Unblocking Soil: Drainage Solutions For Soil Pans

Soil pans, or hardpans, are dense layers of soil that are largely impervious to water, impeding drainage and restricting the growth of plant roots. They are usually found below the uppermost topsoil layer and are formed by deposits in the soil that fuse and bind soil particles. To get a soil pan to drain, it must be broken up either mechanically (e.g. through digging or plowing) or by using soil amendments to alter the soil structure.

Break up the soil pan with a broadfork, spade or a digging fork

Breaking up a soil pan can be done through mechanical means such as digging or plowing. This can be achieved with a broadfork, spade, or a digging fork.

Broadfork

The broadfork is a large, heavy tool designed to cultivate and aerate soil. Its weight allows gravity to do most of the work. To use it, hold the two handles upright and press down on the crossbar with your foot, allowing the long tines to sink into the ground. Pull the handles toward you, causing the tines to lift and loosen the soil and open up air channels. This tool is also good for prepping new beds as it can break up compaction almost twice as deep as a spading fork and can work on tougher clay.

Spade

A spade is a tool similar to a shovel. It pierces the ground more easily than a shovel and is great for pre-loosening soil that can then be lifted out with a shovel.

Digging Fork

The digging fork, or spading fork, is a tool with four heavy tines. It is great for pre-loosening soil, breaking up heavy soil clumps, and prying out root crops. It is also a good soil aerator.

Use soil amendments to alter the soil structure

Soil amendments are any materials added to the soil to improve its physical properties and create a better environment for roots. They can be organic (derived from living materials) or inorganic (mineral or man-made).

Organic amendments, such as compost, increase soil organic matter content, improve soil aeration, water infiltration, and the water- and nutrient-holding capacity of the soil. They also act as organic slow-release fertilizers, offering nutrients to the soil. Compost loosens up dense soil and helps bind soil that is too loose, promoting root growth.

Inorganic soil amendments are typically used for specialty growing and are tailored to the type of garden being designed and planted. For example, rock and gravel amendments are often added to garden beds to improve drainage, although scientific papers have found that this can sometimes make drainage worse.

Before adding any amendment to the soil, it is crucial to do a soil test to get accurate data and amendment recommendations. Amendments must also be thoroughly mixed into the soil to be effective.

• Coconut coir – This fibrous material, extracted from coconut husks, improves the soil's ability to retain water and nutrients. It is best for sandy soil.
• Vermiculite – This finely crushed mineral helps the soil retain water and nutrients, promotes root growth, and facilitates the anchoring of young roots. It is best for sandy soil.
• Sawdust – Ensure the sawdust is well-decayed and not fresh, and mix it lightly into the soil to avoid clumping and creating a barrier to water flow. It is best for clay soil and other hard, compacted soils.
• Perlite – This crushed volcanic material is often found in soilless potting mixes and can be used to improve soil aeration and drainage.
• Straw – Inexpensive straw improves the structure of dense soils, making it more porous and improving aeration to help roots grow. It can be directly worked into the soil without detrimental effects on the nitrogen balance. It provides microorganisms like fungi and bacteria with carbohydrates as an energy source.
• Wood – Finely shredded bark or wood chips can be used to aerate dense, compacted soil and create spaces for plant roots, water, and nutrients to move through the soil more easily. They also stabilize silty, slippery soil that is too loose, making it less prone to erosion. However, fresh wood ties up nitrogen in the soil, leading to nitrogen deficiency in plants. Therefore, only use composted wood chips and bark. It is best for clay soil and silty soil.
• Dried animal blood – This byproduct from slaughtering animals is high in nitrogen, which is beneficial for plants that require extra nitrogen, such as green leafy vegetables and ferns.
• Bone meal – The finely ground animal bones and waste products from slaughterhouses add phosphate and calcium to the soil, stimulating larger, improved fruits and blooms. It is best for vegetables, tubers, flowers, and bulbs.
• Manure – Similar to compost, manure is an excellent soil amendment that helps with water and nutrient retention. Ensure that the manure is composted or aged, as its high nitrogen content can burn plants if fresh. It is best for any type of soil to add organic matter and improve soil structure.
• Garden lime – Also called agricultural lime or limestone, garden lime is a rock powder that is added to soil to make it more alkaline. It is best for highly acidic soil or when growing plants that need alkaline soil.
• Wood ashes – These can be used as a no-cost alternative to garden lime to increase the soil pH and make it more alkaline. However, wood ashes should be limited to no more than 20 pounds per 1,000 square feet annually, as they are high in salt, which can affect germination.
• Worm castings – Also called vermicompost, worm castings contain nutrients and microbes, improve soil aeration and water retention, and anchor nutrients so they don't wash out with water. They are sold in bags but are more expensive than compost. They are best for any soil outdoors or potted plants.
• Pea gravel – Working a 2-inch layer of pea gravel into clay soil opens up spaces for plant roots, water, and nutrients. It is also suitable for stabilizing soft, slippery soils prone to erosion.
• Gypsum – When the soil pH is right but other factors are off, gypsum can help modify the soil without significantly changing the soil pH. It increases water penetration, loosens compacted clay soils, and promotes easier root penetration. It is great for vegetable gardens with plants that have higher calcium needs, such as tomatoes.

Improve drainage by adding organic matter

Soil pans, or hardpans, are dense layers of soil that are largely impervious to water. They can impede drainage and restrict the growth of plant roots. One way to address this issue is by improving the soil's drainage through the addition of organic matter. This method works for almost any soil type and can help alleviate problems caused by soil that drains too quickly or too slowly.

