soil Flashcards
state 9 features of fertile soil
water content / soluble materials / air content / dead organic matter / pH / soil biota / soil texture / soil structure / soil depth
why is water content important for fertile soil
essential for all organisms living in the soil, including plants, has good water drainage so as to not get waterlogged but retain enough for survival of soil biota
what soluble materials are in fertile soil
macronutrients eg nitrogen phosphorous , in ionic form as nitrates and phosphates / micronutrients eg boron, cobalt, copper, iron / toxic ions eg aluminium and heavy metals are absorbed onto the surface of mineral particles so they cant dissolve in water where they could harm soil organisms
why is air content important in soil fertility
living organisms in soil and processes that increase fertility are aerobic so well aerated soils are more fertile
why is dead organic matter important to fertile soil
they release plant nutrients as it they decompose, increase water retention and provides food for soil biota
what is a good pH for fertile soils
ranges from 5.5 - 7, in range for most plants and soil biota
what happens in the soil if the soil is too acidic
acidic soils increase leaching of plant nutrients and damage root cell membranes
what happens in the soil if the soil is too alkaline
phosphates become insoluble
name 5 living organisms in soil that affect soil fertility
detritivores / decomposers / nitrogen-fixing bacteria / nitrifying bacteria / mycorrhizal fungi
how do detritivores affect soil fertility
break up dead organic matter and release nutrients into the soil, (earthworms) increase soil drainage and aeration by creating tunnels in the soil
how do decomposers affect soil fertility
break down dead organic matter, secrete digestive enzymes to break up dead organic matter and increase its surface area
how do nitrogen-fixing bacteria affect soil fertility
convert gaseous nitrogen into ammonium ions
how do nitrifying bacteria affect soil fertility
oxidise ammonium ions to nitrite ions and then to nitrate ions
how does mycorrhizal fungi affect soil fertility
forms a symbiotic relationship with plant roots and aids phosphate taken up by plants
list 7 features of soil texture
drainage rate / capillary action / aeration / nutrient retention / thermal capacity / root penetration / ease of cultivation
what are the 3 types of soil texture
clay, sand and silt
compare the drainage rate of sandy and clay soils
sandy has larger pore spaces and allows rapid drainage which reduces water content and increases aeration, clay soil is poorly drained
compare the capillary action between sandy and clay soil
tiny pore spaces between clay particles allows water underground to rise towards the surface. no capillary rise between sandy soil
compare the aeration between sandy and clay soil
pore spaces in well drained sandy soils are filled with air air. clay soils are more likely to be waterlogged with a low aeration rate
compare the nutrient retention between sandy and clay soil
nutrient ions adsorb easily to clay particles but not sand particles
compare the thermal capacity between sandy and clay soil
high water content of clay soils produce a high thermal capacity so they warm up and cool down slowly. sandy soils have lower thermal capacities so they warm up more rapidly after cold weather
compare the root penetration between sandy and clay soil
clay particles are held together by capillary water on the particles surfaces, makes it harder for plant roots to force their way between soil particles. root penetration is easier in sandy soils
compare the ease of cultivation between sandy and clay soil
lack of adhesion between particles in sandy soil makes it easier to cultivate than clay soil
how does soil structure affect soil fertility
soil particles form peds which affects soil properties and fertility
what are crumb peds
small and round peds, good drainage, aeration and easy root penetration so improve soil fertility
what are platy peds
large and flat peds, reduce drainage and aeration and minimise root penetration so produce less fertile soils
how does soil depth affect soil fertility
deeper soils are less likely to become waterlogged or to dry out rapidly, aid good root anchorage
name 5 human activities that affect soil fertility
aeration by ploughing and drainage / soil nutrient levels / irrigation / soil compaction / pH control
how does aeration by ploughing and drainage affect soil fertility
makes soil more aerobic, increases rate or nitrogen fixation, nitrification, decomposition of dead organic matter
how do farmers increase soil nutrient levels
adding inorganic fertilisers, organic matter or by supporting natural processes that increase nutrient levels such as bacterial nitrogen fixation
how do farmers deplete soil nutrient levels
soil erosion, biomass removal, inhibiting natural processes that increase nutrient levels or by increasing leaching of dissolved nutrients
how does irrigation affect the soil fertility
increases fertility of soil where water is a limiting factor on growth, dissolves nutrients what can be absorbed by plants in ionic form
how does soil compaction affect soil fertility
excessive use of heavy machinery or high density of livestock can compact the soil, reducing aeration and making waterlogging more likely
how does pH control affect soil fertility
helps to ensure nutrients are soluble but not too easily leached
what are the two types of soil erosion
wind erosion and water erosion
what is wind erosion
dry soils, with low clay content typically, are likely to be loose with little cohesion to hold the soil together, unprotected soil could blow away, can cover crops or land in urban areas
