Topic 5 Study Guide AK (4) PDF

Topic 5 Checking Your Understanding 5.1 Introduction to Soil Systems 1. Draw and label a diagram that illustrates the di4erent soil horizons. 2. Draw a systems diagram of soil including the following storages and flows (transfers and transformations, inputs and outputs).  Storages: organic mat...

Topic 5 Checking Your Understanding 5.1 Introduction to Soil Systems 1. Draw and label a diagram that illustrates the di4erent soil horizons. 2. Draw a systems diagram of soil including the following storages and flows (transfers and transformations, inputs and outputs).  Storages: organic matter, organisms, nutrients, minerals, air, and water. Inputs: leaf litter, inorganic matter from parent material. Outputs: uptake by plants, soil erosion. Transfers: Biological mixing, leaching. Transformation: decomposition, weathering, nutrient cycling. 3. Explain how soil can be viewed as an ecosystem. An ecosystem is a community and the physical environment with which it interacts. In soil there are many populations of organisms that live in the soil, like large organisms like moles or badgers to smaller invertebrates such as earthworms and beetle larvae and microorganims like bacteria and archaebacteria. Their physical environment consists of decomposing organic matter, inorganic rock particles (minerals), water and air. 4. Contrast sand, clay, and loam soils in their mineral and nutrient content drainage water holding capacity air spaces biota potential to hold organic matter Sand Clay Loam mineral and very low as high as clays are mainly aluminium silicates with varying This depends on nutrient mainly amounts of important nutrients such as potassium, calcium, the mix of sand, content silicon magnesium, and iron. The clay particles are also negatively silt and clay but dioxide charged and so attract other positive ions such as potassium should be good. (K+), calcium (Ca++), magnesium (Mg++), and the ammonium form of nitrogen (NH.+)  Sand Clay Loam drainage Very well Very poorly drained Good drainage drained water Low High Moderate holding capacity air spaces High low moderate potential to Low High Good hold organic matter 5. Based on the answer to the previous question, discuss the productivity potential of the three soil types. Sandy soils have low productivity due to their low nutrient levels and water holding capacity. Clay soils can have higher productivity but tend to become water logged which can lead to anoxic conditions and anaerobic respiration of soil organisms. Loam should be high productivity due to the well drained soil, good nutrient content and high air, water holding and organic matter. 6. Be able to use a soil texture triangle to identify soil types Where the lines intersect should also indicate percent silt. On the graph above, you can see that it is about 8% silt. 5) Wherever your lines intersect indicates the soil type you have. In this situation, with 65% sand, 27% clay, and 8% silt, it is sandy clay loam. % Texture Sand %Silt %Clay Name Properties a 75 10 15 Sandy loam Water infiltration, aeration, workability b 10 83 7 Silt Medium for all properties - nutrient holding capacity, water infiltration, water-holding, aeration and workability c 42 21 37 Clay loam Moderate nutrient holding and water-infiltration and water-holding, aeration adn workability. d 21 52 27 Silt loam Medium for all properties e 15 35 50 Clay Good nutrient-holding and water-holding but poor water infiltration, aeration and workability f 30 49 21 Loam Medium for all properties g 5 70 25 Silt loam Medium for all properties h 55 5 40 Sandy clay Medium for all properties  % Texture Sand %Silt %Clay Name Properties i 45 45 10 Loam Medium for all properties Checking Your Understanding 5.2 Terrestrial Food Production Systems 1. Define subsistence farming, cash cropping, and commercial farming. Subsistence farming is farming or a system of farming that provides all or almost all the goods required by the farm family usually without any significant surplus for sale. Cash cropping is growing a crop which has a high value on the (usually) export market and often replaces land that would be used otherwise to grow crops for local consumption. This is often driven by demand from markets in more economically developed countries. Examples include, cotton, chocolate, co_ee, roses, bananas, oranges and vegetables for export such as green beans. Commercial farming is the production of crops and farm animals for sale, usually with the use of modern technology.This is often motivated by profit and generating income. 