Regularly spreading organic matter over the soil surface is the best long-term solution to soil compaction. Organic matter includes compost, shredded leaf mulch, wood chips, straw and chopped leaves. Apply a 3- to 4-inch layer of compost or a layer of wood chips or shredded leaf mulch 2 to 3 inches deep over bare soil in flower beds. Without any further help, soil organisms will incorporate the organic matter and begin to open up the soil. If you'd like to quickly break up a hard soil surface for planting, mix the organic matter into the top 3 to 6 inches of soil with a spade.
To help soften hard soil in a vegetable garden, add a 2-inch layer of compost twice a year and mix it into the top 2 inches of soil. If the soil in your garden or vegetable patch is bare over winter, spread a layer of mulch over it to protect it from heavy rainfall. You can improve clay soil, but don't work it when it's wet, and avoid walking on it so it doesn't become compacted. When it's dry, add three to four inches of organic materials, such as compost, leaf mold or well-rotted manure , and work them into the soil about six inches deep. Mulch the soil with bark, wood chips or some other type of mulch that decomposes slowly.
Over time, the sun and rain break down the mulch, which will also improve your soil. Rototilling is a popular option for loosening dense soil, but has drawbacks. Rototillers, especially smaller home-garden models, are also sometimes ineffective at loosening severely compacted soils, or may only loosen soil to a few inches. Tilling compost into the soil can help reduce compaction and increase the soil's water and nutrient holding capacity.
Compost can be incorporated into new landscape soils using tillage. A 1-inch layer of compost incorporated with tillage is usually enough to improve the top 6 inches of soil. When selecting an organic amendment material to add to a compacted soil, make sure it is well composted. Organic materials that are not well composted tend to have high carbon to nitrogen ratios. Therefore, you should never incorporate uncomposted mulch into the soil.
As a rule of thumb, if you can see what it was before it became compost (e.g. leaves, twigs, wood chips), then it is not ready to be incorporated. Working wet soil will pack soil particles tightly, leaving less room for water and air to penetrate. Compacted soil also makes it more difficult for plant roots and gardening equipment to move through the soil. The compression forms tight clumps of soil that become hard as rocks upon drying and are difficult to break up.
In addition to making it difficult for plants to grow, compacted soils also tend to drain more slowly, in turn delaying the ability to work the soil after the next rainfall. Cover crops, also called green manure crops, help loosen clay or compacted soils with their roots and by adding organic matter. They also prevent nutrient loss and erosion during the non-growing season. Leguminous cover crops, such as winter rye, alfalfa, hairy vetch and clover, which add nitrogen to the soil, are usually planted at the end of summer or early fall.
Compaction increases the load bearing strength of soils, by reorienting particles into a stronger, but denser structure. Compacted soils provide a stable foundation for homes, but they are not ideal for plant growth or water movement through the soil. In fact, it may be nearly impossible to establish plants in compacted soils. Soil compaction reduces the total number and size of pores, which are critical in supplying the plant roots with water and oxygen . Soil compaction also increases resistance to root penetration, making it harder for roots to grow through the soil.
How To Loosen Compacted Garden Soil Soil compaction can extend more than one foot below the surface, with the most compacted depths being greater than 6 inches below the surface. This can cause development of a shallow rooting zone, which can lead to poor plant growth and increases the need for irrigation and fertilization. As a result, significant soil compaction can lead to added costs for the landscape professional or homeowner if dead or declining plants require extra care or replacement.
Soil compaction can also have detrimental effects on the environment. Weighty gardening equipment, foot traffic and heavy downpours cause soil compaction, and clay and loam soils are most susceptible. However, even sandy soils can harden when compressed by heavy equipment. Excessive weight and rain close the open pores between the soil particles; as a result, the soil hardens. Clay soils often drain very slowly after rainfall, and then they harden and crack when the weather turns dry and warm.
