1.Get the bed ready
Several weeks before planting tomatoes, check the soil you’ve selected. The soil is ready to work when it is dry enough not to clod up when squeezed into a ball and won’t stick to your garden tools.Begin preparing your soil by cultivating the bed 18-25 cm deep with a garden spade or tiller/cultivator. Remove debris, break up soil clods, work in 5-8 cm of compost or other organic matter into the top 15 cm. This is the most important step in preparing your soil for planting tomatoes whether you have rich, black loam or terrible dirt.
2.Let the soil warm
Tomatoes like warm soil. Even if air temperatures start to heat up in the spring, it takes the dirt a while to catch up. You can help prevent transplant shock by covering your greenhouse plot with sheets of black plastic, which absorbs heat from the sun and accelerates the warming process.Then, a couple of weeks before planting tomatoes, start preparing the soil temperature-wise. Position the black plastic in your greenhouse and secure it with rocks, bricks, buckets, or other sturdy anchor. Remove the plastic when you place your tomato plants in the greenhouse, unless you choose to use it as a weed deterrent (mulch) around the newly planted seedlings.
3.Test your soil
You also need to prepare your soil by checking its nutrient and chemical contents. Take a simple soil test of your soil to know how to amend it. Purchase an inexpensive soil test kit online. Or contact your local extension office and ask about local soil testing services.
4.Check the soil’s pH
Soil testing will tell you the soil’s pH. You can use a simple pH test kit to determine the pH in your tomato patch. If you’re planting a large number of tomatoes, then test several areas across the planting area. A neutral pH level is 7.0. Numbers lower than 7.0 indicate acidic soil – the lower the number, the more acidic the soil. Numbers higher than 7.0 indicate alkaline soil – the higher the number, the more alkaline the soil. Tomatoes grow best in slightly acidic soil with a pH level between 6.0 and 7.0 – optimum is between 6.5 and 7.0. If your soil’s pH isn’t within that range, make proper adjustments.
To lower your soil’s pH, work sulfur into the soil.
To raise your soil’s pH, work lime into the soil.
An appropriate pH is an important component to preparing the soil for planting tomatoes.
Check soil test results for an even balance between nitrogen, phosphorus, and potassium, all necessary for strong tomato production. Evaluating nutrients will go a long way in preparing your soil because you will know what you need to add.
Potassium helps promote growth and disease resistance in your tomato plants. Weak plants and slow growth indicate a potassium deficiency. In more severe cases, leaf edges will brown. An easy way to amend the soil is to add wood ash, which is 5% potassium. Best rate is about 10-15 pounds to a 300 square foot bed. Work in wood ash in the fall or winter.
Good organic fertilizer sources of potassium – wood ash, granite dust (also called rock potash) – slow-releasing leaf mold
Good inorganic potassium sources – potassium sulfate, rock sand
Compost is broken-down organic matter. It’s not particularly high in nutrients but it’s a fantastic way to improve your soil. Compost improves soil structure, increases its cultivability, aids in nutrient retention, reduces compaction, attracts earthworms, increases microbes, and protects plants from disease. Adding compost is the singular most important step you can take to preparing your soil for planting tomatoes. You can save money and make your own compost when you start your own compost pile at any time of the year.