The Dirt on Dirt – Clay

Clay soils also provide a wonderful foundation for plants to get their roots into; a lot of perennials and annuals thrive in clay soils since they can get a firm grip on the soil with their roots. This firm grip allows them to survive extremes of temperature and moisture that plants in sandy soil cannot (with clay soil there is a minimum of heaving due to cycles of freezing and thawing, the plants are less likely to “jump” out of the ground). So with a clay soil you water less, fertilize less, get a better foundation for your plants and extend their hardiness when extremes in weather or other factors occur. I bet right now you are feeling a bit better about that clay soil you’ve been cursing!

A few bad things: So, it is likely obvious that a heavy clay soil is going to be more work to till or shovel than a sandy soil. However, when you are planting a landscape most of the digging is only done once and then you get to reap all the benefits of clay soils for the rest of the life of the landscape. No doubt, a clay soil is heavier and more likely to compact than a sandy soil, but you do get a lot of benefits for your labor.

A clay soil can get very mucky if it is too wet. If your clay soil is sticking to your shovel, stop working. The soil is too wet to work with and you will compound the common problems of clay soil by working with it while it is wet. Basically, your soil will be even more compacted after you are done digging.

Clay soil has all those nooks and crannies to hold water and fertilizer, which is great. However, clay soils will hold tight to the bad things too, like salts. Ridding clay soil of extra salt build up or changing the pH of the soil will be more difficult due to the gripping ability of soil particles that make up clay soil. Clay soils latch on to all minerals and this can be good (fertilizer) and bad (salt). Should you have a problem clay soil, just know that it is generally a long term process to rehabilitate the soil but in the end, you will usually prevail.

One last thing that might be a draw back to a clay soil is when you are in a boggy area, clay soils can limit the amount of air plant roots get when they are saturated, so if you have a boggy area select plants that tolerate this condition and watch out for plants that need lots of air around their roots when planting in clay soils.

How to fertilize clay soils most effectively – One of the things we all need to learn is how to avoid wasting fertilizers as they eventually run off into our lakes, streams and groundwater if we use them thoughtlessly. Clay soils are great ‘nutrient’ banks, so you do not need to fertilize as much and you’ll still have a nice garden. When you are gardening in clay it is fine to use liquid fertilizers, granular fertilizer, slow release fertilizers, and organic fertilizers (like fish emulsion). Simply make sure that whatever fertilizer you choose, you use it responsibly. One of the biggest pollutants in our steams and lakes is the run off from lawns in urban area where gardeners are using excess fertilizer and water to try to get the perfect lawn, it is not worth the cost.

Most landscapes and gardens need a liquid fertilizer about every 2 weeks, OR a granular fertilizer about every month, OR a slow release fertilizer 2-3 times per season. Over fertilizing is just wasting money and potentially damaging the environment. If you are one of those people who love to fertilize try using a liquid feed and just wetting the foliage of your plants, not soaking them. Plants can pick up a lot of nutrient right through their leaves and by doing this in small doses you are less likely to cause problems in your garden. Did you know that over-fertilized plants tend to be more susceptible to insect and disease problems? This may seem counter-intuitive but over-fertilized plants tend to be really lush because they have been pushed to grow fast, this weakens the plants and makes them more susceptible to pests and disease

Because clay soils hold on to fertilizers well you should use a light hand when applying fertilizer. Start out fertilizing at a slightly lower rate or waiting a bit longer than recommended between fertilizer applications. If the plants remain healthy and happy you are fertilizing often enough. If the leaves start to turn a yellow color you aren’t fertilizing quite enough. Armed with this knowledge you should fertilize a bit more often or at a slightly stronger rate. A bit of trial and error will tell you how often you need to fertilize with your specific soil. That clay soil just might save you money due to lower fertilizer costs. For more information on fertilizing click here.

How to water clay soils most effectively – Watering is the biggest challenge most gardeners’ face and most people over-water their plants, it is the single biggest cause of plants dying. Clay soil tends to hold water for long periods of time, therefore, if your garden soil is made up of clay, you should be watering less frequently. Spots in your yard that stay wet almost constantly are a sure sign you need to cut back on the amount of water you are applying. Check with your local county extension service to see what recommended watering rates are in your town.

Most landscapes and garden plants need to be watered just as plants are beginning to wilt a little, watering less frequently and more deeply will help develop deep root systems. Frequent light watering encourages shallow roots which will make plants less drought tolerant. The best way to water is deeply and infrequently (except for recently planted flowers and landscapes, these need water frequently to get established). If you have a sprinkler system, make sure to check and see that it is not over-watering on a regular basis, plants will get used to whatever watering cycle you give them, so plants that are regularly overwatered are more likely to collapse when the water isn’t there, the reverse is also true, plants that have to work just a little bit in between watering are tougher and more likely to handle short dry periods. For more on watering landscapes click here.

How to make clay soils better:

Incorporating compost – tired of chipping away at a clay soil that is hard and heavy? Try mixing in organic matter (compost, straw, fine wood bark, peat moss). Adding these things to your soil will make it more difficult for the soil to clump together and harden. This is especially true around trees and shrubs. In the garden a good compost to soil percentage can make digging a breeze and reduce the most common problems associated with clay soils. Adding compost can also help, somewhat, with drainage, keeps the soil for compacting which can block water flow – resulting in soils that remain wet and boggy. The compost will also act as a slow release fertilizer (it will container nitrogen and other nutrients) and as an additional way to hold water for your growing plants! Click here to learn more about compost.

Does digging up an entire flower bed and incorporating compost sound too daunting? While tackling an entire bed at once is the most efficient way of improving soils you can improve your soil a bit at a time. One method for accomplishing this would be too improve each little spot where you are planting a plant. To do this, dig a hole 2 to 3 times larger and deeper than what is necessary for the plant you are transplanting. Incorporate a healthy dose of compost by mixing it in with the soil you dug out of the hole. Fill some soil back into the hole, place your plant in the hole and then refill the rest of the hole with the compost enriched soil. While the surrounding soil isn’t enhanced the new plant is happily ensconced in good, compost rich soil. Over several years you will gradually improve the soil in the entire bed. This is also an effective way of improving soil in existing, already planted beds.