To avoid compacting soil, create paths to avoid walking on growing areas. Don't dig the soil excessively or when it's wet, and don't mix sand into clay soil, which makes it like concrete. To alleviate soil compaction, it is often necessary to break up the compacted soil by tillage as a first step. Tillage can be performed by a rototiller, but for an established lawn, core aeration is a common practice.
Rototilling a compacted soil may require heavy equipment, but remember to try to avoid bigger, heavier equipment. Core aeration leaves most of the yard surface and lawn vegetation intact but pulls cores (typically ½ to ¾ inch in diameter and 3 to 4 inches deep) from the ground. Therefore, core aeration only treats shallow compaction, but it can rapidly and significantly improve conditions in the topsoil. With improved growing conditions, vegetation and other organisms' activity will gradually benefit the loosening soil.
Adding organic matter is the key to loosening hard soils. The mineral particles in hard soils are pressed closely together, leaving little room for the air and water that plants need. Earthworms and other soil organisms draw the compost, leaf mulch or other matter down below the surface, breaking up the compacted particles. You can lightly dig organic matter into the top few inches of soil to help speed up the process. Another way to break up clay soil is by planting cover crops with deep taproots.
Daikon radish is one such cover crop that is commonly used to improve water and air movement through soil. Many vegetable gardeners like to use cover crops to protect soil from erosion, add organic matter, and provide nitrogen. Organic matter in soil serves as food for earthworms, insects, bacteria and fungi-they transform it to soil nutrients and humus. Through this decomposition process, materials are made available as foods to growing plants. In finely textured clay soils, organic material creates aggregates of the soil particles, improving drainage and making it easier to work. Earthworms are especially helpful in making and keeping soil porous and well draining, said Brewer.
Healthy soil typically is more than 40 percent pore space, with large pores that promote drainage and small pores which help store water. This combination enables air and water to penetrate, promotes good drainage, and allows soil organisms to breathe and plant roots to grow. Machinery, foot traffic and pounding rain compact the soil and make life in the soil difficult.
Compacted soils can flood and also be susceptible to drought, since water runs off rather than infiltrating. You can repair compacted soil by rebuilding its spongy structure. In addition to helping loosen heavily compacted soils and improve overall soil health, adding organic matter is a good way to improve both clay and sandy soils. Aside from improving soil texture, adding organic matter can have other benefits as well.
One of which is the addition of beneficial soil microbes, such as fungi and bacteria. These microbes help with plant nutrient uptake by making nutrients more available for root uptake. Top-dressing planting beds with several inches of compost will improve lightly compacted soils.
Earthworms and other soil fauna will gradually pull it down into the soil, loosening it and improving water-holding capacity. A 2- or 3-inch layer of shredded leaf mulch or wood chips will provide similar benefits. By aerating your clay soil and adding an amendment, you can break it down fast and encourage new growth. Wait until the ground's completely wet or dry, since it'll be harder to work with soil that's partially damp. Then, turn your soil by digging up small amounts where you want to put plants to aerate it.
Once you've turned the soil, mix in an amendment, like compost, biochar, manure, or a commercial soil conditioner, to add some extra nutrients. If your plants still struggle to grow, lay an extra layer of topsoil over the clay. To fix compacted soil, which is soil that has little to no air space, break it up to make it hospitable for your plants again. Start by shifting livestock, machinery, vehicles, and foot traffic away from the compacted area to give the soil a rest.
If you use the compacted area for farming or gardening, move your plants somewhere else for at least 1 growing cycle. Instead, plant a cover crop, like winter wheat or ryegrass, to allow the roots to break up the soil. For smaller, grassy areas that are compacted, use a small metal garden fork to poke holes in the soil so air, water, and roots can enter the area. However, when tackling a larger area, use a rototiller with an aeration attachment. Compaction is most likely to occur with heavier soils like clay and loam, but when heavy equipment is used, sandy soils can become compacted.
These are soil particles that are packed closely together. The problem may be compounded by events that have happened to the soil over the course of years. The pore spaces are reduced to the point that air and water cannot move freely and plant roots cannot grow easily into the surrounding soil. The soil could remain overly wet longer than is healthy for the plants growing there.
