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  • Writer's pictureBrad DeBroux

Soil Blocks: The Sustainable Way to Grow

Updated: May 4, 2023

Starting seeds with soil blocks is one of my favorite springtime gardening activities here on FarmYourLot; from January to May each year, we're making lots of blocks of all sizes, all with a purpose and long lifespan. For a vegetable gardener in Wisconsin, spring starts early; I'm convinced making soil blocks in January adds years to my life, and I know it improves my attitude; even though it's cold, just having my hands in the soil bridges the gap between minus 20° and three months or more to go before planting in the ground. Filling the soil blocks with soil and pressing them down can be tiring and takes some practice, but it's good exercise while gardening. In addition, by planting seeds and seedlings in the soil blocks, you'll need to bend over and reach into the soil blocks to plant the seeds; Overall, making soil blocks is an excellent way to keep in shape, especially if you regularly do it.

Dog on a tote watching soil block making
Walter is staying warm while I make soil blocks in January

Sustainability in Action

Soil blocks stay with our plants through their lifespans and become part of the living soil, your garden, and our environment. I think I've tried every possible way to make and use soil blocks on our urban farm with excellent results; When people visit, they see the soil blocks, they'll say they look like brownies, and I'll sometimes find a remnant of one laying next to plant after it's grown out of its original home, it makes me smile; so all around, these things pack a pretty big punch!

Soil block seed-starting systems are gaining popularity among gardeners and farmers as an eco-friendly, cost-effective, and efficient alternative to traditional plastic trays or pots. I've been growing in soil blocking since 2017; before that, I purchased pre-grown plants from nurseries or used trays and pots with almost no success. Since using soil blocks, I've been rewarded with high propagation, a more vigorous plant, and higher yields at harvest; I produce healthier root systems by air pruning the roots in the soil blocks, making the plants less likely to suffer transplant shock or be attacked by pests.

Simple Approach to Seed Starting

Keeping things simple offers you several advantages, and we use various strategies at FarmYourLot to maintain simplicity in the garden. When I use my Ladbrooke Soil Block Makers, the decisions are easy; What soil block size, what seed depth/insert is needed, and what soil to use for the seeds to be sown?

Those three decisions are all I need to successfully start the vegetables we grow from soil blocks on our urban farm; I compile that decision based on the seed to be sown. Here's my example with this short list below.


Block Size

Depth / Insert

Soil Mix


Mini 4, Two Inch Blocks

1/4 Inch

Peat, Worm Castings, Perlite, Vermiculite, and Sulfur


Mico 20, 3/4 Inch Blocks


Peat, Warm Casting, and Perlite


Mini 4 Two-Inch Blocks

1/2 Inch

Peat, Worm Castings, Perlite, and Sulfur

Simple Decisions

Simple decision-making has other advantages, better focus, reduced stress, more accessible communication, greater flexibility, and better decision-making; When I worked as a systems administrator in mortgage banking technology, I promoted the idea of using a decision tree, yes, there's a real thing In data analysis and machine learning, decision trees, often used as a predictive model to classify data points based on their features or attributes.

The decision tree algorithm uses a series of if-then statements to split the data into subsets and create a tree-like structure that can be used to make predictions about new data points.

Increased Productivity

These trees are so fitting for gardening and are often used to evaluate different options and their potential outcomes in real-life decision-making processes like the garden. By mapping out the other possible decisions and outcomes like the pH of your water, gardeners and farmers can assess the risks and benefits of each option and make an informed decision based on their goals and priorities. This applies to the three decisions on soil blocks; I know by experience that I need the Mini 4 with 2-inch blocks, a quarter-inch insert, and soil made of (peat, perlite, vermiculite, worm castings, and a little sulfur) to make up the soil blocks for tomato and pepper seedlings to thrive. I've learned that if I follow these simple principles, the seedlings I propagate have the best chance for success. In the first batch I started in 2023, 146 tomatoes and peppers, and I had 143 propagate; that's pretty good.

Tools for Success

I use the Ladbrooke soil block makers, and it's time to mention; I sell things to make a living; I'm mentioning products I want you to buy here on my blog; when you purchase through the ads or links that I put here, I get paid, and when you buy from the ads I put here. I'll hear your feedback and questions about the products and respond accordingly. The Ladbrooke soil block maker, available in three sizes, has been used on our urban farm for years of reliable service; I highly recommend their line of products. They have a few options to consider.

* Micro 20: Makes twenty 3/4" soil blocks.

* Mini 4: Makes four 2" soil blocks.

* Maxi: Makes 4" soil blocks.

The Mini 4 is the most popular size, as it is versatile and easy to use. The Micro 20 is a good option for starting tiny seeds, while the Maxi is for larger seeds or seedlings.

