Is clay soil good for plant growth? The facts


When you purchase your new land and decide to build a garden, the first thing to assess is your soil conditions. There are 6 main soil makeups that are typically found, but more on those later. In this article, we are going to look at clay soils. 

Is clay soil good for plant growth? Clay soils hold huge amounts of nutrients, but they really have their issues for plant growth. You can still grow in clay soils by amending them. Otherwise, you will face challenges. Although this won’t stop you growing plants.

What are the problems with clay soils for plant growth?

Clay soils have one advantage of being able to hold lots of nutrients and micronutrients. However, they also have their challenges for the gardener when looking to get good plant growth. They are as follows.

  1. Clay Soil Compaction
  2. Clay Soil Air Movement
  3. Clay Soil Water retention

Clay Soil Compaction

Clay soil is made up of lots of very small particles that combine and compact together that creates a very solid soil that holds water and nutrients. You would think this is good for plant growth, but this is not the case. The soil is so compact that it limits root growth due to lack of air. 

The smaller the particle size the more compaction that occurs and although this soil type. Over time these particles get smaller and smaller which makes the soil even worse. This can be seen during the summer when your soil goes as hard as concrete and cracks. 

Clay Soil Air Movement

Due to the particle size of the minerals in the soil, as I have already explained these compact together, this makes for a very dense soil. It does not allow air movement within the soil. Soil requires air to prevent it from turning anaerobic, (Meaning without air) and this has a negative impact on soil life.

Something I have always said is to look after the soil life and this will look after you. Clay soil prevents this air from moving around and soil life begins to die.

Clay Soil Water Retention

Clay soil sucks up water and holds it for a period. When large quantities of water are applied the soil becomes sticky, further preventing air penetration. When it releases this soil or it dries out the ground becomes hard like concrete and cracks.

The 3 reasons above are the main causes of why clay soils are not good for plant growth. However, there is a caveat to this and we will cover that as we proceed. Starting with amendments

Amending Clay Soil For Good Plant Growth

Now you know the issues with having clay soil, what actions could we take to make clay soil good for plant growth?

The first thing is to start amending the soil to improve water, air and compaction. It is important to note that this is not a quick process, essentially we are terraforming our little section of earth and this takes time.

There are various things we can do to amend clay soils for good plant growth. We do not need to feed clay soils initially as this holds lots of nutrients and micronutrients. So we need to improve the 3 issues above and can do that with adding organic matter. 

Adding organic matter to clay soils is a very good practice as this will lighten up the structure, improve air circulation and water retention over time.

What Organic matter can we add to improve clay soil for plant growth?

There are loads of different organic matter sources one can add to improve clay soils. The following list is not exhaustive but are the main ones that are easily available to most gardeners.

  1. Farmyard manure
  2. Cover crops (Green Manure)
  3. Compost
  4. Leaf Mould

Farmyard Manure

Farmyard manure covers all vegetarian animals such as cow, horse, sheep, rabbit, poultry, alpaca, and even pig can all be used to improve soil quality. It is important to note the meat-eating animals such and dog and cat faeces should not be added, these contain harmful bacteria and pathogens.

This adds organic matter that helps to break down clay compaction, hold water and creates air pockets within your clay soils. It provides food for soil life. This, in turn, feeds the soil adding more organic matter as they leave faeces behind and their little bodies as they die.

Cover Crops

Cover crops are plants grown to protect the soil surface when it is baren or dormant. It provides food for soil life, adds nitrogen to the soil and some are even a biofumigant. These plants also have the ability to add tons of organic matter to the soil.

This is usually done by chopping down and incorporating the plants into the soil, or if you prefer no-dig or no-till gardening then chopping and leaving on the surface until the soil life such as worms take it down and incorporate it on your behalf.

There are many different cover crops which can be used for this. It deserves a post of its own. Lucky for you I have already written that post and if this is something you wish to know more about in detail then click here to be taken to that post.

Compost

This is one of the most popular ingredients used to improve clay soils for plant growth. Compost has the same benefits as farmyard manure, but you can make this at home from all the garden waste. Simply add this once a year and allow the worms to take it down or incorporate into the soil.

Older gardeners will dig out a trench 2 spits deep (A Spit is the depth of a spade) then adding copious amounts of compost and backfilling the soil on top. This is ok if you prefer to dig, but if you are like me who prefers to disturb the soil as little as possible then its better to just add a layer around 2-4 inches above the soil.

Composting for some is a real challenge. So I have a very informative blog post you can read here that will show you exactly how to get reliable and the best quality compost for your garden. Alternatively, watch the video below.

How To Make Compost – Composting Process

Leaf Mould

Leaf mould is such a good organic matter to add to the garden. Unfortunately, you cannot buy this in a garden centre. You have to make it yourself. Why is it so good? It has the ability to hold huge amounts of water, it’s light and allows air movement.

Have you ever walked in a forest or wooded area? The ground will have felt soft like a sponge under your feet. This is decomposed leaves they hold nutrients, water and air. An added bonus is that Leaf mould is fantastic at controlling weeds by blocking out the light.

Soil life loves leaf mould, but leaf mould will also bring in fungal spores to your garden, these grow underground creating little tunnels as the roots penetrate into new areas. These tunnels carry air through the soil. The video below will show you how to make your own leaf mould at home.

How To Make LEAF MOULD – Turn Fallen Leaves into LEAF COMPOST

With using the 4 ingredients above you will be able to really make the clay soil very good for plant growth but it is important to note, this is a long term project. It will not happen overnight and may take multiple years of applications to get the clay soil into a good enough shape for good plant growth.

Related Questions for clay soil plant growth

Other products to add to clay soil to improve plant growth?

As discussed clay soils are full of nutrients. This is the one good thing about clay soils, but there is one product called gypsum that can be added to your clay soil to help plant growth.

Gypsum is basically calcium sulfate and this has the ability to break up the minerals and particles of the clay soil, stopping them from sticking together. Gardeners use this product but for some reason, it doesn’t really get spoken about in the text. 

Is Clay Soil Acidic or Alkaline?

A lot of people think that clay soils are neutral. However, this is not correct. Clay soils are usually more alkaline and although there are some plants that grow well in clay soils such as hostas. Most will struggle to grow in unamended clay soils. 

Even though plants will grow, the plant growth in unamended soil will never hit their full potential and could possibly show signs of illness such as yellowing leaves. 

Conclusion

Although clay soils have their issues for plant growth, It is not a lost cause. By amending the soil you can vastly improve the air, water and compaction abilities and this will make clay soils the perfect soil for plant growth. 

Think about all the nutrients already in the clay soil. So once we have done the work and added the organic matter we will really have a good soil that a lot of gardeners would die for.

I hope you enjoyed this blog post about clay soil. I trust it answered your question fully. If this was of interest to you, why not consider subscribing to the blog so you don’t miss future content.

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And remember folks, You Reap What You Sow!

Tony O'Neill

I am Tony O'Neill, A full-time firefighter and long term gardener. I have spent most of my life gardening. From the age of 7 until the present day at 45. My goal is to use my love and knowledge of gardening to support you and to simplify the gardening process so you are more productive

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