Table of Contents

How to Make Soil Blocks: A Comprehensive Guide to Seed Starting Success

Soil blocks offer a superior method of seed starting, fostering stronger, healthier seedlings with minimal root disturbance. By creating self-contained plantable units, you eliminate the need for plastic cells and significantly reduce transplant shock, leading to earlier harvests and more resilient plants.

What are Soil Blocks and Why Use Them?

Soil blocks are compressed cubes of soil, formed without the use of a container. They provide a stable, nutrient-rich environment for young seedlings, encouraging air pruning of roots, which results in a dense and robust root ball. This allows for easier transplanting with minimal disruption to the delicate root system.

Benefits of Soil Blocking

Reduced Transplant Shock: Air pruning encourages lateral root growth instead of circling, preventing rootbound seedlings and minimizing transplant shock.
Improved Root Health: The open structure of the block allows for excellent aeration and drainage, preventing root rot and promoting healthy root development.
Elimination of Plastic Waste: Ditch the plastic seed starting trays and pots. Soil blocks are an environmentally friendly alternative.
Nutrient Rich Start: You control the ingredients, ensuring your seedlings receive the perfect balance of nutrients for optimal growth.
Earlier Harvests: Healthier seedlings translate to faster growth after transplanting and ultimately, earlier harvests.
Stronger Plants: The air pruning process results in a more robust root system, leading to stronger, more resilient plants.

Choosing the Right Soil Block Maker

Selecting the appropriate soil block maker is crucial for success. They come in various sizes, from small micro-block makers for tiny seeds to larger block makers for plants requiring a more substantial root system. Consider the types of plants you plan to grow and choose a block maker accordingly.

Types of Soil Block Makers

Micro-Block Makers: Ideal for starting very small seeds like lettuce, herbs, and flowers.
Standard Block Makers: Suitable for a wide range of vegetables, herbs, and flowers.
Nesting Block Makers: Create blocks with a pre-formed hole for transplanting smaller blocks into larger ones, allowing for progressive root development.
Multi-Block Makers: Produce multiple blocks at once, saving time and effort.

Considerations When Choosing a Block Maker

Size of Blocks: Match the block size to the needs of your plants.
Number of Blocks: Consider the number of seedlings you plan to start.
Durability: Opt for a well-constructed block maker that will withstand repeated use.
Ease of Use: Choose a model that is comfortable and easy to operate.

Crafting the Perfect Soil Block Mix

The key to successful soil blocking lies in the quality of your mix. A well-balanced mix should retain moisture, provide adequate drainage, and supply essential nutrients for seedling growth.

Essential Ingredients for Soil Block Mix

Peat Moss or Coco Coir: Provides moisture retention and aeration. Coco coir is an excellent sustainable alternative to peat moss.
Compost: Adds essential nutrients and beneficial microorganisms. Ensure it’s well-decomposed.
Garden Soil: Provides structure and minerals. Sift to remove large debris. Use cautiously as some garden soil may contain pathogens.
Worm Castings: A rich source of nutrients and beneficial microbes.
Sand or Perlite: Improves drainage and aeration.
Rock Phosphate: A source of phosphorus, essential for root development.
Greensand: A source of potassium and trace minerals.
Lime (Optional): Adjusts the pH of the mix, especially if using peat moss, which is acidic.

Soil Block Mix Recipe (Example)

This is a general recipe, adjust based on your local soil conditions and plant needs:

4 parts Peat Moss or Coco Coir
2 parts Compost
1 part Garden Soil (optional, sifted)
1 part Worm Castings
1/2 part Sand or Perlite
1/4 cup Rock Phosphate per bushel
1/4 cup Greensand per bushel
1/8 cup Lime per bushel (if using peat moss)

Step-by-Step Guide to Making Soil Blocks

Prepare the Soil Mix: Thoroughly mix all ingredients in a large container.
Moisten the Mix: Add water gradually, mixing until the soil is damp but not soggy. The ideal consistency is when you can squeeze a handful and it holds its shape without dripping.
Pack the Block Maker: Scoop the moistened soil mix into the block maker, pressing firmly to ensure it is completely filled and compacted.
Eject the Blocks: Use the ejection mechanism (usually a lever or plunger) to release the formed soil blocks onto a tray or flat surface.
Sow Seeds: Gently press a seed into the center of each block. Cover lightly with soil mix or vermiculite.
Water Carefully: Use a gentle spray or bottom watering to avoid dislodging the seeds.

