Chapter 3: Agriculture

Question 1

Soil composition

Answer 1

inorganic mineral particles
organic content
air (rich in CO2)
water

Question 2

Define humus

Answer 2

organic matter of living plants, animals and microorganisms and their decaying remains

Question 3

Clay

Answer 3

less than 0.002 mm
tiny spaces
greatest water holding capacity
smallest particles
drains slowly
takes longer to warm up

Question 4

Silt

Answer 4

between 0.002 and 0.05 mm
well drained
holds more moisture
easily wet

Question 5

Sand

Answer 5

between 0.05 and 2 mm
water drains easily
warms up quickly
dries easily
prone to become acidic

Question 6

Define leaching

Answer 6

rain washes away plant nutrients so soil becomes infertile and acidic

Question 7

Loam

Answer 7

mixture of clay silt sand
well drained
fertile
easily cultivated

Question 8

Soils are a medium for plant growth

Answer 8

mineral ions
organic content
pH

Question 9

Mineral ions

Answer 9

nitrogen (nitrate ions) - combines with glucose to form amino acids for proteins

phosphorus (phosphate ions) - cell membrane for respiration

potassium - enzymes for photosynthesis

magnesium - manufacturing chlorophyll for photosynthesis

Question 10

Organic matter

Answer 10

remains of a dead plant or animal decomposed by microorganisms into humus

reservoir for nutrients for absorption by plants
improves water holding capacity of soil
prevents water logging
improve soil structure by binding
prevents soil erosion
increased infiltration prevents drying

Question 11

pH of soil for agriculture

Answer 11

ability of plants to absorb nutrients from mineral ions/ organic matter in soil water

nutrient deficiency as some nutrients aren’t dissolved so no uptake - disproportioned

acidic - phosphorus and magnesium low while metal ions reach toxic levels

alkaline - plant growth restricted as lack of iron, decrease in solubility as high level of calcium and uptake of potassium

Question 12

pH of soil over time

Answer 12

becomes acidic

rainfall weathers soil- leaches out magnesium
decomposition
burning of fossil fuels causes acid rainfall
chemical based fertilisers

Question 13

How farmers control pH level

Answer 13

increase:
liming
adding ground limestone/ calcium carbonate with magnesium

decrease:
adding large quantities of organic matter

Question 14

Differences between sandy and clay soil

Answer 14

air content
water content
drainage
ease of cultivation

Question 15

How to make cultivation easier

Answer 15

add organic matter

increases nutrient holding capacity
increases ph levels
improves soil structure
improves water holding capacity
improves drainage

Question 16

types of agriculture

Answer 16

arable, pastoral, mixed

subsistence, commercial

(techniques) intensive, extensive

Question 17

Increasing agricultural yields (*a)

Answer 17

pesticides
controlled environments
irrigation
fertilisers
mechanisation
selective breeding
genetic engineering
rotation

Question 18

Pesticides (alternatives and disadvantages)

Answer 18

fungicides - kill fungi attacking plants

herbicides - kills weeds by making them absorb toxins through leaves or roots

insecticides - kills insects attacking plants

ecological impacts
harmful to non pest species
breaks food chain
bioaccumulation of pesticides
immunity and resistance to toxins

labour intensive methods (hand pulling or hoeing, pick insects by hand)
natural pesticides

Question 19

Controlled environments

Answer 19

in artificial conditions
water light heat food fertiliser controlled
eg. greenhouse

hydroponics - immerse plant roots into water with minerals and nutrients
no pests weeds or diseases

animal welfare issues

Question 20

Irrigation (*a)

Answer 20

artificial supply of water is controlled

sprinkler - hose rotates reduces water logging
in ground - system underground
localised - drops of water reduced evaporation
seepage - water from beneath soil, salinisation
surface - flood, cover area in water evaporation

Question 21

Define water table

Answer 21

the level below which the ground is saturated with water

Question 22

Fertilisers

Answer 22

to replace lost nutrients in soil
provide optimum conditions

use natural animal manure or compost

eutrophication
global warming
soil acidification
greenhouse gas emissions

Question 23

Mechanisation

Answer 23

machines improve efficiency of farms
reduces costs since less labour
intensive farming
satellite imagery and GPS, remote sensing

Question 24

Selective breeding

Answer 24

only breeding from animals or plants with desirable traits so they breed to produce offspring with best traits for survival, profit and aesthetics

Question 25

Genetic engineering

Answer 25

artificially changing the genetic structure of cells of animals or cross by swapping genes across species
mixing good genes to create highly resistant or preferable species

Question 26

Rotation

Answer 26

sequence of changing crop in particular place
provides range of nutrients in soil
less use of pesticides
leguminous crops for nitrogen fixation

Question 27

Impact of agriculture

Answer 27

overproduction
overuse of pesticides
overuse of fertilisers
mismanagement of irrigation (water logging and salinisation)
exhaustion of mineral ion content
soil erosion
cash crops replacing food crops

Question 28

Reasons for overproduction

Answer 28

Demand in MEDCs not enough due to low population growth - market saturated
damage in quality, pests, disease, weather
cosmetic standards- no blemishes or bruises
wastage by consumers

Question 29

Causes of soil erosion

Answer 29

removal of natural vegetation by over cultivation and overgrazing
water and wind erosion

topsoil washed/ blown away
soils depleted of nutrients
soil structure broken down
desertification

Question 30

Impacts of soil erosion

Answer 30

loss of habitat
desertification
sitting of rivers (sedimentation)
displacement of people (no farming)
malnutrition and famine

Question 31

What is desertification

Answer 31

soil erosion in dry areas
results in water tables dropping and salinisation (contamination by soluble salts) and surface water disappears

Question 32

Managing soil erosion

Answer 32

terracing slopes
contour ploughing (furrows/ ridges)
bunds
windbreaks
vegetation cover
cover crops
mixed cropping/ crop rotation

Question 33

vegetation cover

Answer 33

planting trees - root systems anchor soil in place, intercepts rainfall so speed of run off decreases, covers crops from wind

add organic matter - manure allows soil to soak up water slowly, resistant to erosion by amalgamation of soil

hedges - grubbing (ploughing) easily accessible by machinery

wind breaks - prevent soil erosion (lines of trees facing wind to reduce its strength)

cover crops - suppress weeds, improve quality of

Question 34

Cropping systems and ploughing techniques

Answer 34

type of crop- complement each other for erosion protection, soil fertility, soil structure, minerals (leguminous)

sequence of rotation

intercropping - 2 types of crops in same area

mixed cropping - random crops grown in area

contour ploughing - furrows across not down slopes flowing natural contour of land- level, rainwater soaks into soil, no run off

bunds - slow down seepage of water and soil for greater uptake
made of stones or soils close to slope to even it out

Question 35

How can we do sustainable agriculture?

Answer 35

crop rotation
(soil fertility, soil structure, manage pests or diseases, protects soil)
leguminous crops for nitrogen fixation

managed grazing/ livestock rotation
declining yield of milk/ meat
forage restores lose energy reserves, enables it to deepen root systems

organic fertilisers (crop residue or manure)

biocontrol of pests- pest resistant/ gm crops
adapted and crossbred

water use- trickle drip irrigation (evaporation)
rainwater harvesting
low pressure sprinkler systems

Question 36

Define forage

Answer 36

crops grown to be eaten
used in arable farms