Soil Flashcards
name the 5 components of soil
mineral skeleton water air biota DOM
what is meant by mineral skeleton?
particles broken down by weathering of rocks. Proportions of different sized particles = soil texture
why is air important in soil?
provides gases for aerobic processes for organisms i.e. decomposition, N2 fixation and nitrification
why is water important in soil?
plants need it for various processes i.e. photosynthesis and nutrients can only be absorbed if dissolved in it
why is biota important in soil?
responsible for decomposition and aid aeration/draining and nutrient recycling
why is DOM important in soil?
- source of food for some organisms
- produces humus and releases nutrients
- humus helps to bind soil together = soil stability
definition of soil fertility
the ability of soil to sustain plant growth
Name the 6 factors that influence soil fertility
drainage aeration thermal capacity nutrient levels root penetration capillary action
name the 3 types of soil particles from largest to smallest
sand, silt, clay
what does it mean by soil texture?
how big the particles are
Drainage: the _____ the particle, the larger the ____space so drainage is ______. For example _____. This is the opposite for _____ particles like _____.
- larger
- pore
- easier
- sand
- smaller
- clay
Thermal capacity: H2O has a ______ thermal capacity (warm/cool ______). ______ retains more H2O so takes _____ to warm/cool. So the ____ H2O the more temp. _____>
- high
- slowly
- clay
- longer
- more
- stable
How do soil texture influence aeration?
the larger the particle, the larger the pore space = increase aeration/air
which soil texture is the WORST when conserving nutrients and why
sand as it has increased drainage due to large particle size so increase leaching
Is clay good at absorbing nutrients?
Clay absorbs more nutrients/minerals
- Clay have negative charges = positive charged nutrient ions attach
which soil texture is root penetration easiest in?
sandy soils
which soil texture is root penetration hardest in and why?
clay - particles held together by capillary H2O on particle surfaces = harder for roots to penetrate between particles
which texture is best at capillary action and why?
clay - tiny pores = H2O can rise towards surface
no capillary rise in sandy soils
How does soil biota increase soil fertility? and explain
- detritivores break up DOM (i.e. worms) decomposers break down DOM (i.e. fungi secrete enzymes) = releases nutrients
- N2 nitrifying bact. = atmospheric N2 to ammonia
- Nitrifying bact. = oxidise ammonia - nitrite - nitrate
- mycorrhizal fungi (symbiotic relationship with roots) = increase phosphate uptake
difference between micronutrients and macronutrients with examples
micro = plants need in small amounts i.e. magnesium, cobalt, boron macro = need in large amounts i.e. N2, phosphorus, potassium
in fertile soil: _____ ions (i.e. aluminium and _____ metals) are _____ onto surface of particles (usually ___) so does not ______ in ____ where they could harm ____
- toxic
- heavy
- absorbed
- clay
- dissolve
- H2O
- biota
name the 3 reasons why DOM is important
- food for biota
- releases nutrients i.e. humus
- increases H2O retention
definition of a ped
when soil particles aggregates (clump together) - held together by polysaccharide gum
Which is ped is more fertile and why: crumb or platy?
crumb: small round particles = good aeration/drainage/easy root penetration
platy: large/flat so decreases those factors
for soil fertility which is better: deeper or shallow soils?
deeper = less likely to be waterlogged/dry out. Good root drainage.
why do soils need high water content but also good drainage?
- ions are dissolved in H2O
- drainage; avoid anaerobic conditions
How does the pH influence soil fertility?
optimum pH = 5-7
too acidic = cell membrane damage/rapid leaching
too alkali = inhibit nutrient uptake i.e. phosphate becomes insoluble
name the 5 human activities that affect soil fertility and briefly explain
irrigation: increase fertility = allows stomata to be open + continue gas exchange + H2O dissolves nutrients
use of fertilisers: increase nutrients + support processes like N2 cycle
pH control: ensures nutrients soluble not easily leached
compaction: more compact = less aeration/decrease drainage/harder roots to penetrate
ploughing and drainage: increase aeration = more aerobic processes (i.e. more fixation/nitrification/decomp.)
state at least 5 out of the 8 factors that could affect infiltration rate
soil moisture, soil texture, soil structure, organic matter content, vegetation cover, soil depth, gradient, intensity of precipitation
in soils not been affected by _____ activities the rate of erosion is likely to be the same or ____ that rate of soil ______. Erosion is a problem when it occurs _____ rapidly than soil _______
- human
- less
- formation
- more
- formation
all forms of ____ erosion are increased by ______ gradients
- water
2. steeper
Name the 2 types of water erosion
rain splash erosion: particles dislodged, move into pore spaces = reducing infiltration
surface runoff erosion: caused by surface runoff (infiltration capacity of soil exceeded), particles dislodged can cause landslides. loss of roots binding from deforestation affect this.
