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What is Soil?
The outer weathered layer of the earth's crust
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What is the general soil composition?
- Inorganic particles
- Organic matter
- Microorganisms
- Water
- Gases
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What are the three soil phases?
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What is soil texture?
Relative proportions of particles of different sizes
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List the three components from largest to smallest.
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Sand is roughly how many particles per gram?
6000 particles per gram
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What is sand composed of primarily?
Silicon
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What are the characteristics of sand?
- Low surface to volume ratio
- Large volume to pore space ratio
- Low water hold capacity
- Low nutrient holding capacity
- High Percolation Rate
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Clay is the smallest of the three textures and has what characteristics?
- (Opposite of sand)
- High surface area to volume ratio
- Small volume to pore space ratio
- High water holding capacity
- High nutrient holding capacity
- Low percolation rate
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What are the characteristics of silt?
Intermediate everything
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What is an ideal soil texture?
- 30% sand
- 30% clay
- 30% silt
- 5-10% organic matter (you as a producer will NEVER have 10% )
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What is a loam?
A mixture of soil textures
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How can a loam be "guestimated"?
- Using the ribbon test:
- Clay - ribbon 3-4 inches
- Sand - ribbon less than 1 inch
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What does silt, and intermediate texture always have?
Intermediate characteristics
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What is soil structure?
The aggregation(clumping) of mineral particles into compound structures
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What do larger pore spaces allow for?
Provides aeration and better drainage
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What do small pore spaces allow for?
Better water holding capabilities and nutrient holding capabilities
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The preferred soil structure consists of?
- 50% pore space - 1/4 air, 1/4 water
- 45% mineral
- 10% organic matter
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What are some factors influencing the soil aggregate?
- Soil water content
- freezing and thawing
- plant cover
- farming practice
- soil texture
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What is soil aggregate?
The clumping of soil
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The best aggregate possesses what?
1/3 sand, 1/3 clay, 1/3 silt
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Soil texture and soil aggregate of clay:
- small particle
- small pore to volume ration
- poor aeration
- good water holding
- good nutrient holding
- subject to compaction
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Soil texture and aggregate of sand:
- Large particles
- large pore to volume ratio
- good aeration
- poor water holding
- poor nutrient holding
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What is bulk density?
weight of soil per unit volume (g/cc)
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What are the effects of a high bulk density?
- Reduced air space
- Reduced water storage
- Impedes root growth
- Impedes water production
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What are organic factors affecting bulk density?
- Increased organic material decreases bulk density
- Aides in aggregate formation
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How does tillage affect bulk density?
- Beneficial effects:
- loosens the soil
- Downsides:
- Increases bulk density or compaction
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What is the soil profile?
Characterization of the soil by layers to the parent bedrock
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What is the top soil?
Typically considered the upper three feet
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What are soil horizons?
The defined layers of the top soil
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The O-Horizon
- The organic layer
- typically on surface
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The A-Horizon
- Mineral portion with high OM
- High root concentration
- High microbial concentration
- High leeching of nutrients
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The B-Horizon
- Also considered the subsoil
- Often nutrient rich
- Low aeration due to compaction
- Few Roots
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The C-Horizon
deteriorating plant material
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How to remember the order of horizons?
O.A.B.C.R = Oh A Bear Can Run, across horizons ;)
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What is the function of water in plants?
- raw material for synthesis of compounds
- solvent for reactions
- medium for solute movement in plant
- source of tugor pressure
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What does polar covalent mean?
- Covalent = sharing electrons
- Polar = uneven sharing of electrons
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The oxygen in a water molecule..
- greater attraction for shared electrons
- slightly negative
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The hydrogen in a water molecule..
- less attraction for shared electrons
- slightly positive
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The importance of water being covalent is?
- water phases
- solvency
- cohesion
- adhesion
- capillary action
- surface tension
- heat capacity
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Water is solid at?
0 degrees Celcius
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Water is liquid between?