Caring for Your Seedlings in Soil Blocks

Proper care is essential for ensuring your seedlings thrive in their soil blocks.

Watering and Humidity

Keep the blocks consistently moist: Water when the surface of the blocks begins to dry out.
Maintain humidity: Cover the blocks with a humidity dome or plastic wrap until the seedlings emerge.

Light and Temperature

Provide adequate light: Seedlings require bright light to prevent leggy growth. Use grow lights or place the blocks in a sunny window.
Maintain a consistent temperature: Most seeds germinate best in temperatures between 65-75°F (18-24°C).

Hardening Off

Gradually acclimate your seedlings to outdoor conditions before transplanting. This process, known as hardening off, helps them adjust to the sun, wind, and temperature fluctuations.

Transplanting Soil Blocks

Transplanting soil blocks is simple and minimizes root disturbance.

Transplanting Techniques

Dig a hole slightly larger than the soil block.
Gently remove the seedling from the tray.
Place the soil block into the hole.
Backfill with soil and water thoroughly.

Frequently Asked Questions (FAQs)

1. What if my soil blocks are crumbling?

If your soil blocks are crumbling, your soil mix is likely too dry or lacks sufficient binder. Try adding more water to achieve the right consistency. You can also add a small amount of clay or more compost to improve the cohesiveness of the mix.

2. Can I use any type of compost in my soil block mix?

While you can use various types of compost, ensure it is well-decomposed and screened to remove large pieces of debris. Avoid using compost that is too coarse or acidic, as it can hinder seedling growth.

3. How do I prevent algae growth on my soil blocks?

Algae growth is common in humid environments. Improve air circulation around the blocks by removing the humidity dome once the seedlings have emerged. Avoid overwatering and ensure the blocks have adequate drainage.

4. What size soil block should I use for tomatoes?

For tomatoes, a 2-inch soil block is generally recommended for starting. You can then transplant these into a 4-inch block if they need more room before going into the garden.

5. Can I reuse my soil block mix?

It’s generally not recommended to reuse soil block mix, as it may be depleted of nutrients and could harbor pathogens. Fresh mix is always best for optimal seedling health.

6. Do I need to fertilize my seedlings in soil blocks?

Yes, seedlings in soil blocks will eventually need fertilization. Once they develop their first true leaves, you can start feeding them with a diluted organic fertilizer.

7. How often should I water my soil blocks?

Watering frequency depends on the environment and the size of the blocks. Check the moisture level daily and water when the surface of the blocks begins to dry out.

8. Can I make soil blocks without peat moss?

Yes, coco coir is an excellent peat-free alternative that provides similar moisture retention and aeration.

9. How do I store my soil block mix?

Store your soil block mix in a tightly sealed container in a cool, dry place. This will help prevent it from drying out or becoming contaminated.

10. Is it necessary to use garden soil in the soil block mix?

Garden soil is optional and should be used with caution. If you choose to use it, sift it to remove large debris and sterilize it to kill any potential pathogens.

11. What if my seeds don’t germinate in the soil blocks?

Check the viability of your seeds and ensure they are planted at the correct depth. Also, verify that the soil blocks are kept consistently moist and at the appropriate temperature for germination.

12. How long can seedlings stay in soil blocks before transplanting?

Seedlings can stay in soil blocks for several weeks, depending on the size of the block and the growth rate of the plant. Watch for signs of nutrient deficiency or root restriction and transplant when necessary.

How to Make Soil Blocks?