2. Compare and contrast commercial farming to subsistence farming, considering the following factors. Scale; Industrialization; Mechanization; Fossil fuel use; Seed/crop/livestock choices; Water use; Fertilizer use and pest control; Use of pollinators; Antibiotic use; Impacts of legislation on operations Commercial Farming Subsistence Farming Scale large small Industrialisation yes, very very little Mechanisation yes, very little and more low tech  Commercial Farming Subsistence Farming Fossil fuel use yes, very low seed / crop / livestock buys seeds from large agricultural suppliers often harvests own seeds from crops to choices replant grows crops that have highest demand will have a variety of crops to feed family keeps livestock that have good demand livestock are likely to be low in number and provide multiple purposes. water use most likely high and dependent on irrigation most likely low or at least dependent on local conditions fertiliser use High limited and probably from own animals pest control Likely to use pesticides sold by agri-pharma likely to be dependent on hand control companies and natural predators or use hens and ducks as predators. use of pollinators May rent travelling pollinators such as honey bees but largely unavoidable dependence on natural pollinators  Commercial Farming Subsistence Farming antibiotic use depends on local legislation but will use unlikely to use impacts of legislation Very dependent on legislation as likely to be may not be impacted by legislation as too on operations controlled small scale to be controlled. 3. Using the information from the previous question, compare and contrast the sustainability of subsistence v. commercial farming. The sustainability of subsistence agriculture is likely to be higher than commercial agriculture due to the lower inputs to the system. Use of antibiotics, pesticides and heavy machinery reduces the sustainability of commercial agriculture as these can accumulate in the system and degrade the soil, requiring more and more inputs into the system. The use of commercial seeds will reduce the genetic diversity of the crops and reduce the resilience of the system. This in turn, along with the use of pesticides, will reduce the diversity of pollinators and make the system even less resilient. The reasons why subsistence farming may lack resilience are that there may not be enough rotation in the crop use to maintain the fertility of the system. The lack of access to water and other commodities may also mean the subsistence farming system is vulnerable to climatic variability. 4. Compare and contrast the reasons for food waste in MEDCs and LEDCs. The amount of food waste generated in MEDCs and LEDCs is approximately one third of all the food produced. In developing countries the problem is chiefly one of inadequate harvest techniques, poor post-harvest management and logistics, lack of suitable infrastructure, processing and packaging, and lack of marketing information which would allow production to better match demand whereas in developing countries 40 percent of losses occur at post-harvest and processing levels while in industrialized countries more than 40 percent of losses happen at retail and consumer levels. Food losses during harvest and in storage translate into lost income for small farmers and into higher prices for poor consumers, the report noted. Reducing losses could therefore have an "immediate and significant" impact on their livelihoods and food security. 5. Briefly outline four examples of food production systems. Intensive Cereal Production - Corn in Iowa, USA: Maize/corn production is typically a monoculture which can cover kilometers of square land area in the USA - they even call it the corn belt - and covers most of the American mid-west. Notice how, in the image of the United State, corn production lines the Mississippi watershed and is a major contributor to eutrophication and deadzones in the Gulf of Mexico. Intensive corn production is very energy intensive and while the transport and energy sectors are still reliant on fossil fuels agriculture, even arable production, has a big impact on greenhouse gas emissions. Inputs include: Genetically modified seed (probably BT-Maize) which allows, theoretically, for lower amounts of insecticide to be used. Inorganic fertiliser - in this case Liquid ammonia; Solar energy and rainfall - iowa is humid and so less irrigation needed; Farm machinery which use oil for ploughing, seed planting, insecticide and fertiliser spraying and harvesting; Oil powered transport to take crop of maize to storage and processing plants; Outputs from the systems include: Corn/maize - used for animal feed and processed to make modified corn starch used in processed foods Greenhouse gases; Loss of top soil due to leaving the soil bare for long periods of time; Run-o_ containing water enriched with nitrates/phosphates - contributes to eutrophication; Run-o_ containing insecticides - leads to loss of biodiversity in invertebrates and knock on e_ects on food chain; Pollen rich in BT toxin which can lead to loss in biodiversity. Pokkali Rice - Shrimp Farming in Kerala: Pokkali rice is a native rice of Kerala, South India. It is tolerant of saline growing conditions and is grown in the tidal lagoons around the coast. It's growing season follows the monsoon when the lagoons have the lowest salinity. Shrimp are grown alongside the rice, feeding on the dead matter in the water logged conditions. Due to the saline solutions there is little competition with other plants