A Comprehensive Guide on How to Differentiate Agricultural Compound Fertilizers

In agricultural production, compound fertilizers come in various types, with nitrate-sulfate, sulfate-based, chloride-based, urea-based, and dual-sulfur types often causing confusion.

These fertilizers differ significantly in their components, manufacturing processes, application ranges, and effectiveness.

This article introduces the features of each type, helping farmers select and apply fertilizers more effectively to improve crop yields and quality.

Nitrate-Sulfate Compound Fertilizer

✅ Definition and Composition

Nitrate-sulfate compound fertilizers use ammonium nitrate as the nitrogen source and potassium sulfate or dechlorinated potassium chloride as the potassium source. These fertilizers contain both nitrate and ammonium nitrogen, with chloride ion levels below 3% and no biuret. Common products include ammonium nitrate phosphate and ammonium nitrate phosphate-potash.

🏣 Manufacturing Process

• Drum Granulation: Ammonia and nitric acid undergo pressurized neutralization to form ammonium nitrate solution (90%-95% concentration), which is sprayed into a drum granulator and granulated with phosphate and/or potash.

  
  

• Tower Granulation: Concentrated ammonium nitrate (>98%) is reacted with phosphate or potash and granulated via tower spraying.

  
  

• Other methods include the BASF nitrophosphate process and secondary nitrophosphate processing.

  
  

🌿 Application Scope

Best suited for dryland crops such as fruits, vegetables, fruit trees, corn, and tobacco. It performs well on calcareous soils (high pH), benefiting calcium-loving plants like corn, most vegetables, cotton, and other nitrate-preferred crops.

🌟 Efficiency Characteristics

• Rapid Effect: Nitrate nitrogen is readily absorbed by plants, offering fast mobility and nutrient supply. Plant vacuoles can store high nitrate concentrations, releasing them when soil nitrogen is deficient.

  
  

• High Utilization: Promotes phosphate and potassium uptake, minimizes nitrite accumulation, and is a clean, efficient, and environmentally friendly fertilizer.

  
  

💡 Usage

Can be applied as basal or top dressing. Basal application should be deep and covered. Top dressing should avoid direct seed or root contact to prevent burning. As it is acidic, avoid mixing with alkaline fertilizers or pesticides to prevent adverse reactions.

Sulfate-Based Compound Fertilizer

✅ Definition and Composition

Uses potassium sulfate as the potassium source, with chloride ions below 3% per national standards. Sulfur is considered the fourth essential nutrient after nitrogen, phosphorus, and potassium. This fertilizer improves sulfur-deficient soils and supplies sulfur directly to crops.

🏣 Manufacturing Process

Blends potassium sulfate with nitrogen- and phosphorus-containing raw materials through mixing and granulation under strict quality control.

🌿 Application Scope

Suitable for all soils and crops, especially sulfur-demanding crops like onions, leeks, garlic, rapeseed, sugarcane, peanuts, and legumes. Not suitable for aquatic vegetables.

🌟 Efficiency Characteristics

• Improves Soil: Alleviates sulfur deficiency, adjusts pH, supports beneficial microbes, and enhances soil structure and fertility.

  
  

• Enhances Quality: Improves crop appearance and taste; brightens fruit color, enriches vegetable flavor and freshness.

  
  

💡 Usage

It can be used as basic fertilizer, supplementary fertilizer, seed fertilizer and extra-root fertilizer.

For fertilizer, and then mulch; for seed fertilizer, pay attention to fertilizer and seeds to maintain a certain distance, to avoid burning seeds; root fertilizer can be formulated into a certain concentration of fertilizer solution, foliar spraying, pay attention to the spraying time and concentration, to avoid spraying in the high temperature, strong light hours, so as not to burn the leaves.

Chloride-Based Compound Fertilizer

✅ Definition and Composition

Uses potassium chloride as the potassium source. Classified into:

• Single-chloride: Potassium from KCl, nitrogen from chloride-free sources like urea.

