mocks cramming - topic 5 - soil Flashcards
Soil inputs
Minerals: The minerals of a soil come from the weathering of the parent material by physical, chemical and biological processes.
Organic matter: Organic matter comes from the living organisms that are on and in the soil. Soil and vegetation develop together. During succession, the early plants colonize the area before the soil has really developed. When the early plants die, they add organic material to the soil
gases: Certain plants fix atmospheric nitrogen and change it into nitrates and ammonia compounds in the soil. The nitrogen fixation is a process that forms an input into the soil system
Water: The way in which water enters the soil is dependent one whether the soil is on a slope and where it is on that slope. At the top of a slope the soil receives most water through direct precipitation.
soil stores
- organic matter
- organisms
- minerals
soil outputs
- physical erosion: through the action of wind, water and plants and animals
- organic erosion: Plants take nutrients and carbon dioxide from the soil for growth and to photosynthesize.
- leaching water flowing vertically through the soil transports nutrients in solution downward in the soil profile. Many of these nutrients can be completely lost from the soil profile if carried into groundwater and then horizontally transported into rivers, lakes, or oceans.
Soil Profile
four main horizons – O, A, B and C. Soils will not always have all the horizons.
Soil - Organic horizon (referred to as the O horizon)
is on the top of the soil
- includes all the DOM that accumulates on top of the soil.
- Initially the remains can be identified but as decomposition progresses the DOM becomes an unrecognizable jelly like substance (humus) that mixes into the soil over time.
Soil - A horizon
the top soil or mineral layer.
- This layer is usually dark in colour due to the high proportion of organic matter.
- The high organic content means it is a zone of highest biological activity. This layer has often lost its clay as it has been eluviated or washed out. This is often absent.
Soil - B horizon
the sub-soil
- 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.
Soil - 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.
Soil texture
is linked to the relative proportions of sand, silt and clay particles. There are other sizes of particles but these three are the most important.
Soil structure
- describes the way the sand silt and clay particles stick together
- affected by the presence of organic matter and soil organisms.
Fertilizers (3):
Nitrogen-based Fertilizers: Ammonium nitrate and urea were commonly used to provide essential nitrogen for plant growth.
Phosphorus-based Fertilizers: Superphosphate and diammonium phosphate supplied phosphorus, crucial for root development and energy transfer.
Potassium-based Fertilizers: Potash (potassium chloride) helped with plant metabolism and disease resistance.
Pesticides (3):
Insecticides: DDT (dichlorodiphenyltrichloroethane) and organophosphates were used to control insect pests.
Herbicides: Atrazine and glyphosate were employed to manage weeds.
Fungicides: Copper sulfate and sulfur compounds were applied to combat fungal diseases
two kinds of farming
Arable - Focus on crops (Corn, Rice, Wheat)
Pastoral - Any animals or livestock
intensive commercial crop production includes the use of (7)
- High-yielding crop varieties including genetically modified organism (GMOs).
- Fertilizers that provide nutrients to encourage maximum growth.
- Herbicides to kill weeds that compete with the crops for space, water and nutrients.
- Insecticides to kill insects that eat and damage the plants.
- Water (either via rainfall or irrigation) to encourage maximum growth.
- Mechanical equipment that allows large areas to be effectively farmed.
- Automated technologies that can be used to extend the scale of farming by reducing the amount of labour required to manage larger fields, (eg. automatic irrigation systems.)
The impacts (Animal Production) (4)
- High density of animals increases the risk of rapid spread of disease through the animal population.
- Ethical concern over keeping animals under such confined conditions.
- Regular use of medication such as antibiotics to prevent diseases. Use of antibiotics increases the risk of developing resistance within bacteria. This makes future infections more difficult to treat.
- High concentration of organic waste matter produced that can pollute water systems.
environmental impacts (crops)
-
Pesticides kill non-target organisms and can reduce overall biodiversity. Some non-biodegradable chemicals, (eg. DDT), can bioaccumulate and biomagnify building up concentrations through the food chain.
-Fertilizers - eutrophication of waters - Water for agriculture competes with other uses of limited water resources
- Monoculture increases the risk of disease, affecting all crops.
- Mechanical equipment uses non-renewable fossil fuels and emit greenhouse gases, for instance carbon dioxide and nitrous oxides.
- Soil degradation, for example excessive irrigation, can increase nutrient run-off and also cause salinisation.
the great dust Bowl
During the 1930s in the USA, dust storms swept across the Midwestern states of the USA. This period is commonly referred to as the ‘Dust Bowl’ and brought the issue of soil loss to global attention.
Prolonged drought in the 1930s dried out the soil. When wind storms occurred, large amounts of topsoil were swept into the air causing vast dust storms. The cost was immense with no harvests and damage to property. Many people starved or died from dust penetrating into their lungs causing dust pneumonia. Thousands of farmers lost their livelihoods and migrated to urban areas seeking employment. Unfortunately there were few opportunities in the cities and towns during this period of the Great Depression.
The Dust Bowl prompted investment into the study of soils to find solutions to the problem. In 1935, the US Soil Erosion Act came into force to encourage soil conservation practices. Although our understanding of soils and soil conservation has improved since the Dust Bowl, soil loss and degradation continues to be a problem around the world.