Mulching – Clay soils can tend to speed water runoff (water isn’t absorbed as quickly into clay soils as it is other soils) and certainly clay soils stick to the bottoms of your feet and make a mess when you go indoors. But you can solve these problems, and make the most of the positive properties of clay soil, by covering the exposed soil with a thick layer of tree bark, rough compost, shredded wood, or any of the other mulches available. By adding a layer of mulch to clay soil you not only can help keep the house clean, but can reduce the number of weed seeds that sprout (mulch will smother out weeds seeds that might try to germinate) and enhance the amount of moisture that your soil retains for better plant growth. Mulch will slow down water run-off allowing clay soil more time to absorb, and store, the water. A layer of mulch is also cooler than exposed soil so it helps to reduce temperatures overall in the garden.

In general having a clay soil can be wonderful, IF you know what the strengths and weaknesses of that clay soil are and how to garden best in this type of environment. You expend a bit more energy getting things planted and preparing garden beds, but in the long run you’ll use less water and fertilizer than folks gardening in sandy soils AND most plants prefer some clay in the soil to help them get their roots established and improve their hardiness.

Want to learn more about gardening in clay soils? Check out these links:

Learn about shrubs and annuals that are well suited for clay soils.

Learn about Growing Shrubs in Clay Soil.

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There’s no break for people who garden in clay

CORVALLIS – When you walk about your yard on a wet day, do your shoes stick in the mud? Could you make ceramic pots out of the soil in your garden? Odds are you have clay soil, one of the biggest challenges to the home gardener.

Finely textured clay soils are difficult to work up and develop into a good seedbed. If the clay is dry, it tends to be very hard and lumpy. If it is wet, it tends to be very sticky and difficult to manipulate. It seems like a gardener’s nightmare.

But clay soils have their attributes, says Linda Brewer, teaching assistant in the Department of Soil Science at Oregon State University.

“Clay soils hold huge amounts of plant nutrients because they have elevated cation exchange capacities,” said Brewer. This means they are able to hold on to nutrients, fertilizer and pesticides.

Another plus for clay soils is that they hang onto water really well.

“Clay soils hold huge amounts of water at very high tensions because the spaces between the clay particles are so fine,” explained Brewer. “The largest clay particle is more than 1,000 times smaller than the smallest sand particle.”

The best way to improve clay soils is to mix organic materials thoroughly with existing soil, explained Brewer.

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.

“Clay soils are highly structured at the atomic level, much as crystals are,” said Brewer. “No amount of sand can be added to a clay soil to change its texture. The large sand particles tend to provide a surface onto which the tiny clay particles adhere. The result can be a more difficult soil to manage than the original clay.”

When a large amount of organic material is added to the soil, microorganisms multiply rapidly. Since they construct their bodies from the same nutrients that plants use, soil nutrients can be relatively unavailable for a time after an addition of manure or compost. This condition may persist until the organic material is broken down and nutrients are released.

To overcome the temporary lack of nutrients, gardeners might try adding low nitrogen organic material to the soil in the autumn, or smaller amounts at a time in the spring, when warm weather will hasten break down. Or sprinkle in some fertilizer, such as ammonium sulfate at the time of tilling to give an immediate source of nutrients.

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.

Fertile soil with good tilth does not come about with a single or even several additions of organic material, but from a consistent soil-building program. “Repeated additions of organic matter do change the physical properties of clay soils on a broader level, but these additions must be regular in order to maintain the changes,” said Brewer.

“There’s no break for people who garden in clay,” she said with a laugh.

Improving soil structure

Most gardens have soil that provides something less than the ideal environment for many garden plants. Perhaps it’s rocky or scraped bare from new construction; perhaps it’s too claylike or too sandy to suit the plants you want to grow. While changing a soil’s basic texture is very difficult, you can improve its structure–making clay more porous, sand more water retentive–by adding amendments.

The best amendment for soil of any texture is organic matter, the decaying remains of plants and animals. As it decomposes, organic matter releases nutrients that are absorbed by soil-dwelling microorganisms and bacteria. The combination of these creatures’ waste products and their remains, called humus, binds with soil particles. In clay, it forces the tightly packed particles apart; drainage is improved, and the soil is easier for plant roots to penetrate. In sand, it lodges in the large pore spaces and acts as a sponge, slowing drainage so the soil stays moist longer.

Among available organic amendments are compost, well-rotted manure, and soil conditioners (composed of several ingredients); these and others are sold in bags at many full-service nurseries, or in bulk (by the cubic yard) at supply centers. Byproducts of local industries, such as rice hulls, cocoa bean hulls, or mushroom compost, may also be available.

Finely ground tree trimmings (wood chips) and sawdust are also used, but because they are “fresh” (“green”) amendments, they’ll use nitrogen as they decompose, taking it from the soil. To make sure your plants aren’t deprived of the nitrogen they need, add a fast-acting nitrogen source such as ammonium sulfate along with the amendment (use about 1 pound for each 1-inch layer of wood chips or sawdust spread over 100 square feet of ground).

Though the particular organic amendment you use is often decided simply by what’s available at the best price, many experts favor compost over all other choices. Vegetable gardeners in particular prefer compost, and they often also add plenty of well-rotted manure to their planting beds.

Adding amendments: when and how

New beds for landscape plants should be amended before any plants go into the ground. For long-term benefits, choose an amendment that breaks down slowly. Shredded bark and peat moss hold their structure the longest, taking several years to decompose. It’s a good idea to include compost in the mix as well; though it breaks down in just a few months, it bolsters the initial nutrient supply available to soil microorganisms–and these will contribute humus to the soil, improve soil aeration, and help protect your new plants from some diseases.

In beds earmarked for vegetables and annual flowers, amend the soil before each new crop is planted. Compost and well-rotted manure are preferred by most gardeners, since they dramatically improve the soil’s structure, making it hospitable to the fine, tiny roots of seedlings. Unamended soil may dry into hard clods that small roots cannot penetrate, and plants may grow slowly, be stunted, or die as a result. Manure and compost break down rapidly–manure in a few weeks, compost in several months–so be sure to replenish these amendments before you plant each crop.

