LA3 - Sustainable Farm Production Flashcards
(70 cards)
Forms of land degredation
dry land and irrigation salinity; acid soils; the decline of soil structure; and the decrease of soil fertility and soil organic matter due to erosion by wind and water
forms of soil degredation
- erosion, including sheet and rill erosion, gully erosion and wind erosion
- salinisation, including irrigation and dryland salinity
- acidification
- soil structure decline
weathering
breaking of rocks down to smaller pieces of material - forming soil and releasing mineral from rocks for plant use. Volcanic rocks such as basalt break down easy and form rich fertile soils whereas sedimentary rocks such as sandstone are hard to breakdown and form less fertile soil.
erosion
means moving the broken down material to somewhere else - caused by wind or water. first removes the fertile upper horizons that are rich in organic matter and nutrients. the remaining soil is able to support less vegetation.
wind erosion and what increases risk and reduces
removal of soil via wind, commonly occurs in deserts and on coastal dunes and beaches and during drought. soils most at risk when:
- they are bare with little or no ground cover from plants or litter
- they have poor structure
- they have a light, sandy texture
- they have no shelter from wind
Techniques to increase resistance is:
- stubble retention or zero till to maintain ground cover
- planting trees or windbreaks
- maintaining soil structure by crop rotation and incorporation of crop stubble
- restricting grazing so that the soil is not laid bare
- avoiding repeated cropping on light sandy soils.
modes of transport of soil particles
soil creep, saltation, abrasion and attrition, suspension
soil creep
particles grater and 0.5mm in diameter are usually too heavy to be lifted by wind. creep is when wind rolls these particles or they are moved along the surface by bombardment by other moving particles.
saltation
main process that suspends soil particle sin the air - particles between 0.1 and 0.5mm in diameter are lifted by wind then fall back to the ground, so they hop or bounce across the surface.
abrasion and attrition
suspended particles cause abrasion of the soil surface when they fall back to the ground. they can also hit other particles and break into smaller pieces, called attrition.
suspension
small particles less than 0.1mm in diameter that have been ejected into the air by saltation remain suspended as dust and are carried away from the erosion site by the wind.
what will climate change cause resulting in more wind erosion
- less rain, which will support less vegetation
- lower soil moisture, which will decrease the ability of soil particles to bind together into larger heavier aggregates
- large losses of soil and nutrients
- more large dust stoms
- poor air quality
wind erosion can be protected against using:
- windbreaks: which protect against down-wind erosion for about ten times their height
- roughly 50 percent ground cover: which provides control of paddocks
- small shrubs: control wind erosions in rangelands, provided they are evenly spaced at about three times their height.
costs of wind production:
- impacts on human health: dust in the air can impact air quality and cause asthma and other health problems
- loss of agricultural production: wind erosion acts on soil surface so more fertile top layers are removed. can affect grazing and cropping areas. deposited wind can bury or sandblast crops, contaminate wool and deposit salt
- degradation of the environment: material eroded by the wind can choke creeks and deposit salt which can threaten plants and animals
- loss of property and aesthetic value
- loss of economic production: associated with extra cleaning, disruption to commercial activities and transport.
sheet erosion
occurs when raindrops dislodge particles of soil and wash them downslope. whole sheets of soil are washed away and channels or gullies are cut into the slope, exposing lower layers of soil until only rock is left. can be controlled partially by use of contour banks
rill erosion
removal of soil by run-off. small channels generally about 30cm deep form in the slop and these can let the water speed up and carry soil away resulting in the formation of gullies. rills can generally be removed by ploughing.
gully
an open erosion channel cut deeply into the soil by water during or immediently after heavy rain. - generally deeper than 30cm. typically they get bigger as they work go upstream and if left untreated can cause all the soil to be lost from the slope, leaving rare rocky hillside.
contour farming
soil conservation method used to combat soil erosion. farmers may use contour ploughing or contour banks to control washing and erosion and depending on the steepness of the slope may choose to cultivate downslope rather than across the slope and following the contours.
explain how contour ploughing and contour banks may help prevent erosion
the function of contour banks is to intercept runoff and safely channel it into stable grassland waterways, natural depressions or grassed areas adjacent to a paddock. they reduce slope length and intercept runoff before it concentrates and starts to cause erosion.
why may cultivation be preferred to following the contours
cultivation on a slop reduces the risk of sheet and rill erosion developing as the crop acts as a ground cover to bind soil particles. However following the contours tends to lead to a collection of water and a redirected deposit of topsoil.
strip cropping
technique used to help control soil erosion on gently sloping land. planting of crops in strips or bands. strips of crops such as wheat, are planted between the strips of other crops. some strips left bare byt never large areas of bare ground. if erosion occurs it is soon halted by the next strip.
describe how strip cropping helps farmers control soil erosion
strip cropping helps to stop soil erosion by creating natural dams for water, helping to preserve the strength of the soil. certain layers of plants will absorb minerals and water from the soil more efficiently than others.
stubble mulching
involves keeping as much stubble as possible from the previous crop on the soil surface. the retained stubble or mulch absorbs most of the energy of the rain, reducing the breakdown of soil particles. also protects the soil from wind erosion and helps with water retention
zero tillage
also called direct-drill or no tillage. - means that the land is not ploughed at all. seed is sown directly into the undisturbed stubble of the previous crop. chemicals are used to control the weeds.
dryland salinity
occurs in non-irrigated areas where deep rooted perennials are replaced by crops and pastures that use less water because they have shallow root systems. leading to the mobilisation of of salts stored deep in the soil. saline groundwater may rise to the surface or flow directly into streams and rivers.
may also occur by the exposure of naturally saline soils. sodic soils can also cause salinity.
