Horti-Cote Plus in the lab: a gentle start and a stronger finish

Many controlled-release fertilizers give a strong push right after potting and run thinner later in the culture. Just when the crop needs a steady supply. We wanted to see how Horti-Cote Plus compares, so we followed five coated fertilizers in the lab for seven months. The result is a clear and distinctive release pattern.

How the trial was set up

Horti-Cote Plus (16-6-11 + 2 MgO + trace elements) was compared with four widely used coated fertilizers with a similar nitrogen content. Samples were taken every month from October 2023 to April 2024 and analysed by a laboratory in Maastricht. Each round covered nitrogen, phosphorus, potassium, calcium, magnesium, sulphur, six trace elements, EC and pH.

The competing products are shown anonymously as CRF M, CRF OE, CRF O5 and CRF EK.

Nitrogen: a softer start, a stronger finish

In the first round Horti-Cote Plus recorded 378 ppm total nitrogen, the lowest of all five products. The alternatives started between 449 and 707 ppm. A lower starting peak means a calmer first phase for freshly potted plants, while young roots are still establishing.

From December onward the picture turns around. Horti-Cote Plus recorded the highest nitrogen reading in every sampling round, right through to April.

The gap is largest in the final three rounds. From February to April, Horti-Cote Plus averaged 68.3 ppm nitrogen, against 29.3 to 41.0 ppm for the alternatives. That is 67 to 133% higher, at the stage where many CRFs are running out of steam.

A low salt load from day one

EC shows how much salt is in solution. At the first measurement Horti-Cote Plus had an EC of 2.5 mS/cm, 24 to 47% lower than the alternatives. For cuttings and young plants that means a lower risk of salt stress in the most sensitive phase. Across all seven rounds Horti-Cote Plus also had the lowest average EC (1.24 mS/cm).

Potassium and phosphorus follow the same rhythm

Potassium started at 83 ppm, again the lowest first reading, and peaked in November at 291 ppm. In February Horti-Cote Plus recorded 127 ppm, the highest of all products.

Phosphorus stayed remarkably stable at 30 to 35 ppm during the first three rounds, while three alternatives jumped to 83 to 108 ppm in November. From January to March Horti-Cote Plus had the highest phosphorus reading of the group. Worth noting: the 16-6-11 formula contains less phosphate than most alternatives, which makes the steady later readings stand out even more.

Calcium and trace elements: steady supply, no spikes

Manganese shows the gradual profile most clearly. Horti-Cote Plus declined smoothly from 1.97 ppm in October to 0.25 ppm in April, without intermediate peaks, and recorded the highest manganese reading of all products from November through April. Iron and copper also declined evenly, without the sudden jumps seen in some alternatives.

Calcium was highest for Horti-Cote Plus as well, both at the start (30 ppm) and as the average over all seven rounds (10.9 ppm).

What this means for growers

• A calm startLower EC and nitrogen after potting give young roots time to establish, with less salt pressure in the first weeks.
• Nutrition when it countsHigher nitrogen, potassium and phosphorus readings later in the culture keep supporting the crop into spring.
• A predictable patternGradual curves without sudden peaks make the feeding programme easier to plan.

Frequently asked questions