Is Clay Soil Acidic? Understanding Clay Soil PH and How To Amend It

Does your garden soil stick to your shoes and gardening tools when wet? Does it also become rock solid in the summer heat? If the answer to these two questions is yes, then it means that you have a clay soil in your garden.

Any soil that contains at least 50% of clay particles qualifies to be clay soil. And although it can be quite difficult to dig clay, it is one of the most fertile soils that you can have in the garden.

​Clay has both good and negative features, and although it can be stressful and tiring to work with, it can also produce some thriving gardens. But, if you are dealing with it for the first time, the chances are that you are wondering whether clay is acidic or alkaline.

It is right to be concerned about the pH since it determines the plants that you can have in the garden and also the amendments that you should use.

​Is Clay Soil Acidic Or Alkaline?

is clay soil acidic

Soil pH is a result of various things with the organic material and mineral composition being some of the main ones. And so the pH of clay soil will always vary from one geographical place to the other. Also, different gardens might also have varying PH levels even if they are one the same location. The different pH is because other factors like fertilizers and water will also affect the pH.

​So is clay soil acidic or not? The pH of most clay soils will always be on the alkaline side of the scale, unlike sandy soils which tend to be more acidic. While the high pH of clay soil might be suitable for certain plant types like asters, switchgrass, and hostas, it is too alkaline for most other plants. And so it most cases it will be necessary to lower the pH.

Amending Clay Soil pH

If you have clay in your plot, the best thing would be to find crops that tolerate alkaline soils and instead focus on improving the quality of the earth by breaking clay soil up. But, if you have particular plants in mind that you want to have that prefer acidic soils, you can still amend your soil in a few easy steps.

Read more: Best Electric Tillers To Till Your Garden In The Right Way

​Test The pH

Soil test kit

​Before you decide to acidify your clay soil, the first move should be to examine it to determine the exact pH. By knowing the level of alkalinity, you can choose an acidifying compound that will not only lower it but also be gentle on your soil.

​A pH test by a professional is always the best since you get an exact number, but you can still get reliable data by doing it at home with the use of a pH meter or pH strips. However, if you are a serious grower/gardener, it is advisable to use the services of an extension officer or to send a soil sample to your local laboratory. Doing this ensures you get a detailed analysis and recommendations on the best amendments for your clay soil.

​Amend The pH

amending clay soil ph

​Once you determine just how alkaline your clay soil is, the next step is to amend it. However, it might also be necessary to test the water pH before this to ensure that is not too alkaline because it can raise the soil pH. When amending the clay soil, it is important to make sure that you do not work on wet soil because this leads to compaction.

​The pH test results should guide you on what to use and the amounts. Organic matter is always the best solution for most clay soils as it not only helps to lower the pH but will also assist in breaking it up and ensuring that your plants get proper nutrients.

​If the pH test results show that your soil is very alkaline, you should use compounds like sulfur, cottonseed meal, and iron sulfate. And this is because they are more efficient in acidifying soil and also work way much faster than the organic compounds. Gypsum can also be very helpful, and this is more so in places where the soil is also very salty.

​Maintaining The pH

How To Break Up Clay Soil

​It is important to amend the pH several months before you plant in the clay soil because most of these acidifying compounds will require a lot of time to work. And once you get it to the level that you want it is still important to make sure that you maintain it at between 6.3 and 6.8 on the pH scale because this is what most plants prefer. You can do this by applying manure, compost, and other organic compounds every other season.


​Clay soil will in most cases be alkaline without any amendments. While this might be good enough for some plants to thrive, most others will require you to acidify the soil. For this, organic compounds, sulfur, iron sulfate and ammonia-based fertilizers are an excellent choice. But, it is always important to remember that there is no permanent pH change and so you need to maintain the clay soil at the level that you desire.

is clay soil acidic

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