  
  

• Double-chloride: Potassium from KCl, nitrogen from ammonium chloride.

  
  

🏣 Manufacturing Process

KCl is combined with nitrogen and phosphorus sources and granulated. It is simple and cost-effective but requires chloride control.

🌿 Application Scope

Suitable for chloride-tolerant or chloride-loving crops such as coconut, onion, spinach, celery, cabbage, beet, rice, millet, sorghum, barley, wheat, corn, eggplant, pea, chrysanthemum. Moderately tolerant crops include cotton, soybean, rapeseed, tomato, citrus, grape, tea, scallion, radish. Avoid use on chloride-sensitive crops like lettuce, green beans, tobacco, tubers, or saline-alkali soils.

🌟 Efficiency Characteristics

• Crop Specificity: Chloride promotes growth in tolerant crops and enhances fiber development in fiber crops.

  
  

• Fast Action: Nitrogen and potassium are quickly absorbed, offering similar performance to sulfate fertilizers under normal conditions.

  
  

💡 Usage

Suitable as basal or top dressing. Not recommended for seed application. Combine with organic fertilizers in neutral/acidic soils to mitigate chloride effects. Apply top dressing early to allow chloride leaching. Adjust dose based on crop tolerance.

Urea-Based Compound Fertilizer

✅ Definition and Composition

Uses urea as the nitrogen source, blended with MAP, DAP, KCl, or K2SO4. Nitrogen is mainly in amide form (CO(NH2)2), providing sustained nitrogen supply. Also includes phosphorus and potassium.

🏣 Manufacturing Process

• Granulation: Mix urea, phosphate, and potash with water and binders, then granulate via rolling or pressing.

  
  

• Tower Granulation: Molten urea is mixed with other materials and sprayed from a tower to form solidified granules with controlled release.

  
  

🌿 Application Scope

Suitable for most soils and crops, particularly grains (corn, wheat, rice), vegetables, and fruit trees. Best on low-fertility soils. Less effective in alkaline soils due to nitrogen volatilization.

🌟 Efficiency Characteristics

• Long-Lasting: Amide nitrogen converts to ammonium slowly under urease activity, offering prolonged nutrient supply.

  
  

• Balanced Nutrition: Contains N, P, and K; proportions can be tailored to crop and soil needs, enhancing yield and stress resistance.

  
  

💡 Usage

Use as basal or top dressing. Deep placement before sowing/transplanting (7–10 days). For top dressing, bury and cover to prevent ammonia loss. Avoid mixing with alkaline fertilizers like wood ash.

Dual-Sulfur Compound Fertilizer

✅ Definition and Composition

Uses ammonium sulfate as the nitrogen source and potassium sulfate as the potassium source. High in sulfur, and includes N, P, and K.

🏣 Manufacturing Process

Prepared via chemical synthesis from raw materials like sulfuric acid, sulfur, and urea. Precise formulation ensures balanced nutrients and product stability.

🌿 Application Scope

Ideal for high-sulfur-demanding crops or crops with strict quality requirements such as fruits, vegetables, and flowers. Works well in all soils, especially sulfur-deficient ones.

🌟 Efficiency Characteristics

• Stable & Efficient: Improves nutrient stability and uptake, prolonging fertilizer effect.

  
  

• Multifunctional: Enhances root development, soil quality, and crop resistance to stress (drought, flood, pests).

  
  

💡 Usage

Can be used as basal, top dressing, or seed fertilizer. For seed application, separate from seeds to prevent burn. Adjust dosage based on soil fertility and crop growth.

📊 Conclusion and Recommendations

Each compound fertilizer type—nitrate-sulfate, sulfate-based, chloride-based, urea-based, and dual-sulfur—has distinct advantages. Farmers should choose based on:

• Soil characteristics (pH, salinity, fertility)

  
  

• Crop type and nutrient demands

  
  

• Growth stage and fertilization requirements

  
  

• Application methods and budget

Scientific selection and proper use of compound fertilizers will enhance crop yield, quality, and soil health while improving overall agricultural efficiency.