agriculture

Selective breading

Involves the production of offspring from parents that were chosen because of their genetic characteristics. Breeding between genetically similar individuals may produce offspring with similar characteristics but there is an increased risk of inbreeding.

Pros of selective breading

Enhances desirable traits.

Involved disease resistance

Cons of selective breeding

Reduced genetic variation

Inherited health problems

Control of genetics in plants

in natural asexual reproduction, the offspring develop from the parent plant rather than from seeds. Artificial asexual reproduction involves cutting where new plants are produced from sections of leaf, stem or root tissues from the parent plant

pros of controlling genetics in plants

Offspring are genetically identical to the parent plant so their characteristics are predictable. Survival rate is high

Cons of controlling genetics in plants

There is no genetic variation in offspring so there characteristics can’t be improved. Fewer offspring are produced than by sexual reproduction.

Control of genetics in animals

Cloning is an artificial asexual reproduction technique for livestock that is still being developed. The aim is to produce offspring that are genetically identical to a selected individuals will h desirable characteristics.

Pros of controlling genetics in animals

valuable animals that die can be replaced by genetically identical individuals

Large numbers of individuals can be produced

Cons of controlling genetics in animals

Health issues

Animal rights are violated

Expensive process

What is the food conversion rate equation

Mass input/ mass output

What is the energy ratio equation

Energy out in food/ energy gone into food

Principles of agriculture

1. Selection of species

2. Control of abiotic and biotic environmental factors to control production

3. Manipulation of the food species to improve productivity

The selection of species for agriculture

1. Market demand and access

2. Whether environmental conditions are within the range of tolerance of the food species.

3. Whether environmental conditions or the species adaptations can be controlled to improve productivity

Abiotic factors of agriculture and there controls (tempriture)

Temperature- including length of growing periods, frost free periods, thermoregulation

Controls include location of fields, such as low lying areas and south facing slopes in the northern hemisphere

Abiotic factors on agriculture and there controls (light)

Light- important for photosynthesis, milk production, poultry growth and some live stock mating seasons.

Controls- artificial light can be used to extend growing seasons

Abiotic factors on agriculture and there controls (water)

Water- used as a physiological solvent, used as support in cells and needed to transport minerals around the phloem in plants.

Some crops have higher water requirements such as rice which needs to be flooded during early growth.

Control- crop irrigation, soil mulching to reduce evaporation loss, reduction of soil compaction

Abiotic factors of agriculture and there controls (soil fertility)

Soil fertility- plants need a large amount of nutriance for growth, they are called macronutrients such as potassium and nitrogen. Fertile soil has good aeration and availability of nutrients and ideal texture

Controls- legumes can increase nitrogen content in soil. Organic fertilisers and DOM can increase nutrients and soil fertility

Fertiliser application

Organic fertilisers are animal and plant naturists that release nutrients as they decompose. Including: fecal material, animal food production waste, plant food production waste.

What is hydroponics?

Involves growth of crops in a nutrient solution rather that a solid growth medium. Usually carried out in greenhouses. Maximised by controlling limiting factors as much as possible.

Aeration

Uncompacted soils has larger spaces between the soil particles which increases aeration. Important as many soil processes are aerobic such as root respiration. Some processes that reduce aeration include soil compaction from machinery

Control of aeration

Ploughing aerates surface soil but not deeper layers, adding organic matter, low tillage methods, removing livestock reduces soil compaction

Soil salinity

Dissolved salts in soil water are essential for plant growth as they include soil nutrients but excessive salinity can kill plants by osmotic dehydration

Controls of soil salinity

Avoiding farming methods that increase salinity, includes irrigation with salty water .

Soil pH

All plant species have their own range of tolerance for pH. usually between 5 and 7. High pH can inhibit nutrient uptake. It can also mobilise toxic ions in the soil such as aluminium

Soil pH control

Can be increased by adding crushed lime

Can be decreased by spreading powders sulfur

Carbon dioxide concentration

Co2 concentration can be a limiting factor in rate of photosynthesis. It’s not practical to increase co2 for crops grown in fields but crops in greenhouses can have the concentration altered for the optimum photosynthesis rate.

Topography

The undulations of the land surface can affect its suitability for particular crops and the methods used.

Can include aspect, frost pockets, runoff rates, use of machinery.

Topography controls

Not practical to alter topography in areas of large land but can be possible in some areas. A steep gradient can be changed to a series of flat fuels by terracing. Usually done to retain irrigation and reduce soil erosion.

Relief

Altitude of an area can control other factors that affect the choice of species for cultivation e.g crops m- temperature are often colder at high altitude and evaporation rates increase

Livestock such as goats are adapted to survive at high altitude and survive better.

