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Sulfur (S) Nutrient Deficiencies

Sulfur is classified as a secondary nutrient, but it is the fourth major nutrient necessary for plant health. Learn to diagnose and cure sulfur deficiency.

Sulfur (S) Nutrient Deficiencies

Even though sulfur is classified as a secondary nutrient, it is often referred to as the fourth major nutrient necessary for plant health, alongside nitrogen, phosphorus and potassium.

Why Is Sulfur Important?

Sulfur is a nutrient that is required for the production of chlorophyll. The sulfur that is present in plants supports the formation of important enzymes necessary for the development of plant proteins. Sulfur is also a partner in the metabolism of nitrogen in plants. Sulfur is utilized by the plant to produce cells and seeds as well as hormones and vitamins including B1.

Identifying Sulfur Deficiency In Plants

 Sulfur deficiency results in yellowing of the upper, younger leaves. Leaf veins may appear lighter in color than the surrounding areas of the leaf. The visual symptoms of a sulfur deficiency are very similar to the chlorosis found in nitrogen deficiency. To decipher between the two, take note of where the discoloration is occurring. A sulfur deficiency should not be confused with a nitrogen deficiency, which appears first on lower, older leaves before spreading to the whole plant, wherein a sulfur deficiency will present itself first on the upper leaves.

  • New growth starts to yellow
  • New growth is stunted and small




How To Correct Sulfur Deficiency

Any time a nutrient deficiency is suspected, one of the first things to take a look at is pH balance, in both soil and hydroponic growing systems. A pH imbalance will block nutrient uptake through the plant’s roots. It is important to regularly check the pH, and to be sure to keep the pH within the appropriate range for soil or hydroponics. The optimal pH range for most plants is between 5.5 and 6.5. In this range, the nutrients present in the soil or water are soluble, and are easily taken up through the plant’s root system. When the pH level is outside of this range, even when the proper nutrients are present, they are not able to be absorbed by the plant.



If you discover that your sulfur deficiency is a result of a pH imbalance in your soil, it is best to flush your entire growing medium with fresh water that is at the desired pH level after mixing in nutrients, including sulfur. In a hydroponic system, some of the nutrient solution should be drained off and replaced with fresh water that is pH and nutrient balanced. This process should bring your pH level in balance with where it needs to be.

Once you are certain that pH levels are where they need to be for proper nutrient uptake, you may discover that your plants do indeed need an extra boost of sulfur.

One of the simplest ways gardeners and growers improve the sulfur content of their growing medium is through the use of Epsom salt. Epsom salt is made up of magnesium and sulfur, and it helps to improve the creation of chlorophyll, which again is essential to a plant’s health. It’s as simple as diluting Epsom salt in water, dissolve 1 to 2 teaspoons magnesium sulfate per gallon of water, and apply it to the roots and as a foliar spray until symptoms are no longer present.

Organic growers can add mushroom composts or most types of animal manure to correct the deficiency. Make sure to apply only well rotted manures to avoid burning the roots.



Now that you know the benefits of monitoring the sulfur content in your soil and hydroponic growing systems, and what to do when you spot a deficiency, you can be sure to have the necessary tools on hand to keep your plants at their best.


Want to learn more about nutrient deficiencies?

Read our entire nutrient deficiency series as well as learning about micro vs macronutrients.