The Difference Between Water-Soluble Fertilizers and Compound Fertilizers

1. Composition and Nutritional Differences
Water-soluble fertilizers:
Contain macronutrients such as nitrogen, phosphorus, and potassium, along with micronutrients like iron, zinc, manganese, calcium, and magnesium. Some products incorporate functional substances like amino acids and humic acids.
Flexible formulations (e.g., high-nitrogen, high-potassium, balanced types) enable customized nutrient plans for different crop growth stages.
For example, high-nitrogen water-soluble fertilizer promotes shoot and leaf growth during grape bud break, while high-potassium formulations enhance fruit quality during the fruit enlargement stage.
Compound Fertilizer:
Primarily contains nitrogen, phosphorus, and potassium with fixed formulations and limited trace elements.
Offers less targeted nutrition, struggling to meet crops' specific micronutrient demands.
2. Solubility and Absorption Efficiency
Water-soluble fertilizers:
Fully soluble in water with absorption rates exceeding 90%. Rapid efficacy (approx. 20 days) makes them ideal for quick nutrient supplementation.
For instance, foliar sprays are absorbed within hours, alleviating nutrient deficiency symptoms.
Compound fertilizers:
Poor solubility; nutrients require decomposition in soil before absorption, with rates ranging from 30% to 60%.
Long-lasting effect (over 60 days) but slow release, potentially failing to meet urgent crop needs.
3. Application Methods and Flexibility
Water-soluble fertilizers:
Diverse application methods: drip irrigation, sprinkler irrigation, foliar spraying, flushing, etc., suitable for water-fertilizer integration.
Low dosage (5kg per mu), but requires specialized equipment (e.g., drip irrigation systems), resulting in higher costs.
For example, drip irrigation with water-soluble fertilizers is widely adopted in Xinjiang's cotton-growing regions, conserving both water and fertilizer.
Compound Fertilizers:
Primarily applied traditionally: broadcast, furrow, or hole application. Simple operation but low flexibility.
High application rate (40kg per mu), low cost, suitable for large-scale crops.
4. Application Scenarios and Cost
Water-Soluble Fertilizers:
Suitable for: Protected agriculture, cash crops (fruit trees, vegetables), peak nutrient demand periods.
Cost: Unit price is 2-3 times that of compound fertilizer, but lower application rates keep overall costs manageable.
Compound Fertilizer:
Suitable for: Traditional field crops (e.g., wheat, corn), long-term nutrient supply.
Cost: Low, often used as base fertilizer or for extended top-dressing.
5. Environmental Impact and Soil Effects
Water-soluble Fertilizers:
High utilization rate with minimal runoff, reducing soil and water pollution.
Long-term use requires monitoring to prevent salt accumulation (e.g., surface salinization in greenhouse drip irrigation).
Compound Fertilizers:
Prone to residue buildup; prolonged use may cause soil compaction or salt accumulation.
Requires integration with organic fertilizers to improve soil structure.