In your garden soil, sulphur is as important to your plants’ vitality as phosphorous. Plants need exactly 22 things to exist: water, light and 20 essential elements that support biochemical needs. As a gardener, you’re likely to be familiar with at least three of those elements – nitrogen, phosphorous and potassium.
Sulphur in the soil will increase soil biodiversity which helps create a balanced and healthy ecosystem, different types of bacteria, fungi and other microorganisms can help break down organic matter and make nutrients available to the plant.
Sulphur improves the soil structure as it helps form aggregates, clumps of soil particles held together by natural substances; scubas mucilage, waxes or gums. They’re important for soil health because they provide stability and allow water and air to penetrate more easily.
Sulphur helps soil particles to bind together making it easier for plants to draw nutrients which increases plant growth by developing chlorophyll which improves photosynthesis and growth rates.
Gardens in areas with limited rainfall and little limestone have a high pH level, most plants enjoy a moderate pH, so it’s important to lower this level for healthy growth a plant with symptoms of low sulphur content will exhibit a yellowing of the leaf that seems remarkably similar to nitrogen deficiency. With sulphur depletion within the soil and plant the upper and older leaves are first affected, while nitrogen deficiency shows up on the younger leaves first.
The Sulphur cycle
Sulphur is present in various forms in the environment. Up to 95% of the total sulphur in the soil is associated with organic matter. Other sources of sulphur in soils are animal manure, irrigation water, close to the coast or industrial areas, and the atmosphere, where sulphurous gases such as sulphur dioxide and sulphur trioxide are dissolved in rainwater and washed into the soil. The availability of sulphur from industrial emissions is relatively low in countries like Australia and the United Kingdom with legislation aimed at reducing industrial pollution.
In the soil, sulphur is present as organic sulphur compounds, sulphides (S-), elemental sulphur (S 0), and sulphate (SO42-).
Plants cannot absorb organic or elemental sulphur. For plants to be able to utilise sulphur from the soil it must be in the sulphate form. Organic sulphur and elemental sulphur are converted to the sulphate form in the soil.
Sulphur can be removed from soil through uptake by plants, leaching through and out of the root zone by rainfall or irrigation, and by volatilisation (the conversion of a liquid to a vapour). Sulphur can be transformed from one form to another in the soil through various biological and physical processes. This movement in and out of the soil between different chemical forms in the soil is known as the sulphur cycle.
Sulphur comes in various forms and percentages, either in a prill (granular), wettable sulphur (sulphur which will disperse in water) or ground powder. Each of these has its advantages and is used in different situations
Mini Prill (granular grade) is applied at the base of the plant to reduce the pH of the soil, gradually dissolving with either irrigation or rainfall. Applied twice per year (Spring & Autumn) one application (subject to soil condition) will reduce the pH by 1 on the pH table. The benefit of having sulphur within the soil profile will also help with nutrient uptake as various nutrients become locked up within the soil profile when a sulphur deficiency occurs.
Wettable Sulphur is Sulphur that has been ground and formulated so that it can be dissolved in water and applied through spaying devices without the sprayer nozzles clogging. The advantages of wettable sulphur are that it can be applied numerous times throughout the year and is absorbed through the leaf and into the plant therefore being available to the plant immediately. Sulphur over the years has been identified as a deterrent to Powdery Mildew and Blackspot in plants, especially Roses, vegetables and fruits. As the wettable sulphur is applied a film of sulphur spears on the leaf that reduces fungal but is also applied in the winter to stems will reduce spore activity.
Sulphur Powder/Dust (not to be confused with yellow sulphur), this product is applied to the soil mainly in the agricultural industry where immediate pH reduction is required and not used in this country due to application issues.
Sulphur for Roses
Sulphur applied as a drench to the plant reduces the fungal problem either by leaving a film over the leaf surface and therefore reducing the fungi entering the plant system.
Sulphur is as necessary as phosphorus and is considered an essential mineral, sulphur in plants helps form important enzymes and assists in the formation of plant proteins. It is these proteins that ensure a healthy plant which will help produce healthy blooms and leaves, if we have a healthy plant then there will be a reduction in plant disease.
Sulphur for Fruit & Veg
Do you remember when fruit & vegetables used to taste great? Well, one of the reasons why the taste has diminished is due to the lack of sulphur in the atmosphere which eventually ended up in the soil. When sulphur is absorbed by the plant it will increase vitamins, amino acids and enzymes such as Rubisco which gives fruit and veg their great taste.
Sulphur is a key element in plant growth. It is critical in the production of vitamins, amino acids and enzymes. With a sulphur-deficient plant, the plant will exhibit yellowing of its upper and lower leaves. Once there is a deficiency plants become susceptible to diseases such as powdery mildew, certain rusts and leaf blights. This will result in a lack of maturity (if at all) and just as importantly poor nutritive value.
Regular and continuous use of sulphur fruit and veg will keep fruit and vegetables strong and healthy allowing continuous growth and resilience against diseases.
Sulphur for Plants & Shrubs
Applying nutrients to your borders to help plants and shrubs is important but applying the wrong fertiliser for the appropriate plant/shrub can be financially detrimental. A soil test is important to ensure any deficiency in the soil is rectified, but also the soil test will identify if the soil is appropriate for the plant/shrub that you wish to grow. If an ericaceous plant such as rhododendrons an acidic soil is required and the application of Sulphur twice per year can ensure these plants can be grown.
Conclusion
The use of traditional NPK fertilizer is effective in supplying essential nutrients for plant growth. However, to ensure the sustained health and disease resistance of the plant, it is crucial to incorporate a well-balanced feed that includes sulphur and amino acids tailored to the specific needs of the plant.
Added sulphur, either applied to the soil or through the plant leaf will help with the promotion of chlorophyll that permits photosynthesis through plants producing starch, sugars, oils, fats, vitamins and other compounds.