Does anyone still use 'Phostrogen?' I used to use that years ago before I discovered miracle gro.

Bihai
It was cut out in your post above but I believe you were trying to say the best form of nitrogen is nitrate nitrogen? I use 15-5-15 Cal-Mag and it has potassium nitrate and iron and manganese in the ratio you mentioned.

LOL I see what you mean...looks like a blank for the $64,000 question! Yes he said Nitrate Nitrogen.

Where do you get 15-5-15 Cal-Mag from??

Usually, greenhouse growers use a higher than 50-60% nitrate nitrogen to the ammonical/urea ( urea converts to ammonical before it is utilized by the plant-so-same as ammonical)because studies have shown that ammonical doesn't react well to the peatmoss mixes that we use. Sometimes you can even get a ammonical toxicity. Most of the grhouse ferts are higher in nitrate nitrogen. But then, once the plant is in the ground, that you should switch to the ammonical nitrogen as that works better in soil. Did he say why the nitrate would be better if the plant is planted in the ground in soil as opposed to being in a container? Interesting.
I think the 15-5-15 is a base fert? in which case it would, over a period of time, raise the PH of the soil. I use 20-10-20 ( acidic fert) and add the magnesium ( epsom salt). I should see how much iron is in that fert. I do also use 13-2-13 occasionally (base fert). That does have more iron in it.

I think one of the reasons that the Dynamite works better than the Osmocote is that Osmocote doesn't release under 70 degrees soil temps and others release at 45 degrees. Dynamite probably falls under the lower soil degree temps, but I haven't read the label on it. It is probably coated in sulfur-which lowers the PH.

You can get these ferts at either a landscape supply store that sells to the public ( like Lescos) or a grhouse supply business-there must be a few near you. Or go to one of the nurseries and see if they will sell you a few bags, or tell you where they get it. Each bag is around $20.

I think they made the bomb with Ammonium nitrate. I know that fertilizers that have over 15% of it don't meet DOT regulations. Potasium nitrate is what you mix with sulphur and charchol to make gunpowder.
I would go with Nutricote. Dynamite is Nutricote that has been repackaged by a bunch of Mexicans here in Florida and they triple the bag prices for retail. You can find the triple 13 Nutricote, but I am using the 18-6-8 with minors that lasts 360 days. The reason it works differently is that it is polymner coated which works on temperature, mainly, where Osmocote works by osmosis (makes sence huh?) and the problem with this is when we have these 4 inch rains, the Osmocote can actually dump too much and burn stuff.

Cycad-I thought Osmocote was poly coated-which was one reason that it was so much more expensive. I never buy it=there are cheaper slow releases that are just as good, with all the minors that Osmocote has. I think all the slow release work on temps and moisture. I know Osmocote has 3, 6, and 9 month ferts, but have never know them to release and burn in a lot of rain...
Sulfur coated slow release triple 14 is around $20/40 lb bag(5 months ) and poly coated triple 14 is around $ 50/40 lb bag.
I am using a 20-6-12 with the palms.

Osmocote is known to ony work with any merit in soil temps of 70-80F, above 80 it's worthless, releasing/breakdown too quickly. Nutricote releases itself over 80 F, which is typically conditions in containers in FL from March-Nov, and in soils from April-October.

This research on Osmocote was actually done in the Mid-Atlantic region, as they noted the ability of Osmocote to release nutrients in ornamental containers was squat (immediate release to just the shell) once container media reached 80 or above.