Slide 1 Activity of Soil Organisms nutrient availability Slide 2 Slide 3 Microbial relationships nitrogen fixation nitrification denitrification immobilization & mineralization 060628_PEANODULES Slide 4 Nitrogen Fixation ADDITIONS some microbes that live in aerobic environments can “fix” atmospheric nitrogen SYMBIOTIC Bacteria - Rhizobium N2 from the atmosphere is converted to ammonia then to ammonium NH4+ 060628_PEANODULES Slide 5 NON SYMBIOTIC fix atmospheric nitrogen without a relationship with plants contain unique nitrogenase enzyme Eg: Azobacter, cyanobacteria https://en.wikipedia.org/wiki/Azotobacter https://www.cleanlakesalliance.org/cyanobacteria/ Slide 6 Nitrification ADDITIONS soil bacteria collaborate to oxidize ammonia to eventually produce nitrate NO3- Slide 7 ilsensation.neT Denitrification LOSSES microbial reduction of nitrate NO3- to produce Nitrogen gas usually in waterlogged soils high in organic matter Slide 8 ilsensation.neT Immobilization & Mineralization Slide 9 Mineralization Mineralization is the process of converting organic N to plant available forms by a succession of soil microorganisms Slide 10 Immobilization When residues with high C:N ratios are being decomposed, all readily available N within the soil may be tied up by the microbes UNAVAILABLE to plants but NOT LOST from the soil plants show Nitrogen deficiencies Slide 11 Phosphorous in the soil Slide 12 Phosphorous Additions: fertilizer rock phosphate organic matter manures may contain high amounts of phosphorous Losses - removal of organic matter soil erosion ties up with calcium in alkaline soils ties up with iron, manganese and aluminum in acid soils Slide 13 Potassium Additions - organic matter soil minerals ( feldspar/ mica) fertilizer Losses - removing organic matter l plant uptake Slide 14 Potassium in a clay soil Slide 15 Sulfur Cycle – Wikipedia_files