Why Is My Garden Soil Cracking?


If you notice that your garden soil cracking, you are not alone.  Many gardeners face this same problem, which leads them to wonder why it happens and how to fix it.

So, why is your garden soil cracking?  Garden soil will form cracks when it shrinks due to loss of water caused by extended periods of dry weather.  Clay soil is the most likely to crack, since it holds more water than other types of soil, which allows more space to open up cracks during a drought.

You may not be able to control droughts and extended periods of hot, dry weather.  However, you can control the way that you take care of your soil.

Let’s take a closer look at why garden soil forms cracks and how you can fix it.  We’ll also get into how you can prevent this problem in the future.

Why is My Garden Soil Cracking?

Your garden soil is cracking because it is drying out and shrinking.  This is most likely due to a combination of different factors.

One factor that affects soil cracking is the consistency and structure of the soil.  Clay soil is the most likely to crack, since it holds more water than other types of soil.

cracked clay soil
Clay soil is more likely to crack during droughts.

Clay soil particles are small and fine, and so the particles tend to be packed closer together.  If you walk on your soil or park heavy vehicles on it, it will be compacted even more.  This will make the problem of cracking soil even worse.

Another factor that affects soil cracking is the amount of moisture in the soil.  Extremes in either direction will make soil cracking worse.

When soil gets too much water during a rainstorm or from irrigation, it tends to get compacted.  This is especially true if you walk on the soil, park heavy vehicles on the soil, or work the soil (dig or rototill) when it is wet.

During hot and dry weather, water will evaporate faster, which dries out the soil.  Plant roots also take up water to survive the drought, further drying out the soil.

When a large amount of water leaves the soil all at once, a lot of space is freed up.  At that point, the soil can either settle or crack.  If the soil is already heavily compacted, it does not have room to settle, so it will crack.

Cracking soil is a problem for many reasons.  It can interrupt the growth of plants in your garden or grass in your lawn.

Cracking soil can also lead to a loss of nutrients due to runoff of fertilizer (due to erosion).  Since cracked soil also tends to be dry and compacted, it can be difficult to grow anything in such soil.

This is due to the lack of space in compacted soil – it does not allow any room for air, which plant roots need to survive and thrive.  Compacted soil also makes it difficult for plant roots to expand and grow in the soil.  This is a huge problem for root crops, such as potatoes and carrots.

Hopefully this list of problems has convinced you to take steps to fix your garden soil and prevent it from cracking.  So, how do you do that?

How to Fix Cracked Garden Soil

There are a few steps to take if you want to fix your cracked garden soil and prevent it from cracking in the future.  I would suggest taking them in the order that follows.  We’ll start by aerating the soil.

Aerate the Soil

The purpose of aerating the soil is to help reverse the harmful effects of soil compaction.  When you aerate your lawn, you add air to the space between the soil particles.

Aeration allows plant roots to “breathe” and get the oxygen they need.  It also makes air available for beneficial soil organisms, such as earthworms and nitrogen-fixing bacteria.

Earthworms will help to improve soil structure as they digest organic material in your garden.  Bacteria will help to make nutrients available for your plants.

earthworm
Earthworms will help to improve the structure of your soil. Attract them with organic material from compost or manure.

Aeration is good for your garden soil, but how do you aerate the soil?  You can use an aerator, which is a tool that creates holes in the soil to allow space for air.

A spike aerator punches holes in the ground by displacing soil.  However, a spike aerator can lead to additional soil compaction, since it is not removing soil but rather pushing it deeper underground.

A plug aerator removes soil from the ground to create spaces for air.  This will not cause soil compaction.

One word of caution: you should avoid working on your soil too much when it is wet.  In order to aerate the soil in your garden, you will have to walk over part of it.

Walking too much on wet soil will cause more compaction.  Wait until a dry day for soil aeration, and do it before irrigating your soil.

Once you have aerated the soil properly, it is time to add some compost or manure to improve the structure of your soil.

Add Compost or Aged Manure

Compost and aged manure will add organic material to your soil, which will attract beneficial organisms (earthworms and bacteria).  This organic material will also improve your soil’s ability to handle water.

If you have heavy clay soil, adding compost will allow it to drain more easily.  This will reduce the problem of compacted soil.  The organic material will also make the soil looser, allowing plant roots to grow more easily underground.

If you have sandy soil, adding compost will help it to retain a bit more water.  This is helpful if your soil drains too quickly, or if you live in an area prone to droughts.

