Chapter 3 - Agriculture and the environment Flashcards
Describe the composition of soil
Soil contains mineral particles which is a combination of rock fragments and other inorganic substances formed due to physical, chemical and biological weathering of the parent rock.
Organic content is a mixture of living plants, animals, microorganisms and their dead remains.
Air is held within the pore spaces and enters the soil by diffusion.
Water is held within the pore spaces and is available for plant growth. Water enters the soil through precipitation or irrigation.
What are the characteristics of the mineral particle sand?
Sand is 2.0-0.02mm in size. It has a gritty texture, large pore sizes, drains well and contains large air spaces.
What are the characteristics of the mineral particle silt?
Silt is 0.02-0.002mm in size. It feels sticky or soapy, has less friction than sand and has slippery particles.
What are the characteristics of the mineral particle clay?
Clay is 0.002mm in size. It feels sticky when wet, particles are held tightly together, has small air spaces, poor drainage and forms a hard mass when dried.
What four factors soils require for successful plant growth?
Soils are a medium for plant growth. They require a combination of factors to grow successfully including the availability of important mineral nutrients to support plant growth, anchorage to hod the roots securely in one place and a supply of water and oxygen around the root to allow the cells to respire.
Describe soils as a medium for plant growth
Soils provide plants with nitrogen as nitrate ions and phosphorus as phosphate ions. The organic content of the soil is important because it helps the soil to retain water.
What are some examples of mineral ions?
Nitrate ions are supplied as NO3-, phosphorus is supplied as phosphate ions, PO43-, and potassium is supplied as potassium ions, K+.
What is organic content and what are its benefits to soil?
Organic content is a combination of living organisms and their dead remains. It increases the water holding capacity of a well-drained soil, increases the air spaces in the soil, increases the number of decomposing organisms and prevents the loss of mineral nutrients.
How does soil pH affect plant growth?
Soil pH can vary depending on the type of parent rock and the pH of water that flows into the area. It affects the uptake of nutrients by plant roots and the availability of nutrients.
What are some characteristics of sandy soils?
Sandy soils have large pore spaces for draining, low water holding capacity, quickly warms up, easy to cultivate, poor retention of nutrients and a greater risk of erosion.
What are some characteristics of clay soils?
Clay soils have a high-water holding capacity, slow to warm up, small air spaces, water does not drain away easily, hard to cultivate and retains nutrients well.
What is subsistence agriculture?
Subsistence agriculture is the cultivation and production of food to meet the needs of the farmers and their families. There is very little surplus food; if there is any surplus it is often bartered for other things the family may need.
What is commercial agriculture?
Commercial agriculture is the cultivation of products with the main focus of selling them for a profit.
What is arable farming?
Arable farming is the production of plants for consumption by humans.
What is pastoral farming?
Pastoral farming is the production of animal or animal-related products.
What is mixed farming?
Mixed farming is farming that does both rearing livestock and growing crops.
What is extensive production?
Extensive production occurs when there is a relatively small amount of production from a large area of land.
What is intensive production?
Intensive production occurs when large amounts are produced from small areas of land.
What are nine strategies to increase agricultural yields?
Crop rotation, fertilizers, irrigation, control of competing organisms, controlling pests and diseases, mechanization, selective breeding, genetically modified organisms and controlled environments.
How does crop rotation increase agricultural yield?
Crop rotation is the principle of growing different types of plants in different plots each year. This means that diseases in the soil affecting the plant are left behind and have nothing to infect, pests need to find the new site and so their numbers are reducing and the soil in the new plot is more likely to have the nutrients the crop needs.
How do fertilizers increase agricultural yield?
Fertilizers contain minerals such as nitrogen, potassium and phosphorus and can add to the amount of nutrients already present in the soil. Organic fertilizers use natural resources and supplies organic matter but is unpleasant to handle, harder to transport and varies in composition.
