5.9 Fish farming

1. Fish are an attractive product for farmers as they have low fat and high protein. 
2. Fish efficient at turning their nutrient into fish mass 

Advantages of fish farming 

1. fish farming will allow us to control the quality of water.
2. We can control predators
3. we can reduce pests and other forms of disease. 
4. By controlling all the factors above we're contributing to an increase in a yield of fish. 

disadvantages: 

1. However when you have a high density of fish the possibility is for the transmission of disease. 
2. because of this some farmers take antibiotics which is of concern to human health. 
3. the abundance within the fish farm, makes pests common therefore farmers use pesticides. This also is harmful to humans. 

5.4b Biological control

1. In Australia the prickly pair cactus of north america was introduces to garden which escaped into the countryside and the prickly pair cactus flourished under the Australian climate. 
2. However, it started taking up a lot of the agricultural land therefore it was important to get rid of it. 
3. An alien species, a moth (cactoblastis), was introduced, which feeds on the cactus. This moth had no competitors and therefore it was able to eat away at the cactus and remove it from the land. 
4. This is an example of controlling the pest. In this case, the cactus is the pest, which is eaten away by the herbivore. This is called biological control. In this case, we're not using pesticides.
5. Advantages of biological controls: 
1. No toxic chemicals involved means it has less impact on man or on wildlife.
6. Disadvantages 
1. Not a 100 percent effective 
2. There is always a danger that the introduced species will find an alternative prey on which to feed and will not die out once the pest is removed therefore it is difficult to control.
3. It is difficult to match a predator to the prey. you can;t actually find a suitable predatory herbivorous animal to remove your pest. 

5.4 pest control

1. monoculture- a large field of crops all of the same type. eg fields of rice, potatoes. 
2. when we have a monocuture they tend to be very susceptible to pests. 
3. pests use the crop as their own food source. In doing so, it reduces the productivity in farming. E.g. loss of food and financial impact on the farmer.
4. To overcome this, you should use pesticides (chemicals)
5. Advantages of using pesticides: 
1. pesticides kill pests
2. They are easy to obtain because they are chemicals 
3. They are easy to apply 
4. They are very effective 
6. Disadvantages: 
1. Many of these chemicals present in pesticides are  very toxic therefore they will kill other plants and animals other than the pests. They can also be harmful to humans 
2. bioaccumilation- pesticide builds up in the food chain and builds problems for animals in the higher trophic levels. 
3. Mutation in the pests often leads to resistance therefore the pesticide must be applied in higher concentration, it is more toxic or it no longer works. 

5.3 Fertilisers

1. We're looking at the Use of fertilisers to increase crop yield 
2. Lets say we have a plant and we want to increase the growth of the plant. This is achieved by farming by the application of fertilisers to the soil and these normally take the form of nitrates or phosphates. 
3. These compounds go down into the soil and are taken up in the root structure and then moved in the transpiration stream up to the leaf and used in the leaf for the construction of proteins (nitrates) or DNA/ membrane structure (phosphates). 

1. fertilisers can be divides into two groups, organic and artificial fertilisers. 
2. Organic group are produced from animal waste on farms. this usually takes the form of cow faeces. 
3. the faeces go through the process of decomposition and fermentation and forms a substance known as slurry. This is applied to the field, giving the crop plant a supply of nitrate and phosphate to promote growth. 
4. The artificial fertilisers take the form of chemicals which are synthetically produced. Two well known ones are potassium nitrate and ammonium nitrate. They will go into solution in the soil water once applied to the fields.
5. This will release nitrates which will also promote growth. 
6. eutrofication occurs due to the use of artificial fertilisers. 

5.2 Crop Yield

1. We're looking at the increase of crop yields due to higher levels of carbon dioxide and higher temperatures. 
2. This can be related to the rate of photosynthesis. 

Increasing concentration of Carbon Dioxide: 

1. Carbon dioxide is the substrate within photosynthesis. 
2. The rate of photosynthesis will increase therefore we'll have a higher yield up to a point. 

Increasing the temperature 

1. Yield increases until we reach the optimum temperature. 
2. increasing temperature in a glasshouse also has other effects such as avoiding frost damage and provide  constant temperature, contributing to the yield growth. 

5.1 Glasshouses

1. Glass houses (greenhouses)- are constructed on a framework, like a house, all their surfaces are glass, allowing light to penetrate through to the interior. 

1. Ploythene tunnels- also framework with polythene over the surface. Polythene allows light to penetrate through. Associated with things like market gardening. Can be taken down and replaced. Used in cheaper countries. 

Glasshouse:

1. Firstly, we have solar radiation which is our initial source of energy in the form of light. 
2. The light is able to penetrate through the glass to the internal surfaces. 
3. The light is absorbed by surfaces inside the glasshouse. eg the soil the wooden bench surfaces or the plants
4. these surfaces re-emit this energy as heat. 
5. The heat warms the air, raising its average kinetic energy (the temperature increases)
6. The warm air is trapped. Generally it would cool at the upper surfaces and then sink to the floor again to be rewarmed by the surfaces. 

How does this cause an increase in crop yield?

1. Warm air in the glasshouse increases crop yield 
2. The higher temperature in the glasshouse, lead to closer or optimum temperature for enzyme reactions including photosynthesis. 
3. It provides constant temperatures throughout the growing year therefore we have constant production. 
4. The prevention of loss of water vapour. Crops don't dry out. 
5. Able to avoid frost damage to seedlings in the spring time. 
6. Glasshouses are often warmed by the burning of fossil fuels. This leave to two effects. 
1. Increase in Carbon dioxide, which means we have increased the concentration of the substrate for photosynthesis.  
2. burning of the fossil fuels also results in the production of ethene. This gas stimulates fruit ripening.