3 - Agriculture and the Environment

Describe the composition of soils

Most of it (45%) is mineral particles, with a little less (25% each) of air and water and 5% of organic matter

What makes up the mineral particles in soil?

This is a combination of rock fragments and other inorganic substances, formed due to chemical, physical and biological weathering of the parent rock

What makes up the organic content in soil?

Mixture of living plants, animals, microorganisms and their dead remains

Where is air in soil?

Air is help within pore spaces between mineral particles and organic content - air enters the soil by diffusion

Where is water in the soil?

Water that is available for plant growth is held within pore spaces, and it enters the soil when there precipitation or irrigation

What does the proportion of the components of soil depend on?

Type of soil, way it's been managed, local climatic conditions and the size of mineral particles

What are the 3 groups soil can be classified into?

Sand, silt and clay

Compare sand, silt and clay

Clay has the smallest particles, followed by silt then sand with the largest - sand is gritty, silt is silky or soapy and clay is sticky when wet but hard when dried

Why are soils useful to plants?

Soils are a medium for plant growth as its cheap and abundant and water, mineral nutrients an oxygen can be supplied easily - it has a good supply of the minerals a plant needs, such as nitrogen, phosphorus and potassium and has lots of organic content, and the right pH for plant growth

How is soil good for plants in terms of mineral content?

Plants need nitrogen (NO3- ), phosphorus (PO43-) and potassium (K+) to construct proteins and carry out life processes, and soils have an abundant supply of all of these

How is soil good for plants in terms of organic content?

Theres lots of decomposers that produce nutrient rich humus, such as earthworms (break don negation, mic soil and spread organic matter, fungi (feed on dead matter and hard woody items and aid plants to take up nutrients through root), and bacteria (work on organic matter and convert waste to simple chemicals)

How does high levels of organic matter make soil better?

They increase water holding capacity, increase air spaces and the number of decomposers, tunnels and burrows in the soil, providing additional drainage and less compaction and prevent the loss of mineral nutrients

How does soil pH help plants?

Soil pH depends on the type of paint rock and pH of water that flows into that area - it affects the uptake of nutrients by plant roots and the availability of nutrients

Describe the differences in air content between sands and clay soil

Clay soils have small air gaps, limiting oxygen reaching plants and therefore respiration - sandy soils have large air gaps

Describe the differences in water content between sands and clay soil

Clay soil has more particles, so a larger surface compared to sandy soils, so clay holds more water

Describe the differences in drainage between sands and clay soil

Sand drains well as there are large air spaces between particles, whilst clay has poor drainage

Describe the differences ease of cultivation between sands and clay soil

Sand is easier to cultivate as particles don't stick together easily, whilst clay is hard to cultivate, as it is sticky and wet after rain, dries and cracks after lots of sun and is heavy because of high water holding capacity

What are the types of farming based on the reason?

Subsistence and commercial

Describe subsistence farming

Its cultivation of the food to meet the needs of farmers and their families - surplus is set aside for other goods or cash - eg wheat and rice

Describe commercial farming

Cultivation of food with the main aim of selling them for cash - some for may be used by the farmers - examples include tea, coffee, cocoa, sugarcane, cotton, rice, wheat and corn

What are the types of farming based on the products made there?

Arable, pastoral and mixed

Describe arable farming

Production of plants for consumption by humans - eg rice, wheat, maize and soybeans

Describe pastoral farming

Production of animals or animal-related products - eg grass/grain (to feed the animals), milk, wool and eggs

Describe mixed farming

Farms that grow crops for food and rear animals

What are some techniques to increase agricultural yield

Rotation, fertiliser, irrigation, insect, weed and fungi control, mechanisation, selective breeding, genetically modified organisms and controlled environments

How does rotation work?

Crop rotation is the principle of growing different types of plants in different plots each year - for examples, legumes have nitrogen fixing bacteria, and when swapped by leafy crops, which require a lot of nitrogen, its advantageous

How does rotation increase agricultural yield?

