soils Flashcards
how much nitrogen does organic matter add to the soil
90-95%
How much extra sulfur and phosphorus does organic matter put in the soil
25%
how does organic matter aid soil structure
helps with aeration
increases aggregation of soil particles
what is organic matter
it is soil made up of many different plant and animal residues
what are the 4 different soil development processes
1) Accumulation of materials
2) Leaching and losses
3) Transformation and illuviation
4) Podsolisation and Translocation
what is the accumulation of materials?
where different materials gather, might be by water, ice, wind. the start of soil formation
what is leaching and losses
where the different minerals and materials are washed out or taken up by plants. physical and chemical properties of the soil and parent material changed
what is transformation and illuviation
3rd stage of soil formation where materials transform due to chemical weathering. soil is washed from upper horizons into lower ones. animals and plants speed up this process
what is podsolisation and translocation
final stage of soil formation when clay minerals are broken down by strong acidic solutions then distributed among the different horizons. this process is also responsible for the colour changes in soil.
what are the 5 different soil forming factors
1) parent material
2) biological activity
3) climate
4) topography
5) time
what is the size of a transmission pore? in micrometers
50
what is the size of a storage pore? in micrometers
50-0.5
what is the size of a residual pore in micrometers
smaller than 0.5
what is the function of a transmission pore? 3 answers
drainage
root penetration
gas movement
what is the function of a storage pore?
holds water for plant growth
what is the function of a residual pore? 2 answers
holds water that is unavailable to plants, controls the mechanical strength of the soil
Rocks with a lower Si content break down more quickly?
T/F
true
H2O = H(+) +OH(-) is the equation for?
Hydroloysis
What are the 5 soil functions
- medium for plant growth
- recycling system
- habitat for soil organisms
- engineering medium
- system for water supply and purification
what are the 5 different soil horizons that can be found in a soil profile?
- O
- A
- E
- B
- C
what does the O horizon consist of?
organic matter which is made up of plant and animal residues
what does the A horizon consist of?
mixture of minerals and organic matter
what does the E horizon consist of?
zone where soil is depleted of most of its materials due to leaching and losses
what does the B horizon consist of?
The zone of accumulation (translocated humus, translocated silicate clays)
what does the C horizon consist of?
Parent material
what are the two main types of parent material?
Sedentary (pre-glacial geology)
Transported (Drift)
what are the 4 different transport processes that cause material drift?
- Ice: glacial
- Water: glacial, alluvial
- Wind: aolian
- Gravity: colluvial
whats the difference between soil structure and soil texture?
soil structure is the arrangement of soil particles into groups or aggregates.
soil texture is the relative proportions of various sized particles (sand, silt, clay) within a given soil.
how does the soil structure influence plant growth? 3 answers
- aids water movement
- aids aeration
- helps with heat transfer
whats the difference between bulk density and particle density?
Bulk density is the mass of soil particles and pore space combined
Particle density is the mass of soil particles without pore space
Why is soil water so important? 5 answers
- Its a Crop requirement
- its a Solvent
- it creates Chemical reactions
- helps with Transport of nutrients
- Air and temperature regulator
name the two micropores
storage and residual pores
a transmission pore is a type of pore from which class?
micropores
or
macropores
macropore
how do soil colloids effect plant growth
nutrient ions used by plants are held on the colloid surface
what is the optimum temperature for nitrogen fertilisers?
25-30 degrees
amount of organic nitrogen in soil?
94-98%
amount of mineral nitrogen in the soil?
1-2%
All the soil pores are water filled - is the definition of?
saturation
what is gravitational water?
water held in the saturated soil that drains away under gravity
field capacity is defined as?
when all of the gravitational water has drained away after heavy rain
permanent wilting point is?
when the plant can no longer obtain water rapidly enough to recover from turgidity overnight
available water is defined as?
the amount of water held in the soil between the limits of field capacity and wilting point
Unavailable water is defined as?
amount of water held in the soil that is beyond permanent wilting point
