The dirt on food: healthy soils Dr Mary Cole Growers and Eaters 2012

Transcription

1 The dirt on food: healthy soils Dr Mary Cole Growers and Eaters 2012 Monday 23 April, 2012 Gravel Hill Salvation Army Complex Mundy Street, Bendigo

2 WHAT DO WE WANT? DIRT OR SOIL? DIRT: sand. Silt and clay?????????? SOIL: sand, silt,clay, organic matter, microbes, arthropods, worms, etc.

3 Soil, Chemistry, Life. Soil & its chemistry cannot be separated from life in the soil. Dirt is the framework to support life - plant & microbe. Dirt becomes soil when given life by plants & microbes. Balance between soil nutrients & life gives health to plants & microbes.

4 What is soil? 4 major elements: minerals, plant & animal organic matter, water and air all in variable amounts. Soil aggregates (Photograph by Helen Waite)

5 The Soil The Soil Nomadic life to agricultural life >>>>>monoculture Not sustainable constant movement to new land Settlements overuse of same land >>depletion of nutrients Increased inputs >>modern agriculture >>artificial chemicals >>> toxic to soil biota. Natural ecosystems: Top 10cm of good soil contains/ha: Bacteria: 250gms Fungi: 200kg Actinobacteria: 30kg

6 Healthy Soil Biota

7 A Healthy Food Web Will: Suppress Disease (competition, inhibition, consumption; no more pesticides!) Retain nutrients (stop run-off, leaching) Nutrients available at rates plants require (eliminate fertilizer) Decompose toxins Build (re-build) soil structure Reduce water use, increase water holding capacity, rooting depth

8 Poor soil Many small pores relative to large pores high bulk density. Prone to compaction. Indicators of poor soil structure: Water logging; Plant roots confined to shallow depths & growing horizontally.

9 Badly degraded land Compacted. Heavy chemical use. Revegetating.

10 Non-chemical farming

11 Soil Biota Organic matter is the food for soil biota. Most soils -1-3% organic matter. Cultivation causes depletion loss of biodiversity domination by a particular group when a food source (chemicals) is added constantly.

12 Soil Biota Trophic levels Bacteria: rods cocci Compete for food Make glues form microaggregates Why bacterial-bound nutrients do not leach Ref: bacteria

13 Growth - Structure

14 Largest organism living on Earth is a fungus. Fungi do not photosynthesise rely on higher plants and animals for food source Higher plant capture sunlight > energy >carbohydrates > eaten by animals. Both die > recycled by soil biota > elements

15 Role of fungi in soil food web SOIL STABILISATION: Organic matter most important factor. Reduces erosion clear water to subsoil Polysaccharides glues stabilise soil Roots die & leave channels Provides food for microflora & microfauna Supplies nutrients & cations for CEC Increases water holding capacity

16 Role of fungi in soil food web Interaction with bacteria: Plant tissue mycorrhizal fungi > carbon compounds exuded as droplets. Conditions soils around hyphae facilitates interaction with other microbes positive in low water potential areas. Endobacteria inside mycorrhizal fungal hyphae.

17 Working with soils for best wines

18 Protozoa Eat bacteria releasing nutrients Mineralise N

19 Earth worms Earthworms also secrete a plant growth stimulant. Earthworms: make channels; redistribute OM through the soil. Outcome is increased availability of plant nutrients; reduced water run-off. (Photograph by Clive Edwards, The Ohio State University)

20 FUNCTIONS OF SOIL ORGANIC MATTER

21 Carbon : Nitrogen Ratios Bacteria 5:1 - most concentrated N Legume leaf 10:1 Chicken manure 10:1 Fungi 20:1 Humans 30:1 Green Leaves 30:1 Protozoa 30:1 Nematodes 30:1 Brown plant material :1 Deciduous wood 300:1 Conifer wood 500:1

22 Bare Parent Material 100% bacterial Old- growth F:B = 100:1 to 1000:1 Foodweb Development F:B = 0.01 Disturbance Pushes Systems Backwards, But How Far? Depends on Intensity, Frequency FIRE!!! Volcano! Flood Weeds F:B 0.1 Insects Early Annuals F:B = 0.3 Mid-grass, vegies F:B = 0.75 Deciduous Trees F:B = 5:1 to 100:1 Bushes F:B = 2:1 to 5:1 Humans? Pasture, row crops F:B = 1:1 Cattle

23 Soil food web availability of N Protozoa eat bacteria to release N in plant-available form free N C : N Flagellate 30 : 1 1Bacterium 5 : C : OK Must eat 6 bacteria = 30:6 = +5N >mineralisation > NH 4 >NO 2 >plant NO 3 plant available

24 Leaf Surface Microflora With Compost Tea Without Compost Tea

25 Compost is a fertilizer AND an inoculum Compost has the organisms to build soil structure, decrease water use, re-establish disease competitors, consumers, inhibitors Compost has the biology to cycle soil nutrients from plant not-available forms into plant available forms How much of the total nutrients get into compost tea? Soluble pool, plus the biology.

