Abiotic and Biotic Factors in Soil by pptfiles

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									Abiotic and Biotic Factors in Soil
Soil is not dirt! Abiotic soil factors affect plant growth and animal survival in an area. Two such factors are water holding capacity and the pH of soil. Both factors carry from one to another. The water-holding capacity of soil depends on the inorganic material making up the soil, the organic material, or humus, in it and the climate. In turn, the numbers and kinds of plants and animals that can live in an area depend on the water capacity of the soil. If the water-holding capacity drops below 60%, the soil may not contain enough moisture to meet the cellular needs of plants and animals. If its capacity is greater than 80%, the sold may not contain enough Oxygen to support growth and other life processes of organisms. Soil pH is the other abiotic factor that affects plant and animal life. Soil that is too acidic or too basic can inhibit plant growth. Most plants, animals and bacteria grow best is soil with a pH of 5.6 – 7.0. 7.0 is neutral, neither acidic or basic. pH values below 7.0 are acidic and those above 7.0 are basic. Different plants, animals and bacteria have different pH values in which optimum growth occurs. There are also bacteria and plants that can handle fairly low pH levels, pine trees for example. Just because you see something growing in the soil, does not mean that the soil is healthy. Minerals in the soil influence the type and number of organisms that can survive in an area. Many minerals dissolve more rapidly in an acidic medium that in a basic one. Therefore, the pH of soil determines which minerals remain in the upper soil layers and which wash down to the lower layers. Biotic factors are the living element in soil. This includes worms, insects and plants, but also the bacteria and fungi that are in the soil. A healthy soil will have worms to aerate it and plants whose roots will help prevent erosion. Fungi can help breakdown detritus and release nutrients. Bacteria are vital to a healthy soil because they can take minerals like atmospheric Nitrogen and change it to a useable form for plants. If soil is the pH changes, if the water level changes, or if the soil becomes contaminate organisms will die and the biotic factor lessens. The soil will become nutrient depleted and will erode easily.

Remember soil is a living ecosystem…it is NOT dirt!

Moisture Content of Soil
Materials Labeling tape 3 pieces of parafilm (should fit the beaker) 3 250ml of beakers Balance Soil samples Incubator/oven Directions 1. Choose three areas around the school building that you believe will have different levels of water content. a. (ex. flower bed, soil by parking lot, different depths, etc) b. Your group cannot dig up any playing surface! 2. Label each beaker with the name of the site, date, time and your initials. 3. Measure the mass of each beaker. 4. Dig 100ml worth of soil from each site. 5. Cover the beakers with parafilm. 6. Measure the mass of each beaker with soil, take off the parafilm and do not put it back on. It will collect water vapor. 7. Place each beaker in the incubator. 8. Measure the mass of the beaker after 24 hours. a. If the soil is not totally dry after 24 hours put the soil back in the incubator and test the mass again tomorrow. 9. Calculate the percentage of moisture in each sample by using the following formulas. (Mass of Original + Beaker) – Mass of Beaker = Mass of Soil Sample Soil Sample Before Drying (Mass of Dried + Beaker) – Mass of Beaker = Mass of Soil Sample Soil Sample Mass of Soil Sample – Mass of Dried Soil = Mass of Water in Soil Sample Before Drying Mass of Water in Soil Sample Mass of Dried Soil * 100 = Percentage of Moisture in the Soil Sample

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