How To Add Nitrogen To Tomato Plants?

Our experienced writers spend hours deep researching, considering both scientific and experimental info to bring the insights you can trust.  

Quick Answer: How To Add Nitrogen To Tomato Plants?

You may add nitrogen to the soil via organic and inorganic sources. Organic sources are preferable to evenly distribute nutrients over a long time. However, use nitrogen fertilizers in moderation as they may burn the foliage and affect fruit quality.

In this detailed guide, I will discuss different ways you can use to add nitrogen to tomato plants.

Having faced nitrogen deficiency issues while growing tomatoes in my garden, I know how important it is to ensure the proper amount.

Let’s get started!

Why Tomato Plants Need Nitrogen?

Nitrogen is essential for the growth of tomato plants. Its deficiency may cause yellowing of leaves, stunted growth, leggy seedlings, and reduction in fruiting.

Nitrogen is an essential nutrient for tomato plants.

It helps in the vegetative growth and formation of amino acids. It also helps in the synthesis of chlorophyll and ATP.

  1. Tomato plants need nitrogen for proper growth and development.
  2. Nitrogen is an essential nutrient for plant growth and helps to promote green, leafy growth.
  3. Nitrogen is also necessary for the production of chlorophyll, which helps plants to produce food through photosynthesis.
  4. Without adequate nitrogen, tomato plants will produce fewer fruits and vegetables, and the overall yield will be reduced.

What Happens When Your Tomato Plant is Nitrogen Deficient?

A nitrogen deficiency may be caused due to pH imbalance and excess carbon in the soil. It may also occur when the tomato plant is planted for several years in the same place.

It may take away all the nitrogen out of the soil.

There are some serious visible changes you notice when your tomato plant becomes nitrogen-deficient –

  • The older leaves turn yellow or brown when there is nitrogen deficiency. It gradually progresses to the newer leaves.
  • Also, the plant growth will be stunted.
  • There will be a reduction in fruiting, flowering, and starch contents.
  • The stem and veins appear purple.
  • The whole plant is thin and upright.
  • The leggy seedlings are more prone to cracking and splitting. It may be worsened by alteration in pH, low organic matter, and drought conditions.

How To Add Nitrogen To Tomato Plants?

A nitrogen deficiency may occur when plants take away all the nutrients from the soil. The excessive carbon and pH imbalance in the soil cause low nitrogen levels. You may do a soil test to check for nitrogen requirements.

 You may do a soil test to check for the nitrogen level in the soil.

There are several ways to add nitrogen to tomato plants. I have discussed a few below.

1. Organic Sources

Different organic sources, including fish meal, blood meal, worm castings, soybean meal, and coffee grounds provide nitrogen. They take time to add nitrogen but get evenly distributed for a longer period.

I prefer to use organic sources of nitrogen, including fish meal, blood meal, worm castings, and soybean meal. It may take time but gets evenly distributed over time.

Here are some ways that work –

Certain Kinds of Meals

Fish meals and blood meals release nitrogen in the soil more quickly. Soybean meal or worm castings last longer in the soil.

They release nitrogen for a longer period.

Cottonseed meal may work as a slow to medium releaser of nitrogen to the soil.

Another surprising organic source is feather meal with a high concentration of nitrogen.

Corn Gluten

Another organic source is corn gluten which amends soil with nitrogen and prevents weeds.

Coffee grounds

Another popular organic source used by many gardeners is coffee grounds.

It can be mixed directly into the soil or added to the compost pile.

One advantage is that it also helps to improve drainage and aerate the ground.

Other Options

Sometimes,  I add two cups of alfalfa pellets for the slow release of nitrogen for my tomatoes. Take care to dampen them before adding them to the soil.

2. Adding Compost

Compost provides a wide variety of nutrients to tomato plants, including nitrogen. It makes the nitrogen available for the whole growing season. Take care to add carbon-rich ingredients to high-nitrogen compost.

Compost contains many nutrients, including nitrogen.

