“Our house is in what used to be the Pine Forest part of the camp; as a scout troop we use to camp here. When the bulldozers moved in here they moved the dirt around to the point where the old landscape is barely visible. The dirt around our house is clay fill dirt brought in from who-knows-where. When dry the clay is a brick, when wet, sticky and slippery.
We have spent the last two years trying to till and introduce amendments into this, whatever it is. We buy compost by the truck load from the city of High Point and compost the leaves that fall each year. When mixed with our clay the compost seems to reharden in time. The leaves seem to do the best job of breaking up the soil. It has been two years and I have seen only a dozen worms. How do I get them back into the earth and how many worms per square yard should we have; and how do we get them into the soil?
If you have addressed this topic before please send me the link. Thank you” ~ Don Alsop
Hi Don,
Let’s start by first talking about the different types of soils which are out there.
There are six main types of soil:
Clay, Chalky, Peaty (Duncan has a mate named after this type), Silty, Sandy and… Loam,
However out of the six there are three basic types: Clay, Sandy and Loam, with Clay and Sandy standing on the two extreme ends of the scale and Loam soil being in the middle as the perfect type for plant growth.
The other types are somewhere in between.
Clay soils are basically really small particles, so small that it feels lumpy and sticky when it is wet, almost like mud. However once dry it, it compacts together so tightly it turns rock solid and is a nightmare to dig through.
This kind of texture has the advantage of holding in nutrients such as calcium, potassium, and magnesium well.
However this texture makes it a poor soil for growing most plants, since when it compacts together it causes problems with water drainage, oxygen diffusion and generally makes it harder for plant roots to grow into. It is also slower to warm up during the spring.
Sandy soil on the other hand are larger particles and has (as its name suggests) a sandy gritty feel to it.
The problem with this soil is that it is exactly the opposite to clay soil. It is very loose in texture, and because of this it doesn’t hold in water since it evaporates easily. As water easily washes out of sandy soil it takes a lot of the nutrients away making it poor in mineral content, therefore this type of soil needs fertilizing quite often in order for plants to do well.
However because of this loose texture, if fertilized and watered often, is good for crops and vegetables. The sand is easy to root into, and the loose texture allows oxygen to diffuse into the roots easily.
Loam is right smack in the middle of the scale in between sand and clay.
This is what you may call the ideal type of soil for plants.
It has the prefect balance and reveals the advantages of both of the type of soils while displaying none of the disadvantages. It warms up quickly in spring and doesn’t dry out quickly in the summer. Most plants grow well in it, it’s easy to ‘work’ in most weather conditions, and it holds soil moisture and therefore the nutrients quite well.
How do you know what type of soil you have?
here is a simple soil test you can do and all you need to have is a glass jar, your soil sample and some water.
Fill the jar halfway up with the soil sample and fill up the rest of the jar with water. Close the lid and give it a really good shake, then leave the jar somewhere for a few hours to settle.
You will see that as it settles the soil will have separated itself into different layers. The bottom layer will be filled with the largest heaviest particles (stones and then sand) and moving towards the top will be the lightest and smallest (clay and silt). The very top layer will be the organic layer where all the dead (once living) material is.
This soil test is useful since it clearly shows they type of soil you have and how much organic material is in there simply by the proportion of the different layers, which you can then adjust accordingly.
Organic material is important in all types of soils, and when you see that there is a lack of organic material in the soil test it will be time to do some amendments.
No matter what type of soil you have, amending the soil is about balancing these layers.
Most of you will know that amending soil is done through the addition of organic matter because these get used up and need replenishing. Don has also correctly attempted to do this!
But how does the addition of organic matter work?
Organic matter needs to be there for plants, organisms and micro-organisms to grow and flourish.
Organic matter acts as a sponge which can hold moisture and allow excess moisture to drain away.
It also forms a good crumbly texture by holding particles together to form clumps with enough solid matter to crumble away (increase tilth).
This is important for clay soils since small particles forms larger individual clumps, making it less of a watery muddy texture. The larger clumps will create a less compact soil, allowing water to drain and prevent the hard clay texture when dry. The organic matter breaks down into nitrogen which is important for the plants, organism and microbial growth.
So for clay soil, an increase of microbial life is important to consider.
Bacteria are important which helps build up the soil by clumping them together. Organisms such as earthworms help by producing worm cast which clumps up the soil (worm cast is organic material!) and adds more nutrients into the surrounding area.
Now to answer Don’s question, it seems that you are you doing well in adding organic matter and worms to the area.
However on the note of worms, you need to be aware that worms move and they tend to move away from unfavourable conditions.
So if your soil is unfavourable to start off with, don’t expect your worms to stay there and amend it for you!
You will need to sort out the problem first before slowly adding your worms in. When it starts to get favourable, your worms will reproduce and fill the area. So don’t waste money by dumping a load of worms in there.
As I have mentioned, you will need increase microbial life.
You may consider using compost tea. Compost tea will seep really well into clay soil and when used regularly it will give it a constant boost of microbial life which will slowly help with the clay soil texture.
In regards to the organic matter, when you mix it into the clay soil, only do it to the surface 6 inches.
Tilling the soil will help, but only do it to a minimum.
What you want to do is cover the surface with mostly new organic matter and compost to cover the clay soil. The reason for this is if you have a lot of clay soil, you will need to add a lot of organic matter to balance things out, but this needs to be done slowly step by step and not all at once. If the clay soil is brought too much out to the surface, it will only dry up quickly and become hard clay again.
By mixing it slowly once in a while over a couple of years, the clay will stay underneath the new organic layer without drying out, and will give the chance for its own build up in texture by the microbes and organic matter itself.
This will also naturally attract worms to the organic layer which will slowly (but surely) distribute their casts around, including the soft damp clay soil.
You may even start planting some plants with strong roots to the organic layer. The rooting of the plant into the clay soil underneath will no doubt help with the soil structure.
After reading this article and knowing that sand is the opposite end to clay, it is logical to think that adding sand into clay soil will help. This is only true to some extent and you need to be VERY careful. Adding fine sand will only make matters worse!
It will clump together even more and you will end up with a clumped up sand pit. What you need is coarse sand (or builders sand). With this, you will also need to add this in slowly step by step with the organic material. If you add too much all at once, you will get uneven soil meaning a patch of land with the worst of both worlds.
Last thing of all which Don may need to check out is the pH. Have you tested the pH of your soil? Is it too alkali? Too acidic?
This is important to know and amend as this affects the microbial eco-system. If you’ve got acidic clay soil, not only will lime help improve the pH, the calcium will also solidify and help with water drainage!
I have to admit, clay soil is not easy to deal with and takes a lot of patience.
It is not the type of soil which can be amended overnight, and requires time to build up in organic matter and microbial activity. However if you take your time and do things slowly step by step, you should solve it in a couple of years!
