Select Page

Crop Nutrients


Crops need nutrients to make them grow strong and healthy, just like humans. Each nutrient plays a different, but important role in crop growth and development. If crops do not receive the nutrients they need, the result could be weak crop growth and low yield.

Nutrients do exist in the soil, but as the plants grow they use the nutrients up. Farmers need to apply new nutrients every year to replenish the soil. Farmers test their soil to know which nutrients they are low in.

There are four main crop nutrients:

  • Nitrogen
  • Phosphorous
  • Potassium
  • Sulfur

All plants need nitrogen, phosphorus, potassium, and sulfur to grow healthy and strong.


Nitrogen (N) is the most important nutrient for crop growth and development. Plants need nitrogen to:
  • help their cells and tissues grow
  • turn energy from the sun into food (called photosynthesis)
  • grow strong and healthy and be nutritious to eat after harvesting
If there is not enough nitrogen, plants will be weak and not grow very well. Too much nitrogen can cause lush, dark green leaves and a lower quality of fruit or grain. Pulse crops (peas, lentils, and chickpeas) are very unique because they can take nitrogen from the air and soil and turn it into a useable form. Farmers apply less nitrogen to pulse crops.
A close-up of nodules on pea roots that look like white and bumpy.

This pea plant has pea nodules on its roots.

Plants absorb nitrogen through their roots. Nitrogen needs to be available in the soil for the plant roots, but too much nitrogen right beside the seed can burn the seed. Farmers need to carefully apply nitrogen fertilizer. Nitrogen fertilizer can be applied to crops in three different forms:
  • Liquid
  • Solid (small granules) or manure
  • Gas (called anhydrous ammonia)
A tractor pulls an air drill, a red tank with seed, and a white tank with fertilizer on a field to seed the crop.

This farmer is seeding with an air drill. The red tank has seed and some granular fertilizer and the white tank has liquid nitrogen fertilizer.

An illustrated wheat plant is shown, as well as the roots below the soil.
N on the Periodic Table of Elements
Nitrogen makes up about 80% of the air we breathe, but in a form that is not suitable for plant growth. Only pulse crops can convert the nitrogen from the air into a usable form.
Nitrogen is essential for plants because it plays a major role in photosynthesis.
Nitrogen is an important part of many cells and processes (and even our DNA).
Most crops need farmers to add nitrogen fertilizers to the soil in order to reach good yields.


Phosphorus (P) comes from ancient sea life. All living organisms require phosphorus, especially plants. Plants need phosphorus to:

  • Help the plant grow healthy roots
  • Store and transport nutrients throughout the plant
  • Grow normally and produce fruit/seeds at the right time
  • Resist disease (because all the plant parts are well developed)
  • Convert energy from the sun into food (photosynthesis)
  • Help pulse crops fixate nitrogen (turn nitrogen from the air into a useable form)

If there is not enough phosphorus, the crop will have reduced growth, weak roots, thin shoots, and dark leaves. Too much phosphorus does not harm plants, but will cause it to be lacking in other nutrients.

An illustrated canola plant is shown, as well as the roots below the soil.
P on the Periodic Table of Elements
Phosphorus helps to capture the sun’s energy and transforms that energy into chemical energy (photosynthesis), which plants use to grow.
Phosphorus gives crops the energy they need to extract nutrients from the soil.
Phosphorus helps plants to resist or fight off diseases.
Phosphorus helps the plant grow at a good pace so it can reach maturity before winter comes.
Phosphorus is essential for helping plants grow a healthy root system.


Potassium (K) or Potash comes from evaporated oceans. Potassium is needed by plants to:

  • protect plants from diseases by strengthening their root system
  • make plants more resistant to the cold and droughts
  • help the plant to soak up water efficiently
  • help cycle nutrients through leaves, roots, and stems

A lack of potassium will cause reduced growth and yellowing and dead spots on the leaves. Too much potassium is not toxic for plants, but can affect how much of other important nutrients the plant can absorb.