Wind velocity

High wind velocity can increase soil erosion especially in dry areas. Can increase evaporation rates and can damage crops by flattening them in strong winds

Biotic factors and there controls (pest control)

They are organisms that reduce productivity and quality of product. They can be predators that eat crops of livestock. Competition of resources. Carry pathogens. Spoil appearance of crops.

Pest groups and there effects

Weeds- compete for nutriance and light and can spoil taste of crops e.g wild oats

Insects- eat crops and reduce harvest e.g aphids

Fungi- cause growing plants to rot. E.g leaf smut of rice.

Endemic pests

Always present, usually small or moderate numbers.

Epidemic pests

Not normally present but they may be outbreaks where they rapidly become a major problem.

Indigenous pests

Native to the area that reduce productivity

Introduced pest

Not native, often more of an issue as they may not have natural predators

Cultural pest control

Involves non pesticide methods where crops or livestock are cultivated in a way that reduces the risk of pest damage

Crop rotation

Different crops often have their own unique pest species. If the same crop is grown in the same place in consecutive years then pests from the first year may survive until the second so pests are already present. Allows pests to increase population and cause more damage

Companion crops

Crops which if grown together will be more productive. Sometimes both corks will produce a harvestable crop. Nutrients supply such as legumes crops can increase nitrates. Barrier crops can deter insects such as onions mask smell of carrots reducing carrot root flys

Predator habitats

Population of natural predators can increase if there are suitable habitats supplied. Beetle banks and hedgerows are an example.

Biological control

Predators and pathogens can be introduced to front pests. This is useful for non indigenous species that has been introduced and has no Predators

Successful biological control

Cactoblastis moth used to reduce prickly pear cactus as it has no natural predators. Encarsia wasps control population of whitefly’s

Sterile male techniques

Exposing males to gamma radiation. They are then released and there genetic matirial is damaged so they can’t reproduce. The population will then decline. Example includes the screw worm fly.

Pheromone traps

Mates are attracted by a scent. Traps release an artificial scent that attracts pests and they can then be trapped. It can be used to show if a pest is present and used to kill pests.

Genetic resistance to Disease

Selective breeding may enhance the resistance of a variety of pest or disease. Pathogens evolve to overcome crop disease resistance so it’s necessary to regularly introduce new characteristics to maintain resistance

GM crops and pest control

DNA of crops can be modifier to control pests more effectively by reducing susceptibility to pests.

Pest control using chemical pesticides

Properties of pesticides influence their effectiveness and environmental impacts. Pesticides fan inhibit enzyme action in pests with high toxicity. Persistence pests are more stable so require pesticides to or applied more than once

antibiotics

Chemicals that kill microbes such as pathogenic bacteria. Can be used in livestock farming to treat infections and to prevent them. They can also be used to promote growth

Principles of Integrated control

-Use of techniques which make the growth environment less suitable for the pests. E.g maintaining habitats.

-cultivating species that are less likely to suffer pest attacks

-use of other appropriate non pesticide techniques

What is integrated control

Using a combination of techniques can maximise effective pest control while minimising environmental impacts.

Pollinators

Pollinator services can be aided in several ways: provision of food supplies by growing plants that provide nectar, for example a mix of flowering plants along side crops.

Restricting the use of pesticides that harm pollinators and introducing bee hives

Maintenance of soil biota

They are important for soil fertility and crop productivity. Especially detreviors and decomposers. Increase nutrient availability through the breakdown of DOM

Manipulation of food species

Crops and livestock cultivated can be manipulated through their population structure population density and genetics

optimum livestock/ crop density

Increasing the population density can increase the total yield, although yield per individual may be reduced due to inter species competition. High density can increase risk of rapid disease spread.

Monocultures

Involves cultivating a single species, often over a large area. This can make cultivation easier by allowing the use of larger machinery but pests and diseases can spread rapidly if they colonise the field.

Control of genetics- asexual reproduction plants

Plants- natural asexual production the offspring develop from parent plant rather than seeds.

Control of genetics- asexual reproduction animals.

Cloning is an artificial asexual reproduction technique for livestock that is still being developed. The aim is to produce offspring that are genetically identical to a selected individual with desirable characteristics known as a donor

Sexual reproduction

Offspring combine the genes from two parents, so their characteristics cannot be predicted accurately. Producing a veriaty or breed with particular characteristics but without undesirable characteristics

Selective breeding

This involves production of offspring from parents that were chosen because of their genetic characteristics. Breeding between genetically similar individuals may produce offspring with similar characteristics but increased risk of inbreeding.

Cross breeding

Crossbreeding between two different parental breeds may produce a combination of desirable characteristics. Lowers risk of inbreeding. An example is the Zebu cattle which are reared in areas with a hot climate.