measuring soil biology - charles sturt university...1500 2000 2500 3000 3500 4000 v1 control v1...

Measuring soil biologyMeasuring soil biology

Difficult to test for soil biology -is a very complex system

Numbers and types change rapidly withTemperatureTemperature – day/night, depth of soilMoistureMoisture – rain, irrigation, droughtNutrient supplyNutrient supply – organic matter type, & amounts – crop or pasture

Take outside factors into account in tests!

In one single teaspoon of soil there can be In one single teaspoon of soil there can be more soil organisms than there are humans more soil organisms than there are humans on earth!on earth!

Presenter�

Presentation Notes�

When you consider that in one single teaspoon of soil there can be more soil organisms than there are humans on earth, finding a meaningful soil biology test is a tall order. To complicate this even more, soil organisms, particularly microbes change population dynamics rapidly in response to season, rainfall, temperature, plant type, management, even the time of day! So by the time you get the results back, generations have changed and the community might be completely different to the time of sampling. With this in mind, some tests can still be useful if the interpreter takes into account the influences of rainfall, temperature and OM supply. �

How DO we test for soil How DO we test for soil organisms?organisms?

Can use • Direct indicators for presence, activities

and/or numbers– Single or range of species in field e.g. ants– Biological lab tests – enzymes, DNA e.g. micro-

flora and –fauna– Chemical lab tests – microbial biomass, CO2

respiration• Indirect indicators which affect function of

organisms– Organic carbon

• AMOUNT: reasonably stable but assessed withOUT separating into groups

– E.g. bacteria and fungi (microscopy, plate counts- only retrieve 1- 2% actual amount), microbial biomass carbon or nitrogen (most commonly used).

• ACTIVITY – fluctuates with temperature and water and relevant to agriculture

– E.g. enzyme action, decomposition rate, carbon respiration, N- mineralisation

• SPECIES or DIVERSITY: can target specific groups– Nematodes, earthworms, rhizobia, arbuscular mycorrhizal fungi,

DNA, community analysis, microbial functional (Biolog),

And INDIRECT– E.g. Carbon fractions

Tests availableTests availableNumbers/Mass (how many are there?), Diversity (who are they?) and Functions

(what do they do?)

Presenter�


Optional slide: There are 3 main types of soil biology testing: Population analysis: counts the numbers and types of organisms in the soil. These results need to be considered in light of seasonal circumstances and the stage of farming when sampled. Two examples include: nematode analysis (microscopic counting of nematodes and the ratio of population groups- the different ratios of bacterial, fungal feeders and other types can indicate the type of soil functions occurring and the state of the food web), and FAME: fatty acid methyl ester analysis (bacterial to fungal ratios). Biological activity: measure what the soil organisms are doing. These tests are useful to compare sites, techniques and products although are complicated for monitoring as they are sensitive to pH, salinity, cultivation, heavy metals, and chemicals. Generally, recommendations are based on techniques to build SOM. A few of examples include: soil respiration (measures the amount of CO2 produced from the sample), FDA: fluorescein diacetate (measures the amount and types of enzymes produced such as phosphatase and urease used in P and N transformation), and calico test (simple test done on-farm by burying calico strips for a few weeks and comparing sites via calico decomposition- see Appendix 4). Indirect indicators: use tests that only generally indicate ‘healthy soil biology’. For example: SOC levels, POC: particulate organic carbon (approximately 20% SOC), DOC: dissolved organic carbon (biologically available C), and MBC: microbial biomass carbon (measures C contained in microbes). Another indirect way is through groundcover percentage, with low levels of cover discouraging soil biology. �

Nematode NumbersNematode Numbers

Root Knot Nematode density/kg dry soil

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V1 control V1 mulch V2 control V2 mulch V3 control V4 mulch

Sample date

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g dr

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Sep-09Mar-10

Citrus NematodeCitrus Nematode

Citrus Nematode density/kg dry soil

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Sep-09Mar-10

Bacterial feeding NematodesBacterial feeding Nematodes

Bacteria feeding nematode density/kg dry soil

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Predator NematodesPredator Nematodes