To add amendments to unplanted beds like those just discussed, spread the material evenly over the soil, then work it in by hand or with a rototiller to a depth of about 9 inches. If your soil is mostly clay or sand, spread 4 to 5 inches of amendment over it; once this is worked in, the top 9 inches of soil will be about half original soil, half amendment. If the soil is loamy or has been regularly amended each season, add just a 2- to 3-inch layer of amendment; you’ll have a top 9-inch layer of about three-quarters original soil, one-quarter amendment.

Permanent or semipermanent plantings of trees, shrubs, or perennials benefit from soil amendment too, but you need to do the job without damaging plant roots. It’s often sufficient simply to spread the amendment over the soil surface as a mulch; earthworms, microorganisms, rain, and irrigation water will all carry it downward over time, gradually improving the soil’s top layer. If the plant isn’t a shallow-rooted type (that is, if it doesn’t have many roots concentrated near soil level), you can speed up the improvement process by working the amendment into the top inch or so of soil, using a three-pronged cultivator.

Where the climate is generally mild and winters are rainy, amend the soil in established plantings annually after fall cleanup. In cold-winter regions with spring and summer rainfall, do the job as you begin spring gardening.

Sand and peat moss: good amendments for clay soil?

Sand is often recommended to lighten clay soil. This seems a practical suggestion: after all, clay is the finest-textured soil and sand the coarsest, so mixing the two should result in just the right blend. It’s not that simple, though. The problem is that you must add a great deal of sand to make a difference–at least 4 inches of coarse sand to the top 6 inches of clay soil. Improving even a moderate-size planting bed thus requires a great deal of heavy sand and heavy labor. Many gardeners compromise by simply sprinkling a little sand on top of their clay soil, but such small amounts do no good; in fact, they actually compact the soil further.

Peat moss has long been a favorite soil amendment because it breaks down in the soil more slowly than manure or compost and can thus be replaced less frequently. It is also highly absorbent; it holds water in the soil longer than many other amendments do, making it especially beneficial in sandy soils. But if your soil is naturally claylike and drains slowly, the super-absorbency of peat moss can exacerbate the drainage problem, especially if you have heavy winter rains.

How To Easily & Organically Improve Your Clay Soil

There are some patches of earth that seem to have been made for gardens. The soil is loamy, rich and dark and crumbles just right in the hands. This is the type of garden that gardeners with clay soil are insanely jealous of. If you live in an area that is plagued by clay soil, you know how that feels. You sigh when having to put a shovel to the ground because you know that if only your soil was better, that the task of digging would not be nearly so hard. Yet, it is possible to organically improve your clay soil. Keep reading to learn more.

Clay Heavy Soil

How can you tell if your garden has clay heavy soil? One of the biggest indicators is if you take a handful of damp soil and squish it in your hands for a second, when you open your hands and that soil ball you just formed does not crumble, you most likely have clay heavy soil. Some other indicators are a greasy or slimy feel when the soil is wet, a dusty but hard appearance when the soil is dry or if you have drainage issues. All of these things are signs that your soil has too much clay.

Clay heavy soils can create several

problems for a gardener. Clay soils have drainage problems that can literally drown your plants during times of heavy rains, and then when the weather is dry, the soil has a hard time retaining moisture and your plants will shrivel up.

But having clay heavy soil is not a reason to give up on your garden. With a little bit of work and a whole lot of compost, your garden soil can be the source of jealousy for your fellow gardeners as well.

How to Organically Improve Your Clay Soil

One of the best things you can add to your clay soil is a compost of some kind. Whether the compost is well-rotted manure, leaf humus or many of the other options out there, you simply can not add too much to your clay soil.

  • Place the compost on the flower bed that you want to improve the soil of and dig it in with either a shovel or a tiller. Make sure you work in some of the existing soil into the compost, as it will help any flowers you plant acclimate to the surrounding soil both on the side and below the bed.
  • If you have more time (and you want to do less work), you can simply lay the compost on top of the soil and let it sit for a season or two. This works best if you place the compost on the clay soil early in fall and let it sit through to spring. The compost will work its way into the top few inches of the clay and will give your bed a good start.

Gypsum is another thing you can add to clay soil to help improve it. The gypsum helps to push the clay soil particles apart, making room for proper drainage and water retention.

Both compost and gypsum will also help attract worms to your clay soil, which then helps even further as the worms will burrow through the clay soil. The burrowing action of the worms will aerate your clay soil. As the worms burrow through the soil, they will also leave behind their castings too, which will help add nutrients to the soil.

As you can see, you can easily improve your clay soil with just a few steps. In no time at all, you will find that your garden will have the kind of soil that you only use to dream of.

Improving Clay Soil

There is no doubt about it; working in heavy soil is a pain in the back. It sticks to your shoes and your tools and seems to be a more challenging option than gardening with sand. But with all the hard work, clay soil has its benefits. It has the capacity to hold on to nutrients that your plants need, and it also holds moisture better than other soil types. With some amendments, you can turn your sticky clay into humus-rich, fertile goodness that your plants will thank you for.

Amending Clay Soil

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There is a notion in circulation that adding sand to heavy clay soil with help lighten it. That is a myth, and 99 percent of the time it turns your ground into cement. Soil treated this way becomes so tough that worms can’t live in it. Instead, reach for organic matter, such as compost, leaf mold, and well-rotted manure. Organic matter is the best way to amend clay soil: It lightens the soil texture, discourages compaction, adds nutrients, improves drainage and aeration, moderates soil temperature, and provides pore space, which is essential to plant growth.

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Amending your soil takes some time and patience but rewards you many times over in the end. The first step should be to add as much organic matter as you can and mix it into your existing soil as deeply as possible. Before you start, have a soil test done so that you can incorporate lime, phosphorus, or whatever was recommended at the same time you are tilling in the organic matter. If you are creating a new bed this will be much easier.

Start the process by using a tiller to loosen the existing soil (if it is a large area) or a spade (if it is a more manageable size). Spread about 2 inches of compost on top of the tilled soil and work that in. Repeat the process two more times. Remember to only work in your clay soil if it is relatively dry. Working or walking on wet clay soil seriously damages the structure you are trying to improve.

Working around existing plants will take more time and caution. Autumn is a great time to do this because the weather is generally drier than in the springtime. Another reason you should do this in autumn is that the cooler temperatures are more pleasant to work in, and it becomes an annual part of putting the garden to bed for winter.

