Fertilizing Tomatoes Tomatoes

How To Fertilize Tomatoes: From Planting To Harvest

Updated: October 29, 2022

Fertilizing your tomato plants is a significant issue for becoming a successful gardener. Unfortunately, most garden soil doesn’t contain the nutrients needed for plant development.

A proper portion of fertilization during cultivation season is necessary to get a better yield and avoid some problems.

Irregular and imbalanced nutrient supply can hamper plant growth and make it susceptible to some diseases.

To become an intelligent gardener, you must know how to fertilize tomatoes.

 Soil test before fertilization:

Soil pH test kit

How much nutrients demanded in your garden soil will come from your garden soil test results?

It is easier to supply proper nutrients to your garden soil after getting the soil test result.

For taking the soil test, you can collect a soil test kit from the nearest home improvement or garden stores. You can also order online stores for the kit set.

Your local agricultural extension center can help you to provide the service if you find difficulties.

Which fertilizer should you use on tomato plants?

Usually, two types of fertilizer (natural and chemical fertilizer) can be used for gardening. Both perform well and have some limitations.

Natural fertilizer:

Mainly contain organic matters like different types of manures, fish emulsion, suitable household and kitchen garbage, and other diseased-free garden debris.

It is also known as organic fertilizer, homemade fertilizer, or environmentally friendly compost fertilizer.

It releases slowly in the soil and provides nutrients to tomato plants for a more extended period. It also develops soil quality.

You may purchase organic fertilizer from your local gardening stores or eCommerce stores like amazon.com, eBay.com, gardeners.com, organicag.com, and other renowned companies.

Using household and kitchen garbage, you can also make your fertilizer. But make sure all the nutrients are present in your homemade compost for growing healthy plants. It is also time-consuming and needs a place to prepare them.

You have to use an organic fertilizer at the beginning when you prepare your soil for planting tomatoes. Gradually the compost will mix with the ground and provide nutrients to the plants.

When you need to provide additional nutrients to the plants, organic fertilizer or homemade fertilizer and mulching is the best solution.

Chemical fertilizer:

Chemical fertilizers release quickly in the soil and work faster than natural fertilizers.

You should use chemical fertilizer if you need to provide argent nutrients to the plants.

Chemical fertilizers last only a short time, and you must maintain a fertilization schedule depending on plant growth and demand.

Continuous and extreme uses of chemical fertilizer can become infertile in the soil and reduce production.

Besides, chemical fertilizers can mix with the local water sources through rainwater or irrigation water. This causes water pollution and becomes a threat to the environment.

Essential nutrients for fertilizing tomato plants:

Tomato plants need nitrogen, phosphorous, and potassium as primary nutrients to grow and produce fruits.

Nitrogen– helps to develop foliage.

Phosphorous– helps to grow roots, bloom flowers, and set fruits.

Potassium– fights diseases and helps to improve roots and stems.

Besides the essential nutrients you need, provide some secondary nutrients such as calcium, magnesium, and sulfur to your tomato plants.

Calcium sulfate, also known as gypsum, can prevent tomato plants’ blossom end rot problem. It also develops stem health and makes the fruits more nutritious.

Magnesium –controls the process of photosynthesis and chlorophyll and maintains overall quality.

Sulfur– provides proteins and amino acids to tomato plants. Lacking magnesium and sulfur can cause yellow leaf problems.

How to prepare the soil for tomato plants:

preparing soil for tomato plants

Unfortunately, only providing nutrients to your tomato plants doesn’t bring you success.

You must also ensure the followings:

  • Proper drainage system.
  • Choose loamy and sandy soil for your tomato plants. If your soil contains a large amount of silt and clay, add a proper portion of sand, compost, sawdust, and peat moss to develop the soil texture.
  • Till the soil as much as possible.
  • Test your garden soil to provide the required nutrients.
  • Keep up soil pH above 6.5 on the scale.
  • At least 6 hours of direct sunlight, and avoid planting under the shade of a big tree or multi-storied building.
  • Keep maintaining proper spacing between two plants.
  • Mix up your garden soil with a small amount of organic matter like poultry manure or any other manure, peat moss, and compost fertilizers as supplementary nutrients before planting.

How much fertilizer to use on tomato plants:

Plants need three essential nutrients from the soil to grow, develop roots, flourish, bloom, set fruit, and harvest. Therefore, applying the vital fertilizers in an equal ratio for your tomato plants will be a complete fertilizer.

