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.
Nitrogen
Role within the plant
Proteins and chlorophyll production
Water uptake and osmosis
Leaf growth
If there’s not enough
Yellowing of leaves
Raised salt levels in soil
Mobility
Nitrate in soil - easily leached in water
Very mobile in plant
If there’s too much
Soft lush leaves prone to pest and frost damage
Phosphorus
Role within the plant
Required in ATP for energy transfer - important in seedling growth and for young plants
If there’s not enough
Poor root growth
blue green leaves
brown patches
small flowers and fruits
Mobility
Immobile in soil and very mobile within the plant
If there’s too much
Stunted growth
deficiencies in iron
zinc cobalt or calcium
yellowing of leaves
Potassium
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
If there’s not enough
Scorched patches on leaves
leaves roll in and down
Mobility
Moderately mobile in soil
very mobile in the plant
If there’s too much
Leads to Nitrogen deficiency
Stunted growth
Yellow foliage on older parts
Red tint to veins on leaves
Calcium
Role within the plant
Wall structure and strength of the plant
Provides for normal transport
Retention of other elements within the plant
If there’s not enough
Effects younger leaves turning them pale
Necrotic tissues on fruits due to weakening of cell walls
Mobility
Immobile in the plant
If there’s too much
Causes an increase in pH leading to deficiencies in other nutrients mainly magnesium and potassium
Magnesium
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.
If there’s not enough
Yellowing of older leaves - interveinal chlorosis as chlorophyll isn't produced
Growth is reduced as photosynthesis is impaired
Mobility
Very mobile in the plant
If there’s too much
Interferes with the uptake of calcium and potassium leading to deficiencies
Iron
Role within the plant
Involved in chlorophyll production
If there’s not enough
Stunted growth
Chlorosis in younger leaves
Mobility
Moderately mobile - can be locked up by calcium
If there’s too much
The same as too little
Boron
Role within the plant
Involve in carbohydrate movement
Affects flowering and pollination
Fruiting cell division
Nitrogen metabolising
Movement of hormones within the plant
If there’s not enough
Yellow leaves
Withered tips on young growth
Mobility
Mobile within soil
Mobility restricted in some plants but not in others.
If there’s too much
Yellowing or browning of foliage
Eventually taking over the whole leaf
Sulphur
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.
If there’s not enough
Reduced growth
Yellowing of younger leaves due to lack of chlorophyll
Mobility
Highly mobile in soil
If there’s too much
Depressed growth