Inorganic fertilizers meet a particular need and are easier to store but have a high manufacturing cost and transportation costs. Inorganic fertilisers are quick acting can swiftly deal with deficiency problems but can easily leach out in heavy rain. Organic fertilisers are slow acting is long lasty so there is no need to reapply but there is little immediate impact if plants already have a deficiency problem.
How does irrigation increase agricultural yield?
Irrigation supplies water to the crops, is essential for cell activity, used in photosynthesis, and required for mineral uptake. However, the water needs to be free from pollution and low in salt.
Overhead sprinklers are easy to set up, can cover a large area from one sprinkler and you do not need to attach pipes to each plant, but large droplets may cap the soil, small droplets may be blown away by the wind and water that lands on leaves or the soil could evaporate quickly.
Clay pot irrigation uses simple technology, it is easy to check the amount of water, and it has a high efficiency, but it is only suitable for permanent plans and has a high labor cost.
Trickle drip irrigation places water at the base of the plant, automated and water is used efficiently but it can be expensive to install, complex to maintain, grit can block tubes, and it is difficult to move.
Flood irrigation is cheap and can cover large areas of land quickly but is an inefficient use of water and damages the structure of the soil.
How does controlling competing organisms increase agricultural yield?
Control of competing organisms using herbicides which are chemicals used to control weeds. Weeds need to be controlled because they compete with crops for water, light and nutrients, reduce the quality of a seed or grain crop, may be poisonous, make cultivation difficult, can block drainage systems with excessive growth, can be a source of pests and diseases that also attack the crop and look untidy. Herbicides are easy to manage, more effective than alternatives, cheaper, more predictable results, less labor needed, and the effect is more rapid.
How does controlling pests and diseases increase agricultural yield?
Controlling pests and diseases using insecticides which are chemicals that kill insects. Fungicide are chemicals used to control fungal diseases. Biological control leaves no chemical residue on the crop, doesn’t impact the surrounding ecosystem, no need for reapplication, naturally reduce the number of predators and there is no need for protective clothing, however biological control is not as instant as chemical control, climate conditions could affect it, the predator may move elsewhere, and the predator could escape and impact the natural ecosystem.
How does mechanization increase agricultural yield?
Mechanization means using machines such as tractors to cultivate larger areas of land, reduced labor costs, ploughing can be done in any conditions and additional attachments can be done to apply fertilizers and pesticides.
How does selective breeding increase agricultural yield?
Selective breeding is choosing the parents that exhibit the desired characteristics of the species, breeding those parents together and then selecting the best offspring that shows the desired characteristics and repeating the process until the whole population shows the desired characteristics.
How does using genetically modified organisms increase agricultural yield?
Genetically modified organisms are organisms whose genetic material has been altered by genetic engineering. Advantages of genetic engineering include disease and pest resistance, nourishing value, growth of plants in inhospitable areas, higher yields, herbicide resistance, less use of pesticides and crops with longer lives. However, disadvantages include unknown impacts on human health, unnatural products, genes may get into wild plants if they breed with genetically modified plants and there could be issues for other insects cause by insect resistant varieties.
How does using controlled environments increase agricultural yield?
Controlled environments could include the use of greenhouses or hydroponics, providing shade for cattle, using windbreaks at the edges of crops and removing trees that shade a crop in order to maximize the light the plants receive. Advantages of hydroponics include no need for soil, can be used anywhere, an intensive system that produces high yields, easy to harvest, plants are given exactly the nutrients they need in the irrigation water, water is efficiently recycled, no weeds or pests and pollutants are not released into the environment. However, disadvantages include being costly, only suitable in small production areas, requires a lot of technical knowledge, disease could spread rapidly through the water and plants could die if conditions are not maintained at optimum levels.
What are seven impacts of agriculture?
Overuse of insecticides and herbicides, overuse of fertilizers, misuse of irrigation, overproduction of waste, exhaustion of mineral ion content, soil erosion and cash crops replacing food crops.
What is overuse of insecticides and herbicides and how do you prevent it?