Spread a few inches of compost over the ground between the plants and use a narrow spade to turn the compost into the soil. Repeat that at least one more time and plant to make that part of your regular routine. Always work in such a way that you are walking backward and not over your freshly turned soil.

In the long term, regular applications of compost, manure, and other organic matter will continue to improve the structure, tilth, and overall health of your soil. It will become much easier for you to work in and easier for your plants to root in.

One last word on gardening in clay soil: Choose plants that are naturally adapted to growing in clay. It is always better to work with what you have then to try and change it entirely. Happily, for all of us that garden with heavy clay soil, there is an abundance of beautiful plants to choose from.

More On Organic Matter

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  • Emulate how nature works. In wild areas, stems and leaves fall on the ground and rot, amending the soil from the top down. To follow nature’s lead, mulch poor soils with organic matter such as leaves, hulls, or bark.
  • Use what organic material is most available in your region. Whether it’s leaves, pine needles, hulls, or seaweed, it’s all useful for soil improvement. Don’t believe the old myth that pine needles or oak leaves make soil acidic; it’s not true.
  • When using leaves for mulch and amendments, chop them with a lawn mower or chipper. Chopped leaves stay in place, are more weed-smothering, and break down more quickly.
  • Apply top-down soil amendments in layers only 2 or 3 inches deep to allow rain to percolate through.
  • Employ the power of roots to break up heavy soils and add organic matter. Plant marigolds, zinnias, or other annuals in new gardens, cutting them off at ground level at the end of the season. The roots rot in the soil, improving soil structure.
  • By Peggy Anne Montgomery

When I was growing up my Mom always complained to my Dad about her garden and flower beds. She would say things like “Nothing grows in this red dirt!”, or “I’m not planting anything this year, it never grows!”

I always thought Mom just didn’t have a green thumb.

Fast forward about twenty years, and now I understand her struggle.

Digging in my flower beds and garden used to be like playing in a big mud pie that was left out in the sun to dry. The flowers and vegetable plants I planted always showed signs of being over-watered. Because yes, I have clay soil.

I’ve figured out a few ways that have improved the quality of my garden and flower bed soil. These tips have made my efforts in the garden more fruitful and less back-breaking.

Let’s start with the first step: determining if you actually have clay soil. Then I’ll show you what to do to to fix it.

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Discovering The Signs Of Clay Soil

Dry clay cracks in the heat, creating crevices that weed seeds can fall into. Source: Kitty Terwolbeck

For me, the largest problem with my heavy clay soil was the compacting of the dirt. It was heavy and wasn’t easy to till or dig into.

In addition to that, I also have waterlogged soil every spring after the snow melts. Compaction leads to poor drainage, and that leads to clumps in my tiller. Plants have a hard time developing good roots, as well.

First, you need to determine if clay is the problem. This simple test will help you determine the type of soil you are dealing with.

Pick up a handful of soil. Squeeze it in the palm of your hand. If it forms a sausage shape and stays together when you open your hand its clay based soil. Sandier soils will crumble more readily if you poke at the soil blob.

Also, check out your soil’s color. Many are rich in iron oxide, which gives soil a reddish or rusty tone. This is not universally true, but may offer a helpful hint. Red clay soils tend to be fairly common around the world.

Finally, there’s the “clay snake” method. Make that sausage shape mentioned above, then roll it between your fingertips to make it into a thin, long snake. Soil that stubbornly clings to its snake shape over 2 inches of length is likely clay.

How To Amend Clay Soil

Adding mulch to your heavy clay soil builds the soil over time. Source: charel.irrthum

Here’s some tips that I’ve discovered that helped improve my clay soil. These also make my gardening more enjoyable and less backbreaking.

Check The Soil Moisture First

There’s two ways of working with clay soil: when it’s really wet, or when it’s really dry.

Anything in between will cause the soil to stick to your shovel and become agonizing to deal with. It clumps and clings, and is just impossible. So it’s important to only dig when the soil is either very muddy and extremely soft, or when it’s fully dried out.

Even then, be careful. If you’re working with the soil while it’s wet, you’re going to create hard clods of dirt once it dries out. The only way to avoid this is to amend the soil heavily while it’s still muddy, so you can break up all the clods and evenly blend the amendment in.

Don’t Overwork The Soil

Related to the last section is to avoid overworking your soil. If you go out and turn your wet soil without amendment, all you’ll end up with is a bunch of heavy, dry clods. Anyone who’s ever dealt with heavy clay blobs knows that they’re hard to break apart later!

Along the same line, try to avoid over-compacting your soil as well. Don’t walk on areas you’re improving. Clay compacts itself naturally if you, the kids, or your pets walk on it. All you’re doing is making the problem worse.

Add Quality Amendments

No matter what time of year it is, adding aged compost can be beneficial. Compost is filled with plant matter that will help break up the clay particulate. It’s also just really good for your plants in general, and can help improve their growth significantly.

Biochar is another option. This light and porous charcoal can help improve drainage in clay soil while it also adds more organic matter to break up clods. It’s gained popularity in farming, too, and is starting to replace gypsum in a lot of areas.

Consider opting for perlite if you’re still having drainage issues. Perlite helps hold open pathways for water to filter through, and also keeps your soil aerated, which is good for breaking down plant matter like compost.

Looking for how to improve clay soil for lawns? Consider using greensand. Greensand is made of a mineral called glauconite, and it improves clay soil while adding some great micronutrients and a good potassium kick for your grass. It works well in gardens, too!

When all else fails, consider working in a commercial soil conditioner blend. There’s many options available on the market, and working that in over time will gradually improve the upper structure of your soil.

Consider Soil Builder Mulches

Amending the soil with straw mulch improves it as it breaks down. Source: Joe Hoover

Cover your worked areas with compost, bark, mulch, grass clippings, fall leaves, or even manure. I used shavings from my barn. Try to coat the worked areas 2-3″ deep with these organic matter.

When you add products like this over your soil, the materials begin to decompose and break down. Over time, they will work themselves into your soil, helping to keep the soil broken up and workable in subsequent years.

