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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 Living, dead, decomposing, decomposed % 10% 5% dead & decomposed plant roots living 85% What is special about Organic compounds? They have ENERGY Food chain passes energy along through photosynthesis and respiration Photosynthesis: CO2 + H2O + solar energy C6H12O6 + O2 organic ! Respiration: C6H12O6 + O2 ENERGY + CO2 + H2O Energy is passed from one trophic level to the next. What is an organic compound? Bank of energy 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 earthworms Beetles Springtails bacteria mites actinomycetes: geosmin, antibiotics nematodes pseudoscorpion Arthropods Invertebrates with external skeleton Spring or hop Detrivores 100,000 / m3 topsoil Arthropods; order Coleoptera 400,000 species (40% of all known insect species) Some omnivores, some eat plants, fungi, some are carnivores Larvae (grubs) Arachnid Joint-legged invertebrate Carnivorous: eat larvae, ants, mites, flies 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 Roundworms Occupy many positions in soil food web > 28,000 species Most microscopic Can be predatory or parasitic arachnids Extracted from one ft2 of top two inches of forest litter and soil Abundant; most important decomposers Adaptable Specialized: Non-photosynthetic Photosynthetic Oxidize ammonium, nitrite, iron, manganese Oxidize sulfur Nitrogen-fixing Aerobic, anaerobic 1 ton / acre Bacteria and fungal hyphae 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 Filamentous morphology varies adaptable to drought neutral pH usually aerobic heterotrophs break down wide range of organic compounds A respiration process: Organic matter + O2 Energy for decomposers CO2 + H2O Nutrients, that were in the original organic tissue, for plants Carbon, nitrogen, etc. for the decomposers HUMUS ! Ultimate decay product of decomposition “Amorphous, colloidal mixture of complex organic substances, not identifiable as tissue”. < 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 A supply of N, P, S for plants Holds water Provides structure Glue that allows soil to have spaces Prevents erosion Carbon : organic compounds stores energy Cycled back and forth from atmosphere to biosphere ▪ photosynthesis and respiration ▪ 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 Manure SOIL Respiration 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 Restore the humus portion!!!! Organic farming Non-chemical no-till Manage trees and forests Keep green manure Diversify crops Compost Mulch Speeding up decomposition by making breeding grounds for decomposers 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) 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? 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 Intense competition for N Microbes will build their bodies first, then give up N for plants; N deficiency Plenty of N to be released for plants 1 compost 4”green” 1 compost 8 “brown”