SCSC 105 Exam 2 Katherine Carson Latest Update 2023-2024 Questions and Verified Correct Answers Guaranteed Success Briefly describe a soil profile. (think layers; top to bottom ) - Correct Answer:O horizon - organic matter layer of plant material
A horizon (called topsoil) - highest in fertility and organic matter
- Brown or black in color
- Plant roots and soil organisms found here
B horizon (subsoil) - zone that accumulates compounds and minerals that water has leached from the surface horizons
C horizon - zone with few plant roots and little weathering (similar to rocky parent material beneath)
Define the term weed. - Correct Answer:A weed is a plant growing where it is not wanted i.e. Bermuda Grass - Front Lawn vs Corn Field
Explain the difference between gravitational water, field capacity, and permanent wilting
point. - Correct Answer:1) Gravitational water
- drains readily through the soil
2) Field capacity
- water is held in the pore spaces but is readily available to plants
3) Permanent wilting point
- water is held tightly by soil particle and is not available to plants
How do soil textures affect the agricultural use of soil? - Correct Answer:The
composition of the soil affects the levels of nutrients and the water capacity of the soil which determines the necessary steps to utilize the land for cultivation
How does pH affect plant growth, nutrient availability, and soil organisms? - Correct Answer:Acidic (pH<5): Nutrient deficiencies with toxic levels of Fe, Mn, and Al
Neutral (pH 6-8): ideal plant growth
*true ideal range for most is 6-7, but there are exceptions
Alkaline (pH 8-9) & Highly Alkaline (pH>9): Nutrient deficiencies with toxic levels of carbonate, bicarbonate, aluminate, and salts (sodicity)
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How does salinity occur in soils? - Correct Answer:It occurs due to the accumulation of soluble salts (Na, Ca, Mg, K) that dissolve in water
Most are:
- sulfates
- chlorides
- carbonates
- bicarbonates
How many MOAs are there? - Correct Answer:There are 8 Modes of Action:
1)Growth Regulators -hormones and protein synthesis disruption
2)Amino Acid Synthesis Inhibitors -enzyme disruption
3) Lipid Synthesis Inhibitors -only grasses, prevent fatty acid formation
4)Nitrogen Metabolism Inhibitors -impede glutamine production by enzyme
5) Seedling Growth Inhibitors -Disruptions to shoot and root germination
6) Photosynthesis Inhibitors -prevent photosynthesis
7) Cell Membrane Inhibitors -disturbs/destroy membranes (quick)
8) Pigment Inhibitors -prevent carotenoids (protect chlorophyll)
How many soil orders are in Texas? - Correct Answer:There are 7 predominant soil orders (Alfisols, Aridisols, Entisols, Inceptisols, Mollisols, Ultisols, and Vertisols)
All Are Entrapped In Mars UniVersity
Identify 4 ways that weeds can be classified - Correct Answer:1) Invasiveness
2) Environments 3) Life Cycles 4) Morphology (Monocot vs Dicot)
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