IT’S A
GREEN WORLD
Plants need
minerals too
Starter
What is ‘slash and
burn’ agriculture?
What problems can arise from using this
method?
Plants need minerals too
Learning objectives
Understand that:
 The production of many
important compounds by
plants requires
elements that are
obtained from soil
minerals
 Fertilisers contain
minerals
Success criteria
Complete a table stating
what how various
minerals are used by
plants
Completion of worksheets
on fertiliser usage
What do plants need for a balanced diet?
Plants need carbon dioxide and water for photosynthesis.
Do they need any other nutrients to keep healthy?
Just like humans, plants need a balanced diet
that includes small amounts of mineral elements.
What mineral elements do they need?
What minerals do plants need?
Plants need mineral elements for healthy growth.
Some of the most important minerals needed by plants are:
nitrogen
nitrates
phosphorus
phosphates
potassium
potassium ions
magnesium
magnesium ions
How do plants obtain these minerals?
The mineral elements are found in salts dissolved in water.
Plants obtain minerals when they absorb water from the soil.
What type of salt are each of these elements found in?
What are minerals needed for?
Use p67 of the textbook to complete the table below
Minerals
How mineral is used in
plants
What happens to these
minerals
Nitrates
Used to make proteins
(for growth)
Nitrogen is used to make amino
acids which are then joined
together to make different proteins
Phosphates
Used in respiration and
growth esp in roots
Phosphorus is used to make cell
membranes and DNA ( which
carries genetic information)
Potassium
compounds
Used in respiration and
photosynthesis
Used to make some enzymes
needed in respiration and
photosynthesis
Magnesium Used in photosynthesis
compounds
Used to make chlorophyll
molecules
Where do minerals come from?
What are the sources of minerals in the soil?
Rocks: The minerals in rocks are
slowly dissolved by slightly acidic
rainwater. These minerals are
washed into the soil.
Natural fertilizers: Animal faeces
and the decay of dead plants and
animals return minerals to the soil.
Artificial fertilizers: These
contain a ready-made mixture
of the minerals needed by plants.
Task - Fertilisers
Complete worksheet B4d3 – Rothamsted
experiment
 Extension – complete worksheet B4d2 Nitrogen fertilisers
B4d3 – Rothamsted experiment
 As a control/comparison
 Potatoes do not need much nitrogen but wheat
does
 Field 4; a fertiliser containing nitrogen,
phosphorous and potassium would be
expensive – the increase in crop yield may not
justify the expense
 Soil type (clay, sand, chalk), drainage,
aeration, climate conditions, pests, disease
B4d2 – Nitrogen fertilisers
 0.7 tonnes/hectare
 This uses ‘the law of diminishing returns’ – by doubling
the amount of fertiliser from 0 to 50, the crop increases
from 2.5 to 7 tonnes/hectare, almost three times the
size
If the amount of fertiliser is again doubled from 50 to
100 tonnes/hectare, the crop only increases from 7 to
8.4 tonnes/hectare
 It is tempting to state the highest amount of fertiliser,
as this would give the largest crop, however by spending
more and more money, the farmer’s increase in yield
becomes less and less; the correct amount of fertiliser
depends partly on its cost
Most farmers would choose 50 kg of fertiliser/hectare
Plenary
Organic farmers do not use artificial
fertilisers.
 Who would pay more for organic food
and why?
Plants need minerals too
Learning objectives
Understand that:
 The production of many
important compounds by
plants requires
elements that are
obtained from soil
minerals
 Fertilisers contain
minerals
Success criteria
Complete a table stating
what how various
minerals are used by
plants
Completion of worksheets
on fertiliser usage