Most of the time, tomato plants need a balanced or complete fertilizer which means a 10-10-10 ratio of NPK, which stands for nitrogen (N), phosphorous (P), and potassium (K).

How much fertilizer do you need, and does the ratio depend on your garden soil test result?

If your soil contains lower nitrogen, higher phosphorous, and potassium, you should use a fertilizer like 10-5-5.

On the other hand, if your soil contains higher nitrogen and lowers phosphorous and potassium, you can go for a 5-10-10 ratio.

If your soil slightly lacks any of the nutrients, apply a balanced fertilizer like 8-8-8 or 10-10-10

Or, if your soil naturally contains a balanced nutrient, apply compost fertilizer or slow-release fertilizer, depending on the soil test result.

Tomato plant fertilizer schedule:

When to apply which fertilizer?

You have to use tomato plant fertilizer in different stages of plant development. However, applying all the fertilizer at a time is not a good idea; it can damage your plants’ growth.

You can schedule your tomato plants’ fertilization process in three different stages. Such as:

1: From seedling to being mature:

Fertilize your garden soil when planting the tomato seedlings, and give them some days to settle in the environment. At this stage, tomato plants need enough nitrogen to grow the plants and foliage.

2: Flowering time:

Once the plants mature and start blooming flowers, reduce the nitrogen level and increase the phosphorus and potassium level of fertilizer for healthy blooming, setting fruits, and developing stems.

Depending on plant growth and health condition, provide some supplementary nutrients like calcium, magnesium, and sulfur to get a better yield.

3: Setting fruits to harvest:

When the plants set fruits, they need regular nutrients to produce more fruits during the season.

So, provide a schedule fertilizing of phosphorus and potassium every 7 to 15 days until the end of the season.

Provide some supplementary nutrients, if needed, based on your plant’s performance.


Over-fertilization of tomato plants

Usually, plants need fertilizer, and lack of fertilizer damages the plants in different ways. But if you provide excessive fertilizer to your tomato plants will also be harmful. Over-fertilization of your tomato plants may affect different ways:

Signs of over-fertilization:

  • Using an extra amount of fertilizer in the soil produces excessive nitrogen.
  • This excessive nitrogen makes an obstacle for plant roots to absorb water from the soil and pass it to leaves. As a result, plant leaves turn yellow and become wilted. (yellowing plant leaves also may occur due to fungal and bacterial diseases)
  • Produces excessive leaves and few flowers
  • Appear brownish leaf border and tips
  • Unusual death of seedlings
  • Leaves drop off
  • Unsatisfactory plant growth
  • A crust of fertilizer on the soil surface
  • Excessive usages of fertilizer sometime attract insect pests and diseases.

How to remove over-fertilization from your garden soil:

  • First, remove any visible fertilizer indications on the topsoil, like the crust of fertilizer or white salt powder.
  • Use plants like squash, cabbage, broccoli, and corn which absorb the excessive level of nitrogen from the soil. In that case, expect a good harvest from something other than those plants.
  • Using mulch, add scrap softwoods or sawdust to absorb excess nitrogen from the soil.
  • Wash out the excessive fertilizer by providing a strong water flow over the soil surface.
  • For your potting plants, leach the soil with water several times. This will help to come out of the extra fertilizer from your plant roots.

How to control and prevent over-fertilization:

  • Always apply fertilizer to plants after checking the soil nutrients.
  • Take soil tests, once planting tomatoes and twice when setting fruits. These soil tests help you to prevent excessive fertilization.
  • Get rid of the infected leaves.
  • Avoid fertilizing tomato plants during heavy rainfall or windy weather condition.
  • Avoid fertilizing your tomato plants for a couple of weeks to recover from the effects of over-fertilization.
  • Avoid excessive use of slowly released fertilizers.
  • Develop your garden drainage system
  • Prevent adding too much soluble fertilizer in your garden soil at one time
  • Stop using soluble fertilizer several times without leaching the earth.
  • Make a proper combination of slow-release fertilizer with a soluble fertilizer.
  • Steaming your potting soil following the proper method to sterilize it.
  • Only transplant your tomato plants from fertile soil to less fertile soil conditions.


It is scarce to find soil that contains balanced nutrients. If found, your garden plants will absorb the required nutrients and leave the ground infertile.

So fertilize your tomato plants following the proper guidelines and enjoy healthy fruits.

Happy tomato gardening.

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Sources and Citations:

John Michael
John Michael is a self-help writer and a hobby gardener. Michael’s passion in writing is to inspire the beginner gardeners to not just “hang in there” or “make it through” but to thrive. He does this through blogging.

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