For many people spring brings a lot of mud and some of this is due to a combination of melting snow and spring rains but much of it is because your soil is not draining correctly. This can be a problem on unpaved country roads and in fields where you plant and fighting it becomes a never ending battle if you don’t take the time to diagnose and cure the problem.
What Is Hardpan Soil And Why Its Your Enemy
Soil is made up of many different layers. On the top there is normally topsoil for about the first foot and then below that is where most people never look. Depending on the area you live in and your specific location you might live where a layer of hard clay separates the Topsoil layer and the gravely dirt below it.
Topsoil is primarily organic material. It is normally formed from millions of years of Grasses, Trees and other plant material breaking down over thousands or millions of years. This top layer is where things grow. They say the top six inches of topsoil is what supports all life on the earth. Below that can be a mixture of different inorganic materials such as sand which can be thought of a fine form of gravel, Gravel, Rocks and Boulders until you reach the Bedrock of the earth’s crust. What we didn’t mention is clay can also form. Clay is a very fine material made up of ground stone. In its purest form it can be used to make pottery and it is often found in and along stream beds where stones are ground by the water into the dust like material which is clay.
The bad thing about clay is that it is really good at holding water. If you were building a man made pond it is often suggested that you fill the bottom with compacted clay material if you can harvest it from your property or bring it in because it will help hold the water. Natural ponds and lakes do this over thousands or millions of years.
Gravel will not hold water it runs right through it. Just like what you might find on a pathway, driveway or unpaved road.
The problem of Hardpan or Clay Layer Soil is that it will hold the water at the surface and then traffic over it will result in a muddy mess. Even applying Gravel on your road you might see it get sucked down into the Hardpan Clay every year and disappear. This is because the water will travel through the stone and into the clay and then the clay layer won’t be able to support the weight of car or truck traffic.
The opposite is true when the soil is very dry. Clay layers will become extremely hard similar to the pottery that can be made out of them but not quite that bad.
This is a very big problem for Departments of Transportation and if you notice when roads and highways are being built they go through extensive effort to move different types of soil to build the roadbed before asphalt or concrete top layers are applied. If they didn’t then their roads would fail dramatically and quickly but when done correctly the average road can go many years without resurfacing and even then it is almost never a total rip out and do over.
For Farmers Hardpan means that an impermeable layer of clay is sitting below their fields. This can cause a huge number of problems for planting, care and harvesting their products. When the fields are wet they are difficult to drive on and plant. You often have to time your planting of these areas much more carefully than areas with better soil conditions. You will also find that the hardpan clay layer will restrict root growth and you will try to compensate by adding amenities like fertilizer and lime.
Identifying Hardpan Clay Soil
There are a variety of scientific tests that can be done to examine the properties of Soil. Sometimes you will see soil test kits where you collect samples of the top layers of soil to predict amenity / fertilizer requirements for planting. You might also be familiar with Perk Tests that are used for Septic Systems. A Perk or Percolation Test is really more useful because it is testing the ability of the soil to absorb water from your home’s plumbing and then allow it to evaporate within a reasonable amount of time without causing ponding on the surface. Percolation tests normally require state inspection and often you need to dig the test holes when the inspector is present.
If you have a large property and expect to spend a good amount of money building roads, driveways, or farming then it probably is in your best interest to contact a professional to do some testing. You would want to contact a Civil Engineer with Geologists on staff and for farmers you might want to start with your local Department of Agriculture Extension Office which are in most counties and can provide help for free.
However a very easy way to see if you are likely dealing with hardpan is to do a stick probe test. When the soil is in normal conditions neither extremely wet or dry but if you dig down a few inches and crush a handful of soil in your hand it should stick together loosely and not just fall apart you can perform this test.
Take a steel dowel or rod about 3/8″ in thickness and 2 feet in length and slowly penetrate the soil as deep as you can. The rod should travel evenly and smoothly for at least 1 foot or deeper. If you hit a rock then move over and try again. Repeat this test in a variety of locations within the problem area. If you feel resistance below the first 6 inches so hard that you can not penetrate the ground and its not a rock then you likely have hardpan.
The next step would be to use a backhoe or excavator to cleanly remove a bucket or two of soil and then examine the sides of the hole looking at the layers below the topsoil. Unfortunately this is difficult to do unless the conditions are pretty dramatic so soil testing is needed. Samples will be taken and washed with water. Clay, Sand and Rock will be separated and dried in an oven then determined for content. Its not the most difficult thing in the world to do but it has to be done accurately because you are using the results to determine the condition of the soil.
Curing Hardpan Clay Layer Soil Conditions
Curing poor draining clay layers known as Hardpan can be difficult and expensive however if you are preparing a roadway on your property it must be considered at the beginning where expense will be less and the benefits will be lower cost and better conditions for years to come.
If you are preparing a field which was once wooded land and you find that you have poor draining soil the cost and effort of working that property over many years could be benefited by heavy improvement.
Normally this means in both cases to remove the topsoil and then prepare the dirt that is under it. In the case of a roadway it can mean bringing in large amounts of gravely sandy fill and churning the existing dirt by cutting with a bull dozer attachment. In the case of farm land you would want to preserve the topsoil and reapply it after improvement has taken place.
However in many cases a bandaid approach is made by the land owner. Roadways are normally top treated with stone 6 inch minus and then 3/4″ minus applied as the finished road surface. In the case of farming deep plowing might be used to churn the soil however so much activity will change the conditions of the growing material needed for farming and it is possible it could be degraded before improvement is met.
When the hardpan layer isn’t significantly thick then cutting and plowing might improve the situation but in the case of farming you can expect that amenities will be required to rebuild the topsoil.
Final Note
Hardpan Soil is a very difficult problem and it occurs in many locations but if you are investing your time and money into a property and you find you have poor soil conditions you may not have a choice if you expect conditions to improve.
I have seen farmers plant fields over and over again only to complain about those few acres that never seem to dry out. Well this could be for many reasons such as a natural spring or slope of the property funneling all of the water to that area but if it is because of hardpan then nothing they do to the top 6 inches to a foot will ever make improvement.
The same is true for many rural homesteaders. They just expect to order a few truckloads of gravel every spring after they work out the ruts of clay mud. However if they ran a bull dozer with a cutter down their road then the problem could be solved for many decades.
It all comes down to knowing whats under the surface and if you need to hire a professional you do it. If the problem isn’t so bad then in the case of a driveway you just need to raise that driveway and divert water away from it and that doesn’t just mean dig a ditch right at the road edge it means working 50 to 100 feet away and making sure water never gets anywhere near that road.
It can be done and the investment is worth the effort, cost and time.