SOIL ALIVE! Land, then, is not merely soil; it is a foundation of energy flowing through a circuit of soils, plants and animals”. Aldo Leopold

“ Soil is the hidden, secret friend, which is the root domain of lively darkness and silence” Francis Hole Soil by parts: 5% organic, 50% space, 45% mineral

5% Organic Living, dead, decomposing, decomposed

Organic portion composed of: 5% 10% 85%

“organic” What is special about Organic compounds? They have ENERGY Food chain passes energy along through photosynthesis and respiration

Green plants can directly use sun Photosynthesis: CO2 + H2O + solar energy C6H12O6 + O2 organic !

Rest of us are only indirectly solar-powered Respiration: C6H12O6 + O2 ENERGY + CO2 + H2O

Food Chain Concept Energy is passed from one trophic level to the next.

What is an organic compound? Bank of energy

Organic materials in soil: More living biomass below ground than above! Beneath 1 acre: equivalent to 12 horses 1 cubic meter of soil: 50,000 earthworms 50,000 insects and mites 12 million roundworms 1 pea-size bit of soil: 30,000 protozoa 50,000 algae 400,000 fungi Billions of bacteria

fungi Springtails earthworms Beetles bacteria mites actinomycetes: geosmin, antibiotics nematodes pseudoscorpion

Springtails Arthropods Spring or hop Detrivores 100,000 / m3 topsoil Invertebrates with external skeleton Spring or hop Detrivores 100,000 / m3 topsoil

Beetles Arthropods; order Coleoptera 400,000 species (40% of all known insect species) Some omnivores, some eat plants, fungi, some are carnivores Larvae (grubs)

pseudoscorpons Arachnid Carnivorous: eat larvae, ants, mites, flies Joint-legged invertebrate Carnivorous: eat larvae, ants, mites, flies

earthworms Annelids Some 2700 different types 3 categories: Epigeic (leaf litter/compost dwelling ) Endogeic (topsoil or subsoil dwelling ) Anecic (deep burrow drillers)

Giant Benefits to soil Move air in and out of soil Castings are rich in available nutrients Produce 10 lbs / yr

Nematodes Roundworms Occupy many positions in soil food web > 28,000 species Most microscopic Can be predatory or parasitic

Mites arachnids

Extracted from one ft2 of top two inches of forest litter and soil

Bacteria Abundant; most important decomposers Adaptable Specialized: Non-photosynthetic Photosynthetic Oxidize ammonium, nitrite, iron, manganese Oxidize sulfur Nitrogen-fixing Aerobic, anaerobic

bacteria 1 ton / acre

Bacteria and fungal hyphae

Fungi Break down OM, esp important where bacteria are less active branched hyphae form mycelium: bears spores attack any organic residue

Symbiotic ; infecting plant roots, formed by some fungi Mycorrhizae: s Symbiotic ; infecting plant roots, formed by some fungi normal feature of root systems, esp. trees increase nutrient availability in return for energy supply plants native to an area have well-developed relationship with mycorrhizal fungi

Higher fungi have basidium : club-shaped structure , bearing fruiting body toadstools, mushrooms, puffballs, bracket fungi

Actinomycetes Filamentous morphology varies adaptable to drought neutral pH usually aerobic heterotrophs break down wide range of organic compounds

Decomposition A respiration process: Organic matter + O2

Products of decomposition… Energy for decomposers CO2 + H2O Nutrients, that were in the original organic tissue, for plants Carbon, nitrogen, etc. for the decomposers HUMUS !

What is HUMUS? Ultimate decay product of decomposition “Amorphous, colloidal mixture of complex organic substances, not identifiable as tissue”.

Colloidal in size: tiny! < 0.00001 mm in diameter Nutrients and water attach to surface area of soil particles Smaller the particle, the greater the surface area per unit volume

Humus <0.00001 mm Sand 0.05 – 2.0 mm Silt 0.05 – 0.002 Clay <0.002 Humus <0.00001 mm Tremendous ability to hold water and nutrients

Functions of humus: A supply of N, P, S for plants Holds water Provides structure Glue that allows soil to have spaces Prevents erosion

About structure…

Humus sequesters carbon!!! Carbon : organic compounds stores energy Cycled back and forth from atmosphere to biosphere photosynthesis and respiration

sequestration Take carbon from atmosphere and move it into long-lived soil pools where it is securely stored for very, very long time SOIL CARBON POOLS: Fast 1-2 yrs Slow 15-100 years Passive (stable) 500-5000

CARBON OUT CARBON IN SOIL Plant residues Harvesting plants Respiration Manure Compost Erosion

Two Main Causes of Increased CO2 Emissions: 1. Fossil Fuel Burning 2. Net Loss of Soil Organic Carbon Soil Carbon Sequestration: Potential to offset fossil fuel emissions by 0.4 to 1.2 gigatons of carbon per year, 5-15% of global fossil-fuel emissions

How? Restore the humus portion!!!! Organic farming Non-chemical no-till Manage trees and forests Keep green manure Diversify crops Compost Mulch

COMPOSTING Speeding up decomposition by making breeding grounds for decomposers

Composting is creating habitat for decomposers to make humus! Making soil Need to pay attention to amounts of carbon relative to nitrogen in the organic waste you throw into the compost. This is the C:N ratio

Amount of N is more critical than amount of C : Carbon usually makes up 45 – 55% of dry weight of tissue Nitrogen can vary from 0.5% - 6.0% For a residue with: 50% carbon and 0.5% N, C:N ratio would be ? 100:1 (wide/high C:N) 50% carbon and 3.0% N, C:N ratio would be ? 16:1 (narrow/low C:N)

Carbon : Nitrogen ratio C:N ratio High C:N means not much nitrogen (“BROWN”) Slow to decompose Sawdust 600:1 ; straw 80:1 ; newspaper 120:1 Low C:N means plenty of nitrogen (“GREEN”) Fast to decompose Rotted manure 20:1 ; household compost 15:1 Break-point between high and low = 25:1 WHY?

…because microbes have needs too! Soil microbes’ cells need 8C: 1N Only 1/3 of C from compost is taken into the cells Therefore they need compost with 24 : 1

If C:N is > 24:1 Intense competition for N Microbes will build their bodies first, then give up N for plants; N deficiency

If C:N < 24:1 Plenty of N to be released for plants

1 compost 4”green” 1 compost 8 “brown”