describe wind erosion
soils are dry/unprotected, wind can carry it away as little cohesion between particles
name the 5 ways how vegetation reduces soil erosion
- decrease wind velocity
- more infiltration = less runoff
- roots bind the soil
- organic matter/humus bind soil
- increased interception (vegetation/leaf litter) = impact of raindrops reduced
FOR REMOVAL OF VEGETATION IT IS THE OPPOSITE
name the 6 activities that can increase soil erosion
- removal of vegetation: {give general points}
- ploughing vulnerable soils: breaks up soil structure = particles exposed
- overgrazing: less vege. = increase soil exposure. Hooves = disturbance/root damage
- compaction: due to livestock densities/machinery/lack of detritivores. Smaller pores = less infiltration
- reduced biota: less nutrients for vege., less humus produced = less adhesion between particles. Less worms: less aeration, less infiltration
- cultivating steep slopes: more kinetic energy (carries more particles), disturbing soil
Name the 10 methods of reducing soil erosion
long term crops terracing tied ridging rows of stones windbreaks Zero-tillage cultivation contour ploughing multicropping increasing soil organic matter livestock management
how does long term crops reduce soil erosion
crops used that don’t need to be replanted often = reduces soil disturbance i.e. permanent bush/tree crops (coffee, fruit, tea)
Which method to reduce soil erosion for which gradient:
1. Used for a steep slope
2. Used for predominantly flat land
3. Used for a gentle gradient
4. Used for a slope
And explain briefly what each method does
- terracing: H2O flows over walls quickly, but slows as it goes down = allows H2O to infiltrate
- tied ridging: field has criss-cross pattern of intersecting ridges = retains H2O, increases infiltration
- rows of stones: rows of stones placed in contours, reduces velocity of runoff = soil deposited behind rocks
- contour ploughing: contours made at 90 degrees to slope, kinetic energy lost = soil particles deposited
What is zero tillage cultivation?
not ploughing/sowing but direct drilling of seeds = reduces soil disturbance
How do windbreaks reduce erosion and give examples
reduce wind velocity = less soil particles carried away (hedgerows/rows of trees)
What is multicropping and how does it reduce erosion
growing more than one crop in a field at the same time and harvesting/re-sown at different times. Reduces erosion as: always be vegetation to reduce wind velocity
which uses human labour and which uses machinery: strip cropping and multicropping
strip = machinery multi = human
how does increasing soil organic matter reduce soil erosion
DOM on surface (mulch) = protect from wind/impact from raindrops. DOM decomposes produces humus
how does livestock management reduce erosion?
managing stock density = reduces compaction
managing livestock movement = reducing access to vulnerable soil i.e. riverbanks
what does the universal soil erosion loss equation work out? and what is it?
rate of erosion (annual soil loss) = RxKxLxSxCxP
If you have to rearrange the universal soil erosion loss equation how would you do it?
have erosion rate on the top and all the letters on the bottom
when in a question and it gives u the erosion rate and tells you that the farming methods have changed i.e. contour ploughing used instead of ploughing or fruit was grown instead of wheat what do you do?
erosion rate divided by old method then multiply the whole equation by the new method or change = new erosion rate
Name all the symbols in the universal soil erosion loss equation:
1. R 2. K 3. L 4. S 5. C 6. P
- rainfall erosivity
- soil erodibility
- slope length factor
- slope gradient factor
- crop management factor
- erosion control factor
Name the 5 problems caused by soil erosion
- landslide
- sedimentation: turbid H2O = blocks out light for photosynthetic organisms. O2 levels drop. Sediments deposited, river more narrow = H2O overspills/flooding
- reduced productivity : soil has no fertility = lower food produced
- desertification: when a habitat becomes a desert
- atmospheric particles: dust clouds/sandstorms reduce light penetration
Method for soil water content:
- soil sample collected (i.e. _____ sampler or _____)
- sample placed in sealed bag (reduce water _____ by ___________)
- organisms/large particles _______
- sample placed in pre-weighed __________ basin
- basin ______ at about 100 for __ hours
- basin is ________
- stages 5-6 repeated until _______ ______ is reached
- calculate ______ content
- core, auger
- loss, evaporation
- removed
- evaporating
- heated, 24
- reweighed
- constant mass
- water
what is the equation for % water content?
wet soil mass - dry soil mass / wet soil mass X100
Method for soil organic matter content:
Steps 1-7 of the soil water content method THEN
8. A ___ soil sample places in ________ crucible which is then _______
9. crucible _______ in a ____ or a bunsen burner
10. crucible is _______
11. stages 9-10 repeated until _______ _____ is reached
12. calculate _____ matter content
- dry, preweighed, reweighed
- heated, furnace
- reweighed
- constant mass
- organic
what is the equation for % organic matter content?
dry soil mass - burnt soil mass / dry soil mass X100
