Fertilisers and Pesticides

Question 1

what is an organic fertiliser?

Answer 1

made from the faeces of a range of animals, sometimes mixed with straw

Question 2

what is an inorganic fertiliser?

Answer 2

inorganic compounds carefully formulated to yield a specific concentration of a particular ion when applied according to the manufacturer’s instructions

Question 3

advantages of organic fertilisers

Answer 3

• improves soil structure
• greater range of minerals
• releases minerals over a longer period of time
• less cost to farmer - already available on the farm

Question 4

disadvantages of organic fertilisers

Answer 4

• slow acting - has to be decomposed first
• bulkier, so more difficult than inorganic fertilisers to apply
• may contain pests

Question 5

advantages of inorganic fertilisers

Answer 5

• mineral ions release immediately so fast acting
• contents known
• easy to apply

Question 6

disadvantages of inorganic fertilisers

Answer 6

• can lead to eutrophication is fertiliser is soluble
• requires regular reapplication

Question 7

what is another way of replacing lost nitrates?

Answer 7

• to grow a legume crop, such as clover, in a field one year in four
• these plants have nitrogen-fixing bacteria in nodules on their roots and they convert nitrogen gas in the air into ammonia ions
• some of this is passed to the plants which use it to make proteins
• in autumn the crop is ploughed in and when the protein in the crop and bacteria is broken down (decomposed) ammonia is released into the soil
• the ammonium is then converted to nitrate by nitrifying bacteria and is available to next year’s crops

Question 8

what are pests?

Answer 8

organisms that reduce the yield of crop plants or stock animals - by doing this they cause economic damage to the farmer (any organism can be a pest)

Question 9

what are two ways pests can be controlled?

Answer 9

1. chemicals called pesticides
2. use another organism to reduce the numbers of a pest - biological control

Question 10

what do herbicides kill?

Answer 10

plant pests

Question 11

what to insecticides kill?

Answer 11

insects

Question 12

what do fungicides kill?

Answer 12

fungi

Question 13

what to molluscicides kill?

Answer 13

molluscs (e.g. slugs and snails)

Question 14

what are pesticides used for?

Answer 14

to kill specific pests and so improve the yield from the crops and livestock

Question 15

when are pests a problem?

Answer 15

when they are present in sufficient numbers to cause economic damage - the increase in income must be set against the cost of the pesticide

Question 16

how may pesticides damage ecosystems?

Answer 16

the pesticide molecules are simply passed higher up the food chain, becoming concentrated in the tissues of top carnivores