Agriculture
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what is the definition of agroecosystems?
The control of terrestrial ecosystems to divert energy and nutrients into the human food chain
What are the four factors considered when selecting a species for agriculture?
The choice of which animal species and plant variety are cultivated is a result of: 1. market demand/ culture 2. is there a suitable range of tolerance 3. can the abiotic factors be manipulated to increase production 4. is it cost effective
What proportion of the earths land is covered with: permanent pasture? Cultivated farmland?
Farmland covers a large proportion of the Earths land area with about 10% being cultivated and a further 25% used as permanent pasture. With a growing population it is important to ensure that future agriculture is sustainable. Agriculture affects large areas of natural habitats and affects many important natural processes.
what are the three principles of agriculture?
Agriculture involves the control of terrestrial ecosystems to divert energy and nutrients into the human food chain. Key principles are: - selection of species -control of abiotic and biotic environmental factors to control production - manipulation of the food species to improve productivity
Abiotic factors water How is it important?
-physiological functions- cell turgidity, universal solvent - nutrient absorption- dissolves as ions in water - transport- oxygen, glucose and minerals -transpiration- water leaves via stomata which allows exchange, lack of water causes stomata to close, thus halting plant growth
Abiotic factors water How is it controlled?
• irrigation -soil mulching/ increase organic matter content • increase filtration • reducing soil compaction to avoid flooding
Abiotic factors soil fertility How is it important?
-supports healthy plant growth and crop yields - its the combination of soil properties- availability of nutrients, and water, aeration, texture and structure
Abiotic factors soil fertility How is it controlled?
-fertiliser application (organic/ artificial -cultural methods
Abiotic factors Aeration How is it important? (off spec)
-allows root respiration -allows nitrogen fixation -allows decomposition -allows Prescence of detritivores
Abiotic factors Aeration How is it controlled? (off spec)
-ploughing- turns over and aerates surface soil -adding organic matter provides food for soil biota that increases aeration -low tillage methods prevent disturbance to soil and killing of soil organisms during ploughing -removing livestock from fields when soil is very wet decreases compaction caused by trampling
Abiotic factors Temperature How is it important?
-Thermal growing season- temperature not just suitable for survival but also to grow -frost-free period- crops can be damaged by frost -biogeochemical reactions- enzyme activity - thermoregulation- hot and cold blooded animals temperature regulation
Abiotic factors temperature how is it controlled?
-avoid low lying areas- frost and temperature inversions - south- facing slopes (on northern hemisphere)- receive more solar insolation -greenhouse/ woven plastic cloth -livestock providing them with shelters or buildings
Abiotic factors Light How is it important?
-rate of photosynthesis- glucose, biological molecules, growth -photoperiodism- (day length) affects growth and development of some crops (longer periods for flowering= oats) -affect reproductive function (e.g. long day length increases milk production)
Abiotic factors light How is it controlled?
-artificial lighting- to extend the growing season - artificial production of Autumn lighting conditions - in spring will produce another mating season for sheep, with a second lambing season in Autumn
How does artificially increasing the biocapacity through agriculture affect the biocapacity if agricultural practice stop?
Raises the biocapacity and the carrying capacity beyond its normal range to meet our high demand/ ecological footprint. Agricultural practices if done unsustainably will remove nutrient/ abiotic factors from the land If these practice stop, it will lower the biocapacity below its natural state
define biocapacity?
a measure of the biological productivity of an area
define ecological footprint?
A method of assessing the sustainability of lifestyles by estimating the biologically productive area needed to provide the resources and services needed by an individual or group
define global hectare?
A unit of measurement for biocapacity and ecological footprint, representing a hectare of biologically productive land or water with world-average productivity
what are the 11 abiotic factors which affect productivity?
light: intensity, day length water availability carbon dioxide temperature soil fertility pH soil salinity topography relief nutrient supply
Abiotic factors soil salinity How is it important?
Dissolved salts in water are essential for plant growth as they include soil nutrients but excessive salinity can kill plants by osmotic dehydration
Abiotic factors soil salinity How is it controlled?
the main method to control salinity is to avoid farming methods that increase salinity, especially irrigating with groundwater that has a high salt content. The salt concentration of the soil increases as the salts are left in the soil when water evaporates from the soil. Extra water can be used to wash the salts out of the soil but this greatly increases water consumption and can cause ecological problems by increasing the salinity of local rivers
Abiotic factors carbon dioxide How is it important?
carbon dioxide concentration can be the limiting factor on the rate of photosynthesis
Abiotic factors carbon dioxide How is it controlled?
it is not practical to increase the carbon dioxide concentration for crops grown in fields. however crops growth rate in greenhouses may be increased by burning carbon- based fuel such as gas or paraffin. the co2 is kept in the greenhouse rather than being lost and the increased costs may be justified by the high market value of greenhouse crops
Abiotic factors soil pH How is it important?
All plant species have their own range of tolerance for pH, usually between pH 5 and pH 7. A high pH (highest = 14) can inhibit nutrient solubility. A low pH (lowest= 1) can increase the leaching of nutrients and inhibit nutrient uptake. It can also mobilise toxic ions in the soil such as aluminium and lead.