0-100 degrees Celcius
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Water is a gas at what temperature?
100 degrees Celcius
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What is a universal solvent?
dissolving of one substance in another
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What is cohesion?
Attraction between similar compounds (water attracts water)
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What is adhesion?
Attraction between dissimilar molecule (water attaches to soil particles)
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What is capillary action in reference to water?
The combined action of cohesion and adhesion, why water can stay in soil profile
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What are the characteristics of adhesive water?
- attracts dissimilar molecules
- strong bond
- water not available to root
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What are the characteristics of cohesion?
- Also known as capillary water
- weakly bonded
- plant roots easily remove water from soil profile
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What are the characteristics of gravitational water?
- water held in soil profile against gravity
- temporary, occurs after rain
- very weakly bonded
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What are some factors influencing soil/water relations?
- Soil texture - smaller the particle size the greater the surface area which allows more bonding sites for water
- Organic Matter which improves soil structure
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What are the characteristics of a saturated soil?
- All pores full, happens after it rains
- generally short termed
- reduces available air content of soil
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What is field capacity?
Amount of water held in soil against gravity (50% water, 50% air space)
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What is the wilting point?
Water in soil that isnt available to the plant, this includes adhesion
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What is the water infiltration rate?
ability of water to penetrate soil profile, also known as percolation rate
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What is percolation rate also known as?
water infiltration rate
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What is the importance of infiltration rate?
- Getting water to root zone
- Getting excess water out of root zone
- Controlling run-off water
- Controlling soil erosion
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Infiltration rate depends on what?
- Soil structure
- Soil texture
- Farming practices
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What are the eighteen essential elements required for plant growth and development?
- Oxygen
- Hydrogen
- Carbon
- Nitrogen
- Potassium
- Calcium
- Phosphorous
- Magnesium
- Manganese
- Molybdenum
- Sulfur
- Iron
- Boron
- Chlorine
- Copper
- Zinc
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What is the anagram used to remember the eighteen essential elements?
C HOPKNS CaFe Mg
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What are the three non-mineral elements?
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What are characteristics of minerals?
- available to plant via soil
- dissolve in soil/water solution as ions
- absorbed through plant roots
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What are macronutrients?
required in greater amounts by the plant
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What are micronutrients?
needed in lesser amounts by plant, but still important
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What are the primary macronutrients?
- Nitrogen
- Potassium
- Phosphorous
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What are the essential micronutrients?
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What is the nutrient required in the greatest amount?
Nitrogen
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What is the function of nitrogen in the plant?
- Stimulates the initiation of new growth
- Is a component of:
- proteins,chlorophyll, nucleic acids, hormones and ATP
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What are the available forms of Nitrogen available to the plant?
- Nitrate
- Ammonium : NH4+ (converted through bacteria)
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What are some symptoms of nitrogen deficiency?
- stunted growth
- yellowing
- lower yields
- lower protein content
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What are some symptoms of excessive nitrogen?
- Plant falls over
- delayed maturity
- less drought tolerance
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What is the function of phosphorous in the plant?
- energy storage and transfer
- structural support
- encourages lateral root development
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What is the function of Potassium in plants?
enzyme activator
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What two components must fertilizers have?
- Must be made up of salts
- Be soluble in water
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What is a cation?
Positively charged ion
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What is an anion?
Negatively charged ion
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What are polyatomic ions?
two or more elements bonded together to form an ion
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What are important polyatomic ions to remember?
Sulfur: SO 4--
Phosphate:PO 4---
Nitrate: NO 3--
Ammonium: NH 4+
Ammonia: NH 3+-
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What is the purpose of fertilizers?
provide soil nutrients in concentrations required by the specific plant to maximize its productivity
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What is the order of the three elements found in fertilizers?
N-P-K
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Don't forget to study the fertilizer problems!!!!!!
~~~~~~~~Don't forget to study the fertilizer problems~~~~~~~~~~
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