MIKROORGANISME & BAHAN ORGANIK TANAH AGROTEKNOLOGI In 1 teaspoon of soil there are… Bacteria 100 million to 1 billion Fungi 6-9 ft fungal strands put end to end Protozoa Several thousand flagellates & amoeba One to several hundred ciliates Nematodes 10 to 20 bacterial feeders and a few fungal feeders Arthropods Up to 100 Earthworms 5 or more Travis & Gugino - PSU Soil Organisms Significance/Fungsinya 1. Decomposition of plant and animal residues 2. Release of nutrients and inorganic elements which feed plants and cause mineral weathering 3. Synthesis of new organic compounds 4. Humus formation to increase cation exchange and structure 5. Nitrogen fixation Soil Organisms Cont. Kind 1. Plant 2. Animal Plants ( bacteria, actinomycetes, fungi, algae) 1. Bacteria 1. Very small single celled organisms 2. Multiply by elongation and dividing into 2 parts 3. Millions or even billions per gram of soil I. Classification of Bacteria (Heterotropic) A. Heterotropic obtain their carbon and energy from various organic compounds 1. Nitrogen fixing derive their nitrogen in gaseous form from the atmosphere or they can obtain their nitrogen from Ammonia or Nitrates a. Non Symbiotic - those that are free living 1. Anaerobic organisms - those not needing free oxygen for respiration Don’t need Host Plant Clostridium – More common in forest soils – Optimum Reaction pH 6.9 - 7.3 – no fixation below pH 5.0 2. Aerobic- need free oxygen Azotobacter – More common in agriculture soils – Very sensitive to acidity – pH below 5.5 to 6.0 no fixation b. Symbiotic - live on host plant to mutual advantage Rhizobium - Find on nudules - Nitrogen from the air c. Aerobic Bacteria- requiring combined Nitrogen Bacillus mycoides - Cause denitrification d. Anaerobic Bacteria - which require combined Nitrogen - Nitrates ---------- Nitrites, ammonia - Sulfates ---------- Sulfites, sulfides Classification of Bacteria (Autotrophic) B. Autotrophic- derive their carbon primarily from CO2 of the atmosphere and their energy from the oxidation of inorganic compound or simple compounds of carbon Cont. 1. Bacteria using nitrogen compounds as an energy source a. Nitrosomes - oxidize ammonium Nitrite NH4+ NO2- Cont. b. Nitrobacter - Oxidize Nitrite to Nitrate NO2NO3- little or no activity below a pH of 6.0 - little or no activity below a temp of 65oF 2. Bacteria using sulfur or sulfur compounds as energy sources. a. Thiobacillus S + O2 + H2O H2SO4 SOIL MICROORGANISM Bacteria UBC EM facility Pseudomonas Arthrobacter CIMC Ed Basgall Bacillus Travis & Gugino - PSU II. Actinomycetes Unicellular micro-organisms Transitional between the bacteria and fungi Effect of soil pH a. Sensitive to acid soil- no activity below pH 5.0, optimum activity between 6.0 - 7.5 Heterotropic Feeders- breaks down organic matter and humus liberating nutrients, especially nitrogen form NH3 Actinomycetes SSSA Paul R. August Univ of Iowa Streptomyces Travis & Gugino - PSU Nitrogen Cycle III. Fungi Heterotropic organisms Fungi will tolerate a wide pH range – abundant in acid soils where bacteria and actinomycetes offer only limited competition Activities of Fungi – Decompose organic residues Fungi Cont. Micorrhiza- fungus roots more common in forest soils fungal roots form a mat around the absorbing root while others penetrate the root cells – Symbiotic relationship- help with nutrient absorption by increasing absorptive surface – Pine seedlings will not grow well without them Microorganisms Aspergillus Fungi Trichoderma K.J. Kwon-Chung PSU Em facility D.C. Straney Fusarium Travis & Gugino - PSU Mycorrhizae IV. Algae minute plants which are photosynthetic found in surface soils but in low amounts Blue green types are important in wet soil – fix nitrogen in rice paddies – give off oxygen to the water Soil Macro Animals Include- rodents, insects, millipedes, centipedes, earthworms Earthworm- most important macro animals – may pass as much as 15 tons of dry earth per acre through their bodies Micro-organisms and the nitrogen cycle Organic matter of mineral soils Source- remains of plants and animals Nematodes Many beneficial effects from activities of microorganisms • Microorganisms produce: – Plant growth hormones – Stimulate plant growth hormones – Compete with disease organisms • SOIL ORGANIC MATTER (BAHAN ORGANIK TANAH) Soil Components The 4 parts of soil About ½ of the soil volume is solid particles Mineral Matter 45% Organic Matter 5% Soil Air 25% Soil Water 25% About ½ of the soil volume is pore space Soil Organic Matter • SOM consists of a broad spectrum of chemical classes, including amino acids, lignin, polysaccharides, proteins, cutins, chitins, melanins, suberins, and