Tomato Fertiliser, Tidying up for Winter

A chat about fertiliser results in some free tomatoes. And very nice they were too. Tidying up in the greenhouses and polytunnel as I prepare for winter.

Fresh tomatoes grown with S-Chelate and a trial fertiliser

Tomato Fertiliser

I had a chat with Barry Langdon, the head chemist at S-Chelate. He’s been running some trials comparing various nutrient formulations in his laboratories at Rothamsted. Although his S-Chelate 12-Star is already an excellent fertiliser, Barry is always looking to improve where possible.

This year he was specifically looking at tomatoes which are a useful indicator of how a fertiliser is performing. They’re sensitive to deficiencies so, for example, plants with Blossom End Rot tell you that they’re lacking in calcium.

Balancing the Nutrients

As most gardeners know, tomatoes need a high level of potassium (potash) to support the fruit production. Hence most specific tomato fertilisers will be formulated to be high in potassium. But it’s not as simple as just increasing the amount of a chemical in the mix. For example, too much potassium will lock up magnesium causing deficiency problems and can effect the uptake of calcium. Balancing the nutrients and keeping the pH (acidity) in range is critical to getting great results.

When you’re growing in the ground, fertiliser composition isn’t as critical, although it still matters. When you’re growing in a pot, especially with coir based composts or growing hydroponically, you have very little room for error and small changes can have a bigger effect than you might expect.

Growing Trial to Prove the Theory

Theory is all very well, but the best way to be certain is to run a growing trial and measure the results. Last year I attempted to do this but unfortunately my trial tomato plants got hit by blight which stopped my trial in its tracks.

Barry discussed this with me prior to running this trial and grew Crimson Crush which is a nice standard tomato that is blight resistant. Not a cast iron guarantee that the plants won’t be hit with blight, but it greatly increases the chances of success.

Having finished his trial, Barry sent me some of the trial tomatoes. One bag grown with S-Chelate 12 Star and the other grown on a trial fertiliser. When I opened the box, Val thought I’d bought some tomatoes and must have lost my mind! I explained what was going on and she cancelled the special jacket with wrap around sleeves.

On the final test of for the trial crops, taste, both passed with flying colours. I didn’t really expect any difference between the two but it’s always worth checking.

Barry will be writing up the details of the trial and the results soon and I’ll link across to that when it’s online.

Closing Up For Winter

Here it’s mainly tidying up and preparing for next year. The Vitavia greenhouse is empty and the border cleared apart from a lonely marigold that I hadn’t the heart to pull. Next job is to clean the glass and replace some of the border soil with home made compost to rejuvenate it for next year.

The Eden greenhouse is near empty too, apart from a a couple of Heartbreaker patio cherry tomatoes which are nearly finished and some spring onions. I tried an experiment, growing spring onions in a wicking tray system. They did OK but I think the conditions were too kind for them or maybe too much fertiliser as they grew very floppy. I’ve had better outdoors, perhaps they like the wind on them.

The polytunnel is near clear except for some leeks and carrots. It’s in need of a good clean though. The wet summer and high humidity has been great for algae growing on the skin which reduces light transmission. Dirty glass or polythene basically means the plants are growing in the shade. Another ‘when we get a decent day’ job