Diseases in the soil affecting the plant are left behind and pests need to find a new site, so their population is reduced - the soil is likely to have essential nutrients and crops ready to harvest at different times, meaning theres less waste, labour and machinery

How do fertilisers increase agricultural yield?

Fertilisers contain minerals such as nitrogen, potassium and phosphorus, helping deficiency problems so plants can grow faster and better

How does irrigation increase agricultural yield?

Irrigation is supplying water to crops - this is essential as a large percentage of a plant is made of water, and its essential for cell activity and photosynthesis - mineral nutrient uptake requires water in the soil ax well, so it helps increase agricultural yield

What are some different organisms that need to be controlled in agriculture to increase agricultural yield?

Insect control, weed control and fungi control

How are insects bad for agriculture?

Insects are pests and attack or feed on crop plants - you can use insecticides or biol

How can you control insects?

Using insecticides (insect controlling chemicals) or biological control

How does biological control work?

Natural predators of the pest or insect is introduced to a crop, so they can feed off the pest and control the infestation

How can you control weeds?

With herbicide

Why should weeds by controlled?

They compete with crops for light, water and nutrients, reducing its quality and making cultivation difficult - they may be poisonous, a source of pests and diseases and look untidy

How does herbicide work?

They are weed killing chemicals which can be sprayed on weeds to kill them

What can be used to control fungi?

Fungi is a pathogen that can cause crop diseases, and can be controlled by fungicides

What is mechanisation?

Mechanisation is the use of machinery in farming, such as tractors

How does mechanisation increase agricultural yield?

This means a larger area can be cultivated, labour costs are reducing, ploughing can be done even when soil is heavy and additional attachments can be done to apply fertilisers and pesticides

What is selective breeding of animals and plants and how does this increase agricultural yield?

Choose parents that exhibit the desired characteristics of the species and raise offspring from these parents - select the best offspring that show the desired characteristics and repeat - this improves the performance of crops and livestock

How do Genetically Modified Organisms (GMO) work and increase agricultural yield?

This is when the DNA of 1 organism is inserted into another - this produces faster crop results, and gives them disease and pest resistance, nutritional value, growth in inhospitable areas, higher yield, herbicide resistance, less use of pesticides and crops with longer storage lives

What are some examples of controlled environments in agriculture?

Greenhouses and hydroponics

How do greenhouses work and increase agricultural yield?

They are structures that support the controlled growth of plants - this allows the farmer to control different environmental factors, such as temperature, light, humidity, day length and water using computer and equipment

How does hydroponics work and increase agricultural yield?

Hydroponics is a system that grows plants using just water and dissolved nutrients - oxygen is bubbled through for plants, ensuring theres are no limiting factors so the plants can grow faster and bigger - theres no need for soil and it can be done anywhere, and there are high yields with easy harvest

What are the impacts of the overuse of insecticides and herbicides on the environment and people?

Overusing some insecticides and herbicides can cause resistance from pests, and beneficial insects like bees are also affected and the food web is disturbed - herbicides can sometimes stay longer in soil and affect the next crop, or leach into nearby lakes when rainfall is heavy

What are the impacts of the overuse of fertilisers on the environment?

Heavy rain can dissolve nutrients and cause leaching, which can lead to eutrophication - large quantities can affect the pH of the soil and in turn the availability of minerals - too much fertilisers can be toxic to the plant and dehydrate it, and the imbalance of nutrients make the plant produce lots of foliage but no flower

What are the impacts of the overuse of fertilisers on people?

Addition of extra minerals is a waste of money and resources in the soil has reached its maximum level, and nitrates from fertilisers if consumed can cause diseases such as blue-baby syndrome

What does mismanagement of irrigation cause?

Salinization and water logging

How does mismanagement of irrigation cause water logging?

Too much irrigation causes water logging, damaging soil and compacting it - plant roots die due to lack of oxygen as the soil is waterlogged - theres also a loss of nutrients as they dissolve and wash away in water, with high levels of runoff causing soil erosion

How does mismanagement of irrigation cause salinisation?