paraffinic macromolecules, as well as organic chemicals produced by humans. SOIL ORGANIC MATTER Soil Organic matter encompasses all organic components of a soil: 1. Fresh residues 2. Decomposing organic matter 3. Stable organic matter 4. Living organisms Composition – of green tissue 75% is water – of dry matter in mature plants Carbohydrates Sugars and starches Hemicellulose Cellulose 1-5% 10-28% 20-50% Fats, waxes, tannins, etc Lignin's 1-8% 10-30% Proteins 1-15% Simples water soluble and crude protein Changes of Organic Compounds in the Soil I. Compounds Characteristic of Fresh Plant Tissue Decompose with difficulty Lignin Fats Oils Resin Decompose easily Cellulose Starches Sugars Proteins II. Complex Intermediate Products of Decay Resistant compounds Decomposition compounds Resigns Amino acids Waxes Amides Oils and Fats Alcohols Lignin Aldehydes III. Products of Soil-Decomposition Processes Resistant complex Simple end products Humus- a colloidal complex carbon dioxide and water nitrates, sulfates phosphates, calcium compounds Rate of Decomposition 1. 2. 3. 4. 5. - Burning process - oxidation Sugars - Starches - simple proteins Rapid Crude proteins Hemicellulose Cellulose Lignins, fats, waxes Very Slow The Carbon Cycle - cycle of life CO2 energy cycle Animal To Atm. Green Manure & Crop Residue Soil Reactions CO3 , HCO3 Farm Manure Microbial Activity Carbon Dioxide Drainage losses CO2 & Carbonates & Bicarbonates of Ca, Mg, K, Etc. Humus Humus is a mixture of complex compounds and is not a single material. These compounds are either (a) resistant materials (b) compounds synthesized within microbial tissue. Definition- Humus is a complex and rather resistant mixture of brown or dark brown amorphous and colloidal substances that have been modified from the original tissue or have been synthesized by various soil organisms Humus Properties 1. highly colloidal 2. amorphous (not crystalline) 3. cation exchange Cap. 150-300 me/100 gms. Clay 8-100 me/100 gms. 4. absorption of water from sat. atmosphere 8090% clay 15-20% Carbon : Nitrogen Ratio Carbon : Nitrogen ratio fairly constant in soils – in cultivated soils 10 or 12:1 is a common ratio – in plant material Legumes 20:1 Straw 90:1 Sawdust 150:1 Thus it can be seen that organic matter contains large amounts of carbon and comparatively small amounts of nitrogen. Influence of Soil Organic Matter on Soil Properties 1. Soil Color - brown to black 2. Influence on physical properties - granulation encouraged - plasticity cohesion reduced - H2O holding capacity increased 3. High cation adsorption - 2 x 20 x clay - 30 - 90% adsorbing power of mineral soils 4. Supply and availability of nutrients - N, P and S held in organic forms - Manure (10 - 5 - 10)/ ton (5 - 1 - 5) N P K Available QUANTITY IN SOILS SOM in mineral soil up to 18% by weight – Typically 0.5 to 5%. SOM > 18% in organic soils SOM about 50% C – SOM = (OC)(factor) where the factor = 1.8 to 2.0 • For most estimations 2 is a good round number – Older books use a factor = 1.724 How is SOM Measured? SOM is usually measured in the laboratory as organic carbon, Soil organic matter is estimated to contain 58% organic carbon (varies from 40 to 58%) with the rest of the SOM comprising of other elements (eg, 5% N, 0.5% P and 0.5% S). A conversion to SOM from a given organic carbon analysis requires that the organic carbon content be multiplied by a factor of 1.72 (1.00/0.58). Thus, 2% SOM is about 1.2% organic carbon. Testing for Soil Organic Carbon Walkley Black • Oxidize SOM to CO2 using acid dichromate • Assume C is in the zero oxidation state as in carbohydrates (CH2O). 3CH2O + 16H+ + 2Cr2(VI)O72- --> 4Cr3+ + 3CO2 + 11H2O Titrate excess Cr2(VI)O72- with Fe2+ • Not used much any more Components of SOM KESIMPULAN 1. 2. 3. 4. Roles of Soil organisms : Decomposition of plant and animal residues, Release of nutrients and inorganic elements, synthesis of new organic compounds, Humus formation, Nitrogen fixation Soil organic matter : all living organisms (microorganisms, earthworms, etc), fresh residues (old plant roots, crop residues, recently added manures), decomposing organic matter and stable organic matter (humus). Influence of Soil Organic Matter on Soil Properties : Soil Color brown to black, Influence on physical properties (granulation , plasticity , H2O holding capacity ), High cation adsorption, Supply and availability of nutrients. SOM is usually measured in the laboratory as organic carbon, A conversion to SOM from a given organic carbon analysis requires that the organic carbon content be multiplied by a factor of 1.72 (1.00/0.58).