Soil Texture and 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 Triangle To find texture-locate Where all three values meet

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?