Overuse of insecticides and herbicides can cause resistance withing the pest population. To overcome this, you could use a range of different pesticides to ensure unwanted organisms do not build up resistance. Insecticides and herbicides can kill beneficial insects such as bees, cause spray drift, disrupt the growth of other plants, or be leached into rivers and lakes by heavy rainfall.
What is overuse of fertilizers and how do you prevent it?
Overuse of fertilizers causes the addition of extra mineral nutrients, and it is a waste of money and resources because the soil has reached its maximum capacity, heavy rain can dissolve the nutrients and cause nutrients to be leached into nearby waterways which would in return cause eutrophication, large quantities of fertilizer can affect the pH of the soil which would impact the organisms living there and impacting the plants ability to take up nutrients, too many ‘trace elements’ can be toxic towards plants, can reduce the amount of osmosis done by plants. To overcome this, you can set limits on when, where and how the fertilizers are applied or switch to organic fertilizers.
What is misuse of irrigation?
Misuse of irrigation can damage the soil structure by causing soil compaction, cause the death of plant roots as cells cannot respire, leaching of dissolved nutrients, soil erosion, soil capping, prevention of soil cultivation and salinization as the salt content increases as extra water is evaporated and poor management of soil can lead to desertification.
What is overproduction of waste?
Overproduction of waste occurs if too much of a crop is produced but some is not sold, waste of storage space if the crop is taking too long to sell and needs to be stored, waste of transportation to sell a crop at farther distances, waste of quality produce if it has not been sold at an optimal time and it depreciates in value or waste of labor if the crop is not optimal or if not enough has been produced.
What is exhaustion of mineral ion content and how do you prevent it?
Exhaustion of mineral ion content because the farmers use the soil over and over again with little to no rest which leaves the soil depleted of nutrients and minerals. To solve this farmers could use crop rotation, mixed cropping or leaving the land to replete its nutrients.
What is soil erosion?
Soil erosion from overcultivation which leads to a loss in soil structure, and it is more vulnerable to erosion as they break down into smaller particles.
What is cash crops replacing food crops?
Cash crops replacing food crops because most commercial farmers prefer to grow crops that generate more cash. This causes a decline in the stable food available.
What are five causes of soil erosion?
Removal of natural vegetation, over cultivation, over grazing, water erosion and wind erosion.
How does the removal of natural vegetation cause soil erosion?
Removal of natural vegetation as the roots of existing plants that help to bind the soil together are removed, the soil structure is not strong enough to withstand intense rainfall. Flash flood and other rainwater runoff picks up topsoil in its path and moves it away from its original location. When vegetation is removed, there may be nothing left to prevent run off and soil erosion.
How does over cultivation cause soil erosion?
Over cultivation leads to the loss of soil structure. Ploughing or digging breaks up larger clumps into smaller amounts which are easier to move and more vulnerable to soil erosion.
How does over grazing cause soil erosion?
Over grazing can reduce the vegetation to the ground level. Constant hard grazing weakens the plants because they do not have sufficient foliage to photosynthesize, and therefore gradually die out. Lack of vegetation cover means that there are no longer plant roots to hold the soil together and so the soil becomes vulnerable to erosion.
How does water erosion cause soil erosion?
Water erosion can come from heavy rainfall which dislodges soil particles with their force, and they are loose enough to be eroded in other ways, rainwater runoff has excess water that cannot be absorbed by the soil that will transport soil away from the area. Water infiltration may also be reduced if the soil surface has been capped or compacted by machinery.
How does wind erosion cause soil erosion?
Wind erosion can erode soil particles after natural vegetation has been removed. Vegetation may be removed for arable crops, the need for more space or room for machines to operate efficiently.
What are five impacts of soil erosion?
The loss of habitats, desertification, silting of rivers, displacement of people and malnutrition and famine.
What is the loss of habitat and how is it caused by soil erosion?
Loss of habitats due to the loss of topsoil, any organisms that live or breed within the topsoil with lose their habitat. Animals supported by local vegetation have fewer sources of shelter and food.
What is desertification and how is it caused by soil erosion?
Desertification means that soil is no longer adequate to support the growth of plants. This will have an impact on the raising of crops and the rearing of livestock who feed on plant material.