Predator nematode density/kg dry soil

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Sep-09Mar-10

Other Free living nematodesOther Free living nematodes

Other free living nematodes/kg dry soil

0200400600800

100012001400160018002000


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Sep-09Mar-10

Test Information Cotton strip assay Decomposer potential Fungi/bacteria ratio Ecosystem health Microbial biomass C/Total C C turnover CO2 Respiration Overall soil microbial activity CO2

Earthworms (#/sp) C levels, structure

Dung beetles C incorporation Cultivable Functional Groups (eg cellulose degraders)

Specific processes

Microbial enzymes Specific processes

BIOLOG™ Community catabolic diversity

DNA profiles Community ‘fingerprints Bacterial genes Specific bacterial functions Predicta B ™ DNA-based; for pathogens

Microarrays 1000’s genes (function & structure)

Examples of tests availableExamples of tests available Pauline Pauline MeleMele

Vic DPIVic DPI

specific

simple generalised

sophisticated

Presenter�


Optional slide�

Simple onSimple on--farm testsfarm tests……

• Calico strips - monitor decomposition

• Set traps for macro and mesofauna e.g. ants• Monitor dung beetles • Look for worm casts >> earthworm activity• Examine nodules on legumes

Looking for evidence of organisms:

Presenter�


This slide has reveal animation for each test Looking for evidence of organisms: Bury calico strips and monitor decomposition rates across sites Set traps to catch bugs in your paddocks and see which macro and mesofauna are dominating your soil e.g. ants Monitor the presence and type of dung beetles Look for worm casts after warm, wet periods to illustrate earthworm activity, Extract nodules on legumes. �

Low biological High biological acitivity activity

Score: 0.5 / 4.0

Score: 3.5 / 4.0

Soil biology Soil biology ––

how (what) to how (what) to measure and monitormeasure and monitor

Presenter�


Optional slide – can leave until practical if doing strips or have some to hand around. An example of two contrasting soils effects on the breakdown of a calico cloth (unbleached). Cotton (calico) strip assay is proposed as a surrogate indicator of biological activity in soil. The higher the rate of decay of the strip, the greater the biological activity Scoring in this case is purely visual but breakage tension can be measured by specialised laboratories. �

Soil and Water Management Research Unit, USDA-Agricultural Research Service, St. Paul, Minnesota.

http://soils.usda.gov/sqi/concepts/soil_biology/

Casts at the soil surface are evidence that earthworms are shredding, mixing, and burying surface residue.

Presenter�


Optional show if time – have found that some people ask about how to identify worm casts.�

Simple onSimple on--farm testsfarm tests……Dig a hole deep enough so

that you can see the subsoil.• Are the old inactive roots

decomposing? (bacteria and fungi)

• Is there evidence of bioturbation? (macrofauna, e.g. earthworms and beetles)

• Does the soil smell “earthy”? (actinomycetes)

• Is the soil dark in colour? (SOC)

• Is the soil well-structured? (soil aggregation)

Presenter�


This slide has reveal animation for each test.�

Simple onSimple on--farm testsfarm tests……Assessing the soil environment

from soil properties and chemical tests:

• SOC levels• Subsoil colour (grey or mottling

indicates waterlogging)• Soil chemistry: pHCa , salinity,

sodicity, toxicities. • Structural problems:

compaction, erosion, or surface crusting

Other:• Groundcover assessment

Presenter�


This slide has reveal animation for each test. �

What is most important when What is most important when using soil biological data?using soil biological data?

1. Monitor –see if the values are increasing or decreasing

over time.

2. Interpret from more than one set of results

many readings from one site, different times, different types of information

3. Soil biological information is complexinteracts with whole environment: not many

generalities yet (but some emerging)

Presenter�


This is one of the quiz questions. Monitoring - Remind to keep written, and/or photographic records Interpretation – replication, randomisation to get many readings at same time as well as over time, use different types of info e.g. monitor worms and ants, or calico strips and dung beetles Use rainfall info, pasture or crop records to help explain what is happening to soil organisms�

Carbon fractions are a good surrogate!!!

Presenter�


Soil test may help measure more accurately – is the organic matter content changing? as it feeds the soil organisms.�

measuring soil biology - charles sturt university...1500 2000 2500 3000 3500 4000 v1 control v1...

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