Fertilizer Toxicity vs. Nutrient Deficiency: Spotting the Difference in Your Plants

Written by Amir Tajer


Posted on February 21 2018

Fertilizer toxicity and nutrient deficiency are common plant conditions with very different causes that can both destroy a crop while looking exactly the same.

What is fertilizer toxicity or nutrient deficiency? How can you tell if either of these are happening to your plants?

Here's what you need to know about fertilizer toxicity, nutrient deficiency, and how to figure out which of these conditions is affecting your plants.

What is Fertilizer Toxicity in Plants?

What is fertilizer toxicity?

Fertilizer toxicity, sometimes called "fertilizer burn," is what happens when too much fertilizer is applied to your plants.

Although fertilizer can be beneficial to your garden, when the level of nutrients introduced goes so far beyond the needs of your plants that you start seeing reduced yield, growth, and quality, that's the point where the fertilizer becomes toxic.

This is because many fertilizers contain a lot of ammonia and salt. High levels of ammonia can be toxic to seeds while high salt levels will strip plants of the moisture that they need to thrive.

What Causes Fertilizer Toxicity?

Fertilizer toxicity typically happens from over-fertilizing or using a fertilizer with too many nutrients for your soil type although in theory run-off or fertilizer toxicity in a nearby area can also be a problem.

Signs of Fertilizer Toxicity

Symptoms may vary depending on severity, but here are a few signs that your plants may be suffering from fertilizer toxicity:

  • Slow to mature
  • Tall plants with weak stems
  • Chlorosis, or paling, yellow discoloration on leaves
  • Lesions on the roots and stems
  • Leaves falling prematurely
  • Reduced root growth

If these symptoms are present and there's a salty crust forming on top of the soil, that's a likely indication that there's too much fertilizer present.

Did You Know?: It's easier to go from deficient to toxic with micronutrients as opposed to macronutrients in plants. The plant needing less of a particular nutrient makes it easier to accidentally give it too much.

Can Fertilizer Toxicity Be Fixed?

Fertilizer toxicity can really damage your plants, but the good news is that if you act fast you can salvage the situation by flushing the plants with water in order to push the fertilizer deeper into the soil and beyond the reach of your plants' roots.

Done over the course of a few days, while being careful not to drown your plants, flushing can go a long way towards remedying fertilizer toxicity.

What is Nutrient Deficiency in Plants?

Tomato Blossom End Rot

Remember how earlier we talked about how fertilizer becomes toxic when there are too many nutrients in the soil? Nutrient deficiency is the other side of that coin.

When there aren't enough nutrients in the soil to satisfy the needs of a plant, then there is said to be a nutrient deficiency.

What Causes Nutrient Deficiency?

There are a lot of reasons why plants may fail to receive the nutrients they need.

Sometimes the soil conditions may be poor or salty, the pH level may be too high, making the soil very alkaline, or there may be a drought preventing the plant roots from absorbing the nutrients they normally would.

In many cases, it's an accumulation of things as opposed to one single cause.

Signs of Nutrient Deficiency

The signs of a nutritional deficiency in plants share a few things in common with fertilizer toxicity although there are also some differences:

  • Chlorosis
  • Generalized symptoms as opposed to localized
  • Stunted growth
  • Leaves turning purple or reddish
  • Interveinal chlorosis, or chlorosis between leaf veins while veins remain green
  • Necrosis, or dying plant tissue



Did You Know?: Nutrients can be divided into mobile and immobile categories. As the name suggests, mobile nutrients are nutrients that can travel to other parts of the plant as needed while immobile nutrients are nutrients that don't have this ability.

Why Does it Matter?

Because for mobile nutrients like phosphorus, magnesium, and nitrogen, symptoms will likely appear in older leaves first.

In contrast, with immobile nutrients like calcium or iron, the symptoms will first appear in the younger areas of the plant, making deficiencies easier to spot and treat early.

Can a Nutrient Deficiency Be Fixed?

Yes it can but it requires a multi-tiered approach.

In the short-term, you'll want to treat specific nutrient deficiencies while taking care not to add too much.

Going long-term, however, you may need to add soil amendments, incorporate slow-releasing fertilizers, or use different fertilizers that complement the strengths and weaknesses of your climate and your soil in the future.

Nutrient Deficiency or Fertilizer Toxicity? How Do You Know Which Is Which?

The difficulty with diagnosing your plants is that fertilizer toxicity and nutrient deficiency often have similar symptoms like chlorosis and stunted growth, and both can be present in the same plant at the same time.

How do you tell these two apart?

One easy trick is to think of chlorosis and other symptoms less as definitive symptoms and more as indicators of nutrient distress before evaluating your overall growth environment and soil conditions.

If you prepared your soil well and you know the general conditions are adequate, no pests, acceptable soil pH level, and so on, but you're still seeing leaf discoloration early in the season, you may have a nutrient deficiency.

On the other hand, if you were applying fertilizer heavily, the fertilizer you used was mismatched to your soil, or your soil is showing signs of excessive salt content, then fertilizer toxicity could very well be your problem.

Simply because sometimes too much of one nutrient can create a deficiency of another in plants, if you treat the deficiency without addressing the toxicity, you may end up accidentally poisoning your plants. That's why holistic analysis is important.

Nourish Your Plants With Greenway Biotech

Plants handle nutrients like Goldilocks handles porridge.

Too much can harm them and too little can harm them, but they'll grow and thrive if the amount of nutrients they're given is just right.

Here at Greenway Biotech, our fertilizers are specifically formulated to be eco-friendly and free from heavy metals. Whether you've got too much fertilizer, too little, or you're simply looking for a readily available nutrient, we're here to help.

Shop our fertilizer collection below to find something your plants will love! Our line of organic fertilizers, speciality fertilizers, water-soluble fertilizers and hydroponic nutrients offers a solution for every need.


Related Posts:



Leave a Comment