Irrigation water soaks into soil, dissolving with salt - when water evaporates from the field, water and salts are drawn to the surface, but salt remains there and kills plant roots

What are the impacts of overproduction and waste on the environment and people?

Overproduction means many crops are unsold - extra crops waste storage space, so it takes longer to sell and some crops need special conditions - this also wastes transportation as farmers travel further to sell - low quality products also means low demand, and theres a waste of labour so its an inefficient use of time if too much is produced

What are the impacts of exhaustion of mineral ion content on the environment and people?

The farmers use soil over and over again with no rest, leaving the soil depleted of nutrients and minerals - this weakens soil structure and loss of habitat for soil dwelling organisms, and decreased agricultural productivity and nutritional deficiencies for humans consuming crops grown there

What are the impacts of soil erosion on the environment and people?

Soils that are cultivated regularly lose soil structure and are more vulnerable to erosion as they break down to smaller particles - this leads to loss of soil fertility and decreased biodiversity as there is habitat destruction - it can also cause loss of agricultural productivity and food insecurity for humans

What are the impacts of cash crops replacing food crops on the environment and people?

Most commercial farmers prefer to grow crops that generate more cash - this causes a decline in the staple food available.

What are some of the causes of soil erosion?

Removal of natural negation by over cultivation and overgrazing , and water and wind erosion

How does removal of natural vegetation cause soil erosion?

No more roots to bind the soil together, or slow down the torrents of water, so flash flooding and rainwater run off pick the soil and carry it away

How does over cultivation cause soil erosion?

Ploughing breaks soil into smaller and lighter particles, which are more easily carried away by wind

How does overgrazing cause soil erosion?

Livestock reduces vexation to nearly ground level, sometimes leaving no roots to hold the soill, and animals trample down on plants and compact the ground

How does water erosion cause soil erosion?

Excess run off water that cant be absorbed by soil and heavy rainfall carries soil particles away - soil compaction also reduces infiltration

How does wind erosion cause soil erosion?

Deforestation (due to need for space, excessive grazing, increase in development of arable crops) increases the chance of soil getting eroded by wind.

What are some of the impacts of soil erosion?

Loss of habitats, desertification, displacement of people, malnutrition and famine and silting of rivers.

How does soil erosion cause loss of habitats?

As soil is eroded, the topsoil is removed - this is the most productive layer as the subsoil lacks in nutrients and air spaces - as this is lost, organism living or feeding off the soil lose their habitat, which impacts the entire ecosystem

How does soil erosion cause desertification?

This is the process by which fertile land becomes desert - therefore the soil can no longer support the growth of plants, impacting both raising crops and rearing livestock

How does soil erosion cause displacement of people?

Soil erosion causes a decrease in the productivity of land, so locals are forced to relocate - droughts can even cause the migration of a whole community

How does soil erosion cause displacement of people?

Soil erosion means agricultural and livestock land can decrease in productivity, meaning less crops or having to relocate - this means its hard to find a reliable source of food until crops start growing again, risking famine and malnutrition.

How does soil erosion cause silting of rivers?

Flowing water carrying soil particles settle, silting water courses - this can lower the capacity of water bodies to hold water and cause flooding - its also a problem for bots as waterways become shallower - silt deposits can form small lagoons, providing breeding opportunities for mosquitoes, and can affect quality of drinking stare and the health of aquatic organisms

What are some strategies for managing and reducing soil erosion?

Terracing, contour ploughing, bunds, wind breaks, maintaining vegetation cover, addition of organic matter to improve soil structure, planting trees, mixed cropping, intercropping and crop rotation

How does terracing help reduce soil erosion?

Terracing prevents the erosion of soil by rainwater on steep slopes - in a natural slop, water runs down, increasing in speed and volume, carrying soil in the run off, but in terraced slopes, water is held in flat terraced areas, causing less risk of run off and more chance of infiltration

How does contour ploughing help reduce soil erosion?

