AGRO 105 Test 2

The outer weathered layer of the earth's crust

• Inorganic particles
• Organic matter
• Microorganisms
• Water
• Gases

• Water
• Gas
• Liquid

Relative proportions of particles of different sizes

• Sand
• Silt
• Clay

6000 particles per gram

Silicon

• Low surface to volume ratio
• Large volume to pore space ratio
• Low water hold capacity
• Low nutrient holding capacity
• High Percolation Rate

• (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

Intermediate everything

• 30% sand
• 30% clay
• 30% silt
• 5-10% organic matter (you as a producer will NEVER have 10% )

A mixture of soil textures

• Using the ribbon test:
• Clay - ribbon 3-4 inches
• Sand - ribbon less than 1 inch

Intermediate characteristics

The aggregation(clumping) of mineral particles into compound structures

Provides aeration and better drainage

Better water holding capabilities and nutrient holding capabilities

• 50% pore space - 1/4 air, 1/4 water
• 45% mineral
• 10% organic matter

• Soil water content
• freezing and thawing
• plant cover
• farming practice
• soil texture

The clumping of soil

1/3 sand, 1/3 clay, 1/3 silt

• small particle
• small pore to volume ration
• poor aeration
• good water holding
• good nutrient holding
• subject to compaction

• Large particles
• large pore to volume ratio
• good aeration
• poor water holding
• poor nutrient holding

weight of soil per unit volume (g/cc)

• Reduced air space
• Reduced water storage
• Impedes root growth
• Impedes water production

• Increased organic material decreases bulk density
• Aides in aggregate formation

• Beneficial effects:
• loosens the soil

• Downsides:
• Increases bulk density or compaction

Characterization of the soil by layers to the parent bedrock

Typically considered the upper three feet

The defined layers of the top soil

• The organic layer
• typically on surface

• Mineral portion with high OM
• High root concentration
• High microbial concentration
• High leeching of nutrients

• Also considered the subsoil
• Often nutrient rich
• Low aeration due to compaction
• Few Roots

deteriorating plant material

Bed Rock

O.A.B.C.R = Oh A Bear Can Run, across horizons ;)

• raw material for synthesis of compounds
• solvent for reactions
• medium for solute movement in plant
• source of tugor pressure

• Covalent = sharing electrons
• Polar = uneven sharing of electrons

• greater attraction for shared electrons
• slightly negative

• less attraction for shared electrons
• slightly positive

• water phases
• solvency
• cohesion
• adhesion
• capillary action
• surface tension
• heat capacity

0 degrees Celcius

0-100 degrees Celcius

100 degrees Celcius

dissolving of one substance in another

Attraction between similar compounds (water attracts water)

Attraction between dissimilar molecule (water attaches to soil particles)

The combined action of cohesion and adhesion, why water can stay in soil profile

• attracts dissimilar molecules
• strong bond
• water not available to root

• Also known as capillary water
• weakly bonded
• plant roots easily remove water from soil profile

• water held in soil profile against gravity
• temporary, occurs after rain
• very weakly bonded

• Soil texture - smaller the particle size the greater the surface area which allows more bonding sites for water
• Organic Matter which improves soil structure

• All pores full, happens after it rains
• generally short termed
• reduces available air content of soil

Amount of water held in soil against gravity (50% water, 50% air space)

Water in soil that isnt available to the plant, this includes adhesion

ability of water to penetrate soil profile, also known as percolation rate

water infiltration rate

• Getting water to root zone
• Getting excess water out of root zone
• Controlling run-off water
• Controlling soil erosion

• Soil structure
• Soil texture
• Farming practices

• Oxygen
• Hydrogen
• Carbon
• Nitrogen
• Potassium
• Calcium
• Phosphorous
• Magnesium
• Manganese
• Molybdenum
• Sulfur
• Iron
• Boron
• Chlorine
• Copper
• Zinc

C HOPKNS CaFe Mg

• Carbon
• Hydrogen
• Oxygen

• available to plant via soil
• dissolve in soil/water solution as ions
• absorbed through plant roots

required in greater amounts by the plant

needed in lesser amounts by plant, but still important

• Nitrogen 
• Potassium
• Phosphorous

• B
• Cu
• Fe
• Cl
• Mn
• Mo
• Zn

Nitrogen

• Stimulates the initiation of new growth
• Is a component of:
• proteins,chlorophyll, nucleic acids, hormones and ATP

• Nitrate 
• Ammonium : NH⁴⁺ (converted through bacteria)

• stunted growth
• yellowing
• lower yields
• lower protein content

• Plant falls over
• delayed maturity
• less drought tolerance

• energy storage and transfer
• structural support
• encourages lateral root development

enzyme activator

• Must be made up of salts
• Be soluble in water

Positively charged ion

Negatively charged ion

two or more elements bonded together to form an ion

Sulfur: SO₄--

Phosphate:PO₄^---

Nitrate: NO₃^--

Ammonium: NH₄+

• Ammonia: NH₃⁺

provide soil nutrients in concentrations required by the specific plant to maximize its productivity

N-P-K

~~~~~~~~Don't forget to study the fertilizer problems~~~~~~~~~~