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Lecture 27 Soil Organisms I

Lecture 27 Soil Organisms I - Homework III The State Soil...

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Unformatted text preview: Homework III: The State Soil of Florida Posted on website 5 bonus points Type all answers Soil Organisms, Biology, and Nutrients Mineral and Organic Components Functions of soils: recycler of raw materials Nutrient availability, replenishment 1 Organic Matter and Soil Biology Soil Organic Matter Accumulation of partially disintegrated and decomposed plant and animal residues plus biomass. 1 – 5% (by weight) in a typical, well-drained mineral soil Transitory soil constituent (hours to 100s of years) Requires continual addition to maintain O.M. levels. Constantly being broken down by soil micoorganisms Release/recycling of important plant nutrients Soil Organisms 2 What creatures live in soil? 22 species Harvester Ant Colony Fauna Macro Micro Mammals, reptiles, amphibians, insects Nematodes, Protozoa, Rotifers Flora 20,000 species Plant roots, algae, fungi, actinomycetes (filamentous bacteria), bacteria unicellular Basic Classification of Organisms Food Oxygen Demand Energy Source 3 Based on food: live or dead Herbivores – Eat live plants Insects, mammals, reptiles Detritivores • Eat dead tissues: • Fungi, bacteria & actinomycetes Predators – Eat other animals Insects, mammals, reptiles Based on O2 demand Aerobic – Active in O2 rich environment – Use free oxygen for metabolism Anaerobic – Active in O2 poor environment – Use combined oxygen (NO3- , SO4-2) SO4-2 => H2S Still Ponds O2 NO3SO4-2 SO4-2 H2S 4 Based on energy & C source Autotrophic (CO2) – Solar energy (photoautotrophs) (photoautotrophs) – Chemical reaction w/inorganic elements N, S, & Fe (chemoautotrophs) (chemoautotrophs) Heterotrophic From breakdown of organic matter (Carbon) Most Numerous Quantification of Soil Organisms Quantification of Soil Organisms Three Criteria Numbers of organisms – Extremely numerous – 1,000,000-1,000,000,000 /g soil 1,000,000– 10,000 species /g soil Biomass – 1-8% of total soil organic matter Metabolic activity – Respiration: CO2 CO – Proportional to # & biomass 5 Soil Organisms in Surface Soils Organisms Microflora Bacteria Actinomycetes Fungi Algae #/g soil Biomass (g/m2) 108 -109 107 -108 105 -106 104 -105 40-500 4040-500 40100-1,500 1001-50 Fauna Protozoa Nematodes Mites Earthworms 104 -105 10 -102 1 -10 1 -10 2-20 1-15 1-2 10-150 10- Note those in White Earthworms 1,000,000 per acre five pairs of hearts Mostly intestine 22 ft. long (Afr. and Aus.) Earthworm cast Casts: earthworm’s wastes earthworm’ Eat soil organics: 2-30 times of their own wt. 2- Earthworms Abundance of earthworms – 10-1,000/m3 10– 3,000 species Benefits of earthworms - soil fertility by producing cast (concentration of nutrients) - aeration & drainage - size & stability of soil aggregates 6 Soil Algae Autotrophs Capable of photosynthesis (chlorophyll) 1-10 billion/ m2 (can be “mat” of algae (can mat” on surface) Prefer moist environments Rich in wetland and paddy soils Fixing atmospheric N2 (B-G algae) (BSome soil algae “swim” by flagella swim” Soil Fungi Yeasts, molds, mushrooms 10 - 100 billion/m2 Cell with a nuclear membrane and cell wall Most versatile & most active in acid forest soils Tolerate extremes in pH (bacteria do not) Mycorrhizae symbiosis Association between fungi & plant root Increased SA (up to 10 times) Increased nutrient uptake, especially P Mycorrhizae Fungi 1. Ions in solution 2. Movement from solution to root (diffusion) Phosphorous granule hyphae Root hair 7 Symbiosis – Fungi provide nutrients – Plant root provides carbon – Ectomycorrhiza Root surfaces and cortex in forest trees – Endomycorrhiza Penetrate root cell walls agronomic cropscropscorn, cotton, wheat, & rice 10-100 trillion/m2 10Single-celled organism SingleRapid reproduction Small (4-5 µm) (4Mostly heterotrophic Soil Bacteria N oxidation: nitrification NH4+ ⇒ NO3NO S oxidation S + 3O2 + 2H2O ⇒ H2SO4 N fixation fixation N2 ⇒ NH4+ NH rhizobium Oxygen, moisture, temperature, O.M., pH Benefits of Soil Organisms OM decomposition The most significant contribution N, S, & P nutrients Nitrogen fixation (N2 ⇒ NH4+) NH Algae: wetland Bacteria: legumes Elemental transformations N (NH4+ ⇒ NO3-) NO S (S ⇒ SO4), SO Fe (Fe2+ ⇔ Fe3+) Fe Mn (Mn2+ ⇔ Mn4+) Mn Breakdown toxic organics (bioremediation) Pesticide degradation: DDT Oil & gasoline degradation 8 Effect of Organisms on Nutrient Availability Soil Organic Matter •Carbon •Hydrogen •Oxygen •Phosphorus •Nitrogen •Sulfur Soil Organic Matter Biomass: Detritus: Humus: Living organisms Identifiable dead tissue Nonliving tissue Humic Nonhumic 60 -80% SOM Complex Resistant 20 -30% SOM Less complex Less resistant Fulvic acid, humic acid, humin (Undefined, high molecular wt.) Polysaccharides, proteins, acids (defined, lower molec. Wt.) 9 ...
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