Tomato soil is important if you want to grow tasty tomatoes. Tomatoes like a rich soil as they are heavy feeders so a good, crumbly, well drained, slightly acid (with a pH of 6.0 to 6.8) soil which is complemented by a layer of compost, is ideal. The compost will break down and add the essential nutrients such as calcium, phosphorus, potassium and nitrogen to your soil. Don’t despair if your soil doesn’t match this description. Even if you have a sandy soil or a clayey soil you can “work it up” to a good quality loam.
Sandy soils don’t retain moisture and they are low in nutrients. However, they are well drained. If your soil is sandy it needs large quantities of compost to give it the nutrients tomatoes want. You can do this by first growing a legume crop which is rich in nitrogen. So you can plant lupins, beans or hairy vetch. These need to be dug back in early enough so that the composting process has begun before you plant your tomatoes and then the broken down nutrients are available for the tomato roots.
The following year follow the same process and continue year on year until you get a friable, crumbly soil. Mulching and manuring your soil will help to retain moisture in the soil and it will ultimately break down to contribute to the compost you have added to the soil. The process of converting your sandy soil to a friable loam will take years and during the build-up phase you will need to add extra fertilizers to compensate for the lack of nutrients in your sandy soil.
Soil microorganisms are also important. These feed on the compost and break it down into usable nutrients by the plant roots, so without compost you have no soil microorganisms. Worms play a role here, too. Bad news but it’s not all bad! If you haven’t got the patience, use pots while you work up your soil.
Coarse Grained Sandy Soil – notice the absence of “structure” – the lumpy bits which stick together in a friable loamy soil.
The problem with clay soil is that it has very fine texture, i.e., very small particles which are prone to cause waterlogging and become “sticky” when wet. However, clay soils do contain lots of nutrients and they retain moisture well. So the problem is to improve the drainage in clay soils.
If your soil is clayey, (you can tell if water doesn’t drain away quickly), you need to break up the clay layers with gypsum. Break up the clay and dig in the gypsum. Use amounts according to the manufacturer. Then, as with a sandy soil, you need to add plenty of compost to improve the drainage and make available the nutrients for your tomatoes. As with a sandy soil, it will take years of “working up” to make a good friable loamy soil. Just keep adding lots of compost!
Let’s hope this is not a picture of your clay soil! Notice how it cracks when it dries. However, even this can be worked up to a loam with the techniques above. Plenty of gypsum and even some sand plus plenty of compost will help to achieve this.
The ideal soil is “loam” which, technically speaking is a combination of sand, silt and clay in the proportions 40 – 40 – 20 respectively. Needless to say, most fertile soils around the world don’t comply with these ratios exactly, they vary according to location and the soil forming processes. But whatever the deficiencies, they can be rectified using the techniques above to make a more balanced, slightly acidic to neutral soil, ideal for growing your tomatoes.
