Topic 5 - Soil systems and terrestrial food production system

what does soil consist of?

• minerals

• organic matter

• air

• water

what are the main functions of soil?

• medium for plant growth

• supplies plants with nutrients and water and a place for them to anchor (roots)

• water storage and purification system

• provides a habitat for over one quarter of all living species (such as bacteria, insects and mammals)

• modifies the atmosphere through respiration of the soil organisms and plant roots

pedosphere

soil

what is the best type of soil for agriculture?

loam (mix of sand silt and clay)

lithosphere

rock

hydrosphere

water

atmosphere

air

biosphere

living

how does the pedosphere (soil) interact with lithosphere (rocks)?

pedosphere → lithosphere = leaching

lithosphere → pedosphere = minerals

how does the pedosphere (soil) interact with hydrosphere (water)?

pedosphere → hydrosphere = evaporation

hydrosphere → pedosphere = infiltration

how does pedosphere (soil) interact with atmosphere (air)?

pedosphere → atmosphere = gaseous emissions

atmosphere → pedosphere = gaseous exchange

how does pedosphere (soil) interact with biosphere (living)?

pedosphere → biosphere = plant uptake

biosphere → pedosphere = feces

factors affecting soil characteristics

• Climate = precipitation/evaporation balance

• Organisms

• Relief = The elevation of the land, the aspect of the slope

• Parent material = This is the original material that the soil develops from

• Time

micro organisms in soil

bacteria, algae and fungi

macro organisms in soil

earthworms, insects, mites, millipedes and mammals, such as moles

importance of bacteria and fungi and small insects in soil system?

break down the leaves and organic matter on the top layer of the soi

what does decomposition produce and why is it important to soil?

plant nutrients and microbial remains, binds the soil and gives it crumb structure

what function does rhizobia bacteria produce in soil systems

• takes carbohydrates from the plant and provides nitrogen for the plant

what function do earthworms carry out, and why is it important?

• perform the final stage of decomposition by converting dead organic matter to humus and mix it into the soil

• change the soil chemically and physically, distribute microbes throughout the soil, increase availability of phosphorous

• aerate the soil and improve drainage and mix the soil

what function do mites carry out, and why is it important?

Each species browses on a particular type of fungi so the populations are kept in balance

what function do slugs and snails carry out, and why is it important?

burrow through the soil and improve its fertility and mixing

translocation

internal reorganisation of matter and energy

inputs in soil systems

• minerals

• organic matter

• gases

• water

where do minerals come from (input soil systems)

weathering of the parent material

weathering

breakdown of the parent material by physical, chemical and biological processes

where does organic matter come from (inputs, soil system)?

living organisms that are on and in the soil

where does gasses come from (inputs, soil system)?

nitrogen fixation by plants, change nitrogen gas to ammonia compounds

stores in soil systems

• organic matter

• minerals

• air

• water

• nutrients

Organic mater stores in soil systems

• dead organic matter that comes from biotic elements in an ecosystem

• used as a store of nutrients that plants use for growth

Organisms function in stores of soil systems

• These organisms add nutrients to the soil when they deposit waste.

• They remove oxygen and add carbon dioxide to break down dead organic matter

outputs in soil systems

• leaching

• erosion

• nutrient uptake by plants

• gaseous loses

• organic matter removal

• run off

transformations in soil systems

• leaching and evaporation

• decomposition

• weathering

soil profile

a vertical section of the soil that goes from the surface down to the parent material

horizons of the soil profile

• O horizon

• A horizon

• B horizon

• C horizon

what is the O horizon?

top of the soil, includes all the dead organic matter

what is the A horizon?

• the top soil or mineral layer

• usually dark in color due to the high proportions of organic matter

• high organic content means its a zone of highest biological activity

• this layer has often lost its clay as it has been eluviated or washed out

what is the B horizon?

• the sub-soil and tends to be the zone of illuviation or accumulation

• Minerals and particles are washed into this horizon from the ones above

• Plant roots are likely to be found in this layer but very little humus is found here

what is the C horizon?

• the decomposed parent material.

• In most cases this layer is not really affected by soil processes but it has weathered.

• This layer may contain large lumps of parent material

properties of clay soil

• nutrient content = good

• drainage = poor

• water holding capacity = excellent

• air spaces = very small

• biota = limited

• organic matter retention = good (but usually not available for plants)

• primary productivity = poor

properties of sandy soil

• nutrient content = good

• drainage = excellent

• water holding capacity = poor

• air spaces = large

• biota = limited

• organic matter retention = poor

• primary productivity = poor

properties of loam soil

• nutrient content = intermediate

• drainage = good

• water holding capacity = good

• air spaces = intermediate

• biota = good

• organic matter retention = good

• primary productivity = excellent

environmental impacts of intensive commercial farming

• pesticides reduce biodiversity, some can biomagnify and bioaccumulate

• fertilizers cause eutrophication

• monoculture increases risk of disease within crops

• mechanical equipment uses fossil fuels

• soil degradation through over-watering, causing nutrient run-off and salinization

