NPK stands for Nitrogen, Phosphorus and Potassium (K in the periodic table). These are essential for every plant to have a steady, healthy growth. It's usually found in fertilisers, described with the following format: NPK 1-7-11.
Nitrogen, Potassium and Phosphorus and all classified as macronutrients, plants take up large quantities of all three during their life cycle.
■ N - Nitrogen
— What is it?
A group of molecules that bind to roots and help the roots absorb, water and nutrients.
— Where is it?
Nitrogen makes up 78% of breathable air, by volume. It is obtained by the distillation of liquid air. Around 45 million tonnes are extracted each year. The nitrogen cycle, Nitrogen is taken up and used by green plants and algae as nitrates, then used as the building blocks the plants need to grow.
— What does it do?
It's largely responsible for leaf growth. It's essential for chlorophyll and photosynthesis, without it plants cannot build proteins - cell walls.
Nitrogen is a building block in plants for amino acids, proteins, enzymes and especially Chlorophyll the compound plants use to convert light into sugars from water and carbon dioxide, known as photosynthesis. Without nitrogen plants wouldn’t be able to build proteins and so would wither and die. These proteins act as the structural units in the walls of the plant cells.
— Signs of deficiency
Plant not growing, weak stems, leaves discoloration (yellow/white).
■ P - Phosphorus
— What is it?
Phosphorus is an essential chemical element with the symbol P.
— Where is it?
Phosphorus is concentrated in the Earth's crust, around one gram per kilogram. Phosphorus mostly occurs as phosphate in mineral form. Due to its highly reactive properties, phosphorus is not found in concentration as a free element on Earth.
Phosphorus is usually manufactured through a process of heating phosphate rock in the presence of carbon and silica. This produces phosphorus as a vapour, which is then collected, suspended in water.
— What does it do?
Phosphorus is essential to plant growth and is in every living plant cell. It is involved in many of the key functions in plant development, such as, energy transfer, photosynthesis, nutrient movement through the plant, and the transformation of sugars in the plant
It's an essential catalyst for root growth, stem strength and formation of rich fruit and flowers.
Phosphate is one of the most essential nutrient for plants, especially to help them mature during their life cycle. Without phosphate, plants are unable to complete their life cycle. It acts as a building block in the cell walls and helps with the transfer of energy in the plant.
It is especially useful at converting light into compounds the plant needs to grow. It helps with root development, plant stem strength and the formation of rich fruit and flowers. It also provides the plant with a greater resistance to diseases. This nutrient supports plants through their life cycle, and often speed up the time a plant takes to mature.
— Signs of deficiency
Plant not growing, poor fruits, purple stems, dark green/blue leaves.
■ K - Potassium
— What is it?
Potassium is a chemical element with the symbol K. Potassium is a silvery-white metal that reacts rapidly with atmospheric oxygen to form flaky white potassium peroxide in only seconds of exposure.
— Where is it?
It was first derived from potash, the ashes of plants, from which it gets its name.
The vast majority of potassium is made from evaporated salt deposits containing potassium chloride. It is also made from the mineral’s alunite and carnallite. Potassium can also can be made from the electrolysis of potash.
— What does it do?
Potassium is used in nearly all process of plant growth; it is an essential nutrient. Plants with potassium deficiencies are left susceptible to temperature stress, drought and over watering, and are far less resistant to pests and disease. Potassium also increases root growth, helps build the cell walls of the plant, aids photosynthesis and helps the movement of sugars
Potassium is associated with the transportation of water and nutrients in plant tissue. Potassium helps control the opening and closing of the plant’s stomata, which in turn regulates the plants exchange of water vapor, oxygen and carbon dioxide.
It's responsible for regulating nutrients, water and CO2 uptake and make the plant perform correctly. It also triggers activation of enzymes and ATP production; ATP can regulate the rate of photosynthesis.
It also helps maintain water, reducing water loss and wilting, also preventing energy loss through respiration.
— Signs of deficiency
Weak stems, poor fruits, "burned" leaves (brown/yellow on the edges).
Plants need different doses of NPK in different stages of growth, it's essential to have a balanced feed according to the stage, nutrient combination and media being used. NPK and macronutrients play such an essential role in plant development that getting this combination right is the first and most fundamental knowledge all growers need.