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Preparing Soil for Tomatoes: Frequently Asked Questions

Since 2010, Tomato Dirt has garnered 4.6+ million views, making it the web’s leading online source for growing tomatoes in the home garden. Award-winning writer and Tomato Dirt owner Kathy Widenhouse has helped thousands of home gardeners grow healthier tomatoes. Be one of them when you get Tomato Dirt’s Growing Guide here.

Updated 2.7.2024

You’ve chosen a spot to grow tomatoes. Or you have a garden plot from last year and now you’re preparing soil for tomatoes (and maybe some other crops, too.)

But you’ve got some questions. Here’s the dirt.

Q. When should I start preparing soil for tomatoes?

You can start preparing your garden for tomatoes as soon as last season’s crop is spent … or you can wait until the winter winds and cold are past. When early spring teases you with a sunny day – but it’s way too early to plant crops – you can satisfy that inner longing to dig in the dirt by heading to the garden and preparing soil for tomatoes and other crops.

Q. What should I do first in preparing the soil?

1. Clean out. Remove garden debris. If plants had blight or wilt or other disease, then burn them. Otherwise, toss the leftovers onto your compost pile. Pull away mulch and add it to the compost bin, too.
2. Conduct a soil test. Use a home kit or arrange for a soil test from your local extension. Test results can show you what nutrients your soil needs to grow a healthy crop.
3. Add organic matter. Spread a thick layer (2-3 inches) of compost over your soil. If your test results revealed a nutrient deficiency, then amend accordingly. For instance, if phosphorus content is low, then add bone meal to the garden plot.
4. Till. Use a garden tiller or spade to work organic material into the soil, break up clods, and prepare for planting.

Q. What’s the best soil for growing tomatoes?

The best soil for growing tomatoes is well-drained, fertile loam with a pH of 6.0-7.0.

• Well-drained soil: tomatoes grow deep root systems. In fact, just one-third of their stems and foliage reside above ground. When the tomato patch is well-drained, the plants can get the water and nutrients they need but avoid having their below-ground parts be flooded and choked from a lack of oxygen.
• Fertile soil: tomatoes are heavy feeders. Within a matter of a couple of months, a tomato seed must germinate, put down roots and stems and leaves and blossoms, and produce dozens of fruits. That job requires plenty of nutrients. Rich loam, amended each season with 1-2 inches of compost, provides nutrition that plants need.
• pH: tomatoes prefer slightly acidic soil.

Q. How can I grow tomatoes in poor soil?

Determine whether or not your garden soil is truly “poor” – and in what ways the soil is below par.

Does it lack nutrients? Use a soil test to determine its nutrient content. Purchase an inexpensive soil test kit online or at a garden center. Or contact your local extension office and ask about local soil testing services. Check soil test results for an even balance between nitrogen, phosphorus, and potassium, all necessary for strong tomato production. Add appropriate fertilizer accordingly.

Does the soil lack proper texture? The premium garden environment for tomatoes is rich loam. Poorly-texture soil is either too sandy or has too much clay. In most cases, sandy soil and clay soil can be amended to grow healthy tomatoes.

Q. What do I need to know about growing tomatoes in sandy soil?

Soil with 35% or more sand is classified as sandy. But if you’ve got sandy soil, there’s good news! Tomato plants can grow well in almost all types of soil except heavy clay. In fact, sandy loam is the optimum garden environment for growing tomatoes.

Overly sandy soil is an easy fix. Naturally, remove excess rocks and debris. Then improve the texture by adding organic matter. Till or work in 2 to 3 inches of compost to the top 6 inches of your garden’s topsoil. The added organic material will provide plenty of luscious nutrients for your tomato plants and will help the soil retain water.

Q. What do I need to know about growing tomatoes in clay soil?

Tomato plants can grow in almost all types of soil except heavy clay. Compacted clay lacks air pockets. Water accumulates quickly and has trouble draining. Dense, compressed soil suffocates your plants’ roots and prevents them from moving air, water, and nutrients up the stems to the leaves.

But if your garden soil has clay, do not despair immediately! Not all clay soil is equally dense. Heavy clay is a challenge … but light or moderate clay is more manageable. Conduct an experiment. Pour water onto the garden area in question. The soil should absorb at least 1 inch of water within one hour. If you’re within that range, then you simply need to amend your tomato plot to make it a more welcoming environment for your plants.

Work in plenty of organic matter like compost, pine bark, and composted leaves – a layer of several inches, at least. You can even lift entire sections of the dense dirt right out of the ground and replace those areas with a combination of topsoil, compost, peat, manure, and other amendments. But avoid adding sand or peat moss to clay. Those amendments will only increase the soil’s density. Think of the rich soil you’ll build when you add those organic materials regularly or several years.

Q. What’s the ideal soil pH for tomatoes?

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. Use a soil test to find out your garden’s pH level. If the pH is too high (over 7.0), add sulfur. If your soil’s pH is too low (below 6.0), add lime.

Q. How can I prepare soil for tomatoes in pots?

Tomatoes in containers need a loose, well-drained soil with lots of organic matter. Successful gardeners recommend using a good potting mix rather than potting soil or garden soil. Potting soil can be too heavy for containers. Soil harvested straight from the garden is most likely infested with fungi, weed seeds, and pests. Good potting mixes for containers include peat moss, compost, vermiculite, perlite, and sand. The best mix holds moisture but doesn’t stay soggy.

Q. What should I do with soil after growing tomatoes?

When your garden season is over, pull up spent tomato plants and weeds, collect dropped or “mummified” fruit, and rake the garden to remove plant remnants. Doing so can help prevent diseases from spreading in the off season. 

You can also add a light layer (1-2 inches) of leaves. Doing so now will give time for them to break down into leaf mold by next spring and add nutrients to the soil. A layer of leaves or compost in the winter also slows weeds and retains moisture in the soil during the cold winter months.

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