NPK is an acronym you will frequently run across when dealing with plants, particularly field crops. The three letters are merely the chemical symbols of three nutrients:
So why is there so much emphasis on N, P, and K? Each of these nutrients is essential to plants because they serve vital functions.
Gardeners generally think of nitrogen as the nutrient that makes beautiful leafy vegetables. But nitrogen has many other essential functions, as well:
- Making chlorophyll.
- Giving cells their structure.
- Assisting plant growth and reproduction.
- Helping the plant synthesize and use energy.
Gardeners tend to think of phosphorus as the “fruit nutrient,” the element that helps an apple or a tomato grow and ripen properly. Phosphorus does serve in this role, but it also has other purposes:
- Assisting in photosynthesis.
- Giving DNA its structure.
- Enhancing plant growth, particularly in the roots.
- Providing the plant with resistance to diseases, challenging weather conditions, and other sources of stress.
Gardeners typically associate potassium with (you guessed it) roots and tubers because these types of plants tend to feed heavily on potassium, providing the nutrient to the humans who eat them. All plants, however, use large amounts of potassium; root crops simply have a special storage mechanism.
Plants feed heavily on potassium because this nutrient is involved in so many critical functions:
- Activating enzymes.
- Enhancing fruit quality.
- Providing disease resistance.
- Maintaining proper ion balance.
- Helping roots take in water by osmosis.
- Regulating water pressure via small openings in the leaves (stomata).
Nitrogen, phosphorus, and potassium can justly be considered the building blocks of plant nutrition because they are so essential.
Unfortunately, farmers and gardeners all too often focus exclusively on providing their plants with NPK and forget about the trace minerals (also known as micronutrients) that plants need, as well. Plants rarely show overt signs of a zinc, manganese, or molybdenum deficiency, although they often fail to thrive in subtle ways. But when animals and humans eat crops or forages that have been grown on micronutrient-deficient soils, their health may suffer.
But there’s good news! You don’t have to be a chemist to understand what your plants need to eat. By regularly feeding the soil with organic matter and green or animal manures, you will not only keep NPK levels high, but you will enrich the soil with trace minerals, as well.