Why are the plants dying in my garden?

If you’ve ever grown a plant, either indoors or outdoors you may have noticed at some point a symptom of a nutrient deficiency. It may be black tips on the ends of leaves, spots on your apples, yellowing or even death.

You’ve probably grabbed your watering can and pot of ‘Baby Bio’ or ‘Tomorite’ and got busy trying to bring your precious plant back to life.

There are lots of reasons a plant might show a sign of a nutrient deficiency. Not all of them obvious. In this article we will explore how nutrients in your soil or growing media effect the growth of your plants, and look at ways to combat the effects of nutrient deficiencies.

How do specific nutrients affect plant growth?

The mobility of nutrients within soils and in the plants will have a direct influence on deficiency symptoms. If a nutrient moves freely or is ‘mobile’ from one part of the plant to another the deficiency symptom will be seen in the older organs first. When a nutrient is less mobile within the plant the deficiency will be seen in the new growth. Older parts of the plant are more likely to have these nutrients stored for use in periods of shortage.

The three main nutrients you will probably have heard of are Nitrogen, Phosphorus and Potassium, often seen displayed on bags of fertiliser as NPK. There are other nutrients which play a vital role in plant health which we will also look at. For each nutrient it is important to look at in terms of its role in plant growth, its mobility, i.e. its ability to move through soil and plants, the symptoms of deficiency in plants and the symptoms of an excess of a nutrient in plants.

It is important to note that in some situations certain nutrients can build up to toxic levels. An example of this would be copper which is toxic in high doses. These buildups can occur in hydroculture systems where nutrients are circulated in solution. Certain pesticides such as copper sulphate, a fungicide used in conventional and organic agriculture can build up the soil to toxic levels, causing damage to the roots of plants.

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Nitrogen

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Role within the plant

• Proteins and chlorophyll production 

• Water uptake and osmosis

• Leaf growth

Mobility

• Nitrate in soil - easily leached in water

• Very mobile in plant

If there’s not enough

• Yellowing of leaves

• Raised salt levels in soil

If there’s too much

• Soft lush leaves prone to pest and frost damage

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Phosphorus

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Role within the plant

• Required in ATP for energy transfer - important in seedling growth and for young plants

Mobility

• Immobile in soil and very mobile within the plant

If there’s not enough

• Poor root growth

• blue green leaves

• brown patches

• small flowers and fruits

If there’s too much

• Stunted growth

• deficiencies in iron

• zinc cobalt or calcium

• yellowing of leaves

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Potassium 

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Role within the plant

• Helps plants absorb and hold on to water by osmotic regulation

• Involved in flower and fruit production

• Secondary thickening of cell walls

• Leaf growth

Mobility

• Moderately mobile in soil

• very mobile in the plant

If there’s not enough

• Scorched patches on leaves

• leaves roll in and down

If there’s too much

• Leads to Nitrogen deficiency

• Stunted growth

• Yellow foliage on older parts

• Red tint to veins on leaves

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Calcium

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Role within the plant

• Wall structure and strength of the plant

• Provides for normal transport

• Retention of other elements within the plant

Modality

• Immobile in the plant

If there’s not enough

• Effects younger leaves turning them pale

• Necrotic tissues on fruits due to weakening of cell walls

If there’s too much

• Causes an increase in pH leading to deficiencies in other nutrients mainly magnesium and potassium

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Magnesium

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Role within the plant

• Needed for chlorophyll synthesis in all green plants is essential for photosynthesis

• Helps to activate enzymes for growth and to

• Moves phosphorus around the plant.

Mobility

• Very mobile in the plant

If there’s not enough

• Yellowing of older leaves - interveinal chlorosis as chlorophyll isn't produced

• Growth is reduced as photosynthesis is impaired

If there’s too much

• Interferes with the uptake of calcium and potassium leading to deficiencies

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Iron

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Role within the plant

• Involved in chlorophyll production

Mobility

• Moderately mobile - can be locked up by calcium

If there’s not enough

• Stunted growth

• Chlorosis in younger leaves 

If there’s too much

• The same as too little

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Boron

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Role withing the plant

• Involve in carbohydrate movement

• Affects flowering and pollination

• Fruiting cell division

• Nitrogen metabolising

• Movement of hormones within the plant

Mobility

• Mobile within soil

• Mobility restricted in some plants but not in others.

If there’s not enough

• Yellow leaves

• Withered tips on young growth

If there’s too much

• Yellowing or browning of foliage

• Eventually taking over the whole leaf

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Sulphur

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Role within the plant

• Used in the manufacture of proteins and chlorophyll and for the Nitrogen fixing nodules on legumes.

• Is part of an enzyme crucial for Nitrogen uptake by plants.

Mobility

• Highly mobile in soil

If there’s not enough

• Reduced growth

• Yellowing of younger leaves due to lack of chlorophyll

If there’s too much

• Depressed growth