and so herbicides are not needed. The traditional practices mean that no pesticides are applied and the rice is grown organically. Challenges come from pressure for coastal land for development and the lower productivity compared to some varieties but this variety has a higher protein content and grows in conditions not suitable for usual crop cultivation. Rice-Fish Farming, Indonesia: In this system rice are grown together with fish during the flooded period of the rice growth. The rice production benefits from the fish through them eating insects. This reduces the need for insecticides and pesticides. The fish also provide fertiliser to the rice through their faeces. The fish farmed are generally bottom feeders which feed on the decomposing matter in the rice paddy fields (rice grow in flooded fields until harvest time). The Zai technique used in Burkina Faso: This technique was reinstated by Yacouba Sawadogo. It is a simple pratice of digging holes in the dry compacted soil. The holes are filled with some rotting plant material and manure from local animals. Next, a seedling can be planted. The Zai allows for rainwater to collect in the pit and not runo_. Termites are attracted to the decomposing plant material and therefore as they travel to the zai, they create little tunnels under the pit that leads to more water infiltration. Although it takes time and money the yields can be as much as three times what it would be without the zai pits. This is a more resilient system as there is increase water retention and nutrients in the system and allows for increases in biodiversity. 6. How do climate, culture and religion, politics, and socio-economic factors influence a society’s choice of food production systems? Climate: usually limits the type of food production system, for example, rice is grown in areas with excess water (the rice need flood fields) and warm average daily temperatures. Corn is grown in warm areas with high humidity during the growing period. Religion has limited impacts on the food production system but may guide the choice of animals kept, for example traditional hindu systems do not kill cows and so sikhs are often the dairy farmers. Politics will influence the food production system by valuing and promoting certain choices through legislation and subsidies or taxation systems. Socio-economic factors may promote or limit the amount of technology used within a farming system, for example in parts of Italy, vineyards may be controlled through the use of drones to spray the vines. In other parts of Italy more traditional method of vine keeping may be promoted dependent on the socio-economic values of the region. 7. Explain how human population growth will a4ect food production systems and sustainability. Human population growth is predicted to continue to grow, although at a slower rate until it is static or declines by the end of this century. With growing population size there will be growing demand for food but the distribution of need may change and growth occurs in the Global South. If food production systems are to keep up with this demand then they will have to become more e_icient while maintaining and improving their sustainability. This will also help support soils to become more resilient and store more carbon. Societies may also have to decrease their meat and dairy consumption in order to increase food production without land loss. Events during the Ukraine war have shown how the global food supply depends on importing wheat / food and so countries (in Africa) need to look at increasing their local production of food to increase their independence and sustainability. 8. Evaluate strategies to increase sustainability in terrestrial food production systems. Key ways to increase sustainability include a reduction in meat and dairy consumption, increased use of permaculture and polyculture, local food production, lower use of inorganic fertilisers, increased use of organic techniques, and a focus on reducing food waste so that e_iciencies are improved. By reducing the consumption of meat and dairy, the amount of land required for food production is decreased as land is no longer used to produce food for the animals. This is a consequence of the second law of thermodynamics which means that energy is lost between each trophic level. Permaculture is a method of producing food without the need for additional fertilisers or pesticides. Food is grown in nutrient solutions and intermixed to reduce pest loads. This is a method used to produce food in urban environments and reduces transport costs. Polyculture means growing crops in a mixed model so that there are not big monocultures. This increases biodiversity and so increases e_iciency of nutrient use. If combined with no-till agriculture, the soil structure and ecosystem improves, sustaining higher yields without inputs. Local food production means that smaller amounts of food are produced where they are needed making production more e_icient and reducing losses due to transportation and storage. Inorganic fertilisers