Two Important Minerals!
1) Nitrates- nitrates are needed for making amino acids which are then used to make proteins.
2) Magnesium- Magnesium is needed to make chlorophyll which in turn is needed for photosynthesis.
other minerals needed by plants include Potassium and Phosphates, which are used for things like making DNA and cell membranes, and helping the enzymes involved in photosynthesis and respiration to work properly.
Lack of Important Nutrients!
Sometimes plants can't get all of the mineral ions they need to be healthy! This is what happens if you have a:
1) Lack of Nitrates - If the soil is deficient in nitrates, the plant starts to show stunted growth and won't reach it's usual size. This is because proteins are needed for new growth, and they can't be made without nitrates.
2) Lack of Magnesium- if the soil is deficient in Magnesium, the leaves of the plant start to turn yellow! This is because magnesium is needed to make chlorophyll, and this gives the leaves their green colour.
If the plant is left short of the minerals for a long time, it might die!
Deficiencies Can be Cause by Monoculture!
1) Monoculture is where just one type of crop is grown in the same field year after year.
2) All the plants are the same crop, so they need the same minerals. This means the soil becomes deficient in the minerals which that crop uses lots of!
3) Deficiency of just one mineral is enough to cause poor growth and give a reduced yield.
4) This soon results in poor crop unless fertiliser is added to replenish the depleted minerals!