Plant A Cover Crop

When you’ve plucked the last head of cabbage in the fall, plant a cover crop. I like using timothy hay and then working that into the soil as an organic compost in the spring. I’ve also tried other cover crops like clover, alfalfa, and buckwheat.

Even with these tips, it isn’t going to be a quick turn around. Sorry, but it may take several years before you notice a difference in your garden soil.

Should I Use Gypsum?

Often, the immediate recommendation of garden centers is to add gypsum to your soil. Don’t jump straight to doing that, though. Make sure it’s right for your garden.

The effects of gypsum in soil to break apart the clay granules are short-term. In fact, it often only lasts for a few months time. And it has other effects that are much more long-term and problematic.

Adding gypsum to your soil can cause leaching of mineral and nutrient levels. Leaching of aluminum or sodium can be good as it detoxifies the soil, but leaching of iron or manganese can cause nutrient deficiencies in your plants. It may also cause other mineral deficiencies.

In addition, gypsum may make it difficult for beneficial mycorrhizae in your soil to do their jobs. Those beneficial growths often help your plants take up nutrition more easily, and you don’t want to slow the growth of your plants!

A Washington State University study thoroughly examined this topic. The consensus was that while there are applications for commercial farmland, or for extremely hard-compacted soils or sodium-polluted soils, it just isn’t very effective in most home gardens.

Stuck With Clay? How to Garden Anyways

Try to break up the hard-packed clay clods before planting, and add compost. Source: kahunapulej

So if you have clay soil, how do you get around it? Well, let’s break that down a bit further.

Rise Up

Build raised beds on top of a smaller area. I used top of the line soil and grew my tomatoes in raised beds.

This made it easier for me to work in the garden, as the beds put the plants at a much more workable height. It also kept the dogs and kids from compacting the soil that I was working so hard to change.

There’s many different types of raised beds, from planter-style ones to much more elaborate garden styles. You’ll make your garden look better and be able to grow even without doing the necessary soil amendments on your clay.

Warm And Protect Your Soil

In the spring the soil tends to become waterlogged due to the amount of snow we receive. This makes starting vegetable plants in the garden difficult.

My solution was adding window greenhouse boxes made from recycled window panes. This type of small greenhouse or cold frame can easily be built in few hours or less.

A cold frame or greenhouse-type structure will keep the snow off of your growing area, which helps reduce drainage issues in the garden bed. It also keeps the soil beneath it warmer, which helps with plant germination and growth.

Layer On The Mulch

I always mulch my beds over the winter, because snow and rain can really pack down bare soil. Wood chips work extremely well. You can even layer gardens with a thick layer of straw or grass clippings.

Mulch also helps prevent your soil from baking into an extremely hard state during the summer months. If you have areas that look like concrete once the sun has baked them for a while, mulch can help keep them soil-like instead of turning them into impenetrable slabs.

Not only will your mulch slowly work its way into the soil beneath and improve its tilth, but as it breaks down it will provide added nutrients for your plants. It has the added perk of helping prevent many kinds of weeds!

Plant Suggestions When Growing in Clay

Corn growing in a garden that has heavy clay. Source: laura.bell

Plants that grow in this soil type span a wide category. Here’s a few different options for you to choose from.

Grasses

Your grass types depend on your location. Different grasses work best in different climates.

For people in cool regions, varieties of cool season grass that grow in a clay-loam soil include fescues (especially hard fescue and red fescue), annual and perennial ryegrass, colonial bent grass, and Kentucky bluegrass.

People in warmer regions may want to plant plugs of warm-season grasses such as Bermuda grass, buffalo grass, Saint Augustine, or zoysia. All of these tend to tolerate clay-loam soils.

Vegetables

In the years of amending the soil I have found some plants that thrive in clay. I think this information can save you a lot of time and effort, spare you from destroying plants, and save some money, too!

Some vegetable crops that grow well include lettuce, chard, snap beans, broccoli, Brussels sprouts and cabbage. Rice also grows well in clay due to the constant moisture and heaviness of the soil.

Other shallow-rooted brassicas such as cauliflower or broccoli can also thrive in clay, as can sweet corn, squash, or pumpkins. The latter three have strong roots that can shove the clay aside.

Mulching around your vegetables can reduce the risk of fungal diseases from soil moisture or mud splashing onto plant leaves.

If you don’t want to build raised beds to plant other crops in, you can always trade with neighbors or friends for plants that grow better in amended soils, and simply stick with those which work with your soil type.

Flowers

If you have flower beds or are growing a flower garden, these are some of the best performing plants in my beds.

  • Asters: Daisy-like flowers in pink or purple hues.
  • Black Eyed Susans: Rich gold petals with a dark brown or black center.
  • Russian Sage: This can be invasive, but also very beautiful with small purple flowers.
  • Daylilies: A wide variety of colors available. These flowers open in the daylight and close up during the evening.
  • Yarrow: This yellow flower is perfect for dry flower arrangements.
  • Coreopsis: These are great for borders, and usually have pink or purple flowers.
  • Coneflowers: Purple-petaled perennials that are great additions to any garden.

If you want other plants that won’t thrive in clay, buy containers and place them throughout your yard. Not only does it give you the ability to grow plants that prefer lighter soils, but containers provide variable heights and look amazing when they’re in full bloom.

In my experience bulbs do not do well. Not only do they need warm soil, but they don’t do well when soil is soggy and can develop bulb rots.

Best Cover Crops

Some of the best cover crops for clay soil are clover, winter wheat and buckwheat. Crops like alfalfa and fava beans have a deep tap root so they tend to pull nutrients into the topsoil and at the same time help with compaction.

If you do opt to do a cover crop, till it into the soil at the end of its growing season. This adds extra plant matter that breaks down in the soil, adding more nutrition while breaking up soil clods. Be sure to till at least a couple weeks before replanting to start the decomposition process.

Clay Soil Benefits

Once graded, clay can be an excellent surface for a road during dry weather. Source: BluesDawg

Surprise! It’s not all bad news.

Compaction

Many clay soils are naturally more fertile than other soil types. The natural compaction of the soil tends to slow leaching, which would otherwise wash away many plant nutrients.

Watering

You don’t have to water as often in clay. It retains moisture more readily than other types of soil, and you don’t have to add vermiculite or other water-retention amendments.

