Agriculture

mineral particles

(Soil composition)

combination of rock fragments and other inorganic substances

They are formed due to physical, chemical and biological weathering of the parent rock.

organic content

(Soil composition)

mixture of living plants, animals, microorganisms and their dead remains.

Air

(Soil composition)

held within the pore spaces (between the mineral particles and organic content).

enters the soil by diffusion

Water

(soil composition)

held within the pore spaces (water that is available for plant growth).

enters the soil when there's precipitation or when the soil is irrigated.

Sand

Gritty soil (2.0-0.2mm)

Silt

Silky or soapy soil (0.02-0.002mm)

Clay

Sticky when wet and hard when dried soil (

soil

is the cheapest and most abundant medium in which water, mineral nutrients, anchorage and oxygen can be supplied to a plant.

Plants

\________ require a supply of nitrogen, phosphorus, potassium and a range of other elements to construct proteins and carry out life processes.

Nitrogen

Nitrate ions (NO3-)

Phosphorus

Phosphate ions (PO43-)

Potassium

Potassium ions (K+)

organic content

decomposers that produce humus (rich in nutrients):

Earthworms

break down vegetation; mix the soil; aerate the soil; spread organic matter through the soil.

Fungi

feed directly on dead matter; digest hard woody items; aid plants to take up nutrients through their roots.

Bacteria

work on organic matter; convert waste products to simple chemicals; some convert nitrogen to nitrates ؞ important in nitrogen cycle.

High levels of organic matter

Increase the water-holding capacity (like a sponge);

Increase air spaces in the soil;

Increase no. of decomposers, tunnels and burrows in the soil, providing additional drainage and less compaction;

Prevent the loss of mineral nutrients (humus holds on to mineral nutrients).

High level of soil pH

Depends on the type of parent rock and pH of water that flows into the area;

Affects the uptake of nutrients by plant roots;

Affects the availability of nutrients;

Farmers can try changing the pH of the soil either to acidify it (using fertilisers that have an acidic effect) or make it alkaline (adding ground limestone).

Sand

Larger air spaces

Drains well

Poor retention of humus

Easier to cultivate

clay

Poor air spaces

Poor drainage

Retains humus

Hard to cultivate

Drainage

capacity of the soil to drain water must be medium (no water loss; no surplus amount of water).

Cultivation

how easily the soil can be ploughed

subsistence argiculture

agriculture practice where agriculture is produced all or almost sll the goods a family needs, with litter left over to sell

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Cultivation of food to meet the needs of the farmers and their families;

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Surplus is bartered for other goods (or cash).

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Examples: wheat and rice

Commercial Argiculture

Agriculture undertaken primarily to generate products for sale off the farm.

Cultivation of food with the main aim of selling them for cash;

me food may be used by the farmers.

Examples: tea, coffee, cocoa, sugarcane, cotton, rice, wheat and corn.

Arable agriculture

Production of plants for consumption by humans.

Examples: rice, wheat, maize and soybeans.

Pastoral agriculture

Production of animals or animal-related products.

Examples: grass/grain (to feed the animals), milk, wool eggs.

crop rotation

The practice of rotating use of different fields from crop to crop each year, to avoid exhausting the soil. oh

lagumes

have nitrogen-fixing bacteria in their root nodules

leafy crops

vegetables that are required for their leaves (require a lot of nitrogen left by legumes

Root crops

have deep root systems

fallow

the land is ploughed but left barren for a period to restore soil fertility and to avoid surplus production.

Advantages of Crop Rotation

Diseases in the soil affecting the plant are left behind;

Pests need to find a new site ؞ their population is reduced;

The soil in the new plot is likely to have the essential nutrients;

Crops ready to harvest at different times ؞ less potential waste, less labour and machinery needed.

Fertilisers

contain minerals such as nitrogen, potassium and phosphorus. Add on to the nutrients available in the soil.

irrigation

A way of supplying water to an area of land

Pest

an animal that attacks or feeds upon a crop plant.

Pesticides

used to control pests.

Weed control

weed-killing chemicals are known as herbicides.

Greenhouse

used to manage the environment for plant growth.

hydroponics

growing plants without soil, with the nutrients the plant needs dissolved in water

spray drift

off target movement of a pesticide during a liquid application

herbicides stay longer in the soil and may affect the next crop.

soil capping

surface of the soil becomes hard.

Salinization

A process in which mineral salts accumulate in the soil, killing plants; occurs when soils in dry climates are irrigated profusely.

salt content of the soil can increase

Overproduction

waste from the unsold proportion of the crop.

Storage space

Waste of may take longer to sell a crop; some crops need special conditions.

transportation

Waste of to sell a crop, a farmer may need to travel longer distances.

Mineral ion content

Exhaustion of The farmers use the soil over and over again with little to no rest which leaves the soil depleted of nutrients and minerals.

Solution: crop rotation, mixed cropping and leaving the land fallow.

overcultivation

soils that are cultivated regularly lose soil structure and are more vulnerable to erosion as they break down to smaller particles.

cash crop

a readily salable crop that is grown and gathered for the market (as vegetables or cotton or tobacco)

removal of vegetation

(Causes of 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

overcultivation

(Causes of soil erosion)

ploughing breaks the soil into smaller and lighter particles. These are more easily carried away by wind.

overgazing

(Causes of soil erosion)

livestock reduces the vegetation to nearly ground level, sometimes leaving no roots to hold the soil.

Animals trample down the plants and their hoofs compact the ground

wind erosion

(Causes of 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.

water erosion

(Causes of soil erosion)

heavy rainfall carries the particles away.

Excess run-off water that can't be absorbed by soil transports the soil from that area;

Soil compaction reduces infiltration;

Gully erosion (volume of water erodes local soil further) forms deeper and deeper crevice

Topsoil removed

(Impacts of soil erosion)

the most productive layer is absent (subsoil lacks in nutrients ad air spaces).

flooding

occurs as water bodies can't hold excess water (space taken up by silt).

gully erosion

removal of layers of soil, creating channels or ravines too large to be removed by normal tillage operations

Desertification

the process by which fertile land becomes desert, typically as a result of drought, deforestation, or inappropriate agriculture.

famine

extreme scarcity of food

Terracing

prevents the erosion of soil by rainwater on steep slopes.

Natural slope

water runs down, increasing in speed and volume, carrying soil in the run-off.

Terraced slope

water is held in the flat terraced areas, causing less risk of run-off and more chance of infiltration.

Often used for cultivation of rice.

Contour ploughing

A method of ploughing parallel to the contours rather than up or down a slope. It is used to check soil erosion and the formation of gullies.

Bunds

artificial banks at the edges of growing spaces to hold back water.Useful for crops that require moist soils e.g. rice.

The water is retained on the terrace.

Increases the quantity and fertility of the soil.

Windbreaks

Rows of large trees or bushes planted between fields to help block the wind and prevent soil erosion.

no-dig method

Method that Existing vegetation is left until the new crop is grown.

mixed cropping

planting a variety of crops in the same field

Intercropping

An agricultural method in which two or more crop species are planted in the same field at the same time to promote a synergistic interaction.

Disadvantages of organic fertilisers

Are slow acting reduces the risk of eutrophication

Are a waste product reduces them saves on disposal costs;

grazing

Eating the whole plant (above ground parts)

rainwater harvesting

the collection of rainwater, for example from the roofs of buildings, and its storage in a tank or reservoir for later use.

Are a waste product ؞

Are already present on many farms minimal transport costs;

Do not require energy for their manufacture;

Also improve soil structure.