do not help the soil ecosystem and so lead to a dependency on their use. They are also overused as can be seen from their run-o_ into freshwater systems which become eutrophic. Increased organic techniques will help the soil ecosystem improve and become more resilient and less dependent on inputs. This requires a long term view of the system however and also building capacity to cope with losses to pests or climate stress. With one third of all food lost and a large portion of this before it reaches consumers, changes in the food cycle need to happen. This may require legislation such as banning large buyers from refusing to take food produced which does not meet regulation shapes, removing consume by or sell by dates for non-processed food and greater local production to meet more sustainable needs. 9. Evaluate the relative environmental impacts of two given food production systems. Iowa corn production results in large scale runo_ of nitrogen which ends up in the Mississipi watershed causing eutrophication and ultimately dead zones in the Gulf of Mexico. The system is dependent on irrigation and this depletes freshwater aquifers. It also used genetically modified seed which results in the spreading of pollen that is toxic to insects, reducing biodiversity in the areas. As the corn is grown in large monocultures and the removal of land that may act as bu_er zones and biodiversity sources with the use of large fossil fuel dependent machinery, the soil is largely depleted of its own nutrients. Organic cereal production in Switzerland is small scale as small farms have been maintained and so field sizes have not increased. Bu_er zones are used around fields to reduce runo_ and pesticides are also not used. Biodiversity of insects, small mammals and birds is high. Fields are only ploughed shortly before planting or no-till agriculture is used and so soil ecosystems are maintained with limited soil loss. Irrigation is not used. Checking Your Understanding 5.3 Soil Degradation and Conservation 1. Outline the concept of soil degradation. Soil degradation describes what happens when the quality of soil declines and diminishes its capacity to support animals and plants. Soil can lose certain physical, chemical or biological qualities that underpin the web of life within it. Soil erosion is a part of soil degradation. It's when the topsoil and nutrients are lost either naturally, such as via wind erosion, or due to human actions, such as poor land management. Human activities can result in soil degradation - loss of top soil and loss of soil fertility. In extreme cases this can result in desertification, toxification or salination and make the ecosystems unusable without extreme bioremediation. 2. Outline activities that reduce soil fertility including Deforestation: Clear felling great areas of forest leaves the soil open to the weather with little holding the soil in place. This can lead to increased nutrient run-o_ from the soil and loss of top soil. Intensive Grazing: Over-grazing results in bare ground and thus the exposure of soil to rainfall and wind with soil being washed or blown away. This further degrades the land and can lead to desertification. Urbanization: The idea with urbanisation is simple, as more and more land is covered by human settlements, there is less land (and thus soil) to provide ecosystem services. Irrigation: As water evaporates in hot climates it can leave a salty residue on the soil. Monoculture: Growing the same crop over large areas of land for repeated years means that the same minerals are always being taken from the soil. Farmers try to replace these using inorganic fertilisers. 3. Explain why commercial, industrialized food production systems generally tend to reduce soil fertility more than small-scale subsistence farming methods. Commercial, industrialised food production systems tend to rely on heavy machinery, large inputs of inorganic fertiliser, monocultures and irrigation. This leads to compaction, the degradation of the soil ecosystem, nutrient depletion and toxification of the soil. Small scale subsistence farming tends to have manual labour, a variety of crops to support the family, the use of animal manure as fertiliser and maintenance of surrounding ecosystems which provides a source of insect predators which act as pest controls. Crops tend to be rotated which maintains the fertility of the soil. 4. Explain the relationship between soil ecosystem succession and soil fertility. As succession takes place, soil is formed and develops. As organisms die, they add to the soil and increase the fertility of the soil. Over time, the soil ecosystem develops greater biodiversity and the soil structure improves with greater balance of the soil particles and organic. Soil fertility also develops during this process. 