Contour ploughing is ploughing of land along the contour in a parallel way - ridges and troughs run along the contour, each of them holding water and preventing large torrents of water from running down the slope, which prevents the formation of run off soil

How do bunds help reduce soil erosion?

Bunds are artificial banks at the edges of growing spaces to hold back water - this is useful for crops that require moist soils and increases the quantity and fertility of the soil

How do wind breaks help reduce soil erosion?

Wind breaks are a permeable barrier used t reduce the impact of wind on an area - without windbreaks, soil is eroded away - these permeable structures, like vegetation, allow wind to pass through, decreasing its speed, and thus the amount of wind erosion - this also creates additional habitats for beneficial insects and the roots of the windbreak prevent soil erosion due to runoff

How does maintaining vegetation cover help reduce soil erosion?

Cultivated soil is vulnerable to erosion when there is little to hold it together - by maintaining crop cover, which means planting additional plant along with crops, the roots of the ant bind the soil together as the anchor themselves to the ground

How does addition of organic matter to improve soil structure help reduce soil erosion?

It provides additional air gaps and increases decomposers in the soil so they feed on matter, which adds nutrients to the soil after decomposition - it also acts like a sponge, holding extra water and preventing oil dehydration and erosion of soil particles as the organic matter acts like a base for smaller particles

How does planting trees help reduce soil erosion?

A row of tres acts as a windbreak, and the tree canopy can provide shade for smaller plants that dont thrive for sunlight and a habitat for animals that feed on pests - leaves also fall to the ground, adding to the organic matter

How does mixed cropping help reduce soil erosion?

Mixed cropping, which is growing more than one type of plant in the same area means resources in the soil, like nutrients, are used more efficiently - the plants can the roots can also support eachother, holding the soil together

How does intercropping help reduce soil erosion?

Rows of a different crop are grown between the rows of the main crop - this maximises the use of space and other resources.

How does crop rotation help reduce soil erosion?

Planting different crops over successive years in the same plot of land reduces the incidence of pests, improving the quality of soil and making sure nutrients are utilised more effectively

What are some strategies for sustainable agriculture?

Organic fertiliser, such as crop residue and manure, managed grazing including livestock rotation, crop rotation, use of pest resistant and drought resistant varieties of crops, trickle drip irrigation and rainwater harvesting

How are organic fertilisers a strategy for sustainable agriculture?

Organic fertilisers, such as animal manure and composted crop remains - are slow acting reducing risk of eutrophication, are a waste product so it saves disposal costs, are already there on farms so less transport costs , don't require energy to manufacture and improve soil structure

How is managing grazing a strategy for sustainable agriculture?

This prevents overgrazing (when too much foliage is removed) and ensures sufficient grazing, and also allows farmers to maintain appropriate soil fertility by moving livestock between different fields so they fertilise them by animal waste, and good drainage, preventing compaction of soil

How is crop rotation a strategy for sustainable agriculture?

This is planned rotation of crops between different fields - this means less risk of pests + diseases, efficient use of cultivation techniques such as plants that need deep cultivation being sown after root crops, efficient use of fertilisers as plants leave minerals behind in soil, growing a range of crops so theres less oversupply, increasing crop success and providing a wider diet for the farmer

How is the use of pest resistant and drought resistant varieties of crops a strategy for sustainable agriculture?

This reduces pesticide use for pest resistant plants and the ability to combat other plant diseases where no other form exists, reduced irrigation for drought resistant plants, shorter cropping cycles and an extended harvesting season

How is the use of trickle drip irrigation a strategy for sustainable agriculture?

Trickle drip irrigation, which is delivering water to the base of plants using small pipes , is targeted delivery of water to plants, minimising the amount of water used and farmers have the ability to us the system only when plants need water - theres also automation, which reduces labour and a reduced risk of salinisation, as less water evaporates for the soil surface so soil is not drawn up

How is rainwater harvesting a strategy for sustainable agriculture?

This is collecting rainwater from buildings and hard standing areas so it can be stored in tanks and reservoirs until needed - its then pumped through an irrigation system - this is sustainable as it reduces water waste as the water is being reused