An aerial view of a Saskatchewan potash mine with many large buildings and track tracks coming up to the buildings is shown with a cloudy sky over it.

This is a potash mine in Rocanville, SK.

Saskatchewan has the largest potash industry in the world! We have about 45% of the world’s potash. Potash is mined here and sold to countries all around the world. Because most of the soil in Saskatchewan has high levels of potassium, farmers don’t need to add very much to the soil.

An illustrated canola plant is shown, as well as the roots below the soil.
K on the Periodic Table of Elements
Potassium works with nitrogen to promote crop growth.
Potassium helps the plant to be more resistant to the cold, which gives it some frost tolerance.
Potassium is in all crops grown for food.
Potassium protects the plants from diseases and insects.
Potassium helps a plant regulate the amount of water it uses. This can prevent disease and heat damage.

Sulfur (or Sulphur)

Sulfur comes from fossil hydrocarbons which are often found in areas with high volcanic activity. Sulfur is sometimes called the 4th essential nutrient and is very important for plant growth. Plants need sulfur to:

  • Help to make the building blocks of proteins
  • Turn the energy from the sun into food, which is called photosynthesis
  • Make oil
  • Use nitrogen best
  • Produce healthy flowers
  • Grow healthy roots and nodules
A close-up of crystallized, bright yellow sulphur.

Sulfur is a bright yellow crystal in its natural state.

Oilseed crops,  forage crops, and legume crops require more sulfur than other crops such as wheat, barley, or oats.

Plants absorb sulfur from the soil with their roots. Sulfur does not move throughout the plant, so plants need constant access to it throughout the growing season from the time the plant starts to grow, to flowering, to maturity.

An illustrated group of legume crops plants are shown with titles. The Legume crops group includes lentils, chickpeas, peas, and beans.

These legume crops all require more sulfur than many other crops.

An illustrated group of oilseeds crops plants are shown with titles. The oilseed crops group includes canola, flax, mustard, camelina, and sunflower.

These oilseeds crops all require more sulfur than many other crops.

Crops require just 10% as much sulfur as they do nitrogen. If there is not enough sulfur, plants will have short or thin steams, yellow new leaves, delayed and longer flowering, small pods, and reduced yield.

Sulfur and nitrogen work together and a careful balance of both is needed to produce the healthiest crops.

An illustrated canola plant is shown, as well as the roots below the soil.
S on the Periodic Table of Elements
Sulfur works with nitrogen to promote crop growth.

Sulfur helps the plant to be more resistant to the cold, which gives it some frost tolerance.

Photosynthesis depends on sulfur, which is required to produce chlorophyll, which gives plants their green colours. 
Sulfur is required for the plant to grow healthy roots.
Sulfur can only be absorbed by plants through their roots from the soil.

4-R Nutrient Stewardship

The goal of fertilizing crops is to increase the crop’s production, increase profits, protect the environment, and improve sustainability. Farmers are not just trying to grow good crops, they also have a responsibility to take care of the land and water.
A close-up of an unripe, green crop is shown with a blue sky in the background. Illustrated circles and hexagons with different periodic element symbols in them appear to float on the soil.

All plants need the right nutrients, at the right rate, at the right time, and at the right place.

If too much fertilizer is added at the wrong time, then the unused fertilizer can go into the soil and eventually into rivers and lakes. Different crops have different nutrient needs. Different crops grow differently, and they also have different root systems so they cannot absorb the same amount of moisture from the soil.

To be good stewards of the land, farmers follow the 4-R Nutrient Stewardship Guidelines.


What are the 4Rs?



Right Fertilizer


Apply nutrients (N, P, K) that matches what the crop needs.




Right Time


Give the crop the nutrients when it needs it most.




Right Rate


Put the right amount of nutrients to match what the crop needs.



Right Place


Put the nutrients near the roots, where the crops can use them.