It adds organic matter to the soil and promotes the growth of organic matter. It releases nitrogen slowly over the whole growing season.

The advantage of using compost is that it will slowly release nitrogen to the plants over time. You may use fresh grass clippings, fruit, vegetable scraps, and coffee leftovers.

Take care to add carbon-rich ingredients, including hay, straw, leaves, sawdust, or wood chips while creating high-nitrogen compost.

Here is quick composting guide –

3. Adding Manure

Animal waste is high in manure. You may age the manure and add it to the soil to prevent the burning of the foliage. You may also prepare manure tea to provide nitrogen.

Manure is waste from animals, including cows, horses, and chickens. It contains a good amount of nitrogen. It can not be added directly to the soil as it may burn the plants.

It may not work if you want the nutrients immediately.

Take care to age the manure and then add it to your vegetable garden. It will neutralize the pathogens in the manure.

You may add manure to the compost pile and then added to build nitrogen-rich soil.

Some prefer making manure tea that involves adding the manure to a bucket filled with water.

The resulting tea may be diluted and added to the tomato plants to give a nitrogen boost.

4. Plant Nitrogen-fixing Plants

One popular way is to plant nitrogen-fixing plants before growing tomato plants. It gives tomatoes nitrogen-rich soil for their growth. You may reduce the amount of other nitrogen fertilizers.

Legumes, including alfalfa and peas are nitrogen-fixing plants and add nitrogen in the soil.

I recommend planting these plants before growing tomato plants so that they create soil rich in nitrogen. This practice is called crop rotation.

This planned crop rotation helps tomato plants to get nitrogen-rich soil during their growth stage.

Some use composted legumes as a source of nitrogen.

It helps in lesser pest attacks, reduces the incidence of soil-borne diseases, and enhances nutrients in the soil.

You may have to cut back on the other fertilizers in the garden.

5. Fertilizers

You may use inorganic commercially available nitrogen fertilizers. It includes sulfur-coated urea, ammonium nitrate, ammonium sulfate, calcium nitrate, potassium nitrate, and sodium nitrate. Use in moderate amounts.

Many gardening experts recommend using sulfur-coated urea to boost the nitrogen content of the soil. It may be used alone or as a part of the complete fertilizer blend. It releases nitrogen slowly, and you need not apply fertilizers often.

Some of the sources of nitrogen are ammonium nitrate, ammonium sulfate, anhydrous ammonia, calcium nitrate, potassium nitrate, and sodium nitrate.

You may pick one depending on your requirements.

Take care to use the fertilizers in low volumes. It may lead to salt build-ups and burning of the foliage.

Tips And Considerations While Adding Nitrogen

The foliar nitrogen application may not work effectively. High amounts of nitrogen fertilizers may affect the foliage and waterways. It is preferable to use a drip irrigation system.

Nitrogen has to be applied directly to the soil. The foliar nitrogen application to the leaves may not work well as it takes time to absorb.

Few nitrogen fertilizers need to be reapplied as they release nitrogen at different rates.

Avoid applying too much nitrogen as it may be washed away and affect the waterways near.

You may use drip systems to release fertilizer in small and controlled amounts during the growing season. 


What are the symptoms of plants showing excess nitrogen content?

There may be excessive salt buildup in the soil, and higher chances of diseases, including necrosis, early blight, and Fusarium. The vegetive growth increases rapidly followed by poor tomato yield.

Is inorganic fertilizer harmful to the environment?

The inorganic fertilizer requires high temperature and pressure to create. Most of the fertilizer is released into the atmosphere as nitrous oxide which contributes to global warming. It leaches into waterways affecting the species in the water.


I hope this guide has helped you with different ways to add nitrogen to your tomato plant. You may pick your preferred way of supplying nitrogen to the tomatoes from the list above.

If you have queries about adding nitrogen to tomato plants, please write to us.

Do share the article with friends who love gardening!

Happy tomato gardening 🙂