The essential element that has been naturally depleted in soils in recent decades – due to factors such as soil erosion, leaching and organic matter depletion – is sulfur. A deficiency of this element not only hinders plant growth but also impairs the absorption of other nutrients. Among the solutions, granular sulfur has emerged as a scientific, sustainable and effective answer and has earned a place among the best soil amendment fertilizers. If you are also looking to strengthen your agricultural lands, join us in this article from Petro Sepidar Sadr.
Method of producing granular sulfur
Granular sulfur can be considered a refined by-product of petroleum that, when combined with certain additives, is converted into a form that can be absorbed by plants or used in various industries. In fact, the sulfur used in the production of granular sulfur is usually extracted during the refining process of crude oil and natural gas. It is obtained as a byproduct of the desulfurization process, which aims to reduce the sulfur content in oil and gas to prevent environmental pollution. After extraction, the raw sulfur is melted and then mixed with materials such as bentonite to form solid, stable granules. This form is more stable and more practical for agricultural and industrial applications.
What is Granular Sulfur Fertilizer?
As explained above, granular sulfur fertilizer is a chemical fertilizer consisting of compressed, granulated particles, usually made by combining elemental sulfur with bentonite or other swelling agents. This fertilizer swells upon contact with soil moisture, gradually releasing sulfur particles into the soil. Bentonite acts as a swelling agent, helping to break down sulfur more evenly and effectively, thereby increasing its uptake by plant roots.
In terms of composition, this fertilizer typically contains 75 to 90 percent sulfur and 10 to 25 percent bentonite. Its granular form makes it easier to transport, store, and spread evenly over the field, and it is more resistant to wind and washout than other forms of sulfur fertilizer.
What is the difference between granular, powdered, and liquid sulfur?
Powdered sulfur typically reacts more quickly in the soil, but due to its light weight and high dispersion, it is challenging to apply over large areas. It can be carried by wind or washed away by rain before the plant can absorb it. In addition, it oxidizes quickly, increasing the risk of losing sulfur before it can be absorbed by the plant.
In contrast, liquid sulfur is more commonly used for foliar applications and has limited root uptake. Granular sulfur, on the other hand, provides a slow and controlled release, giving plants long-term access to sulfur, leading to more sustainable improvements in soil pH and structure.
Bentonite granular sulfur is available in a variety of forms with varying ratios of sulfur (typically 70% to 90%) to bentonite (10% to 30%). Each type can be selected based on soil type, plant needs, and application method. These characteristics make it an ideal option for amending alkaline and calcareous soils.
How does granular sulfur work in the soil?
Granular sulfur swells when applied to the soil due to moisture. The bentonite in the granules helps the sulfur break down gradually. In this process, sulfur is first converted to elemental sulfur and then, with the help of microorganisms such as Thiobacillus bacteria, to sulfate, a form that is absorbable by plants.
The presence of bentonite in the fertilizer helps retain moisture around the sulfur particles, which increases the speed and uniformity of oxidation. As a result, sulfur is released slowly and has a continuous effect on soil and plant health. This slow-release function not only increases efficiency, but also prevents sulfur from being lost through leaching.
Benefits of Granular Sulfur in Agriculture
Thanks to the clever combination of sulfur and bentonite, granular sulfur offers countless benefits for soil and plants, making it one of the most effective fertilizers in agriculture.
1. Amending alkaline and calcareous soils
One of the key benefits of granular sulfur is its ability to lower soil pH. In many areas, soils are naturally alkaline, which prevents roots from absorbing many essential nutrients. Granular sulfur gradually releases sulfur and converts it to sulfuric acid, causing localized soil acidity and better nutrient absorption – especially effective in calcareous and saline soils.
2. Increases nutrient availability
Sulfur plays a vital role in improving the availability of key nutrients such as nitrogen, phosphorus, potassium, iron, manganese and zinc. When soil pH decreases, these nutrients change from insoluble forms to forms that can be absorbed by the roots. As a result, plant nutrition is significantly improved and nutrient deficiency symptoms are reduced.
3. Improves soil structure
The use of granular sulfur helps increase soil porosity and aeration. The bentonite content improves the soil’s ability to retain water, making it softer and more permeable. This is especially useful in dry areas or heavy soils, where water and air penetration to the roots is often a challenge. It also increases biological activity in the soil.
4. Increases plant growth and crop quality
Granulated sulfur fertilizer creates optimal conditions for nutrient uptake, resulting in faster and stronger plant growth. It also increases protein in grains, oil in oilseeds, and flavor in fruits and vegetables. Many agricultural crops, such as garlic, onions, and radishes, which have strong flavors and aromas, are highly dependent on sulfur.
5. Antifungal and soil disinfectant properties
Another important benefit of granular sulfur is its ability to control soil fungal diseases such as powdery mildew. Sulfur creates an acidic and disinfectant environment that is unfavorable for fungi and some pests. This function not only protects plant health, but also reduces the need for chemical pesticides.
6. Stimulates beneficial microbial activity in the soil
Granular sulfur, due to its organic content and bentonite base, creates a suitable environment for beneficial soil bacteria and fungi. These microbes play a key role in the decomposition of organic matter and the release of nutrients. In addition, the conversion of sulfur to sulfate is carried out by these bacteria, which leads to improved fertility and biological health of the soil.
How to use and apply granular sulfur
To achieve the best results with granular sulfur, the time and method of application are very important. The ideal time for application is usually late autumn before planting or early in the growing season. During these periods, the soil is most ready to absorb nutrients and microbial activity is high.
The method of application also varies depending on the type of crop. Granular sulfur can be applied by surface spreading, banding near the roots of trees or mixing with animal manure.
The recommended application rate varies depending on the field and soil conditions:
In orchards: about 1 to 3 kg per tree
In crops: 500 to 1000 kg per hectare
In greenhouses: about 250 g per square meter
For best results, it is recommended to plow the soil after applying the fertilizer to ensure proper mixing and maximum absorption of nutrients.
Conclusion
In modern, high-yielding agriculture, sulfur is no longer an optional element; it is an essential and vital element for maintaining productivity, crop quality and soil health. The use of bentonite granulated sulfur, with its slow release mechanism, soil stability, and effectiveness in amending alkaline soils, represents a scientifically proven approach to plant nutrition management.
It is strongly recommended that you test your soil before using this fertilizer and consult with agricultural experts to determine the exact dosage and timing of application. Choosing the right type of sulfur and using it strategically can significantly increase the productivity of your land. You have read this article in collaboration with Petro Sepidar Sadr, a manufacturer and supplier of petroleum products
