Soil Organisms and Functions Martha Rosemeyer Ecological Agriculture January 12 2006 Outline Soil Food Web BW Ch 11 The organisms Soil Biology Primer http soils usda gov sqi concepts soil biology The processes they perform Effect of management on the organisms and their functions The WICST Trials For further information on earthworms see posted lecture on masu Food web concept Everything eats everything excretes and everything is food for something z Elaine Ingham 2001 A great resource SWCS NRCS Soil Biology Primer From Soil Biology Primer Food Web of the Compost Pile Dindal D SUNY BW Figure 11 1 Efficiency of soil food web vs the above ground 10 of one trophic level passed on to next in above ground 30 40 50 of one trophic level passed on in below ground food web Functional Groups of Soil Biota Ecosystem engineers e g macrofauna such as termites and earthworms have major impact on soil physical and nutrient properties Decomposers e g microorganisms that have cellulosedegrading enzymes and are responsible for most of energy flow through decomposer food web Micro regulators e g microfauna such as nematodes protozoa that regulate nutrient cycles through microbial grazing an nutrient release Micro symbiont e g Rhizobium and mycorrhizae associated with plant roots and enhance nutrient uptake Soil borne pests and disease e g plant pathogens invertebrate pests Bacterial transformers e g nitrifying bacteria perform specific transformations of C N S Mike Swift TBSFH Function of Soil Organisms Decomposition of organic matter z z z mixing and turnover of soil increase macropores mineralization from organic to inorganic state formation of humus Breakdown of toxic compounds Inorganic transformations z solubilization of P from Iron and Al compounds Bacillus meganthurium increased yields 50 70 in USSR z oxidation of iron and manganese Nitrogen fixation z bacteria cyanobacteria actinomycetes Classification according to size Orders of magnitude difference in sizes of organisms The soil is a heterogeneous environment for soil organisms Microflora cannot be seen without the aid of a microscope Bacteria Primary Consumers Biomass 400 500 kg ha No individuals 1013 1014 g Metabolic activity Metabolism Extremely resistant resting stages Rapid reproduction potential in response to food and environment In decomposition colonize easy to degrade substrates especially with tillage Ability to use diverse substrates z some only catalyzed by bacteria e g nitrifying Heterotrophic parasitic or saprophytic or Autotrophic z z Photoautotrophic energy from sunlight Chemoautotrophic energy from oxidation of inorganic substrates Microbes are ancient Responsible for all major processes on earth including decomposition and photosysnthesis and nutrient cycling Major cycles of Earth could continue without plants and animals Most are beneficial Bacteria can be beneficial to plant growth Often sold as plant inoculants appears to be due to production of plant hormones Cyanobacteria blue green algae can photsynthesize and fix N Most bacteria 99 cannot be cultured How do we know z Direct counts and genetic diversity DNA assessment A ton of microscopic bacteria may be active in each acre of soil Bacteria dot the surface of strands of fungal hyphae From Soil Biology Primer Actinomycetes Filamentous bacteria Actinomycetes such as this Streptomyces give soil and compost its earthy smell from geosmins a type of terpene Soil Microbiology and Biochemistry Slide Set 1976 J P Martin et al eds SSSA Madison WI From Soil Biology Primer Actinomycetes Filamentous bacteria filaments like fungi but finer No nuclear membrane like bacteria prokaryote and spores resemble bacteria Decomposition of OM Some produce antibiotics streptomycin actinomycin and neomycin Some fix N e g Frankia in red alder More drought tolerant than bacteria and fungi acid sensitive Actinomycetes Biomass 5000 kg ha In numbers exceed all except bacteria Can degrade most resistant compounds such as cellulose chitin and phospholipids Important later on in decay and therefore in curing process of compost Numerous in humus in old meadows and pastures Fungi Fungus beginning to decompose leaf veins in grass clippings Soil Microbiology and Biochemistry Slide Set 1976 J P Martin et al eds SSSA Madison WI From Soil Biology Primer Fungi Diverse group 1 million await discovery Numbers smaller than bacteria Dominate biomass at 1000 to 15 000 kg ha in upper 15 cm Efficient 50 of the substance decomposed can become fungal biomass Eukaryote with nuclear membrane and cell wall Yeasts single celled but rest are filamentous and some seen with naked eye Molds vs mushrooms BW Figure 11 19 Fungal hyphae are often twisted together to form what appears like woven ropes forming the body of the fungus or mycelium Fungal activities Decomposers of organic matter in soil Can decompose the difficult cellulose and lignins as well as proteins and sugars Important in humus formation and aggregate formation Form mycotoxins aflatoxin by Aspergillus flavus peanuts and corn humanly toxic Synthesize complex compounds Antibiotic Penicillin from Penicillium Dominate in acid and sandy soils Appear to dominate in forest and no tillage ag systems Mycorrhizae association between fungi and plant root Mycorrhizal fungus stained blue Roots of Common Bean Phaseolus vulgaris from Costa Rica Non mycorrhizal Photo Rosemeyer Predatory Nematode trapping fungi Dindal SUNY From Soil Biology Primer Ring three cells that swell and contract around the nematode BW Ch 11 Fig 11 22 Fungi can be pathogens of insect and mite pests and used as biocontrol e g Beauvaria bassiana on chinch bug turf pest George Barron www versicolor ca Note relative fungal vs bacterial biomass in no till vs conventional Algae 1 to 10 billion per m2 or 10 000 to 100 000 g Diatoms one type 10 500 kg ha of soil algae Are eukarotes nuclear membrane Photosynthesize so found on surface of soil Produce OM polysaccharides Important form mat on soil surface microbiotic crusts in desert and lichens with fungi Algae found on surface BW Figure 11 18 Roots of higher plants May be size of meso or microorganisms Roots grow and die and in text are soil orgs Primary producers of organic matter About 1 of soil volume and 25 30 of respiration 50 60 of NPP in roots in grassland 40 70 of NPP in tree roots in forest Rhizophere zone of soil influenced significantly by the root usually 2mm In this photo sand grains are bound to a root by hyphae from endophytes fungi similar to