Measuring soil biology

Transcription

1 Measuring soil biology

2 In one single teaspoon of soil there can be more soil organisms than there are humans on earth! Difficult to test for soil biology - is a very complex system Numbers and types change rapidly with Temperature day/night, depth of soil Moisture rain, irrigation, drought Nutrient supply organic matter type, & amounts crop or pasture Take outside factors into account in tests!

3 How DO we test for soil 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. microflora and fauna Chemical lab tests microbial biomass, CO2 respiration Indirect indicators which affect function of organisms Organic carbon

4 Tests available 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 Numbers/Mass (how many are there?), Diversity (who are they?) and Functions (what do they do?)

5 Nematode Numbers Root Knot Nematode density/kg dry soil Nematodes/kg dry soil Sep-09 Mar-10 0 V1 control V1 mulch V2 control V2 mulch V3 control V4 mulch Sample date

6 Citrus Nematode Citrus Nematode density/kg dry soil 1200 Nematodes/kg dry soil Sep-09 Mar-10 0 V1 control V1 mulch V2 control V2 mulch V3 control V4 mulch Sample date

7 Bacterial feeding Nematodes Bacteria feeding nematode density/kg dry soil 3000 Nematodes/kg dry soil Sep-09 Mar-10 0 V1 control V1 mulch V2 control V2 mulch V3 control V4 mulch Sample date

8 Predator Nematodes Predator nematode density/kg dry soil Nematodes/kg dry soil V1 control V1 mulch V2 control V2 mulch V3 control V4 mulch Sample date Sep-09 Mar-10

9 Other Free living nematodes Other free living nematodes/kg dry soil Nematodes/kg dry soil V1 control V1 mulch V2 control V2 mulch V3 control V4 mulch Sample date Sep-09 Mar-10

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11 Test Examples of tests available simple Pauline Mele Vic DPI Information generalised Cotton strip assay Decomposer potential Fungi/bacteria ratio Ecosystem health Microbial biomass C/Total C C turnover CO 2 Respiration Overall soil microbial activity CO 2 Earthworms (#/sp) Dung beetles Cultivable Functional Groups (eg cellulose degraders) Microbial enzymes BIOLOG DNA profiles Bacterial genes Predicta B Microarrays sophisticated C levels, structure C incorporation Specific processes Specific processes Community catabolic diversity Community fingerprints Specific bacterial functions DNA-based; for pathogens 1000 s genes (function & structure) specific

12 Simple on-farm tests Looking for evidence of organisms: 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

13 Soil biology how (what) to Low biological acitivity measure and monitor High biological activity Score: 0.5 / 4.0 Score: 3.5 / 4.0

14 Casts at the soil surface are evidence that earthworms are shredding, mixing, and burying surface residue. Soil and Water Management Research Unit, USDA-Agricultural Research Service, St. Paul, Minnesota.

15 Simple on-farm 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)

16 Simple on-farm tests Assessing the soil environment from soil properties and chemical tests: SOC levels Subsoil colour (grey or mottling indicates waterlogging) Soil chemistry: ph Ca, salinity, sodicity, toxicities. Structural problems: compaction, erosion, or surface crusting Other: Groundcover assessment

17 What is most important when 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 complex interacts with whole environment: not many generalities yet (but some emerging)

18 Carbon fractions are a good surrogate!!!

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