• loss of natural habitat

• loss of polinators

intensive commercial farming

Both crops and animals can be commercially farmed with high inputs producing high yields

environmental impacts of intensive animal farming

• high density of animals increases risk of disease

• ethical concern over animal conditions

• use of growth hormones can cause health problems in humans, growth hormones can enter the environment through animal waste

• regular use of antibiotics can increase the risk of bacteria developing resistance

• high concentration of organic waste can pollute water

organic farming

Organic farming prohibits the use of genetically modified organisms (GMOs), chemical fertilizers and restricts the use of chemical pesticides

aim of organic farming

This helps to reduce chemical contamination of food and limits pollution

functions of organic farming

• physical removal of pests and weeds by hand

• biological predators to remove pests

• manure

• crop rotation

• livestock is fed with organic feed, no drugs or growth hormones, have more space to move around

why is organic farming less desirable than intensive farming

• produces lower yields

• is more labour expensive

• therefore prices are more expensive

Subsistence farming systems

The agriculture yields are focused at meeting the demands of the family or community

what do subsistence farming systems include

• shifting cultivation

• nomadic livestock herding

• intensive subsistence farming

shifting cultivation

• area of land cleared out (usually a forest)

• land is farmed for a few years until soil loses its fertility and yields drop

• farmer moves to new area, process is repeated

• old area time recovers by growing back trees, soil and biomass also recovers

pros and cons of shifting cultivation

• sustainable at low poulations

• inputs for this system are low in terms of technology and labour

• at high population there is greater soil damage

nomadic herding

moving with animals such as cattle and goats in search of suitable grazing areas

Intensive subsistence farming

families farm on a plot of land and aim to produce enough food to feed their families with some surplus to sell

ways to promote

• legislation for use of pesticides drugs and hormones

• pollution management

• growing Indigenous crops, which are more resilient to drought and disease

• polyculture farming

• reduction of meat consumption

types of polyculture farming

• inter-cropping

• companion planting

intercropping

• where low growing crops can be planted between taller growing crops

• The low crops provide ground cover and reduce weed growth, intercept water flow and prevent soil erosion

companion planting

• the practice of growing several types of crops near one another

• to enhance crop production

• to reduce pest attacks

advanatges of polyculture farming

• plants less susceptible to disease and pests

• can contribute to improved pollination

• increase in local biodiversity

• higher overall yield per land area used

disadvantages of polyculture farming

• more labour intensive

• harvesting takes longer

• greater planning needed

• higher costs of production

role of soil in primary succession

• occurs in places where no soil initially exists

• colonization of pioneer species, lichens and moses colonize rock and break down the substrate and provide organic matter when they die

• accumulation of dead organic matter and weathered rock particles form the first layer of soil

• as soil deepens and becomes more nutrient rich it is able to support a larger variety of plants

role of soil in secondary succession

• in secondary succession soil quality is increased

• plant diversity increases, different plant species contribute varied organic matter when they die

• soil organisms become more active fungi, earthworms and bacteria break down organic material improving soil structure and nutrient availability

• nutrient cycling, carbon and nitrogen cycle

why is soil a non-renewable source?

soil can be replenished however its formation is slow, it takes 1000 years to produce 5cm of soil, however this depends on climate conditions

soil formation is the fastest under… (and why?)

• sunny, warm and wet conditions when there is maximum plant growth

• this contributes to high amount of plant litter and other dead organic matter which is broken down to form top soil

processes that degrade soil

• water erosion

• wind erosion

• chemical degradation, salinization, acidification, nutrient depletion and chemical pollution

• physical degradation

erosion

Soil particles can be transported from one place to another by either water or wind

effects of erosion

• Erosion typically removes the fertile topsoil

• The loss of organic matter also leads to a reduction in water retention capacity

• Eroded soil can enter water and cause water pollution due to high concentration in nutrients and pesticides

water erosion phases

• Detachment: When the raindrops hit the soil, it frees some of the soil particles. Then run-off detaches more soil particles as it flows

• Transport: The flow of the water carries the soil particles

• Deposition: When the water slows down, the soil particles are deposited.

types of water erosions

• sheet erosion

• rill erosion

• gully erosion

sheet erosion

when a fairly thin even layer of soil is removed by run-off

rill erosion

when the run-off scours channels into the soil called rills

gully erosion

when the force of water is greater enough to create a deep channel

types of chemical degredation that affect soil

• salinization

• acidification

• nutrient depletion

• chemical pollution

human activities that lead to soil degredation

• urbanization

• livestock overgrazing

• deforestation

• farming

• desertification

soil conservation methods

• reducing water erosion

• control grazing

• reducing wind erosion

• reducing salinization

• managing soil nutrient levels