Lecture 19: Soils Flashcards
What is MN’s state soda?
Lester (loam soil) found in south-central MN
What type of soil do tubers like?
Sandy soil
What type of soil do corn, wheat, and soybean like?
Silt loam (60% silt, 20% clay, 10% sand)
What is soil texture?
Combinations of 3 soil particles (sand, silt, clay)
Which soil particle holds the most nutrients?
Clay
Drainage, aeration, and penetration (order particles from most to least)
- Sand
- Silt
- Clay
What determines soil types of an area?
Climate, topography, and crops planted
What is loam?
A soil texture
Cation
Positively charged
Aggregation
“clumps of soil”
Why do soil aggregates need holes?
So H2O, and gases can pass through (O2 availability and CO2 ventilation)
What happens when soil is water logged?
CO2 build up
What is tilth?
soil that holds water and nutrients, but also has good drainage and gas exchange
Two ways to improve soil structure:
1) increase organic matter
2) decrease soil compaction
Why can tillage be bad?
It exposes organic matter to O2 which degrades and can no longer hold aggregates together, leading to soil compaction
What does soil organic matter refer to?
Carbon-based material in soil from plants, animals, microbes, etc.
What is humus?
Transformed former living organisms into soil (can hold up to 6x its weight in water)
Why does humus have a good electro chemical charge?
Organic matter is negatively charged and so it holds positively charged cations in calcium (important for plant growth)
4 ways organic matter can be added to soils:
1) compost
2) raw organic matter
3) green manure
4) incorporating crop residues
What is compost?
Decomposed organic matter added to soil
What is raw organic matter?
uncomposted material is tilled into soil (more nutrients in the long run)
What is green manure?
Crops grown with the sole purpose of being tilled into the land to increase organic matter
How does one incorporate crop residues into soil?
bare minimum or no till…just plant right over residue in the spring
How long must a field be out of conventional farming before it is considered organic?
3 years
What do the numbers on a bag of fertilizer mean?
Nitrogen-Phosphorous-Potassium content
