Recommended Formulas and Precautions for Seedling Substrate Soil

I. Universal Mixing Formulas

The following formulas can be adjusted based on crop requirements and environmental conditions:

1. Classic Universal Formula (Suitable for Most Crops)
   • Formula: Peat moss : Perlite : Vermiculite = 1:1:1 (volume ratio)
   • Features: Balances aeration and water retention, suitable for vegetables and flowers.
   • Variations:
     • High Water Retention Needs (e.g., potted flowers, ornamental plants): Peat moss : Vermiculite : Perlite = 5:2.5:2.5
     • Drought-Tolerant or Low Water Retention Needs (e.g., succulents, cacti): Peat moss : Perlite : Vermiculite = 1:1:1
2. Vegetable-Specific Formula
   • Formula 1: Garden soil 50% + Coco coir 50% + Small amount of bone meal (to enhance fertility)
   • Formula 2: Peat moss 7 parts + Vermiculite 3 parts (suitable for flowers and vegetables)
   • Formula 3: Peat moss 6 parts + Perlite 2 parts + Dried chicken manure 2 parts (for fruit trees/landscaping)
3. Succulent Plant Formula
   • Sowing Substrate: Garden soil 60% + Peat moss 30% + Perlite 5% + Fine vermiculite powder (small amount) + River sand 5% + Coal ash 10%
   • Cultivation Substrate: Garden soil 70% + Peat moss/Leaf mold 10% + Perlite/Vermiculite 5% + River sand 5% + Coal ash 5% + Organic fertilizer 5%
4. Special Crop Adjustments
   • Orchidaceae (High Aeration Needs): Leaf mold 50% + Perlite/Sand 50%
   • Ericaceae (e.g., Azaleas, Prefers Slightly Acidic): Peat moss 30% + Vermiculite 30% + Perlite 30% + Organic fertilizer 10%
   • Pinus tabuliformis Container Seedlings: Peat moss 50% + Perlite 20% + Mushroom compost 30%

II. Key Precautions

1. Sterilization
   • Disinfect before use (e.g., with carbendazim, formalin) to prevent pests and diseases.
   • Method: Dilute 40% formalin 500mL/m³, water, seal for 24 hours, then ventilate for 7-10 days.
2. Moisture Control
   • Recommended substrate moisture content: 60% (forms a ball when squeezed, breaks apart upon light touch).
   • Pre-wetting: Adjust substrate moisture to ~40% before sowing, water until drainage at the bottom.
3. Uniform Filling
   • Fill seedling trays evenly without compacting to maintain aeration; avoid overfilling for large seeds.
4. Fertilizer Addition
   • Add moderate amounts of composted organic fertilizer or compound fertilizer (e.g., 1-2 kg NPK per m³) based on crop needs.
   • If commercial substrates already contain nutrients, no additional fertilization is needed for the first 15 days.
5. pH Adjustment
   • Optimal pH for most crops: 5.5-6.5.
   • High acidity: Add lime or wood ash; high alkalinity: Add ferrous sulfate or sulfur powder.

III. Flexible Adjustment Principles

• Crop Characteristics: Water demand, drought tolerance, root type (e.g., orchids require high aeration).
• Environmental Conditions: Enhance aeration in humid climates (e.g., South), adjust water retention in arid regions (e.g., North).
• Substrate Properties: Peat moss for water retention, perlite for aeration, vermiculite for water absorption.

Recommendation: Start with universal formulas and optimize based on actual growth (e.g., leggy seedlings may indicate excess nitrogen; poor root development may require more vermiculite/perlite).