PK 13-14 by Plagron, a mineral supplement of phosphorus and potassium for flowering

Phosphorus and potassium supplement without nitrogen

6,90 €

Contenance	Price	Price per L	vs 250 ml
250 ml	6,90 €	27,60 €	—
500 ml	9,90 €	19,80 €	−28 %
1 L	13,90 €	13,90 €	−50 %
5 L	54,90 €	10,98 €	−60 %
10 L	99,90 €	9,99 €	−64 %
20 L	189,90 €	9,50 €	−66 %

Plagron's PK 13-14 is a mineral supplement of phosphorus and potassium for the second half of flowering. It is added to the base fertiliser of tomatoes, peppers, aubergines or strawberries, in soil, on coco fibre or in hydroponics, at 2 ml per litre at most from the fourth week of flowering, for firmer fruit.

Ref. TK-PLAG-PK1314-250·Engrais

Contenance : 250 ml

250 ml

500 ml

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The summary

Nature: a colourless liquid mineral supplement, NPK 0-13-14, nitrogen-free.
Preparation: 2 ml per litre at most, then the base fertiliser up to the desired conductivity.
Schedule: at every watering from the fourth week of flowering for fruiting vegetables.
Decoupled aquaponics: in a separate loop or in neighbouring hydroponics, never in the pond.

A targeted boost of phosphorus and potassium when fruiting vegetables come into flower

PK 13-14 by Plagron is a mineral supplement of phosphorus and potassium without nitrogen, from the 250 ml bottle to the 20 litre container. It is added at no more than 2 ml per litre from the fourth week of flowering, before the base fertiliser for tomatoes or peppers. An aquaponic circuit never receives it.

When a tomato, pepper or strawberry plant comes into flower, its demand for phosphorus and potassium rises markedly, while its nitrogen needs level off. A flowering fertiliser covers most of this demand, and PK 13-14, from the Plagron range, lets you boost it just when the plant needs it most. This liquid mineral supplement contains 13% phosphorus pentoxide and 14% potassium oxide, with no nitrogen, and it promotes abundant flowering followed by firmer, heavier fruit.

🌼 Phosphorus and potassium for flowering

Phosphorus is part of the molecules that store and carry energy within the plant, and it plays a direct role in the formation of flowers, seeds and roots. Potassium, for its part, regulates water pressure in the cells and the transport of sugars from the leaves to the fruit, so it determines their size, firmness and flavour. The contents are expressed as oxides, as is customary for fertilisers: 13% P2O5 corresponds to roughly 5.7% phosphorus, and 14% K2O to roughly 11.6% potassium. So you are mainly supplying potassium, the element that fruiting vegetables consume most towards the end of the crop.

1. PK 13-14

2 ml per litre of water, i.e. a 1:500 dilution, shaking the bottle well.

2. The base fertiliser

Added afterwards, until the conductivity targeted for the crop is reached.

3. The pH

Adjusted last, to between 5.5 and 6.5, with a pH corrector.

⚖️ Preparing the solution

Begin by pouring 2 ml of PK 13-14 per litre at most into your tank or watering can, then add your flowering fertiliser up to the conductivity recommended for your crop and its stage. The supplement also contributes to the conductivity of the solution: by dosing it first, you fix its share and then adjust the base fertiliser, rather than overshooting the target value. Finally, adjust the pH to between 5.5 and 6.5, correcting it if necessary with pH Min. The liquid is perfectly clear, which is normal for this formula.

Measure the pH after every preparation

With a mineral fertiliser, the pH of the solution determines how much of each nutrient the roots actually absorb, and adding a concentrated supplement changes it every time. An electronic pH tester with temperature compensation gives you the reading in a few seconds. You can then correct the solution before watering, instead of discovering a deficiency on the leaves later on.

PK 13-14 does not replace bloom fertiliser

This supplement provides no nitrogen, calcium, magnesium or trace elements. Used alone, it unbalances the nutrition and can cause deficiencies within a few weeks. It is always given in addition to your usual flowering fertiliser, never in its place.

The solution is used at every watering from the fourth week of flowering until harvest, in soil, on coco fibre and in hydroponics. It is worthwhile on vegetables that you harvest for their fruit: tomatoes, peppers and chillies, aubergines, courgettes, cucumbers, melons and strawberries. It serves no purpose on salads or herbs harvested for their leaves, whose needs remain dominated by nitrogen. The supplement must not be combined with Green Sensation, which already provides phosphorus and potassium from the same week: one or the other is enough.

