soil texture and soil chemistry. soil texture sandy: coarse and gritty feeling, loose enough to...
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Soil Textureand Soil Chemistry
Soil Texture• Sandy: coarse and gritty feeling, loose enough to
allow for good air flow but does not hold moisture or nutrients well
• Clay: Sticky and smooth, holds moisture and nutrients well, but difficult to dig or till because it tends to clump together
• Silt: Silky, powdery, most fertile soil, better drainage than sand, hold moisture well, silly putty
• Loam: equal parts of sand, silt and clay-best soil for growing plants
Loam
• Combination of soil textures so provides excellent drainage, moisture retention, nutrients, and air.
• Best soil for growing plants and gardening
Soil Texture TriangleTo find texture-locate
Where all three valuesmeet
Soil Microbiology
• Staining Techniques identify soil bacteria as either Gram postive or Gram negative
• Color is due to stain used and the cell wall of the bacteria
• Crystal violet-purple blue stain (gram positive)• Safranin O-red pink stain (gram negative)
counter stain• What were most of the microbes in your
sample?
Identifying Bacteria
• Three basic Shapes-rod, spherical and spiral• Spherical (coccus)• Rod (bacillus)• Spiral (spirillum)• Are Prokaryotic• Gram positive bacteria have thick cell walls, and thick
lipid cell membrane making them more resistant to antibiotics
• Gram negative bacteria have thin cell walls, and are easier to treat with antibiotics
Bacteria Shapes
Gram positive bacteria
Gram Negative
Spirillum
What is the role of these microbes?
• Function in all parts of the nitrogen cycle:• Nitrogen fixation, denitrification, nitrification• Ex: Nitrobacter, Nitrosomonas• Function as decomposers with fungi• Help keep soil fertile• Help keep plants healthy
Wrap up:
• Complete Lab Report (Summary, Data, Conclusion) and include discussion questions by next Wednesday
• Why is it important to study the soil?• Why is it important to know the soil texture?• What are some applications of the gram
staining technique?