5.4 understand the reasons for pest control and the advantages and disadvantages of using pesticides and biological control with crop plants.

 Pesticides are substances that are used to prevent, destroy or repel pests.

There are 3 different types of pesticides, which all target different types of organisms:

-        Herbicides – kills unwanted plants (weeds etc.)

-        Fungicides – kills fungi (e.g mold)

-        Insecticides – kills insects (that prey on the plant)

The use of pesticides can increase food production (crop yield) as it removes things that decrease crop yield.

Pesticides:

Pros:

-        Increases efficiency

-        Immediate results

-        Gets rid of pests completely  

Cons:

-        Bioaccumulation (gets into food chains and causes damage, organisms at the top of the food change have the largest amount of accumulated chemicals)

-        Have to apply continuously/repeat applications

-        Pests can develop a resistance

-        Not specific enough, can kill other non targeted organisms

Biological (organic) pest control: natural predators of the pest are used, they eat the target pest and leave other wildlife unharmed (e.g ladybirds can be used to control aphids)

Pros:

-        Specific targets

-        Lasts a long time

-        Cost effective: can be expensive to set up but once set up takes little effort to sustain

Cons:

-        Possibility of predator eating another pest/organism

-        Can take time, not as fast as using chemical pesticides

-        Reduces the number of pests but doesn’t completely wipe out

5.3 understand the use of fertiliser to increase crop yield

 Fertilisers are substances (organic or artificial) that are applied to plants to increase crop yield. They contain the minerals that allow a plant to grow, which is why they are sometimes referred to as NPK fertilisers. They contain nitrates, phosphates and potassium.

These minerals are taken in by the roots through active transport

The ratio of these minerals can be changed based on what they want to gain from the crop yield, however there needs to be a sufficient amount of each mineral for healthy growth

Nitrates:

They are used to create nucleic and amino acids(àprotein) in the plant, which is needed for growth. If there is a lot of nitrates in the soil, then the plant will be able to grow more and increases crop yield.

Phosphates:

Phosphates are used for respiration and growth and are needed to make DNA and cell membranes. It is also used to make ATP which is the substance which stores energy in cells.

Potassium:

Potassium is also used for respiration and growth, it is needed in enzymes which are involved in respiration and photosynthesis. It is involved in enabling the transfer of minerals across the cell membranes and without it the plant would be unable to carry out reactions.

Organic fertilisers: are often animal waste products which have gone through the process of decomposition and fermentation. This is then applied to the soil providing the plants with the nutrients to increase crop yield and encourage growth.

Artificial fertilisers: are usually synthetically produced chemicals. For example, the Haber process is used to create ammonia, which is then used as a base for other synthetic nitrate fertilisers. When applied to the soil the solution is combined with soil water and the minerals can then be taken in by the plant for an increased crop yield.

*when fertilisers run off (leached) of on fields and into smaller bodies of water, it can cause eutrophication