[13.4] use of natural and artificial fertilisers

Question 1

why do we need fertilisers?

Answer 1

• crops remove mineral ions by absorbing them from soil
• fertilisers are needed to offest this loss of mineral ions

Question 2

how are mineral ions returned in natural ecosystems?

Answer 2

when the plant is decomposed by microorganisms on its death

Question 3

why do mineral ions need to be returned to agricultural systems?

Answer 3

• crop is harvested and transported from its point of origin for consumption
• urine, faeces and dead remains of consumer are rarely returned to the same area of land
• under these conditions, the concentrations of the mineral ions in agricultural land will fall
• therefore, they have to be replenished or their reduced concentrations will become the main limiting factor to plant growth so productivity will be reduced

Question 4

what are 2 types of fertilisers?

Answer 4

• natural (organic) fertilisers
• artificial (inorganic) fertilisers

Question 5

what do natural fertilisers consist of?

Answer 5

• dead and decaying remains of plants and animals
• animal wastes eg. manure, slurry, and bone meal

Question 6

what do artificial fertilisers consist of?

Answer 6

compounds containing the following are almost always there:

• nitrogen
• phosphorus
• potassium

Question 7

how are artificial fertilisers made?

Answer 7

• mine deposits from rocks
• convert into different forms
• blend together to given appropriate balance of minerals for a particular crop

Question 8

how do fertilisers increase productivity? (eg. nitrogen)

Answer 8

• plants require minerals for their growth
• nitrogen is an essential component of AA, ATP and nucleotides in DNA
• if nitrate ions are readily available, plants are likely to develop earlier, grow taller and have greater leaf area
• this increases the rate of photosynthesis and improves crop productivity