5.3 Fertilisers

Understand the use of fertiliser to increase crop yield

1. Fertilisers contain minerals (NITROGEN, POTASSIUM AND PHOSPHORUS) - which help plants grow faster + bigger so that crop yields are increased.

Nitrogen - makes proteins
Phosphates - make DNA + membrane structure

2. They're minerals are first dissolved in water so that plants can absorb them through their roots (done by active transport)

3. Organic Fertilisers

• made from the feaces (farmyard manure) of a range of animals mixed with straw
• goes through a process of decomposition and fermentation --> forms a compound called "slurry"
• applied to the fields - supplying the essentials minerals to promote growth. 

4. Inorganic Fertilisers/Artificial

• made from inorganic compounds (potassium nitrate/ammonium nitrate) 
• carefully formulated to yield a specific amount 
• applied to the field in solution (water) 
• nitrates are released and absorbed by roots of plants

5. Eutrophication

a) Occurs when farmers apply inorganic fertilisers to replace the nitrates + other mineral ions lost from removing crops.

b) The ions are very soluble --> get easliy leached (carried out by water) from the soils and can enter waterways.

c) Level of nitrates rise rapidly in these lakes and rivers --> increase in mineral ions = Eutrophication

d) Eutrophication is a natural process but the speed at which it happens due to leaching ions in fertilisers from soils is not natural and results in disaster for a waterway.

Process:

• Nitrate levels rise and algae reproduce rapidly as they are using the nitrates to make extra proteins
• The algae then produces an algai bloom
• The algae prevents light penetrating into the water
• Plants cannot photosynthesize and die 
• Algae also dies as they run out of nitrates
• Bacteria decay the dead plants 
• The bacteria reproduce due to the large amount of dead matter 
• The water becomes totally anoxic (without oxygen)
• All life in water dies