The Ladbrooke soil block maker offers multiple models to accommodate block quantities and sizes. The Mini 4, a popular choice, creates four 2-inch soil blocks—the Micro 20 yields twenty 3/4-inch soil blocks, while the Maxi forms one 4-inch block. A commercial-grade version is also available, generating twelve 2-inch blocks simultaneously. As a longtime user of Ladbrooke products, I'm drawn to the stand-up model. However, I'm hesitant to adopt it, as it may necessitate changes to my exercise routine and conflict with my principle of only acquiring what's truly necessary.

Practical Applications and Healthy Soil Blocks

Let's make some soil blocks: As I pointed out above, a few quick decisions, and you're ready to go. Mix your dry ingredients first. You'll want to get your mixture wet and let it sit for a while to get the best results; I like overnight; a few hours is enough time if you've got everything mixed well; the peat moss or coconut coir needs to absorb the water; you'll need a lot of water, which might surprise you. More water than you might think, and every time you make soil blocks, there's a new adventure in the outcome and what soil blocks you'll get; it's an art, and one of the joys of gardening overall is creating a healthy, biologically active soil that's rich in organic matter and teeming with microorganisms, such as bacteria, fungi, and other beneficial organisms. These organisms work together to create a well-structured, fertile, and resilient soil environment that supports optimal plant growth, nutrient cycling, and water retention, leading to a more productive and sustainable vegetable garden.

Mastering the art of adding water to the soil for soil block-making involves understanding the ideal moisture content, soil composition, and techniques to achieve perfect soil health and consistency. Here are some steps, and you'll master this skill with a bit of practice:

  1. Choose the right soil mix: A good soil mix for making soil blocks will contain a balanced blend of peat moss, coconut coir, compost, perlite, and vermiculite. This mix will help retain moisture and provide aeration for the roots. A standard ratio is two parts peat moss or coconut coir, two parts compost, and 1 part perlite or vermiculite.

  2. Test the soil's moisture content: Before adding water, it's essential to know the current moisture content of your soil mix. Take a handful of the mixture and squeeze it in your hand. If it holds together without crumbling and releases some water, it's at a good starting point.

  3. Add water gradually: Begin by slowly adding water to the soil mix and stirring it using your scooper or hands. Add small amounts of water at a time to avoid over-saturating the combination.

  4. Check for the right consistency: The ideal consistency for making soil blocks is sticky, crumbly cake, or brownie mix; I think I need a snack! Grab a handful of the soil mix and squeeze it again to test this. It should hold together without falling apart and with some water seeping out.

  5. Adjust as needed: If the soil mix is too wet, add more dry ingredients; for this, I'll mix up more dry ingredients and store them in totes to add during this process to absorb the excess moisture. If it's too dry, add more water until you achieve the desired consistency.

pH makes a big difference

The pH of soil and water is vital for plants because it affects the availability of nutrients and minerals. Plants need nutrients to grow, and the pH of the soil and water determines which nutrients are available and which are not.

For example, plants need nitrogen to grow, but nitrogen is only available to plants when the pH of the soil is in a particular range.

The pH of water is also essential for plants because it affects the water's ability to dissolve nutrients and minerals.

Plants need water to absorb nutrients, and the pH of the water affects how much water can dissolve nutrients and minerals.

For example, plants can absorb more nutrients from water with a pH of 6.5 than from water with a pH of 8.

The pH of soil and water will affect the growth of plants by affecting the growth of bacteria and fungi. Bacteria and fungi help plants grow by breaking down nutrients and making them available to plants. For example, some bacteria and fungi grow better in acidic soil, while others grow better in alkaline soil. If the pH of the soil is too acidic or alkaline, it can kill some bacteria and fungi, which can affect plant growth.

Knowing helps you Grow

Understanding the pH of soil and water will ensure your plants have the nutrients and minerals they need to grow healthy and strong.

A suitable pH range for the soil and water when making soil blocks is typically between 6.0 and 7.0. This range is suitable for most plants, as it allows for optimal nutrient availability and root development in cases where you need to change the pH levels of

your soil and water follow these steps:

  • Test the soil pH: Before making soil blocks, it's essential to test your soil mix's pH. Use a soil pH testing kit or a pH meter.

  • Test the water pH: It's also important to test the pH of the water you'll use to make the soil blocks and water your plants. You can use a water pH testing kit or a digital pH meter.

  • Adjust the water pH: If the pH of your water or soil is outside the desired range, you can adjust it using the following methods:

  • To increase the pH (make it more alkaline), add a small amount of baking soda (sodium bicarbonate).

  • Add a small amount of white vinegar or lemon juice to decrease the pH (make it more acidic).

  • Retest and adjust: After making any adjustments, retest the pH levels of your soil and water to ensure they are within the desired range.

  • Repeat the process if necessary.

For most vegetables in Zone 5a, a pH range of 6.0 to 7.0 is optimal. However, some vegetables may prefer more acidic or alkaline soil conditions: Here's a short list.

