Fertilisers

Question 1

why do we need fertilisers?

Answer 1

to replace mineral ions that are continually taken up by crops grown and when they are harvested and removed, the dead remains aren’t broken down therefore mineral ions aren’t recycled

Question 2

what are the two types of fertilisers?

Answer 2

1- natural organic fertilisers

2- artificial inorganic fertilisers

Question 3

what are natural organic fertilisers?

Answer 3

consist of dead and decaying remains of plants and animals as well as animal waste like manure

Question 4

what are artificial inorganic fertilisers?

Answer 4

mined from rocks and deposits which are converted into different forms and blended together to give the right balance of minerals depending on the crop.

Question 5

advantage of artificial inorganic fertilisers

Answer 5

allows you to add more of one mineral than others

Question 6

how do fertilisers increase productivity?

Answer 6

nitrogen- component of nucleic acids and DNA which are both needed for plant growth
therefore nitrate ions increasing the growth of plants (height, leaf SA) increases rate of photosynthesis, improving crop productivity

Question 7

environmental issues of nitrogen containing fertilisers

Answer 7

1- reduces species diversity- nitrogen rich soils favour the growth of grasses, nettles etc which out compete many other species
2-leaching which leads to pollution of watercourses
3-eutrophication- caused by leaching of fertilisers into watercourses

Question 8

leaching

Answer 8

can cause eutrophication
1-nutrients removed from the soil
2-rainwater dissolves soluble materials like nitrate ions and carries them deep into soil where they cant be reached by roots
3- leached nitrate ions transported into watercourses
4- harmful if watercourse is used for drinking water

Question 9

eutrophication

Answer 9

1- naturally there is a low conc of nitrate in lakes and rivers- limiting factor for plant and algae growth
2- leaching increases nitrate ion conc- stops being limiting factor
3- algae and other plants grow- algal bloom as algae grow at the surface
4-algae surface absorbs light
5- light becomes limiting factor for plants and algae at the lower depths so they die as cant photosynthesise
6-saprobionts increase in pop as they eat dead algae and plants. they respire, decreasing oxygen conc in the water
7-fish die and the nitrates are released from the decaying organisms
8- without the aerobic organisms there is less competition for the anaerobic organisms, whose population rises
9-anaerobic organisms further decompose dead materials, releasing more nitrates and some toxic waste

Question 10

contributing factors to eutrophication

Answer 10

organic manures
animal slurry 
human sewage 
ploughing old grassland 
natural leaching