Phostrogen

Just need you to do half with Phostrogen and half with Miracle-Gro, and report back. Many thanks

 

I bought loads of reduced Phostrogen many years ago when a local garden centre was closing and selling off faded packs.

Then I got all the Miracle Grow that Wilkos had reduced to 30p per large box before they started getting mean about reductions, and that kept me going until last year.

I'm now down to my last box of reduced Chempak from a local garden centre:

 

My money is on the Phostrogen doing a better job than the miracle grow

 

A few years ago I switched from Phostrogen to Miracle-gro and, subjectively, my perception was that Miracle-gro worked better. But not side-by-side and all sorts of other factors involved ...

Perhaps I should feed some side-by-side and see where I get too ...

 

Well its pub quiz night tonight , hope there is a section on NPK levels !

 

I have just been to the Harrogate Flower Show today, and had a very long and interesting chat, on a number of different subjects, with a chap who is a scientific adviser to a number of growers organisations, including the Tomato Growers Association. He made a number of comments saying :-

1) That the trace elements needed by most plants, and supplied in most feeds, were exactly the same. ie Tomorite and Phostrogen have exactly the same trace elements.

2) That the big difference in feeds was the NPK ratio which can change a lot. He said that as long as the NPK ratio was the same there was essentially no difference between feeds. And in answer to my specific question, he said that Tomorite and Phostrogen were essentially identical in every aspect except price.

3) He also gave me the bulk prices paid for a number of the chemicals used. He said that the Phosphorous was the most expensive at £1,400 per tonne, Potassium at £800, and Calcium and Magnesium at £300 each. He didn't mention Nitrogen, but that's a very common substance and I am sure would be no more than any of the others - probably less.

A quick calculation shows that when you pay £3.75 for a litre of Tomorite in Wilkinsons, which has 4.5% Phorphorous and 8% Potassium, the chemical costs are 6.3p for the Phosphorous and 6.4p for the Potassium. Add a few extra pence for the rest and you are talking of less than 20p of chemicals. All the rest is packaging, distribution, advertising and markup etc.

4) Whilst I didn't ask, he told me that the yellowing of leaves has nothing to do with Magnesium deficiency. He said it is an old wives tale and no evidence has ever been found for it in the laboratory. He said yellow leaves will recover by themselves(or drop off if they are dying - my addition).

5) I also asked him about foliar feed with molasses for Brugmansias. He said that was nonsense - Americans were as daft as a box of frogs. I suggested that as plants make sugars and starches by photosynthesis, wouldn't supplying those make life easier for the plant. His reply was that photosynthesis makes the sugars inside the cells, and they have their own cellular transport system. Any sugars supplied from outside would be outside the cell walls. When plants are given a foliar feed of NPK chemicals, the chemicals ionise and being small, simple chemicals, they can with some difficulty pass through the cell walls. He then explained the precise mechanism - which lost me. However he said that sugars were large complex compounds, and that there was no way they could ever pass through the cell wall. So perhaps that's goodbye to another theory.

6) Whilst we didn't directly discuss it, he made it clear that he would agree with the principle of using a balanced/high nitrogen feed early in the season, and then switch to a high Potassium feed for flowering and fruiting later on. Maybe you just use high Potassium all the time for tomatoes as the fruit plays such a large part in their life cycle.

 

Most fertilizer chamicals provide at least 2 elements, MKP (mono potassium phosphate) is commonly used to provide all the P and part of the K. Calcium nitrate (dirt cheap) provides Ca and N, potassium nitrate (K and N).

 

Glad to hear the views on that because that has always been my gut feeling (when using Molasses as a foliar feed). I can understand that as a soil feed it might work, in the sense that it would feed the soil bugs and promote health in that way (in the way that Molasses can be used in Compost Tea to stimulate the growth of beneficial bugs). Still not tried Compost Tea though, I really should because I think I could get hooked on that if I found that it seemed to make a difference

... plus (as I know you know ), in the case of Tomorite [well ... "all liquid feeds"], water!! which adds to the distribution cost too.

Hmmm ... not convinced on that one. My understanding was that its not Magnesium deficiency (in the sense that the plant needs Magnesium, per se) but that the lack of Magnesium prevents the uptake of Calcium. When my Tomatoes go yellow this year I'll not treat a couple of them with Epsom Salts and see what happens ...

 

All nutrients are antagonistic with other nutrients. If you add extra magnesium (epsom) as a preventative measure (just in case) you affect the calcium. The other thing to be aware of is "stimulation", adding something like potassium sulphate to boost the K during fruiting will create a demand for manganese and iron.
Mulder`s chart is a useful reference.
http://www.apal.com.au/site/DefaultSite/filesystem/documents/APAL PLANT NUTRIENT INTERACTIONS July 08.pdf

 

We will all be interested to know how you get on. Last year was the first time ever that I bought some Magnesium salts. I don't grow tomatoes and have never worried about yellowing before, so I have no idea.

I really enjoy talking to people who have some real knowledge on these sorts of subjects. But I suspect that it a bit like internet pages, they can be conflicting and you need to talk to plenty of such people and then take an average of their views. But they are hard to find.

Hex - thats a good point. It just underlines the fact that its a very complex subject, and its difficult for the average amateur, without a laboratory, to know what's going on.

 

Hi Pete,
Its quite useful to get a handle on how nutrients work. Its common for gardeners to add magnesium to fix a deficiency when the issue is more likely to be calcium related. Plants need 11 elements, excessive calcium has an impact on 7 of them ;

 

I was good at maths at Skool, but they never taught me how to take an average where two data points gave you three values

 

I have no doubt you know exactly what you are talking about Hex, its all far too complicated for me.

I'm sure these chemicals we use do interact and create other imbalances.

At some point the science stops though, and plants, being plants just live with it, and get on with growing the best they can, some more tolerant than others.

Often we dont actually know what we are starting with, trace element wise, let alone what to add to correct a problem.
Surely it has to be a shot in the dark for us amateurs.

 

What is in the soil is the wildcard but,to my mind, an educated guess has to be better than a shot in the dark
Mulders chart is fairly straightforward and quite useful for diagnosing nutrient issues especially when its cross referenced to the physical symptoms of the plant.
Lets say you see the new leaves of a plant turning yellow, and a week earlier you`d added some potash to the soil. The shot in the dark method would be do nothing or maybe add some epsom and hope that fixes it
A glance at molder`s chart shows excessive potash can affect the availability of boron and the physical symptoms of a boron deficiency match the plant. Now you know what the problem is and, more importantly, the cause so you can avoid it next time around by adding less potash
The shot in the dark method doesnt fix the issue and it leaves you in the dark as to the cause so you`re likely to run into the same problem again.

 

I see what you are saying Hex, but its still not easy.
Or very practical to add something and then find you need to add something else because the first one has been over done.

Presumably this is why balanced fertilisers with trace elements were invented.