26 Working with soils for best wines

27 Examples of Soil types Schist Otago NZ terra rossa Coonawarra SA

28 European vines Douro Valley, Portugal. Vineyard on Crete, Greece

29 Soil Biota Living soil biota ~6% of the total soil composition; humus ~ 46%; decomposing residue ~35%; fresh material ~ 10-13% Soil populations are very diverse and largely unknown ~5% probably known. Most in top 4-10cms of soil. 1g soil contains >10million individuals. Bacteria: named ~2,500 species Fungi: named ~70,000 species Protozoa: named ~ 40,000 species Nematodes: named ~5,000 species Colembolae: named 6,500 species.

30 HOME AEROBIC COMPOST PILE

31 Fungal:Bacterial ratios

32 Weight of soil Organism in top 15cm of fertile soil Organism Kg of live weight/ha Bacteria 1120 Actinomycete/Actinobacteria 1120 Molds/Fungi 2250 Algae 120 Protozoa 450 Nematodes 56 Insects 120 Worms 1120 Plant roots 2250 From: Bollen, (10)

33 Counting organisms in a compost validity of counts direct vs plating Method Bacteria Fungi Direct Methods Numbers 1,000,000,000/g Biomass 250 ug/g 150 to 300 ug/g Species 22,000/g 5,000/g Plate Methods Numbers 1,000,000 /g 100 to 150 /g Species 12 max 4 to 8 max DNA 25,000/g (or more) 8,000 to 12,000/g

34 Results of conventional agricultural practices Over working soils leads to: Soil loss = nutrient loss Bare soil = nutrient loss = biomass loss 1 mm of soil lost (thickness of a 5cent piece) = loss of 14 tonnes of soil per hectare

35 Rodale Institute 30 year trials Fast Facts Organic yields match conventional yields. Organic outperforms conventional in years of drought. Organic farming systems build rather than deplete soil organic matter, making it a more sustainable system. Organic farming uses 45% less energy and is more efficient. Conventional systems produce 40% more greenhouse gases. Organic farming systems are more profitable than conventional

36 Rodale Institute 30 year trials

37 Phylloplane Fungi Bud burst Flowering Bunch closure Veraison Harvest

38 Biologically dead vineyard

39 Canopy Management

40 Diversity in the Environment Moisture Litter Diversity

41 Organic or biodynamic grape growers and winemakers David Bruer Temple Bruer Julian & Carolann Castagna Castagna Vineyard Ron Laughton Jasper Hill Organic Viticulture: An Australian Manual ed David Madge

42 Does soil influence wine characteristics? Terroir Vineyard practices Winemaker influence working the must Physical soil structure Water availability - Soil fertility Microbiology Right variety in right place

43 Summary Fungi are a part of the soil food web. Disturb one component and all others are disturbed. We would be wise to view soil as a finite resource that must be well managed at all times if our descendants are to inherit land that has a good productivity capacity (Reid, 1990)

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45 Compost and compost tea Alternatives to conventional chemicals?????

46 Compost Facts Aerobic organisms improve soil structure, which improves aeration, reduces disease and increases rooting depth Anaerobic organisms produce plant toxic materials (alcohol), volatize N, S, P, reduce nutrients (plant unavailable) and help disease causing organisms to grow Feed aerobic organisms, build structure

47 If anaerobic, it is NOT compost Beneficial fungi and bacteria are asleep or dead Aerobic nutrient cyclers are dormant or dead Soluble N, P, S have been lost as gases Strong acids have been produced Alcohol, preservatives have been made

48 What is compost? Aerobic decomposition by BACTERIA and FUNGI of a mix of organic material: nutrient cycling requires predators Thermal compost Commercial, back-yard, household Worm or Vermi-compost (cold composting) Batch or flow-through Static compost heat uneven, anaerobic, takes longer Malcolm Beck s Secret Life of Compost

49 House-hold Composting Make pile with 50% Green and 50% Woody Add household wastes into pile, at least 2 feet into pile, spaced through pile, until no more spaces left Added household waste Mix green and woody Add 10% high nitrogen Start compost temperature cycle, measure temperature, moisture

50 Back-Yard Composting As long as you maintain ratios, the seasonal variation in N, green, woody have little effect. Anaerobic starting materials signal carried through composting cycle Minimize turning by reducing Hi N. Offset with increased time. 10% Hi N, 45% green, 45% woody, turn once, but compost for 3-4 months to get rid of E. coli

51 Humus Humus is made up of three fractions: Humic acid extremely resistant to decomposition derived from lignins, proteins, and plant and animal metabolites- dark brown 400,000 C chain. Fulvic acid - made up of additional carbohydrate and protein material golden 100,000 C chain. Humin plant residues and humic acid in association with clay colloids that prevent extraction.

52 What is needed in tea Active organisms attach to leaf surfaces, grow and protect plant surfaces Total bacteria, fungi to assure coverage, to compete with diseases Maximum Diversity so growth continues through whole season Protozoa, nematodes consume diseases, cycle nutrients Soluble nutrients to feed organisms, foliage

53 Aerated Compost Tea 1. AEROBIC, BREWED Conditions are controlled, oxygen is adequate 2. WATER EXTRACT Water quality critical: ph, salts, temperature Energy to extract organisms 3. of COMPOST Compost quality is critical: NOT SMELLY