The Tomato Success Series: How to prepare your soil for growing delicious organic tomatoes

Welcome back to our Tomato Success Series – my challenge here at Grow Inspired is to ensure that all my blog readers have a fantastic crop of tomatoes this season! Did you see last week’s blog on choosing varieties and when to buy? If not, check it out here!

This week, we’re looking at preparing your soil. This is simply critical – tomatoes do have quite a few particular requirements and having the right balance of nourishing nutrients in your plant bed is one of the greatest opportunities we have as gardeners to all but guarantee success.

There is no point going to buy your plants if your soil is not prepared, otherwise they will sit in their pots until you get round to it.

Where should I plant tomatoes?

To plant your tomatoes, I find that a spade depth of friable soil in the garden or a deep pot or container works best. Tomatoes have very strong roots and will spread rapidly under the soil. Did you know that the stem of the tomato is also able to grow roots? So if your tomatoes bend over in your garden, they will spurt roots from along the stem if it’s touching the soil.

What soil type do tomatoes need?

Tomatoes love sandy loamy soil above all others. If you are stuck with clay soil like me, it will require some extra work to prepare. Well-rotted compost or sheep pellets are a must, plus sawdust and Bokashi to create the perfect mix for tomatoes.

Tomatoes turn their noses up at dry soil or water-logged soil, as they much prefer a balance in between, with moisture-retentive soil. Tomatoes like a neutral pH of close to 7, so not too acidic or alkaline. Most garden centres sell a pH meter if you’re keen to test your soil, or I actually picked up a few recently on 1-day.co.nz for a very reasonable price that work well, so keep an eye out elsewhere too. If your pH is too low, you can add a couple of handfuls of lime and this should do the trick to raise the pH, but be sure to water it in.

What nutrients need to be in the soil for growing tomatoes?

Tomatoes are a high potassium vegetable, therefore require higher potassium in their soil than a lot of plants. This is the number one nutrient you need to focus on increasing in your soil.

Good amounts of potassium produce a juicier tomato with higher acidity. A lack of potassium can cause uneven ripening.

Potassium maintains balance and water within your tomato plant. It is also essential for the production and transportation of sugars in the plant and synthesis of proteins, along with enzyme activation. Clever stuff!

Did you know that potassium is required for lycopene, which is the reason your tomatoes are red?

High levels of potassium have been proven to give much higher yields, so it is really a no-brainer – if you do nothing else, remember to add your potassium!

If you are still having fires, save your wood ash (known as potash), as this is fantastic to incorporate into your soil to boost this key nutrient, and continuing later on in the tomatoes’ growing life, as a side dressing of potassium.

IMPORTANT NOTE… If you have kidney problems, please avoid fruit and veg that contain high potassium.

Calcium and magnesium are also essential for your tomato growth. For calcium, I tend to use Nano-cal from Environmental Fertilisers, which is available from Kings Plant Barn. Magnesium can be obtained by watering with Epsom salts, which is really known as Magnesium sulphate. This is available in 20kg sacks from any good farm shop. Remember to add a good balance of these and apply them regularly throughout the growing season, especially when the flowers form.

One nutrient to watch for is nitrogen – tomatoes require lower levels of nitrogen in your soil, as too much can cause rot.

It’s a fine balance and this is why getting your soil profile right in the beginning can really set you up for success. Best of luck in preparing your soil and then heading out to choose your plants! Next week, our Tomato Success Series continues with planting!

Happy gardening!