name 3 types of water erosion
rain splash erosion / surface run off erosion / slumping and landslides
what is rain splash erosion
soil particles are dislodged by splash of raindrop and soil particles are dispersed in all directions, those going downhill are likely to travel further - causes downhill movement of large amount of soil
what is surface runoff erosion
when the infiltration capacity of the soil has been exceeded, can occur at heavy or prolonged rainfall or if water is relatively impermeable, more water flows over ground surface
what is slumping and landslides
soil becomes wet and increased mass and lubrication of water makes downward movement of large amount of soil more likely
when do landslides often occur
when deep soil on steep slopes becomes less stable following deforestation, roots that held soil together decompose so soil is held together less strongly
name factors of vegetation that reduce rate of soil erosion
vegetation / vegetation cover and leaf litter / soil organic matter / plant roots / plants
how does vegetation reduce rate of soil erosion
acts as a natural windbreak, reducing win velocity reduces kinetic energy to carry away soil particles
how does vegetation cover and leaf litter reduce rate of soil erosion
reduce impact of raindrops on soil surface, soil particles are less likely to be dislodged
how does soil organic matter reduce rate of soil erosion
helps bind soil particles together eg collodial material humus
how do plant roots reduce rate of soil erosion
hold soil together
how do plants reduce rate of soil erosion
increase infiltration of water into the soil, reduces rate of runoff
name 6 human activities that increase the rate of soil erosion
vegetation removal / ploughing vulnerable soils / overgrazing / reduced soil biota / soil compaction/ cultivating steep slopes
how does vegetation removal increase rate of soil erosion
removes plants and plant roots and organic soil matter and vegetation cover which protects the soil from soil erosion
how does ploughing vulnerable soils increase the rate of soil erosion
breaks up the soil structure, exposing particles to erosion by wind or water
how does overgrazing increase rate of soil erosion
if livestock density is too high = vegetation is eaten faster than it can grow, exposing soil to risk of erosion / disturbance and root damage due to hooves
how does a reduced soil biota increase rate of soil erosion
living organisms have been removed from the soil, so detritivores cannot break down dead organic matter, release plant nutrients for increased vegetation cover / decomposers aren’t there to produce humus / worms aren’t there to aerate the soil, increase drainage and infiltrate capacity
how does soil compaction increase rate of soil erosion
gives soil smaller interstitial spaces which reduces infiltration rates so more likely for surface runoff and cause erosion
how does cultivating steep slopes increase rate of soil erosion
surface run off occurs more rapidly down a steep slope, more kinetic energy and picks up more soil particles
name 4 effects of accelerated soil erosion
reduced productivity / sedimentation in rivers and reservoirs / increased atmospheric particulates / desertification
how is reduced productivity caused by soil erosion
when soil erodes normally more fertile top soil is lost which leaves less fertile soil to grow in, causing smaller harvests / shallower soil so root penetration may be more difficult
how is sedimentation in rivers and reservoirs caused by soil erosion
soil particles carried into rivers may be deposited if water slows sown and has less kinetic energy. sediments in river reduce river flow capacity so more likely to over flow
how is increased atmospheric particulates caused by soil erosion
wind erosion increases level of atmospheric particulates
name 10 ways to reduce soil erosion
long term crops / zero-tillage cultivation / contour ploughing / tied ridging / terracing / rows of stones / windbreaks / multicropping / increasing soil organic matter / livestock management
how do long term crops help reduce soil erosion
limits amount you need to replant them so reduces soil disturbance, reduces erosion rate
how does zero-tillage cultivation reduce soil erosion
drilling seeds into the ground instead of ploughing, minimises soil disturbance and reduces risk of soil erosion
how does contour ploughing reduce soil erosion
ploughing contours at 90 degree to the slop reduces erosion as water flow is stopped by ploughed furrows it loses kinetic energy so cant carry soil particles, slower flow rate soil particles are deposited in furrow
how does tied ridging reduce soil erosion
water is retained in the criss cross intersecting ridges, increasing infiltration and reducing runoff
how does terracing reduce soil erosion
water flowing over the retaining walls flows quickly but flow slows down when across fields, much of the water infiltrates the soil
how does a row of stones reduce soil erosion
laid across contours, causes slow runoff and reduces erosion rate
how do windbreaks reduce soil erosion
growing crops reduces wing erosion, if plants removed soil is exposed. bushes and trees grown around the field
how does multicropping reduce soil erosion
growing more than one crop at the same rime an reduce wind erosion. harvested and re-sown at different times so always a crop protecting the soil
how does increasing organic matter reduce soil erosion
organic matter on soil surface protects soil from wind and impact of raindrops, as it decomposes it produces humus to help adhere particles
how does livestock management reduce soil erosion
stocking density can be controlled to reduce soil damage
