Soil Biology PrimerU.S. Department of Agriculture, Natural Resources Conservation Service, 1999 - Soil animals |
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Acknowledgments Produced activity agricultural soils amoebae arthropods bacteria and fungi bacterial-feeding biomass burrows carbon cells ciliates complex Conservation Technology Information consume Corvallis crop decomposition disease-causing organisms earthworms Ecosystems fecal pellets feed flagellates forest fungal Fungal hyphae fungal-feeders graze Humus hyphae inch Ingham J.P. Martin Land management Lewandowski Living Soil managing soil microbial mites mycorrhizal fungi Natural Resources Conservation nematodes nitrogen NRCS thanks nutrient cycling Oregon State University pathogens pests Photo Credits Figure plant growth plant litter plant residue plant roots pollutants populations predators predatory nematodes prey Project Manager Arlene protozoa Resources Conservation Service rhizosphere Root-feeders Service Soil Service with assistance shred Shredders soil aggregates Soil Arthropods Soil Biology Primer soil food soil food web soil for today soil organic matter soil particles Soil Quality Institute soil structure soil surface species springtails SQI Editor Ann SQI Illustrations Nancy Technology Information Center thanks many individuals tillage todes trophic level Tugel
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Page 10 - Coleman, DC and DA Crossley, Jr. 1996. Fundamentals of soil ecology. Academic Press, San Diego, California, USA.
Page 7 - Amoebae are further divided into testate amoebae (which make a shell-like covering) and naked amoebae (without a covering). Flagellates are the smallest of the protozoa and use a few whip-like flagella to move. What Do Protozoa Do? Protozoa play an important role in mineralizing nutrients, making them available for use by plants and other soil organisms. Protozoa (and nematodes) have a lower concentration of nitrogen in their cells than the bacteria they eat. (The ratio of carbon to nitrogen...
Page 4 - Fungi are able to use nitrogen from the soil, allowing them to decompose surface residue which is often low in nitrogen. Fungi are aerobic organisms. Soil which becomes anaerobic for significant periods generally loses its fungal component. Anaerobic conditions often occur in waterlogged soil and in compacted soils. Fungi are especially extensive in forested lands. Forests have been observed to increase in productivity as fungal biomass increases.
Page 7 - Protozoa are classified into three groups based on their shape: dilates are the largest and move by means of hair-like cilia. They eat the other two types of protozoa, as well as bacteria. Amoebae also can be quite large and move by means of a temporary foot or "pseudopod.
Page 4 - Where Are Fungi? Saprophytic fungi are commonly active around woody plant residue. Fungal hyphae have advantages over bacteria in some soil environments. Under dry conditions, fungi can bridge gaps between pockets of moisture and continue to survive and grow, even when soil moisture is too low for most bacteria to be active. Fungi are able to use nitrogen from the soil, allowing them to decompose surface residue which is often low in nitrogen.
Page 5 - A single hypha can span in length from a few cells to many yards. A few fungi, such as yeast, are single cells. Hyphae sometimes group into masses called mycelium or thick, cord-like "rhizomorphs
Page 8 - ... bacteria.) Bacteria eaten by protozoa contain too much nitrogen for the amount of carbon protozoa need. They release the excess nitrogen in the form of ammonium (NH4+). This usually occurs near the root system of a plant. Bacteria and other organisms rapidly take up most of the ammonium, but some is used by the plant.
Page 7 - They are several times larger than bacteria - ranging from 1/5000 to 1/50 of an inch (5 to 500 |jm) in diameter. As they eat bacteria, protozoa release excess nitrogen that can then be used by plants and other members of the food web. Protozoa are classified into three groups based on their shape: dilates are the largest and move by means of hair-like cilia.
Page 2 - Nitrifying bacteria change ammonium (NH4+) to nitrite (NO2~) then to nitrate (NO3~) - a preferred form of nitrogen for grasses and most row crops. Nitrate is leached more easily from the soil, so some farmers use nitrification inhibitors to reduce the activity of one type of nitrifying bacteria. Nitrifying bacteria are suppressed in forest soils, so that most of the nitrogen remains as ammonium.
Page 10 - Edwards, CA and PJ Bohlen. 1996. Biology and Ecology of Earthworms, 3rd ed., Chapman & Hall, London.