5. Discuss the influences of human activities on soil fertility and soil erosion. The human activities outlined in question two impact soil fertility and can lead to soil erosion. These are deforestation, ubranisation, farming practices including intensification, overgrazing, monocultures, overcultivation of semi-arid land and irrigation. Clear felling great areas of forest leaves the soil open to the weather with little holding the soil in place. This can lead to increased nutrient run-o_ from the soil and loss of top soil. This sediment enters water bodies and cause eutrophication. In tropical areas, most of the minerals are actually present in the biomass of the organisms, rather than the soil due to the fast cycling of mineral nutrients. This means that the exposed soil after deforestation can be quickly exhausted of any of its fertility and doesn't make good agricultural land. Another problem in tropical areas is that the heavy rains can leach the minerals from the top soil horizons into the lower soil horizons, resulting again with infertile soil as plant roots can't reach the minerals they need. Emergent properties from complex systems are visible in deforestation. Rainforests ‘short-circuit’ the water cycle by rapidly releasing back into atmospheric storage up to 90% of the precipitation it receives by means of evapotranspiration. Some of the desertification around the Sahel in West Africa is believed to be associated with clearance of tropical rainforest upwind along the west coast of Africa in Cameroon and the Ivory Coast. Over-grazing has occurred with a decrease in nomadic activity and increasing pressure on available grazing land. Once over- grazing starts, the species composition of the grazing land changes, usually for the worse. Palatable and nutritious plants disappear because they are over-grazed, and they are replaced by more hardy but unpalatable plants; as pressure builds on grazing land the amount of bare ground - occupied by sand dunes - increases. Large areas of bare ground begin to appear, often first around villages and watering holes. Sheep, goats and cows tend to graze within 5-6 km of accessible water, so overgrazing is concentrated initially around water sources. This over-grazing results in bare ground and thus the exposure of soil to rainfall and wind with soil being washed or blown away. This further degrades the land and can lead to desertification. The idea with urbanisation is simple, as more and more land is covered by human settlements, there is less land (and thus soil) to provide ecosystem services. As land is covered by cement, asphalt and buildings, water isn't able to infiltrate the soil, gases such as oxygen aren't able to di_use into the soil to provide microorganisms with oxygen and there is no more cycling of minerals in the soil. It is thought that the eleven ancient civilisations in Mesopotamia crashed due to the gradual salinisation of the soil through irrigation practices. As water evaporates in hot climates it can leave a salty residue on the soil. This tends to be a problem in semi-arid areas of the world including parts of California and the Mid-East of the United States, Central Asia, the bordering areas of the Sahara region of Africa, Northern China and Australia. Growing the same crop over large areas of land for repeated years means that the same minerals are always being taken from the soil. Farmers try to replace these using inorganic fertilisers. Another consequence of growing the same crop over large areas is the selective advantage pest species have and their ability to exploit this abundance of food. This results in farmers using large amounts of pesticides to combat the pest species. The poor maintenance of soil can lead to the loss of resilience in the soil system and the ability of the soil to self-regulate and provide nutrient cycling. This can result in the build up of toxic levels of some elements such as Aluminium and other salts. This is called toxification. Over-cultivation of marginal arid lands, particularly where population levels and densities have increased sharply in the 20th century, has led to desertification. It is not as widespread as overgrazing but often arises partly due to the introduction of mechanised machinery, such as tractors and disc ploughs, which can destroy native perennial vegetation and encourage soil degradation and desertification. Once this happens wind erosion occurs and valuable topsoil can be blown away, leaving infertile, dry soil behind. 6. Evaluate the soil management strategies of a given commercial farming system and of a given subsistence farming system. Iowa intensive corn production does not have grear soil management strategies. The soil is left exposed after harvesting for long periods of time, there are heavy inputs of inorganic fertilers, pesticides and genetically modifed seeds are used. There are no wind breaks or bu_er zones. The Zai technique used in Burkina Faso involves digging pits, filling them with dead plant material and animal manure and planting in these pits. The pits increase water infiltration and water holding capacity of the soil. They also encourage termites to visit the pits which increases the soil fertility and structure of the soil. Footnotes 1. ^ https://www.nhm.ac.uk/discover/soil-degradation.htm