Organic matter acts as a sponge, helping to retain water in the soil. It improves the structure of the soil, making it less compact and allowing water to drain more easily. Good organic amendments include compost, peat moss, coconut coir, and green manure cover crops. For an unplanted bed, spread 3-4 inches of organic matter across the surface of the soil and work it into the top 8-12 inches using a garden tiller or pitchfork. For already planted beds, add a couple of inches of compost to the soil surface each year and let nature do the mixing.

When choosing organic amendments, it is important to ensure they have not been treated with herbicides as these can be carried over into the soil. In addition, some organic materials, such as manure, can take years to break down, so it is recommended to compost them before adding them to an existing garden. To speed up the composting process, mix manure with a source of nitrogen, such as lawn clippings or vegetable scraps, and turn the pile regularly.

Inorganic amendments, such as perlite, sand, and vermiculite, can also be used to improve drainage. However, they function primarily as wedges that increase soil porosity and aeration rather than directly affecting drainage like organic matter. It is important to note that improving drainage through the addition of organic matter may take several years, and mechanical means such as digging or plowing may be necessary for more difficult hardpans.

Avoid soil compaction by reducing walking or driving on the soil

Soil pans, or hardpans, are dense layers of soil that are largely impervious to water. They are often a problem in farming and gardening as they impede drainage and restrict root growth. Soil pans can be caused by deposits in the soil that fuse and bind soil particles, such as dissolved silica or iron oxides. They can also be man-made, caused by compaction from repeated ploughing, heavy traffic, or pollution.

To get a soil pan to drain, you will need to break up the hardpan layer. This can be done mechanically, by digging or ploughing, or through the use of soil amendments. Here are some ways to avoid soil compaction by reducing walking or driving on the soil:

• Create designated areas for walking and driving: Construct pathways, fences, or walls to protect your garden from foot and vehicular traffic. This will help direct foot and vehicle traffic to designated areas, reducing soil compaction in planting areas.
• Avoid working on wet soil: Soil is more susceptible to compaction when it is wet. Avoid walking, digging, or driving on wet soil to prevent soil compaction.
• Cover bare soils: Bare soils are more prone to compaction. Cover bare areas with vegetation or mulch to protect them from compaction.
• Use lightweight equipment: When using construction or maintenance equipment, opt for lighter options to reduce the weight exerted on the soil. This will help minimise soil compaction.
• Avoid removing organic matter: Removing organic matter such as leaves, grass clippings, and branches reduces the organic content of the soil over time, making it more prone to compaction.
• Increase soil organic matter: Adding compost, cover crops, or crop residue can increase soil organic matter, improving soil structure and making it more resistant to compaction.
• Reduce axle load: Heavy machinery with high axle loads can cause significant soil compaction. Reduce the axle load of machinery or increase the number of axles to distribute the weight over a larger area.
• Use larger tires: Installing larger-diameter tires on tractors and other equipment can help distribute the weight over a larger surface area, reducing the pressure on the soil and minimising compaction.

Install a drain tile to move water away from the problem area

If you're looking to install a drain tile to move water away from a problem area in your yard or garden, there are a few methods you can try. Drain tiles, also known as foundation drains or weeping tiles, can be installed during construction or in a finished home, and they offer a lot of versatility in terms of waterproofing your basement. Here's a detailed guide on how to install a drain tile system effectively:

Planning and Preparation:

Before you begin, it's essential to identify the source of your water problem. Observe how the water flows off the roof and onto the ground, especially during rainfall. Look for areas where water pools or slopes towards your house. Ensure your gutters and downspouts are properly installed and direct roof water away from the foundation. If simple fixes like adjusting the slope of the ground or improving gutters don't work, you may need to install a drain tile system.

Additionally, before starting any digging project, it's crucial to locate underground utilities, including electrical, telephone, TV cables, and gas piping. Contact your local utilities to determine the exact locations of these lines to avoid any accidental damage.

Installing a Drain Tile System:

• Dig a Trench: Start by digging an 18-inch deep trench in the problem area. The trench should be deep enough to accommodate the drain tile and any additional materials.
• Line the Trench: Place a layer of gravel at the bottom of the trench. This will promote water absorption and provide a stable base for the drain tile.
• Install Perforated Pipe: Place a perforated pipe, also known as drain tubing, in the trench. This pipe will carry excess water away from the problem area. Ensure the pipe is perforated to allow water to drain as it is carried away.
• Cover the Pipe: Before covering the pipe, ensure it is protected from soil and debris. You can use gravel or a rot-resistant fabric sleeve (a "sock") to cover the pipe. The fabric sock will also help prevent the tube from clogging with sludge or small particles of soil.
• Connect to a Sump Pump or Storm Sewer: Depending on your setup, you can connect the drain tile to a sump pump or storm sewer. Alternatively, you can direct the water towards daylight, ensuring it flows away from your foundation.
• Fill the Trench: Once the pipe is in place and connected, carefully fill the trench with soil, ensuring the pipe remains covered and protected.

Additional Tips:

• If you're installing a drain tile system in your basement, you may need to break out and remove a strip of concrete around the walls to expose the footing and underlying dirt.
• When purchasing materials, opt for perforated or unperforated drain tubing based on your specific needs. Perforated tubing is ideal if you want it to drain as it carries water, while unperforated tubing is better for delivering water from one spot to another.
• If you're connecting the drain tile to a sump pump, ensure the discharge pipe runs at least 6 feet away from the foundation to avoid dumping water back against the wall.
• Consider using landscape fabric or silt-blocking fabric to wrap around the dry well or tubing to prevent erosion and block silt buildup.
• Always follow safety precautions and consider seeking professional help if you're unsure about any part of the installation process.

By following these steps and adapting them to your specific needs, you can effectively install a drain tile system to move water away from problem areas in your yard or basement.

Frequently asked questions