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Sulphur for Plant Growth: The Forgotten Hero

When it comes to discussing essential elements for plant growth, nitrogen, phosphorus, and potassium often steal the spotlight. However, in the list of essential plant nutrients, sulphur, with its remarkable benefits, deserves recognition. Often overlooked, this vital element plays a crucial role in the development and overall health of plants. In this article, we will uncover the importance of sulphur in plant growth and its undeniable impact on the flourishing green world around us.

Sulphur: A Powerful Ally for Plant Health

Sulphur, a naturally occurring element, is a vital nutrient necessary for the synthesis of proteins, enzymes, and vitamins within plants. Just as we rely on protein for our growth and development, plants also require an ample supply of sulphur to thrive. Although plants do not require sulphur in as large quantities as nitrogen, phosphorus, and potassium, it is by no means a micronutrient, and it needs to be available in good quantities for optimal growth.

Sulphur deficiencies a modern problem!

Up until the 1970s sulphur deficiencies in crops were fairly rare. This was due to factors. In the developed world, sulphur was being supplied to agricultural fields as dissolved sulphur dioxide; a pollutant from a number of industrial processes. As industry has cleaned up its act, and we have moved away from coal-fired power stations, the supply of sulphur nutrition from pollution has dramatically reduced. Secondly, the organic matter content of soils has reduced. Organic matter/ humus is a good source of sulphur (and some micronutrients) for plants.

So together these two factors, reduced pollution and reduced organic matter content, have resulted in a number of crops suffering from sulphur deficiencies. However, there are two problems for growers/farmers wishing to address sulphur deficiencies. Firstly; sulphur deficiencies are hard to spot and often mistaken for signs of nitrogen or iron deficiency. This is because the main symptom is chlorosis of leaves, very similar to nitrogen deficiency. However, unlike nitrogen deficiency the chlorosis presents on younger leaves first. Unfortunately your plants may be suffering significant reductions in growth (stunting) before chlorosis become visible.
The second major hurdle to addressing sulphur deficiencies is that many ‘complete/compound’ fertilisers completely lack sulphur. This is because sulphur can react with the other nutrients in the mix, and because many of these traditional ‘old school’ fertilisers were developed before sulphur deficiency became an issue. Therefore, I strongly advise that you check the label on your fertiliser and see if it contains a good amount of sulphur. If it does not, consider supplementing the feeding of your plants with one of these three sulphur fertiliser options:

  • Ammonium thiosulphate: A soluble form of soluble sulphur. Allows for both instant and medium-term sulphur release to the plants.
  • Liquid Gypsum: Combines calcium and sulphur. Also flocculates (breaks up) clay soils.
  • Lime Sulphur: Calcium and sulphur, but also has a sterilising effect on the plant surface and in the soil. So use when pests or diseases get out of hand. Very popular with rose growers to control Black Spot fungus.
  • Epsom salts: magnesium sulphate. A good option for lawns where you want to green them up, without stimulating excessive leafy growth.

Avoid powdered sulphur as a fertiliser. It is not plant-available or soluble. Plus it is converted to sulphuric acid and acidifies the soil.

The Role of Sulphur in Plants

  1. Aiding in Protein Synthesis: Proteins are the building blocks of life, and sulphur plays a key role in their formation. Sulphur-containing amino acids, such as cysteine and methionine, are essential components of proteins. These amino acids provide structural stability and contribute to the functionality of enzymes, hormones, and chlorophyll molecules, thus supporting the overall growth and development of plants.
  2. Enhancing Nutrient Uptake and Efficiency: Sulphur promotes the efficient uptake and utilization of other essential nutrients. It aids in the absorption of nitrogen, phosphorus, and potassium, allowing plants to maximize the benefits of these macronutrients. Sulphur also contributes to the activation of enzymes responsible for nutrient metabolism, ensuring that plants have a well-balanced diet.
  3. Stimulating Root Development: Strong and healthy roots are the foundation for robust plant growth. Sulphur plays a crucial role in the formation of roots by encouraging cell division, elongation, and differentiation. By facilitating root development, sulphur promotes better nutrient and water absorption, leading to overall plant vigor.
  4. Boosting Disease Resistance: Sulphur is known for its fungicidal and bactericidal properties. By producing chemical compounds that inhibit the growth of pathogens, sulphur enhances the plant’s natural defense mechanisms. This reduces the risk of diseases caused by fungi, bacteria, and certain pests, ensuring healthier plants and higher crop yields.
  5. Contributing to Flavor and Aroma: In addition to its essential functions in plant growth, sulphur also plays a role in enhancing the flavor and aroma of certain crops. For example, it is responsible for the distinctive taste and aroma of onions, garlic, and cruciferous vegetables like broccoli and cabbage. Sulphur compounds contribute to the pungent and aromatic qualities that make these foods so appealing.


While often overshadowed by other essential nutrients, sulphur is undeniably critical for plant growth and overall plant health. From protein synthesis and nutrient uptake to root development and disease resistance, the role of sulphur is multifaceted and essential for the flourishing of plant life. By recognising the significance of this hidden hero, farmers and gardeners can unlock its full potential to cultivate healthier crops, promote sustainable agriculture, and nourish the world with bountiful harvests.

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