for mutualism.

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References

Doran, J.W. and M.R. Zeiss. 2000. Soil health and sustainability: managing the biotic

component of soil quality. Appl. Soil Ecol. 15:3-11.

Hunt, H.W. et al. 1987. The detrital food web in a shortgrass prairie. Biology and

Fertility of Soils. 3:17-68.

Kladivko, E. and J. Clapperton. 2011. Soil Biology. In: Hatfield, J.L. and T.J. Sauer

(editors). Soil Management: Building a Stable Base for Agriculture. American

Society of Agronomy and Soil Science Society of America, Madison, WI.

Magdoff, F. and H. Van Es. 2009. Building Soils for Better Crops, 3rd Ed. Sustainable

Agriculture Research and Education Program.

Turner, J. S. 2000. The Extended Organism. Harvard University Press, Cambridge, MA.

Wardle, D. 2002. Communities and Ecosystems: Linking the aboveground and

belowground components. Princeton University Press.

Wolters, V., K. Ekschmitt. 1997. Gastropods, Isopods, Diplopods, and Chilopods:

Neglected groups of the decomposer food web. In: G. Benckiser (editor). Fauna in

Soil Ecosystems: Recycling Processes, Nutrient Fluxes, and Agricultural

Production. Marcel Dekker, Inc, New York.

Photos: Clark County Historical Collection, Caitlin Price Youngquist, Andy Bary

Thank you!

Doug Collins

WSU Small Farms Program

dpcollins@wsu.edu

253-445-4658

Examples of biologically-based soil health indicators

• Soil carbon / organic matter

• Soluble carbon / active carbon

• Microbial biomass

• Fungal to bacterial biomass ratio

• Microbial community diversity

• Enzyme activity

• Nematode indices

• Microarthopods

• Earthworms

Different soils will have different initial soil quality. Monitoring

through time is the best way to evaluate management

Soil A

Soil B

Time

Soil

Qual

ity