Fertilizing

You may not need to fertilize as often. Because the clay particles are so fine and tend to cling together, fertilizer tends to stay in the soil for longer. However, this doesn’t mean you don’t need to fertilize at all! You just may have to do it less often.

Long Term Root Development

Once plant roots have become established, the dense structure of the soil can be a great foundation for many types of plants. The roots will remain securely in place, and may be partially protected from temperature changes.

I’ll bet right now you are feeling a bit better about that garden soil you’ve been cursing!

Don’t Skip This Important Step

No matter how you opt to improve your soil, don’t miss one year of amending your soil once you start. Keep at it to build better quality soil.

It doesn’t take long for the soil to return to its original hard, clumpy state if you don’t keep adding new material to it. Since you went through a lot of effort to amend the soil the first time, maintaining it year after year is easier than starting from scratch!

After many years, you may be able to change the quality of your soil overall, making this less of an annual necessity. But it’s better to go into it knowing that you need to do this simple chore every year for a while. It’s worth the time and effort.

About The Author: Alex writes for Woodtex, a preferred nationwide builder of prefabricated storage sheds, garages, and cabins. He is passionate about sustainability, healthy living, good food and exercise.

The Green Thumbs Behind This Article:

Lorin Nielsen
Lifetime Gardener
Kevin Espiritu
Founder Did this article help you? × How can we improve it? × Thanks for your feedback!

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Sometimes people recommend you add sand to clay soil to make it easier to work. It’s true that this used to be really common advice, but as we’ve learned more about the differences between soil structure and soil texture and how to improve our soils using organic amendments, it’s fallen out of practice because we’ve found better ways. Adding sand to prairie soils is not recommended. The danger of adding sand—especially in small amounts—is that large sand particles mixed with tiny clay particles will result in a concrete-like mixture. It takes the addition of 50% of total soil volume to significantly change the texture of clay soils. That means adding a truckload of sand to a small garden patch to change soil texture and using fairly aggressive means to mix it together thoroughly. The problem with clay soil is not the texture, but the lack of aggregate structure. Adding sand will not fix this.

Is there a better way?
Clay soil is nutrient-rich, but tends to be slow to drain, poorly aerated, easily compacted and extremely hard if it lacks good aggregate structure. How do you build the aggregate structure?

  • Ensure you lay plenty of compost on top of your soil when it’s time to plant – no need to mix it in, especially if you’re adding a layer of mulch next.
  • Stop rototilling your soil. While rototilling may initially break up the pieces and “fluff” it up, it will settle each year and your soil will be more cement-like with every tilling unless you’re adding significant organic matter each time. It is especially critical you never rototill when the soil is wet as this will severely damage your soil structure. No-till gardening is your best choice, but if you’re not quite ready for that yet try to minimize it as much as you can and ensure you add ample rotted leaves, compost, or other easy to break down sources of organic matter. Peat moss does work but is not an ideal choice for this as it tends to hold water, which isn’t necessary for clay and doesn’t break down as quickly as other alternatives.
  • Use mulch to improve the aggregate structure of clay soil and protect it from compaction. Even walking the same path down your garden can injure your soil. No need to dig it in just lay mulch on top of the soil. Give it time and you won’t believe the difference! Here’s a guide to mulching for beginners and there’s a lot more information in the Soil section of our website.

My childhood home sat atop a bluff overlooking the Mill Creek Valley near Quincy. The view over bucolic farm fields and pastures likely was the kicker for why my parents purchased the property. It is a view that still holds me in a trance whenever I’m visiting my folks. However, the bluff upon which our house resided, was comprised of thick, red, gumbo clay!

My parents would send me out with a shovel so I could dig holes, much to my childhood delight. After all what better entertainment for a child! It is my assumption today they knew the soil was so heavy; my digging wouldn’t take me down to China as I had hoped. Instead, my holes were a handful of inches. Regardless, I scraped away, with my oversized shovel. Who needs television when you have a shovel and an active imagination?

Over the years of gardening and landscaping on this property, we continually had to battle the clay soils. Only after efforts to build raised beds and add organic matter to the land with wood mulch, horse manure, and shredded leaves, did we begin to see a positive response from the garden and landscape plants.

First some hard truths about clay soil:

  1. Clay soil particles are the smallest of soil particles. Sand is the largest soil particle, with silt falling in the middle.
  2. Clay’s soil particle shape is flat, or plate-like; meaning it’s good at stacking on top of each other and creating a very “tight” soil.
  3. Clay is very good at preventing water from infiltrating into the soil profile, which leads to runoff and erosion problems.
  4. Clay is also very good at holding water. Clayey soils will stay wet longer than other soil types.

All these factors can create an environment that is not favorable to some plants or the gardener.

One garden misconception repeated routinely is to till sand into clay soil to break up the clay structure and facilitate better drainage. The idea stems from the fact that if clay is the smallest soil particle leading to poor drainage, and sand is the largest soil particle causing fast drainage, mixing the two will equal out to well-drained soil.

Unfortunately, it doesn’t work that way.

When sand mixes with clay, it creates a soil structure akin to concrete. To create a real change in a clayey soil structure, you would need to add a 1:1 ratio of sand to clay. Considering the actual volume of clay soil underfoot, that equates to a lot of sand.

It is far more practical to use organic matter to help break up clay soil. Compost is your best bet, but organic matter can come from other sources like wood mulch, composted manure, shredded leaves, or even cover crops.

And sometimes the best course of action is to accept your lousy soil and use plants that prefer clayey conditions. Yes, these plants do exist! Plants such as columbine (Aquilegia canadensis), New England aster (Aster novae-angliae), purple coneflower (Echinacea purpurea), blazing star (Liatris), and many others will tolerate the sticky, wet mess of clay soils.

I suppose that if you do opt for the sand method, it does help to have a child with a love for digging holes, and lacking the sense to know any better.

Is Clay Soil Acidic? Understanding Clay Soil PH and How To Amend It

Does your garden soil stick to your shoes and gardening tools when wet? Does it also become rock solid in the summer heat? If the answer to these two questions is yes, then it means that you have a clay soil in your garden.

Any soil that contains at least 50% of clay particles qualifies to be clay soil. And although it can be quite difficult to dig clay, it is one of the most fertile soils that you can have in the garden.

