I. Chemical Composition and Key Characteristics

1. MOP (Potassium Chloride, KCl)
   • Composition: Contains ~60% potassium oxide (K₂O) and ~47% chlorine (Cl).
   • Characteristics:
     • Abundant in resources and low-cost, dominating the global potassium fertilizer market (over 95% of usage).
     • Highly water-soluble with rapid efficacy, but chloride ions may harm chloride-sensitive crops.
     • Long-term application may acidify soil, requiring supplementation with alkaline fertilizers (e.g., lime).
2. SOP (Potassium Sulfate, K₂SO₄)
   • Composition: Contains ~50–52% K₂O and ~18% sulfur (S).
   • Characteristics:
     • Chemically neutral and physiologically acidic, free of chloride ions, suitable for chloride-intolerant crops.
     • Provides sulfur to promote chlorophyll synthesis and protein formation, enhancing disease resistance.
     • Higher cost but significantly improves fruit quality (e.g., sugar content, color).

II. Suitable Crops and Scenarios

1. MOP Application Scenarios
   • Field Crops: Corn, wheat, rice, and other chloride-tolerant crops for cost-effective potassium supplementation.
   • Neutral/Alkaline Soils: Chloride ions can lower soil pH but require caution to avoid salt damage from overuse.
   • Cost-Priority Cases: Short-term use during non-critical growth stages of chloride-sensitive crops or in soils with low chloride content.
2. SOP Application Scenarios
   • Chloride-Sensitive Crops: Tobacco, grapes, tea, potatoes, sugar beets, and watermelons, where chloride inhibits growth or reduces quality.
   • Acidic Soils: Sulfur neutralizes acidity and improves soil aeration.
   • High-Quality Demand: Fruits and vegetables requiring enhanced sugar content, firmness, or storage life.
   • Saline-Alkali Soils: Avoids chloride accumulation exacerbating salinity issues.

III. Performance Comparison

IV. Market Trends and Data

• Global Sales: In 2020, potassium sulfate sales reached 7.255 million tons, with a projected market value of $48.48 billion by 2030 (CAGR 3.1%).
• Regional Distribution: Major producers include China, the U.S., Chile, and Germany, with China accounting for ~20% of global output.
• Price Dynamics: Sulfate prices fluctuate with sulfur costs, while chloride prices are influenced by international potash markets.

V. Recommendations

1. Opt for MOP when:
   • Growing chloride-tolerant field crops with cost constraints.
   • Soil chloride levels are low, and acidification risks are minimal.
2. Choose SOP when:
   • Cultivating chloride-sensitive cash crops or targeting premium fruit quality.
   • Managing acidic soils or requiring sulfur supplementation.
   • Working in saline-alkali or chloride-sensitive regions.
3. Blended Use Suggestions:
   • Apply MOP during early growth stages of chloride-sensitive crops, then switch to SOP later.
   • Combine with organic or alkaline fertilizers (e.g., lime) to balance chloride and soil acidity.