🐟 Phosphorus, potassium and aquaponics

In a coupled aquaponic system, where the same water circulates between the pond and the roots, PK 13-14 has no place: it supplies concentrated mineral salts, designed for a solution without livestock, and an excess of phosphorus in water exposed to light encourages algae to proliferate. The need it targets does nonetheless exist in your system, since potassium is among the elements most often deficient, along with calcium and iron. The aquaponics guide from New Mexico State University recommends supplying it as hydroxide when the pH drops, and potassium bicarbonate plays the same dual role of buffer and fertiliser.

PK 13-14 comes back into its own as soon as the plant water no longer returns to the fish. In a decoupled system, the pond water feeds a separate growing loop, and your tomatoes or peppers receive the nitrogen produced by the fish there, topped up with the phosphorus and potassium needed for flowering. The supplement also suits a hydroponic system set up alongside your aquaponics and fruiting vegetables grown in pots. The article on fertilisers in aquaponics explains in detail what the fish circuit will tolerate.

🧴 Sizes and consumption

At 2 ml per litre, the 250 ml bottle makes 125 litres of solution and the 1-litre bottle makes 500. To give you an idea, around ten tomato plants watered with 30 litres a week over two months of flowering use about 500 ml. The 5, 10 and 20-litre containers, which make from 2,500 to 10,000 litres, are aimed at greenhouses and large hydroponic systems. Keep the container closed, away from frost and heat and out of reach of children, and shake it before each dose.

⏱️ The right moment

The supplement comes late in the crop cycle, from the fourth week of flowering. On a tomato, this corresponds to the point when the first trusses have set and the fruits begin to swell. Before this date, the flowering fertiliser covers the plant's needs on its own. The concentrate, perfectly colourless, has a conductivity of 155 mS/cm and a pH of 7.1: this is why it is dosed at one five-hundredth, with a syringe rather than the cap, and why the final conductivity is always adjusted with the base fertiliser, Terra Bloom in soil, for example. Unopened, the container keeps for 4 years after manufacture, between 0 and 35 °C, away from frost and sunlight.

Technical specifications

The analysis

Type: Liquid mineral supplement
NPK: 0-13-14That is roughly 5.7% phosphorus and 11.6% potassium
Appearance: Clear liquid
Grow media: Soil, coco fibre, hydroponics

Usage

Dose: A maximum of 2 ml per litreThen the base fertiliser according to conductivity
Period: From the 4th week of floweringUntil the fruit harvest
Recommended pH: 5.5 to 6.5Adjusted last, after the base fertiliser
Combined with: The usual flowering fertiliser

With the other products

Order of preparation: PK 13-14, then the base fertiliser
Green Sensation: Do not combineThe booster already supplies phosphorus and potassium

The concentrate

pH: 7.1
Conductivity: 155 mS/cmHence a dose of one five-hundredth
Storage: 4 years, unopened containerBetween 0 and 35 °C
Hazard classification: Unranked

6 further specifications are available in the detailed view.

In the box

1 bottle or 1 container of PK 13-14, from 250 ml to 20 L depending on the size chosen

Analysis, dose, period and pH taken from plagron.com (PK 13-14 page, October 2024 technical data sheet), classification from the 2026 safety data sheet. Oxides converted using the usual coefficients.

Manufacturer and product safety

Manufacturer: Bertels B.V.
Website: plagron.com

Information provided under Regulation (EU) 2023/988 on general product safety.

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delivery time

Bottles and cans are dispatched as parcels from a distributor's warehouse in France, with sealed caps and wedged against leaks. The exact shipping cost is shown in your basket.

Frequently asked questions

6 questions

6 key questions

How much PK 13-14 for a 10-litre watering can?

Do you need to adjust the pH and conductivity?

What do the numbers 13 and 14 mean?

Which bottle for around ten tomato plants?

Can it be used on lettuces?

Does PK 13-14 have a use around aquaponics?

PK 13-14 for your solution

Enter the volume of water. The calculation gives the maximum dose of PK 13-14, to be poured in before the base fertiliser.

Water to prepare

1 L500 L

0ml

PK 13-14 at most

Only from the fourth week of flowering, and never at the same time as Green Sensation.

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Phosphorus and potassium supplement without nitrogen

The summary