​Clay has both good and negative features, and although it can be stressful and tiring to work with, it can also produce some thriving gardens. But, if you are dealing with it for the first time, the chances are that you are wondering whether clay is acidic or alkaline.

It is right to be concerned about the pH since it determines the plants that you can have in the garden and also the amendments that you should use.

​Is Clay Soil Acidic Or Alkaline?

Soil pH is a result of various things with the organic material and mineral composition being some of the main ones. And so the pH of clay soil will always vary from one geographical place to the other. Also, different gardens might also have varying PH levels even if they are one the same location. The different pH is because other factors like fertilizers and water will also affect the pH.

​So is clay soil acidic or not? The pH of most clay soils will always be on the alkaline side of the scale, unlike sandy soils which tend to be more acidic. While the high pH of clay soil might be suitable for certain plant types like asters, switchgrass, and hostas, it is too alkaline for most other plants. And so it most cases it will be necessary to lower the pH.

Amending Clay Soil pH

If you have clay in your plot, the best thing would be to find crops that tolerate alkaline soils and instead focus on improving the quality of the earth by breaking clay soil up. But, if you have particular plants in mind that you want to have that prefer acidic soils, you can still amend your soil in a few easy steps.

Read more: Best Electric Tillers To Till Your Garden In The Right Way

​Test The pH

​Before you decide to acidify your clay soil, the first move should be to examine it to determine the exact pH. By knowing the level of alkalinity, you can choose an acidifying compound that will not only lower it but also be gentle on your soil.

​A pH test by a professional is always the best since you get an exact number, but you can still get reliable data by doing it at home with the use of a pH meter or pH strips. However, if you are a serious grower/gardener, it is advisable to use the services of an extension officer or to send a soil sample to your local laboratory. Doing this ensures you get a detailed analysis and recommendations on the best amendments for your clay soil.

​Amend The pH

​Once you determine just how alkaline your clay soil is, the next step is to amend it. However, it might also be necessary to test the water pH before this to ensure that is not too alkaline because it can raise the soil pH. When amending the clay soil, it is important to make sure that you do not work on wet soil because this leads to compaction.

​The pH test results should guide you on what to use and the amounts. Organic matter is always the best solution for most clay soils as it not only helps to lower the pH but will also assist in breaking it up and ensuring that your plants get proper nutrients.

​If the pH test results show that your soil is very alkaline, you should use compounds like sulfur, cottonseed meal, and iron sulfate. And this is because they are more efficient in acidifying soil and also work way much faster than the organic compounds. Gypsum can also be very helpful, and this is more so in places where the soil is also very salty.

​Maintaining The pH

​It is important to amend the pH several months before you plant in the clay soil because most of these acidifying compounds will require a lot of time to work. And once you get it to the level that you want it is still important to make sure that you maintain it at between 6.3 and 6.8 on the pH scale because this is what most plants prefer. You can do this by applying manure, compost, and other organic compounds every other season.

Conclusion​

​Clay soil will in most cases be alkaline without any amendments. While this might be good enough for some plants to thrive, most others will require you to acidify the soil. For this, organic compounds, sulfur, iron sulfate and ammonia-based fertilizers are an excellent choice. But, it is always important to remember that there is no permanent pH change and so you need to maintain the clay soil at the level that you desire.

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Clay Soil Test

SERIES 17 | Episode 20

Clay often gets bad press in gardening books. But clay soils can be the best in the garden, depending on the type of clay and how it’s managed. By understanding clay and what gives it its unique properties, it can be turned into a beautiful growing medium.

Soil scientist Simon Leake is passionate about clay. Not only can he explain its make up he can show some simple tests to improve clay soils in the garden.

Simon says: “Clay is a special mineral. It’s like flat, little, platelets, with an enormous surface area. For example a gram of bentonite clay has the surface area of a football field. It also has a weak negative charge which is the key to its nutrient and water holding ability.

“Sands and silts don’t have that negative charge and that huge surface area, which explains why their water and nutrient holding is so much poorer than clay.”

Apart from knowing all you would ever want to know about clay, Simon also runs his own soil testing lab, where he has spent over 20 years solving soil problems.

He says the first test on soil is called the aggregate stability test and you can do it at home.

“Dry any little crumbs of clay and make sure they are nice and dry. Then get a jar or petri dish of good quality water. Drop the crumbs into the water and watch their behaviour. A halo of clay or milky cloud occurring around the aggregate is called dispersion. They magnetically repel each other to form a milky cloud. And that’s an indication of problem clay.

“The next behaviour and you’ve got to watch closely to see – is the way the little aggregates fall apart. That is called slaking. Under heavy rain it will all fall apart and form a crust, or slake. It’s the second worst kind of clay behaviour.

“The particles are not repelling each other to the point where they go into solution but are just falling apart.

“The next test is a gypsum requirement test to determine how to stop that dispersion.

“To do this get some clean jars. Put some soil in clean water and shake it until it goes milky. Then stand it for about five or 10 minutes. If it doesn’t clear in the water, chances are it is going to respond to gypsum.

“Do the test adding some gypsum. See whether the gypsum makes the clay flocculate, or clump together.”

“Where the soil falls apart you need to add organic matter. Red or your yellow clays are more likely to slake and fall apart, whereas lots of organic matter and dark, black coloured clay are more likely to stay together.” According to Simon, organic matter represents the glue.

When using gypsum on a new clay start with about 200 grams per square metre. That’s about two cupfuls. Dig that in, and do the gypsum test again. “If it settles out in the jar within five or 10 minutes you don’t need any more,” Simon says.

So….clay doesn’t necessarily have to be a bad thing. With some simple testing and the right sort of treatment, it’s possible to turn a nasty, heavy clay into a beautiful crumbly top soil that will grow virtually anything. The secret is to throw away the green waste bin and put every bit of organic matter back into your soil.

Lightening Up That Heavy Soil / Clay can be turned into decent dirt

First in a Two-Part Series

Clay soil is the curse of many Bay Area gardens. It’s sticky and mushy when wet; hard as cement when dry. In fact, dried clay soil is so hard that people in underdeveloped countries have traditionally used it to make bricks for houses.