  • Potatoes: pH 5.0-6.5

  • Radishes: pH 6.0-7.0

  • Tomatoes: pH 6.0-6.8

  • Spinach: pH 6.0-7.5

  • Broccoli: pH 6.0-7.0

  • Carrots: pH 6.0-6.8

  • Peas: pH 6.0-7.5

  • Lettuce: pH 6.0-6.5

My experience has been if the soil pH is off, let's say it is 7.0, and I'm trying to grow lots of tomatoes, forget about it! I did; I heard Lefty in the 1997 film Donnie Brasco, "forget about it," "capiche." "Hey" With a soil pH of 7.0, the tomato plants will grow and do their best, but the harvest will not be as big, many, or flavorful as it will be when the soil is 6.5 and feed 6.8 water with its nutrients. I test the soil-block soil, add a pinch of sulfur to the soil and bring the ph down to 6.5. There's a much better chance for a large, flavorful bounty; Yes, I understand it's not that simple, that nutrients, light, and temperatures all matter, but none matter when the pH is off.

Fresh Lettuce in Soil Blocks
Springtime lettuce in Soil Blocks

Test the Soil, Test the Water, and Adjust

Test your soil's pH before planting and make necessary adjustments based on the vegetables you plan to grow. You can raise the pH by adding lime and lowering it by adding elemental sulfur, a squirt of lemon juice, and even organic matter such as peat moss. Adjusting soil pH takes time, so starting the process well before planting your vegetables is a good idea.

The ideal pH range will vary depending on your growing plants, as seen in the list above. Some plants prefer slightly more acidic or alkaline soil, so research the pH requirements of your chosen plants for the best results.

Ready for a workout?

Here's a step-by-step guide on how to make soil blocks:

  1. Prepare the soil mix as described above. Ensure the mixture is free of large debris, such as sticks or rocks, and adjust the moisture content and pH for the seeds to be sown.

  2. Prepare your work area: Lay out a plastic sheet or tarp on a flat surface to keep your work area clean and make it easier to move the soil blocks later. I like a medium mixing tub to mix and work the soil.

  3. Use your Ladbrooke soil blocker with the appropriate block size for the seeds or seedlings you'll be sowing or transplanting.

  4. Fill the soil blocker: Press it into the moist soil mix, ensuring it is filled with the mixture. Twist the blocker slightly and apply pressure to compact the soil inside the chambers. This will help the soil blocks hold their shape.

  5. Release the soil blocks: Hold the soil blocker over your prepared work surface and press the handle or plunger to release the soil blocks. Depending on the design of your soil blocker, the blocks should come out with minimal effort. If they don't release easily, gently tap the blocker on the side to encourage the blocks to come out, and rinse your blocker off before you dip it back into the soil.

  6. Arrange the soil blocks: Carefully arrange the soil blocks on your work surface; the 1020 Trays work well, leaving a small space between each block to allow for air circulation and to prevent the blocks from merging as they dry.

  7. Plant seeds or transplant seedlings: Once the soil blocks are formed, you can plant seeds or transplant seedlings into the small holes or depressions on the top of each block. Follow the specific planting depth recommendations for your seeds or seedlings. If you have some vermiculite, sprinkle it over your seeds to prevent damping off. My friend Jean likes to pinch the blocks' holes to keep the seeds in. Just like us, a rough road sometimes gives you the best ride. These seedlings need to go through some shit.

  8. Water the soil blocks: Gently water the soil blocks to settle the seeds or seedlings into place. Use a fine mist spray or a watering can with a fine hose attachment to prevent the blocks from disintegrating.

  9. Provide proper care: Place the soil blocks in a suitable environment for germination and growth, such as a greenhouse, cold frame, or indoors under grow lights. Maintain proper temperature, humidity, and lighting conditions for your growing plants.

  10. Transplant the soil blocks: Once the seedlings have developed a strong root system and are large enough to be transplanted, carefully move each soil block to its final growing location. The advantage of soil blocks is that they can be planted directly into the ground or in larger containers with minimal root disturbance.

Remember to monitor the moisture content of the soil blocks throughout the germination and growth process, ensuring they don't dry out or become too wet. These steps will create strong, healthy soil blocks for your seeds and seedlings.

Radish in 2 Inch Soil Blocks in 1020 Tray
Radish in 2 Inch Soil Blocks in 1020 Tray

Wait until you taste this tomato, "common, common melt in your mouth. I call it communion. FORGET ABOUT IT!" You're one of us now, and when I introduce you, it'll be as "a friend of ours" Soil blocks are the real deal; they hit every aspect of what a sustainable organic gardener and farmer needs; Cost, productively, longevity, and environmentally, so when it comes to how successful you'll be when you are with your soil block, Forget about it! You got this.


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