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:

%

dead & decomposedplant rootsliving

85%

5%10%

“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

SpringtailsBeetles

pseudoscorpion

earthworms

nematodes

mites

actinomycetes:geosmin, antibiotics

bacteria

fungi

Springtails

Arthropods 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 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

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

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 yrsSlow 15-100 yearsPassive (stable) 500-5000

SOIL

CARBON IN CARBON OUTPlant residues

Manure

Compost

Harvesting

plants

Respiration

Erosion

Two Main Causes of Increased CO2 Emissions:

1. Fossil Fuel Burning2. 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

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 compost4”green”

1 compost

8 “brown”