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What do fertilisers provide for plants?
- Nitrates for amino acid synthesis
- Phosphates for synthesising DNA, RNA and ATP
- Potassium for maintaining the balance of positive and negative ions in and out of the cells
What will happen to productivity of plants if mineral ions are in short supply?
- They will become a limiting factor
- Productivity will decrease
How may fertilisers have negative effects on plants?
If too much is added the water potential in the soil may be affected
Why is less fertiliser than the amount needed for maximum productivity added?
- Fertiliser is expensive
- The slight increase in yield is not worth the increase in costs
Give 3 examples of natural fertiliser
- Animal manure
- Sewage sludge
What are the advantages of natural fertiliser?
- Feeds soil microbes important in the nitrogen cycle
- Improves humus content of the soil allowing it to hold more water and reduce leeching of minerals during rainfall
- Releases minerals over a long period
- Less soluble than inorganic- not leeched as easily
What are the disadvantages of natural fertiliser?
- Bulky to store
- Difficult to apply to the land
- Farmer cannot know the ratio of Nitrogen Potassium and Phosphor
- Takes time for microbes to convert it into nitrates
What are the advantages of artificial (inorganic fertiliser?
- High nutrient content
- Precise ratios of Potassium, Phosphor and Nitrogen
- Soluble and releases minerals quickly
- Easy to store
What are the disadvantages of inorganic fertiliser?
- Does not improve humus levels of soil
- Easily leeched from the soil after rainfall