Soil biota - living organisms are involved in many soil processes that affect soil fertility. e.g. 1. detritivores break UP dead organic matter and release nutrients into the soil and increase soil drainage and aeration by making tunnels in the soil. 2. decomposers like bacteria and fungi break DOWN dead organic matter, secrete digestive enzymes rely on detritivores to physically break up dom and increase its surface area. 3. nitrogen fixing bacteria convert gaseous nitrogen into ammoniUM ions. 4. NitrIFYING bacteria oxidise ammoniUM ions to nitrite ions then to nitrate ions. 5. Mycorrhizal fungi form symbiotic relationships with plant roots and aid phosphate uptake by the plants

Soil structure - soil particles form aggregates called peds. Particles bound together by polysaccharide gums produced by: decomposition, fungal hyphae, roots, the action of soil biota and hygroscopic clay particles. ped type affects soil properties and fertility. Crumb peds = small and round = good drainage, aeration and easy root penetration = fertile. platy peds = large and flat = less drainage, aeration and root penetration = less fertile

A natural process as soil particles are removed by wind or water. In soils that have not been affected by human activities, the rate of erosion is NOT going to be higher than the rate of soil erosion (soil unaffected in those areas). Erosion is a problem when it occurs faster than soil formation

with dry soils likely with low clay content bc they are likely to become loose with little cohesion (sticking together) between particles = soil isn't held together = if its windy soil and soil is unprotected then it might blow away. Problem for the area that looses soil and for areas where the soil is deposited as it may cover crops or land in urban areas

rain splash erosion - soil particles are dislodged by the splash of a raindrop, soil particles dispersed in all directions but those going downhill are likely to travel further. over time, it can cause the downhill movement of large amounts of soil

surface runoff erosion - when water from rain, snowmelt or other sources flow over the land surface (surface runoff) and the infiltration capacity (no more water can be absorbed) of the soil has been exceeded. basically plants overwatered. can occur when rainfall is heavy or prolonged, or if the soil is relatively impermeable so more of the water flows over the ground surface

slumping and landslides - occurs when soil on slopes becomes very wet, the increased mass and lubrication of the water makes the downward movement of large amounts of soil more likely. Often occurs when deep soil on steep slopes becomes less stable following deforestation. The soil is held together less strongly and landslides following heavy rain become more likely

vegetation acts as a natural windbreak, reducing wind velocity and therefore the kinetic energy to carry away soil particles

vegetation cover and leaf litter reduce the impact of raindrops on the soil surface, so soil particles are less likely to become dislodged

soil organic matter, including humus, helps to bind soil particles together

plant roots hold soil together

plants help to increase the infiltration of water into the soil. This reduces the rate of runoff which reduces water erosion

vegetation removal - removes the protection from erosion

ploughing vulnerable soils - breaks up the soil structure, exposing soil particles to erosion

overgrazing - if the livestock density is too high then the veg will be eaten faster than it can grow = increased exposure of the soil = the risk of erosion. disturbance and root damage by hooves increase the risk of erosion

reduced soil biota (living organisms in the soil) - this can be done by ploughing, reducing organic matter in the soil and the use of agrochemicals (fertiliser). Living organisms are important in reducing soil erosion. e.g. 1. detritivores break down dom, releasing plant nutrients which may increase veg cover. 2. decomposition produces humus which increases adhesion between soil particles. 3. worms aerate the soil, increasing drainage rates and the infiltration capacity of the soil which reduces the rate of runoff which reduces water erosion

cultivating steep slopes - surface runoff water flows more rapidly down steeper slopes so it has more kinetic energy to pick up and carry soil particles. Cultivating with techniques that disturb the soil add to the erosion risk

soil compaction - use of heavy farm machinery, high livestock densities and reduction in soil detritivores makes it more likely that soil will become compacted. Has smaller interstitial spaces which reduces the infiltration rate so it is more likely that rainfall will produce surface runoff and cause erosion

reduced productivity - erosion = most fertile topsoil lost, rest of the soil = less fertile = reduced growth = smaller harvests. erosion can leave shallower soil so root penetration may be more difficult

sedimentation (heavier particles of an insoluble solid in a liquid settle down to form a layer) in rivers and reservoirs - soil particles carried into rivers + water slows down and had less kinetic energy. soil that sediments in a river reduces its flow capacity so its more likely to overflow and cause heavy rain followed by flooding

increased atmospheric particulates - increased by wind erosion. can make health problems such as asthma worse

desertification - soil erosion makes it more difficult for veg to grow which contributes to further soil erosion and reduced rainfall

long-term crops - don't require frequent replanting and soil disturbance. e.g. permanent grassland or bush and tree crops such as fruit, tea, coffee and cotton

strip cropping - an extension of multicropping where machinery may be used. The strips are most effective if they are arranged at 90 degrees to the prevailing wind direction

contour ploughing - ploughing up and down a slope creates gulleys(channels) that increase the velocity of runoff and cause more rapid erosion. Instead ploughing along the contours at 90 degrees reduces erosion as the water flow is stopped by the ploughed furrows (trenches) and loses its kinetic energy. With a slower flow rate soil particles are deposited in the furrow so they work well until the furrows overflow

tied ridging - used on land that is almost flat. the field is divided with a criss-cross of intersecting ridges. These retain water when it rains, increasing infiltration and reducing the runoff that may have caused erosion

terracing - where sloping land is cultivated, a series of narrow fields are created with the soil held in place by retaining walls built along the contours. Water flowing over the walls flows quickly, but it slows down as it flows across the fields. Much of this water may infiltrate into the soil.

Mulching - when a layer of material is applied to the surface of the soil e.g. hay, saw dust, leaves, woodchips etc. This protects the soil from wind and the impact of raindrops

windbreaks - any growing crop reduces the velocity of the wind and occurrence of wind erosion but this is lost when the crop is harvested. This protection is maintained when hedgerows or trees are allowed to grow round a field

multicropping - having more than one type of crop in a field at one to ensure there is always a crop in the field to protect the soil from wind erosion. This works most easily where farming uses human labour rather than machinery

increasing soil organic matter - any method that retains or adds som will reduce the risk of erosion. As organic matter decomposes it produces humus which helps the soil particles to adhere to each other

livestock management - stocking density = trampling damage, livestock movement = reducing access to riverbanks where trampling is more likely to cause erosion into the river, livestock removed at high risk times e.g. just after heavy rain

A (rate of soil erosion/annual soil loss) = R x K x L x S x C x P