Urea-based, Sulfur-based, and Chlorine-based Compound Fertilizers: Raw Material Ratios, Production Process Difficulty, and Chlorine-sensitive Crop Selection

 Compound fertilizers on the market are mainly divided into three categories based on their potassium and nitrogen sources: urea-based, sulfur-based, and chlorine-based. The production processes, raw material ratios, and applicable crops differ significantly among these three types. Choosing the wrong type may lead to reduced yields or even crop failure. This article analyzes these differences from two dimensions: production principles and application scenarios.

I. Differences in Raw Material Ratios

Urea-based Compound Fertilizer: Uses urea as the main nitrogen source (a small amount of ammonium nitrogen may also be added), and the potassium source is usually potassium chloride. Typical formulations include high-nitrogen products such as 28-6-6 and 25-10-10. Urea is easily melted during granulation, requiring high temperature control in the process.

Sulfur-based Compound Fertilizer: Uses potassium sulfate or potassium magnesium sulfate as the potassium source, and the nitrogen source can be urea, ammonium sulfate, or ammonium chloride. The formulation has a higher sulfur content (generally ≥5%), suitable for sulfur-loving crops. The raw material cost is significantly higher than that of chlorine-based fertilizers.

Chlorine-based compound fertilizer: The potassium source is potassium chloride, and the nitrogen source can be urea or ammonium chloride. It is the most common and lowest-cost type on the market. It has a relatively high chloride ion content (usually between 10% and 15%), and the production process is relatively simple.

II. Production Difficulty

Urea-based compound fertilizer: Because urea softens and melts above 65℃, the granulation and drying processes must be strictly temperature controlled (usually granulation temperature ≤60℃, drying air temperature ≤150℃), otherwise it will stick to the walls, clump, and even pose a risk of biuret poisoning. The production line needs to be equipped with a low-temperature, high-volume drying system. Equipment investment and operation difficulty are moderate.

Sulfate-based compound fertilizer: Potassium sulfate has low hygroscopicity and poor flowability, requiring the addition of more binders or steam assistance during granulation. Sulfate-based products also easily generate acidic gases, requiring high corrosion resistance in equipment (stainless steel lining is required). Overall, it has the highest production difficulty, energy consumption, and cost.

Chlorine-based compound fertilizer: Potassium chloride is widely available and inexpensive. During granulation, it provides moderate material viscosity and a wide temperature control window, making it easy to produce using conventional drum or roller pressing processes. The drying and cooling processes are highly forgiving, making it the simplest type of fertilizer to use.

III. Safety Recommendations for Chlorine-Sensitive Crops

Chloride ions are essential micronutrients for crops, but excessive amounts can inhibit starch and sugar accumulation and are toxic to some plants.

List of Chlorine-Sensitive Crops: Tobacco, potatoes, sweet potatoes, sugar beets, sugarcane, citrus, grapes, tea trees, watermelons, strawberries, etc. Chlorine-based compound fertilizers should be absolutely avoided on these crops, otherwise, problems such as poor combustibility of tobacco leaves, reduced starch content in tubers, decreased sugar content in fruits, and scorched leaves will occur.

Safe Alternative: Sulfate-based compound fertilizers should be chosen for the above crops. The sulfur in potassium sulfate can also promote protein synthesis and increase the content of flavor compounds, and it also has a yield-increasing and quality-improving effect on onions, garlic, and cruciferous vegetables.

Chlorine-Tolerant Crops: Rice, wheat, corn, cotton, and hemp are not sensitive to chlorine and can safely use chlorine-based compound fertilizers, offering better cost-effectiveness.

The positioning of urea-based compound fertilizers: Urea-based products have a high nitrogen content, but if the potassium source is potassium chloride, it also contains chlorine and cannot be used for chlorine-sensitive crops. Only products clearly labeled "potassium sulfate type" or "sulfur-based" are suitable for chlorine-sensitive crops.

IV. Summary

When purchasing compound fertilizers, farmers should carefully check the "chlorine ion content" label on the packaging. Products labeled "low chlorine," "medium chlorine," or "high chlorine" should not be used for chlorine-sensitive crops; products labeled "potassium sulfate type" or "sulfur-based" are the safest choice for chlorine-sensitive crops. We specialize in the research and development and manufacturing of complete production lines for urea-based, sulfur-based, and chlorine-based compound fertilizers. All three process routes can be customized—from low-temperature anti-sticking to corrosion-resistant and acid-resistant—our professional team will tailor a design to your specific needs, ensuring your production line precisely matches crop requirements and market positioning.

The distinction between urea‑based, sulfur‑based, and chlorine‑based compound fertilizers is not merely a matter of raw material choice—it directly influences production technology, equipment selection, and field performance. Effective npk fertilizer formula processing must account for the source of potassium and nitrogen, as each type demands specific handling during npk fertilizer raw materials processing: urea‑based formulas require strict temperature control (granulation ≤60°C, drying air ≤150°C) to prevent melting and biuret formation; sulfur‑based formulations necessitate corrosion‑resistant equipment and additional binders; while chlorine‑based products are the most forgiving and cost‑effective to manufacture. For granulation, the npk fertilizer granulator machine selection varies accordingly—a double roller press granulator is particularly well‑suited for dry compaction of chlorine‑based and high‑urea formulations, as it eliminates the need for drying and reduces energy consumption, while a rotary drum granulator with steam injection is often preferred for sulfur‑based products to improve flowability and binding. The entire npk fertilizer manufacturing process—from weighing, mixing, granulation, drying, cooling, to screening—must be optimized for each type, ensuring nutrient uniformity and particle strength. For downstream blending, an npk bulk blending machine can combine base granules of different types to create custom blends, provided that chloride‑sensitive crops are strictly segregated from chlorine‑containing products. Ultimately, understanding these differences enables producers to tailor their production line and quality control measures to match both agronomic requirements and market positioning, delivering the right fertilizer for the right crop at the right cost.