Why use Clay Breaker?
Clay Breakers or Gypsum are used to literally break-down clay. Traditionally, gypsum was used on heavy sodic clays in agricultural environments. These clays have a high content of sodium which reduces the porosity and water retention of soils, and hence plant growth. Soil scientists call this problem Sodicity. The calcium present in the Clay Breaker swaps with the sodium in the soil, and helps to bind the soil together. It improves porosity and water retention of soil, and thus plant growth also improves.
In your own backyard, you would use Clay Breaker in a similar way. People often use Clay Breaker when starting or improving a garden. In Australia, including Canberra, we often have heavy clay soils in our backyards. Gardens can be sparse, as there is not enough water in the soil for even grass to grow! So, when thinking about putting in a veggie or other garden, Clay Breaker comes to mind as a way of getting more moisture into the soil and improving plant growth. However, it isn't always the best option...
Example of a sodic soil; with a hard surface that plants can't get through!
Why is Clay Breaker not always the best option?
Gypsum targets a specific type of soil, not necessarily the one in your backyard. Gypsum is great for targetting problems of sodic soils. However, not all clays are sodic! In fact, in Australia most sodic soils are found in river terraces, plains and in drainage areas; areas where sodium builds up from water movement and where sodium is naturally occuring. Some researchers say Sodic Soils make up about 28% of Australia. This means that the soil in your backyard may not necessarily be sodic. In fact, your soil may actually have heaps of calcium to help bind it, and this is when Gypsum may cause problems!
Gypsum can be unkind to your plants. Soils have a natural amount of salts present; natural salts of Calcium, Magnesium, Iron, Sodium etc. When you add Gypsum, you increase the salt content of the soil. If you add too much Gypsum, you can cause your soil to become too salty. When this happens, many plants refuse to grow or some start to grow and then wither and die. They are intolerant to the amount of salt in the soil as a result of the Gypsum application.
But do not fear!! It actually may be another problem causing your clay to have poor plant growth, and there are other ways of fixing it. First, you can work out what is wrong with your soil, and then what to add to get better plant growth.
Does your backyard look like this?
You may have a problem with compaction and carbon!
What other problems could it be and what can I do about it?
If Gypsum is not what you need to use in your Garden, how can you tell and what else can it be? You can do a few tests on your soil to work out the problem and how to solve it!
Step 1: Is it Sodicity?
- Pull out your pH kit. If it has a pH greater than 7 (basic), it may be sodic.
- Now, get a dish and add 1cm deep of rain or bottle water. Place 3 pieces of soil (about 1.5cm diameter) into the dish and leave for 5 minutes. If the water goes cloudy, then it is likely to be Sodic. Follow the Cure below. If your soil falls apart or does nothing, go to Step 2.
Sodic soil with Gypsum added (white flecks).
This soil is very saline and has only a few plants growing in it.
Step 2: Is it Carbon and Compaction (or both)?
- Get a dish and add 1cm deep of rain or bottle water. Place 3 pieces of soil (about 1.5cm diameter) into the dish and leave for 5 minutes. If the peds fall apart or stay solid (but you still can't get anything to grow), then the problem is probably compaction and a lack of organic matter.
- Now for the hoe test! Get a shovel or hoe and try to dig a hole. If you are able to dig a bit of a hole without too much strain you probably have a Carbon problem. If the hole is really hard to dig, and you can bearly go down a few centimeters, the problem is Compaction. Check out the Cures for each below.
Compaction Cure: Compaction usually happens with house construction. Heavy machinery tamper down soil, and reduce the ability of soil to hold water, roots to get into the soil and bugs to cycle nutrients. The best way to deal with this is a bit of Hard Yakka, mixed with some organic matter! Get out the hoe and the shovel and dig as deep as you can!!! If you can, get a loan of a rotary hoe and get nice and deep! But don't forget to check Dial before you Dig first! Add some mulch mix (as above), and double it!! Again, it may take some time to see results, but it will happen.
And if you still want to use Clay Breaker anyway, limit it to 100-200g per meter square. Otherwise you may risk killing your plants!
Sodic soil (middle) with no treatment and with different treatments of Gypsum and Mulches.
Before you go for the bag of Clay Breaker, ask yourself 'Do I really need this?' Don't give into the fertiliser companies! You may not need Gypsum/Clay Breaker, and in fact, you may be killing your plants. Instead, do a few tests and work out if you need to use Clay Breaker, or if you need some Organic Matter!
For more info on Sodic Soils, check out this neat Guide by Central West CMA. And if you want to get some more Info on your soil, gypsum application and Sodicity, you can send it away to a lab for analysis. Always happy to answer questions.
Happy Spring Gardening!