How can I determine the best soil composition for my plants? This page introduces an Excel tool to calculate optimal soil mixes for various plants.
Different plants from different environments thrive best in different soils. But how can you determine the most suitable soil composition based on those that you own? Blow, I introduce an excel spreadsheet that will help you do exactly that!
Interface
Below, you can see the interface on the first sheet of the workbook. In order for it to work, you will need to trust the file and enable macro’s (this is required for the button’s click-functionality).
You can select either a plant type or, when you are not sure about the plant type, the environment in which it typically grows. Click the checkbox for which option you would like the calculator for work, and use the drop-down under ‘type’ to select your choice.
For example, below, I selected ‘climate/habitat’ for the selection category, and then ‘desert’ for type.
Once you’ve done that, you will see that a graph has appeared in the box on the right. This graph shows your ideal soil composition, considering six criteria:
- the ratio organic/inorganic material,
- the soil aeration (how easily oxygen can make it to the roots),
- water retention capacity (how much water can the soil absorb),
- drainage (how easily water can pass through),
- nutrient content, and
- pH-level.
Except for the organic/inorganic share, where the ratio is a value between 0 and 1, each criterion ranges from low (1) to high (5).
Now, on the left, you see a number of soil components. Using the up and down buttons beside the input cells, you can add or remove ‘one part’ (i.e. one cup, one shovel) of that particular type of soil.
When you do that, you will see another (dashed) line appear in the graph. This line resembles the characteristics of your current soil composition.
By adding and removing parts of soil that you have access to, you can try to get as close to the ‘ideal’ line with your own unique composition.
Taking our ‘desert-type’ example, I see that I can get pretty close to the ideal soil composition by adding equal parts of sand, perlite, and potting soil.
Of course, you may not have perlite available, or you simply find it too expensive. No problem! We see that by replacing one part perlite with another part sand, we get similar results.
You can ‘up’ or ‘down’ the ‘acceptable deviation’ percentage at the bottom of the sheet to increase or decrease the blue area in the graph. This is an handy indicator to determine whether your current soil composition is ‘good enough.’
One important side-note: all the data used in the spreadsheet was provided to me by ChatGPT. While I did not check the data, I haven’t seen any strange suggestions in the results. Nevertheless; use the sheet with caution!
And one last thing: I protected the first worksheet to make sure you do not break it. If you want to change things, you can easily lift the restrictions (I did not use a password to protect it).
That’s it! You can download the calculator via the link below. Have fun planting!