Phosphorus Deficiency in Tomatoes: How to Identify and Treat It

Phosphorus deficiency is a common problem on tomato leaves.

Two conditions lead to the deficiency in tomato plants:
1. Limited phosphorus in the soil
2. Limited phosphorus uptake by the tomato plants

Why Tomato Plants Need Phosphorus

Phosphorus is one of the Big Four macronutrients that tomato plants need in order to be healthy – nitrogen (N), phosphorus (P), potassium (K), and calcium (Ca).
In fact, the first three are known as the N-P-K ratio in fertilizers. Fertilizers of all kinds are labeled with three numbers (such as 5-10-10) which indicate each of the three nutrients’ percentage amounts in that product (in this case, 5% nitrogen, 10% phosphorus, 10% potassium).
Each of these nutrients has a specific role in growing healthy plants. In simple terms, phosphorus is a converter.
It is a nutrient converter. When other nutrients come into the tomato plant, phosphorus helps convert them into usable building blocks (proteins and nucleic acids), which allow the tomato plant to grow.
It is an energy converter. Phosphorus is a go-between for two kinds of energy in the metabolic process: high energy (ATP) and low energy (ADP). As ATP (high energy) loses phosphorus, it releases energy. That creates ADP (low energy). Then ADP gains phosphorus, turning back into ATP.
Phosphorus is important during each step of a tomato plant’s life cycle.
In seedlings: phosphorus encourages healthy root development
In young plants: phosphorus provides for strong stems and leaves
During flowering and fruit set: phosphorus promotes fruit development
During ripening: phosphorus boosts nutrition in tomatoes.

What Causes Phosphorus Deficiency in Tomato Plants?

• Cold soil temperatures, which inhibit phosphorus uptake
• Improper soil pH (acidity below 6.5 or alkalinity greater than 7.5), which inhibits phosphorus uptake
• Deficiency in the soil, which means phosphorus is unavailable or less available

What Does Phosphorus Deficiency in Tomatoes Do

Phosphorus deficiency in tomatoes
Look for these phosphorus deficiency symptoms in tomatoes:
Color
Tomato leaves become purplish (or reddish-purple), most often first on their undersides and later on the tops. Here’s why: when phosphorus becomes unavailable, energy cannot be converted. Sugars pool together, producing an abnormal dark-green color. This allows anthocyanin pigments to develop, producing a reddish-purple color. Tomato leaf veins, leaf stalks (also called “petioles”) and tomato stems may become purple, too. In severe cases, an entire tomato plant can take on a purplish color or its already-purpled veins may turn brown. Over an extended time, tomato leaves may turn blue-gray.
Curling
Leaves on affected plants may curl.
Slow Growth
Phosphorus plays a key role in the growth process. If your tomato plant can’t convert nutrients to energy building blocks or can’t gain and release energy, then the plant can’t grow. Phosphorus-deficient tomato plants grow slowly. They are often dwarfed or stunted and may appear to be younger plants or stressed plants. Once-healthy plants lose vigor.
If you don’t want to have problems of your tomatoes like phosphorous deficiency, you can apply VAN IPEREN fertilizers, like phosphate products and many water soluble NPK fertilizers with different level of phosphorus. For more expert advice about which type of fertilizers, doses, concentrations and method of application, you can to ask and will received it from expert HORTICENTAR team.