The combined use of calcium-magnesium fertilizers and humic acid is a common practice in agricultural production, with each offering unique functions and benefits. Below is a detailed analysis of whether they can be mixed, along with the reasons and considerations:

I. Functions and Roles of Calcium-Magnesium Fertilizers

1. Nutrient Supply

• Nitrogen, Phosphorus, and Potassium Content: Calcium-magnesium fertilizers are rich in essential macronutrients like nitrogen (N), phosphorus (P), and potassium (K), which promote crop growth and development.
• Micronutrient Supplementation: Besides macronutrients, these fertilizers contain micronutrients such as calcium (Ca) and magnesium (Mg), which enhance disease resistance and stress tolerance in plants.

2. Soil Improvement

• Soil Structure Enhancement: Calcium ions in the fertilizer react with hydrogen ions in the soil to form insoluble calcium carbonate, increasing soil porosity, aeration, and water retention.
• Soil Fertility Boost: Magnesium ions regulate soil pH, creating a more plant-friendly environment while stimulating microbial activity and improving soil fertility.

3. Stress Resistance

• Enhanced Disease Resistance: Micronutrients in calcium-magnesium fertilizers strengthen plants' immune systems, reducing susceptibility to diseases.
• Drought Tolerance: Calcium ions help balance water uptake in plants, enabling better growth under drought conditions.

4. Yield and Quality Improvement

• Increased Crop Yields: The nutrients in calcium-magnesium fertilizers provide energy and materials for plant growth.
• Better Crop Quality: These fertilizers improve taste, nutritional value, and marketability of crops.

II. Functions and Roles of Humic Acid

1. Soil Improvement

• Toxin Adsorption: Humic acid binds heavy metals and other soil contaminants, reducing their harm to crops. It also promotes beneficial microbial growth, enhancing soil bioactivity.
• Organic Matter Release: Humic acid supplies organic matter, enriching soil nutrients and increasing the availability of microelements for plants.

2. Disease and Stress Resistance

• Antimicrobial Effects: Organic acids in humic acid inhibit pathogen growth, reducing disease incidence. It also boosts plants' natural immunity.
• Water Regulation: Humic acid's organic matter helps plants maintain water balance, improving drought resilience.

3. Yield and Quality Improvement

• Higher Yields: Humic acid provides nutrients that directly support crop growth.
• Enhanced Quality: Crops treated with humic acid often exhibit better taste and nutritional profiles.

III. Feasibility and Advantages of Combining Calcium-Magnesium Fertilizers and Humic Acid

1. Synergistic Benefits

• Complementarity: The two products complement each other. For example, humic acid enhances the absorption of micronutrients from calcium-magnesium fertilizers, while the latter stabilizes humic acid and prolongs its effects.
• Enhanced Efficacy: Mixing promotes nutrient uptake (e.g., humic acid boosts NPK absorption) and improves soil properties (e.g., pH balance and water retention).

2. Application Considerations

• Proportion Control: Use slightly less humic acid than calcium-magnesium fertilizer to avoid overapplication.
• Application Method: Deep placement or furrow application ensures even distribution. Timing and methods should minimize risks of fertilizer damage.

3. Practical Examples

• Field Success: Farmers report improved soil health, higher yields, and cost savings when combining these products.
• Sustainable Impact: This practice reduces environmental pollution and supports sustainable agriculture.

IV. Potential Issues and Solutions

1. Risks

• Nutrient Imbalance: Excessive humic acid may inhibit nutrient absorption from calcium-magnesium fertilizers.
• Soil pH Changes: Humic acid might lower soil pH, affecting beneficial microbes.

2. Mitigation Strategies

• Scientific Ratios: Test soil and crop needs to determine optimal mixing ratios.
• Soil Testing: Analyze soil pH and microbial activity before application to adjust practices.
• Risk Management: Monitor soil health regularly and modify fertilization plans as needed.

V. Future Prospects and Promotion

1. Policy and Education

• Government Support: Subsidies and tax incentives can encourage adoption.
• Training Programs: Educate farmers on best practices to maximize benefits.

2. Application Expansion

• Food Crops: Improve staple crops like wheat and corn.
• Cash Crops: Enhance economic crops like cotton and tobacco.

3. Long-Term Impact

• Sustainability: This approach reduces environmental harm and preserves soil resources.
• Technological Advancements: Future innovations may optimize fertilizer efficiency further.

Combining calcium-magnesium fertilizers and humic acid offers significant agricultural benefits. By ensuring scientific ratios, regular monitoring, and risk assessment, this practice can improve productivity, soil health, and sustainability. Widespread adoption could advance modern agriculture while promoting environmental stewardship.