Of all soil types, clay soil is made up of the finest microscopic particles, says Bob Raabe, professor emeritus of plant pathology at the University of California at Berkeley. “As a result, there is very little air space between the soil particles.”

And this causes problems.

“Lack of air causes clay soil to hold moisture,” says Ann King, environmental horticulture adviser at the UC Cooperative Extension for San Francisco and San Mateo counties. “Moist conditions and limited air at the root zone lead to root disease.” And low oxygen at the root zone also means that plants have difficulty absorbing nutrients.

To determine whether you have clay soil, try the “sausage test,” says Lou Truesdell, president of American Soil Products Inc. in Berkeley, a company that recycles urban green waste into compost and other horticultural products.

Roll some damp soil in your fingers to make a sausage a quarter of an inch wide and about an inch long. Then hold the sausage at one end. If it doesn’t break, you probably have clay soil, says Truesdell. If it crumbles, you have a loamy soil, and if you can’t even form a sausage, it’s sandy.

NOT ALL BAD

Despite its drawbacks, clay — which makes up most of the Bay Area’s soil and a good deal of California’s — does have some benefits.

“I happen to have sandy soil in my yard, and I’d much rather have clay soil,” says Raabe. “Sandy soil doesn’t retain water and nutrients like clay soil. Clay soil needs to be watered and fertilized much less than sandy soil.”

Clay soil is also bulky and helps keep large plants anchored and stable.

Best of all, if clay soil is amended on a regular basis with organic

materials, it can become a rich, easy-to-work soil that will encourage plants to thrive, says Raabe.

“We’ve been amending a garden plot of clay soil at the university for the last 20 years, and its structure has really changed,” he says. “Now the soil is aerated, drains well and can be easily worked. Sandy soil doesn’t change as much when amended.”

Amending with organic matter, says King, “adds air space to the soil and promotes better drainage. It also relieves the stretching and shrinking that occurs with clay when the ground becomes wet and dries out.”

Good soil amendments include homemade or bagged compost (the favorite of most experts), composted manure, planter mix, peat moss (in combination with other organic matter), leaf mold, bagged shredded bark and ground-up garden waste.

Some experts suggest composting ground-up garden waste until it breaks down before amending soil with it, but Truesdell says it’s often not necessary to wait long.

“I think it’s good to amend with materials that will continue to break down, because then you get better biological activity in the soil,” he says.

USE FERTILIZER

“Some people warn against this, because it can cause a loss of nitrogen. But I don’t think it’s usually a problem. If your plants have a high nitrogen requirement, simply add a slow-release nitrogen fertilizer or composted animal manure to compensate.”

Other experts suggest adding gypsum to clay soil to improve drainage, leach salt from the ground and add calcium to the soil. The higher the calcium level, the more acidic the soil. And acidic soil is better for most plants.

You wouldn’t want your soil too acidic, however, warns Truesdell, or plant growth will suffer. To determine your soil’s pH and to know what amendments to use, Truesdell advises getting a soil test. You can get your soil analyzed at a soil agricultural lab for about $25.

And, for the month of March, Truesdell’s company, American Soil Products, is offering free soil pH tests.

Although it seems like a logical amendment, never mix sand into clay soil, says King. “Concrete is made of clay and sand, and concrete is what you’ll get if you mix these two,” she says.

Instead, regularly amend with a lot of organic matter. One small application won’t do much. If you have a heavy clay soil, it will take years of continuous amending to get the soil in good shape, as bacteria convert the amendment into much smaller amounts of humus.

DIGGING IT IN

“Add as much organic matter as you can,” says Truesdell, who suggests adding one-third to one- half amendment to the top six inches of soil. Do this by spreading two to three inches of amendment on top of the ground, then mixing it in thoroughly with a spade or rotary tiller.

“Although this may seem like a lot, after a year, one-third to one- half of what you added will be gone,” he says. Gardeners with particularly heavy soil may have to amend it three or four times a year to keep it in good condition.

In warm weather, the surface of clay soil hardens and cracks, which impedes the infiltration of water and air into the soil. To combat this, experts suggest mulching — spreading organic material on top of the soil. Mulching will allow better water penetration and slow down water evaporation from the soil into the atmosphere. Mulch also slowly breaks down and adds nutrients to the soil.

Never amend or plant in wet clay soil, as working it then will badly damage the soil structure. When the soil dries, you’ll end up with hard clods of earth that are nearly impossible to break up.

To determine whether clay soil is ready to be worked, Raabe suggests sticking a spade into the ground and pulling it to one side. If the soil looks glossy and slippery, it’s too wet to work. If it has a dull surface, go ahead and dig.

WAITING PERIOD

How long you’ll have to wait after rain can range from several days to a week or more, depending on how much clay the soil has and how warm the weather is.

Be careful not to overwater clay soil; it needs less than other types. Don’t automatically irrigate when the surface is dry, because underneath it might be very moist. Make sure the top inch or two is dry before watering.

Plants that thrive in well-draining soil may not do well in clay. Although perennials and annuals often have little trouble, some larger woody plants with deeper roots may have difficulty, says Raabe. Azaleas, rhododendrons and daphne, for example, often have problems in clay soil.

If you amend heavily and plant properly, however, you can grow most things in clay soil.

(NEXT WEEK: Sandy, rocky and soggy soils)

PLANTS THAT THRIVE IN CLAY SOIL

Although gardening in clay can be challenging, many plants thrive in this type of soil. Consider the following:

— Glossy abelia (Abelia grandiflora)

— Anemone

— Aster

— Bailey acacia (Acacia baileyana)

— Bottlebrush (Callistemon citrinus ‘Jeffersii’)

— Lemon bottlebrush (Callistemon citrinus)

— Bougainvillea

— Century plant (Agave americana)

— Coreopsis

— Creeping mirror plant (Coprosma kirkii)

— Lily-of-the-Nile (Agapanthus orientalis)

— Manzanita

— Naked lady lily (Amaryllis belladonna)

— Peppermint tree (Agonis flexuosa)

— Thrift (Armeria maritima)

— Western columbine (Aquilegia formosa)

— White fir (Abies concolor)

— Wild lilac (Ceanothus ‘Tilden Park,’ C. ‘Julia Phelps’)

— Yarrow (Achillea)

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