What is silting of rivers and how is it caused by soil erosion?
Silting of rivers can form small lagoons, which provides new breeding opportunities for insects such as mosquitoes, a vector of malaria. Silt can also affect the quality and availability of water for drinking.
What is displacement of people and how is it caused by soil erosion?
Displacement of people due to a loss of farmland for food and animals which could reduce their main source of income, thus having to relocate to have another job.
What is malnutrition and famine and how is it caused by soil erosion?
Malnutrition is not having enough of the correct nutrients to eat, causing ill health and famine is a lack of access to food, often over a large area. These can arise due to the loss of a reliable food source. Foraging for food and fuel can also further have a negative impact on the natural vegetation in the new area as well.
What are ten ways to manage soil erosion?
Terracing, contour ploughing, bunds, wind breaks, maintaining crop cover, addition of organic matter to improve soil structure, planting trees, mixed cropping, intercropping and crop rotation.
How does terracing help to manage soil erosion?
Terracing changes the shape of the hillside and slows down the volume of water running down the hillside due to gravity. Without terracing, the high volume of water at high speeds would dislodge the soil, which is then carried within the surface run off. Terracing is often used for the cultivation of rice, using the pools of water formed to grow plants in.
Adding fertilisers is one technique used to increase the yield of maize. Identify two other techniques that this farmer is using to increase the yield of maize. Only identify techniques shown in the photograph (2)
irrigation ;
wide spacing of crops ;
weeds have been removed ;
crops grown on a slope facing the sun plants not shaded/ open site ;
taller crops shelter other crops / shelter belt ;
Describe the activity that has happened in this part of the forest (1)
land clearance / harvest of wood / slash and burn / trees cut down ;
Explain why there is a risk of soil erosion in this part of the forest (2)
no vegetation to protect soil / less interception;
so more rain hits soil surface;
increased run off;
fewer roots to bind the soil;
increased wind erosion / fewer wind breaks;
Describe the impact on the environment if a soil has a reading of 53mg/kg for nitrate ions (3)
run-off / leaching;
nutrient enrichment;
algae blooms;
eutrophication;
changes pH of water;
Explain why it is not possible to grow crops at Halley scientific research station in Antarctica (4)
lack of sunlight;
(extreme) cold;
no, rain / precipitation;
water trapped as ice / no available water;
prevents photosynthesis;
built on ice / no soil / ground frozen;
Suggest four strategies that these farmers could use to reduce soil erosion (4)
build terraces;
build bunds;
use wind breaks;
add organic matter to the soil;
control irrigation / control drainage;
vegetation to reduce bare soil;
use contour ploughing;
Explain why the climate of Spain is suitable for growing vegetables (3)
hot / warm / high temperatures (for growth);
high rainfall (for growth);
(conditions suitable for) photosynthesis / stated equation / to produce glucose;
irrigation / water can be stored;
Use the photograph to explain why some farmers use bunds (2)
to hold / capture / store water / keep( in the field);
to collect surface run-off; / rainwater;
irrigation/ to increase water infiltration / absorption;
to prevent soil erosion / plant / minerals being washed away;
Describe how the bund in the photograph is constructed (1)
idea of raising up the soil e.g. ridge / line / mound;
built along contour lines;
Suggest why the prickly pear cactus spread so rapidly in Australia (2)
no natural predators;
no natural diseases;
favourable environmental conditions, e.g. temperature;
resistant to other methods of control;
out-competed other plants;
Suggest the impact of the prickly pear cactus on the farmlands of Australia (2)
destruction of farmland;
reduction in crop yield;
lack of grazing land for animals;
reduction in profit;
cost of trying to control;
Use the photograph to explain why this is an example of good agricultural practice (3)
terraced fields;
trees / vegetation hold soil / prevent erosion;
prevent soil erosion;
maintain fertility;
irrigation used;
by gravity / without need for pumps / using bunds / walls;
bunds / walls used;
prevent (wind) erosion / help, shelter trees / vegetation;