When adding compost to your garden soil, use a layer about 2 inches (5 centimeters) deep.  Work the compost into the soil by digging, but only when the soil is dry.  As mentioned earlier, working the soil when it is wet will lead to further compaction.

compost bin
Compost improves soil structure and adds nutrients for your plants. You can make it from kitchen scraps and yard waste.

You can buy compost online or at a garden center.  You can also make your own compost, using ordinary yard and kitchen scraps lying around, such as:

  • Grass clippings
  • Fallen leaves
  • Banana peels, orange rinds, and other fruit/vegetable remains

To learn more about what you can use for compost and how to make it, you can read my article on compost here.https://greenupside.com/quick-and-easy-methods-for-making-compost/

When using manure in your garden, just make sure that it has aged properly before adding it to the soil.  Manure that has not aged properly will contain too much nitrogen, and it can burn your plants.  You could mix manure into your compost and age everything altogether.

Once you add some organic material to your soil, it is time to make sure the moisture levels are correct and under control.

Control Water through Irrigation and Drainage

You can certainly control how much water you add to your soil.  During a drought, you can use a handheld hose, a sprinkler, a drip irrigation system, or even a watering can to irrigate your plants.

After aerating your soil and adding organic material, it may be time to try adding water to dry soil again.  The aeration and organic material should help the soil to handle the moisture and avoid cracking. 

If you are really having trouble with dry soil, you can learn a bit more about how to treat it here.

On the other hand, all you can do during a few days of heavy rain is to stop watering.  If this isn’t enough, you will need to find a way to direct excess water away from your plants.

To do this, you will need a drainage system of some kind in your garden.  One method is to plant some of your crops in slightly elevated soil (like a raised bed).  With raised beds, the excess water will drain out of the soil more easily.

Another method is to use trenches or underground pipes to divert water away from your garden.  Just remember to find out where utility lines (electrical and gas) are located before digging!

Once you have your irrigation and drainage under control, it is time to add some mulch to help retain water in the soil.

Add Mulch On Top of Soil

Adding mulch on top of soil has several benefits.  It helps to insulate the soil, so it can prevent cold damage to plants that were started before a late spring frost.

Mulch will also eventually break down, providing nutrients and organic material to your soil.  However, the main benefit of mulch that we are interested in is water retention for dry soil.

With a layer of mulch on top, the soil underneath will be able to retain water much more easily.  This means that the water in the soil will not evaporate quickly in a drought (which is what causes cracking in dry soil).

wood chip mulch
A layer of mulch on top of your soil will help to prevent rapid evaporation, dry soil, and cracking.

You can use wood chips, grass clippings, fallen leaves, sawdust, or even compost as mulch.

Plant Cover Crops (Green Manure)

This step is optional, but it can help to improve the structure of your soil while also providing some nutrients for your plants.  A cover crop is one that you plant and then till into the soil to restore nutrients.

A good cover crop, such as alfalfa, will grow its roots deep into the soil.  The roots will then pull up nutrients from deep in the soil, which may not be available to shallow-rooted crops.

When you till the cover crop into the soil, these nutrients become available to the next crop you plant.  The cover crop will also provide organic material when tilled into the soil (thus the name “green manure”).

alfalfa
Alfalfa (Lucerne) is a good cover crop (green manure) to improve the soil.

The roots of cover crops can also help to improve soil structure and prevent erosion due to wind and water.  You can learn more about green manure and the different cover crops you can use here.

What to Avoid to Prevent Cracks in Garden Soil

To prevent cracks in your garden soil, here are a few things you will want to do to avoid compaction:

  • Walking on the soil
  • Parking heavy vehicles or equipment on the soil
  • Rototilling or digging when the soil is wet (over tilling causes soil to become too fine, and when wet or compacted by walking, problem gets worse)
  • Adding sand to clay (you will get something like concrete!)

Over watering will make the problem of compaction worse, so keep an eye on your irrigation (don’t leave the hose running when you are not there, or put your sprinklers on a timer).

Conclusion

Now you know why your garden soil is cracking, and how to treat the problem.  You also know what steps to take each year to prevent the problem or reduce its severity.

I hope you found this article helpful – if so, please share it with someone who will find the information useful.  Best of luck with restoring your soil to a crack-free condition!

jonathon.david.madore

Hi, I'm Jon. Let's solve your gardening problems, spend more time growing, and get the best harvest every year!

Recent Content