Unit 3.1-3.5 - Agriculture

Key Words + Topics

Soil

Soil

a habitat for plants and other organisms that grow within it

What is Soil made up of?

1. Mineral Particles (Rock fragments + Smaller inorganic items)

2. Organic Content (Living plants & animals + Dead Remains)

3. Air

4. Water

Weathering

The process that causes rocks to be broken down into smaller pieces/The erosion of the parent rock (rock underlying the soil)

1. Physical Weathering: caused by frost, heat, water, ice, wind

2. Chemical Weathering: caused by chemical reactions such as acid rain

3. Biological Weathering: caused by natural processes such as the movement of animals, the organisms in the soil, growth of plant roots into cracks of rocks

Diffusion

the process of movement of a substance to spread evenly

Types of Soil Particles

1. Sand

   • Largest mineral component of soil

   • Don’t compact easily due to its size and irregular shape => large pores => allows water, air and organisms to move through

2. Slit

   • Smaller than sand

   • Slip over each other easily

3. Clay

   • Smallest mineral component

   • Packs closely together due to its small size => reduces ability for water + air to pass through

Factors for Successful Plant Growth

1. Availability of important mineral nutrients to support plant growth

2. Anchorage to hold the roots securely in place in the soil

3. A supply of water

4. Oxygen around the roots to enable the root cels to respire

aka what’s needed for photosynthesis

Mineral Ions

• Plants require these to photosynthesise

• Usually absorbed through the roots of the plant

• Nitrogen —> Nitrate Ions

• Phosphorous —> Phosphate Ions

• Potassium —> Potassium Ions

Soil pH Level

• Affects how much nutrients are taken up by the plants’ roots even if there isn’t a problem with the supply

• Affects the availability of mineral nutrients within the soil

• Helps farmers maximise their yield

More on the Organic Content of Soil

Types of Decomposers

1. Earthworms

2. Fungi

3. Bacteria

Benefits:

1. Increased water-holding capacity => less irrigation needed

2. Increased air spaces in soil => more oxygen in soil => respiration

3. Prevents loss of mineral nutrients

Sandy Soils vs. Clay Soils

Air content

1. Clay —> small air spaces => limit amount of oxygen reaching roots => limits respiration & root growth

2. Sand —> large air gaps => good levels of oxygen => healthy roots

Water Contents

1. Clay —> more particles => larger surface area => holds more water

2. Sand —> less particles => water flows through not absorbed

Loam

a soil that is a mixture of sand, silt and clay

Common Signs of Nutrient Deficiencies

1. Nitrogen —> Slowed growth, yellowing leaves

2. Phosphorus —> Leaves dull with blue-green color, leaves fall early

3. Potassium —> Poor quality fruits & seeds, leaves with brown edges

Susistence Farming

the production of food to meet the needs of farmers and their families

Commercial Farming

the production of food for profit, usually done at a larger scale

Arable Farming

the production of plants, could be subsistence or commercial

Pastoral/Lifestock Farming

the production of animals or animal-related products

Mixed Farming

the production of plants AND animals

Extensive Production

low production from large area of land

Intensive Production

high output from small area of land (usually has high costs due to the eed of machinery, fertilisers and ways to make production more efficient)

Crop Rotation

growing different types of plants in different plots each year

• The Types of plants

  1. Legumes: plants that are able to fix nitrogen from the ar using bacteria in their roots to produce a source of nitrates

  2. Leafy Crops: require a lot of nitrogen fertiliser which the legumes provide and they grow in a plot after the legumes (usually)

  3. Root Crops: crops which have deep root systems which help break up soil but also require a lot of cultivation to harvest which supports the growth of future legumes

  4. Fallow: no crops are grown and the land is left to rest

Fertilisers

Organic: derived from natural sources such as animal manure, composted plant materials, bone meal, dried blood, etc.

