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How to Turn Dry Clay Into Healthy Soil

It’s frustrating. It’s frustrating to buy seeds, take them home while you’re all excited like a kid on Christmas, only to find that you have to put your back into breaking up ground that feels more like rock than it does soil.

I live in southern California, and if you didn’t know already, the dirt here is often bone dry with high amounts of clay. This is a problem for anyone trying to grow, well, anything.

With this kind of growing medium, plants usually don’t have the nutrients they need. There’s also runoff and the dense and dry ground preventing roots and beneficial life like earthworms and bacteria from spreading.

But, there are ways to transform your dry clay dirt into healthy, lush soil.

Using sand, organic matter, or cover crops are some of the most proven methods. So, with a few adjustments, you can start feeding your soil what it needs to give your plants the best growth.

Where does clay soil come from?

When treating your soil, it might help to know where clay comes from.

Your clay soil is formed from the weathering of rocks and soil over long periods of time. It’s often comprised of minerals such as silicates, iron, aluminum hydrous-oxide minerals, and mica. Over time, these tightly packed minerals form a hardened clay ground[1].

Why is it bad for gardening?

The dry clay soil in my backyard
A patch of dry ground I haven’t amended yet

Clay dirt can make it incredibly difficult for garden plants to thrive. Clay is kind of a perfect storm of ingredients that can disrupt your garden.

  • Not enough space for water and air
  • Lacks certain nutrients
  • pH balance is off (clay is too alkaline)

First off, good soil needs to have a healthy amount of space in it. If it’s packed too tight (as clay dirt often is), water can’t drain.

An everyday example of this is when we make coffee.

When coffee beans are ground too fine, the grinds can become tightly packed, not allowing space for water to flow through. This is why the “pressing” of a French Press requires coarse grinds. If you’ve ever had a French Press backfire and splash everywhere, this could be why.

So, if the dense clay dirt can be broken up by roots and organic matter, water can better seep into the ground. Meaning your ground-water reservoir will increase, more rainfall will be captured, and you can water your plants less. And who doesn’t want to pay less for their water utility bill?

Now, when it comes to pH, if it’s out of balance, it can pose a couple of issues. The most common are that nutrients either can’t be absorbed or aren’t available in the right amounts.

By testing your soil and introducing organic matter, the acidity and alkalinity can be balanced and provide better for your garden plants. Let’s get into some more details.

How can I fix clay soil?

my soil being amended by an annual ryegrass cover crop in my backyard

As mentioned, sand, organic matter, and cover crops are some of the best ways to fix your clay dirt. You can try all of these methods, or you can pick one and you’ll still likely be better from where you started.

First, here are some tools you may need to start:

  • Soil test kit
  • Compost or other organic material
  • Cover crop
  • Buckets or wheelbarrow
  • Rake
  • Shovel
  • Hand spade

Let’s recall the common issues that come with clay.

  • Density
  • Nutrients
  • pH

Now, let’s explore how to amend these using the three methods.

1. Sand

Sand under a microscope
Image credit: Wired magazine

Sand is a very fine particle. If you’ve ever looked at sand under a microscope, it’s pretty psychedelic.

By adding sand, the dense clay can be easily broken up. Not only that, but sand is naturally acidic. Meaning, the alkalinity from the clay can be better balanced, resulting in a better soil pH. This is great for many plants, including tropical varieties like moringa and Malabar spinach.

To achieve a proper balance of sand to clay, most say a 1:1 ratio is best.

But chances are, you have a lot of ground to cover (literally).

This would result in a ton of sand (maybe literally).

So, although sand is a good option to treat clay dirt, adding enough for your garden purposes will likely add up to A LOT of sand.

Because adding that much sand isn’t exactly practical, the next method has long been popular with gardeners.

2. Organic matter

a pile of organic matter from food scraps that is helping amend the clay soil

So, I somehow convinced my parents to start composting. And they LOVE it. I kept it simple at first. I took a medium-sized Tupperware and stuck a note on the lid, “eggshells, coffee grinds, tea bags”, and left it next to their coffee maker. Then, I repurposed a spare trash bin they had outside and helped them with the composting process.

a container full of kitchen scraps that will be used for treating the soil
It started as three, but soon expanded to most food scraps

They quickly loved the idea of not using as much garbage space and seeing their garden grow. It became a game of “Is this compostable?”. They tossed in juice pulp, paper, and all the fruits and veggies they could. I have no idea how much rich topsoil we’ve added to their garden, but it’s definitely working.

Aside from the organic matter breaking up the clay, compost also provides nutrients. You can still buy synthetic fertilizer such as sulfur, magnesium, and calcium to benefit your soil. But most of these elements can be found from everyday food from your kitchen.

Coffee grinds contain phosphorus, potassium, magnesium and copper, while eggshells provide calcium, sulfur, magnesium, potassium, and sodium. And adding vegetable matter can provide even more nutrients and minerals.

There’s a reason why compost is hailed as gold to the garden. Think about it–it’s the circle of life. Food breaks down to make more food. Just instead of your kitchen scraps decomposing in a garbage dump, you’re bringing it to your backyard.

With the help of earthworms and beneficial bacteria, these food scraps will break down quickly into organic matter, transforming the dry clay into rich soil.

How much compost to add

farmland with a fresh layer of healthy soil or compost added on top

Generally, if we were adding compost to the top of our soil, 1/4 to 1/2 inches would work.

But since we are amending the clay soil, 1 to 2 inches of compost works best.

You can start your own compost pile, using kitchen scraps and pruned plants (like my parents did), or you can, of course, buy it at most home improvement stores.

Over time, these compost additions will add up to more soil volume than most realize. And more than likely, you won’t need to add anything else to your clay dirt. With most composting foods only taking 2-3 weeks to break down, healthy soil is achievable sooner than you might think.

3. Cover crops

My annual ryegrass helping treat the dry soil
My annual ryegrass helping treat the soil

I started testing cover crops a couple of months ago after watching The Biggest Little Farm documentary.

There was a section of the garden that I was using for veggies and herbs, but the adjacent section had incredibly dense clay that was tough to break into. So, I thought I’d let cover crops do the work for me.

I found there are three main benefits to using cover crops for your backyard clay dirt.

  • Breaks up the clay
  • Drainage
  • Compost for soil
My ryegrass breaking up the clay with its roots and turning it into good soil
You can see how the roots are already breaking up the soil and keeping moisture in

The fast-growing roots help break up the clay into smaller pieces while improving drainage. When the crop matures a bit, tilling it into the (now loose) soil and letting it compost will keep the clay from clumping again. This organic material is also great not only for worms but also for bacteria and other beneficial microorganisms. As a bonus, the crop protects the soil from baking in the sun, keeping moisture in and the ground soft.

While cover crops do take some time to grow, they can speed up the process of amending your soil. Especially while you are waiting for your kitchen scraps to compost.

When I first broke ground on my clay soil, I had no idea what I was doing. It was almost rock hard and bone dry, with little too no semblance of life. I found that sand, organic matter, and cover crops were some natural tools that could reverse this trend. While sand isn’t exactly practical, using both cover crops and composting worked best for me, and my soil is already turning around for the better. My plants love it, I love it, and the tiny bacteria are having a party.