One standard and very successful workaround for heavily compacted clay soils is to do raised beds directly on top of them. It is not an overnight fix.....improving soils is a longterm process. Bark products, such as finely shredded bark mulch is sometimes sold as a "soil conditioner". This material is meant to be incorporated into the soil to add organic matter deeper in the soil and help loosen compacted soils. These products are excellent for adding organic matter to both clay and sandy soils. Half of a healthy soil's makeup is pore space, with the other half composed of organic matter and mineral particles .
Pore space provides room for air and water to circulate around the mineral particles, providing a healthy environment for plant roots and beneficial microorganisms. In compacted soils, the particles are pressed together so tightly that the space for air and water is greatly reduced. Gypsum is easily applied to the soil surface with a regular lawn spreader. It's an ideal amendment for improving soil structure and relieving compaction in existing lawns and gardens.
In a garden bed, the best way to introduce organic material without digging , is to apply layers on top and let nature do the work for you. Simply pile your garden bed high with organic material – it can be wood chips, shredded paper, straw, chopped leaves, lawn clippings – whatever you can lay your hands on. It might be slow, but the wait will give you time to get to know your land before you plant. Amending your soil properly can overcome heavy, compacted clay and get it back on track for healthy lawn and garden growth. Adding materials such as organic compost, pine bark, composted leaves and gypsum to heavy clay can improve its structure and help eliminate drainage and compaction problems. Soil amendments are most commonly used in vegetable gardens and landscape beds.
It is important to evaluate various types of soil amendments and determine which ones will provide the most benefit. This often leads to a combination of different amendments to supply organic matter, nutrients, and improve the soil texture. There are many combinations but a good general-purpose ratio is one part composted manure, to three parts garden compost to one part soil conditioner. This amendment mixture can then be tilled in prior to planting.
The addition of organic matter is beneficial but too much can be detrimental to plant health. Start with adding 25% by volume or 2 inches of organic matter into the top 6 inches of the soil. Clay is held together by water - turning the soil and leaving it open to the frost freezes the water and breaks the clay apart. I wouldn't glysophate the lawn, lift the turf and bury it a spade depth down.
The addition of grit and plenty of organic matter will improve drainage and the structure of the soil. It will be hard work, but there are no quick solutions to heavy clay soils. Bark, sawdust, manure, leaf mold, compost and peat moss are among the organic amendments commonly used to improve clay soil. Two or three inches of organic materials should be spread and rototilled, forked or dug into the top six or seven inches of your garden beds.
A hugel bed, composting in place, layers of wood chips - I am trying it all. Now I am trying to decide how to proceed in the worst area of the yard. There were several inches of decomposed granite spread over the center of the yard, upon which the previous owners had a batting cage. Prior to that I have learned they used to ride dirt bikes around the yard. Basically when we bought the place last year there were only some trees on the edges of the property.
I have been doing some experiments and while kitchen stuff is composting on top, not much is going down. Test plants that usually grow like crazy are staying alive but the roots aren't going down, mostly sideways under the mulch. So now I wonder before I do another chunk of piling organic matter to build soil, if I should go ahead and break up the top layer an inch or two? I want to be a no-till garden but I think this tough dead zone might need some help at first.
Common soil amendments include compost, grass clippings, straw, shredded leaves, rotted manure and dried seaweed. Some gardeners recommend adding sand to amend clay soils, but numerous university extension experts advise against this, as adding too little can actually make the problem worse. Cover crops help break up hard soils with their roots and by adding plant matter to the soil. Sow cover crops when the soil is bare, such as over winter. Before planting the area with desired plants in spring, dig up the cover crop and bury the plants in the soil.
Cover crops include buckwheat , cereal rye and crimson clover , which are annual plants that naturally die down at the end of their growing seasons. Department of Agriculture plant hardiness zones 10 through 12, and cereal rye is hardy in USDA zones 3 through 7. Crimson clover is a winter annual in USDA zones 6 through 9 and a summer annual in zones 3 through 4.