Inorganic: manufactured within factories and formulated specially for each plant

Trace Elements

a larger selection of nutrients that are needed in relatively tiny amounts compared to NPK (like zinc, iron, boron)

Irrigation

1. Overhead Sprinkler System: a special sprinkler nozzle forces water out under pressure in droplets on top of crops

2. Clay Pot System: porous clay pots are buried in the soil next to the roots of the plants and each pot is filled with water which slowly seeps int the soil around the roots

3. Trickle Drip Systems/Leaky Pipes: a series of flat polythene hoses are laid on the surface of the soil between the rows of crops, water can be transported to these hoses through pipes and released slowly at the soil surface via tiny holes in the hoses

4. Flood Irrigation: water is delivered to the field by a soil channel or pipe allowed to flow freely in the ground through the crops

Weeds

plants growing in an inappropriate place, usually grows excessively

Competing Organisms

organisms which compete with plants for nutrients and water by feeding on, weakening and killing plants

Herbicides

used to completely clear uncultivated areas before sowing or planting crops, can also be used selectively to kill weeds growing among crops

• Herbicide Granules: herbicides but heavier and dissolve in water in the soil rather than by the leaves

Pests

animals that attack or feed upon the crop plants

Crop Diseases

pathogens (fungi, bacteria, viruses) that attack the plant

Chemical Control of Pests + Diseases

Pests —> Pesticides, Insecticides

Diseases —> Fungicides

Biological Control of Pests

using natural predators to feed on pests (i.e. ladybugs)

Selective Breeding

the traditional method used for improving the performance of crops & livestock by breeding the parents with the best charactersitics

Genetic Modification

Mapping the DNA of different organisms to understand their genetic code which can help inserting DNA from one organism to another (the end product called genetically modified organisms (GMO))

Greenhouses

structures that support the controlled growth of plants

Hydropnics

Growing plants without soil by floating plants on polystyrene rafts on a reservoir of water

Impacts of the Overuse of Insecticides and Herbicides

1. Pests and weeds start to grow resistance towards the same brand

2. Potentially kills beneficial insects

3. Impacts the food web

4. Spray drift (chemicals reaching an unintended target)

Solution: Changing the brand of insecticides and herbicides or using more biological control

Impacts of the Misuse of Fertilisers

1. Certain weather conditions could waste fertilisers (i.e. rain + dry conditions)

2. Eutrophication

3. Altered pH levels => affects other plants’ ability to absorb nutrients + affects the availability of nutrients

4. Affects the plants’ ability to take up water (osmosis) due to the increased concentration of solutes in the soil => water to flow out of the plant => dehydrates plant (scorching)

5. Could lead to lush growth (plants growths too fast and can’t support itself) => less likely to flower + more foliage => less sunlight absorbed + more energy used

Osmosis

the process by which mineral molecules pass through a semi-permeable membrane from a waker solution to a more concentrated solution to make the concentration of the mineral the same on both sides of the membrane

Impacts of the Misuse of irrigation

1. Damage to soil structure because there’s less air pockets => waterlogged soil

2. Death of plant roots because there’s not even oxygen

3. Loss of nutrients

4. Soil capping (top soil to become more compact and hard => hard for plants to grow through soil)

5. Soil Erosion

6. Salinisation (salts dissolve in water => sun evaporates water => leaves salt left in soil => too much salt in soil => hard to do osmosis since membrane is blocked => no water going up to the plant => plant unable to do photosynthesis)

7. Preventing Soil Cultivation because the soil is too heavy to cultivate, especially for machinery

8. Desertification

Impacts of Overproduction & Waste of Crops

1. Over-production —> excess crops not sold and burned in waste dumps

2. Storage Space —> Fossil Fuels used as power source

3. Transportation —> Fuel to transport goods

4. Quality Produce —> Decrease in quality when stored in storage space => decrease in price => unprofitable => wasted

5. Waste of Labour —> Not an efficient use of time and effort

Impacts of Mechanisation

1. The need for larger fields => loss of vegetation => loss of habitats + loss of natural predators

2. Fossil Fuels => Pollution

3. High pressure on soil => more compact soil => reduce root growth + reduce drainage of soil

4. Takes jobs away