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Elrik

[in]soluble fertilizer blues

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So I'm gearing up for a large project and I went to check out the fertilizers available. I have always bought the expensive instant fertilizer with trace minerals but seeing a 25 kilo sack of cheap 16-16-16 for the same price as a 3 kilo box of the good stuff I finally gave in to temptation. At home I tried to dissolve some into water. Tried. I re-read the bag, 'soluble fertilizer'. I shook it more. I put it on my magnetic stir plate for 15 minutes. Some of the pellets just dont dissolve! The ingredients just say urea, monoammonium phosphate, ammonium sulfate, potassium chloride. Perhaps the urea is stubborn?

How do you all deal with situations like that? My best guess is powder it and try to keep any non-dissolving stuff suspended while applying?

 

For my project I got a bale of spoiled feed hay, chopped it up, moistened and inoculated it. For a decade I've saved up all salty or decomposed potting soil, I washed that out, drained, and mixed with the inoculated hay before packing into storage bins to compost for the next 4 months. While that works I'll be turning 20 Pereskiopsis clones into a great deal more. In the past my pereskiopsis grafting skill has been mediocre at best, I plan to correct that through sheer grafting volume. :wink: After 4 months of composting and then a year growing pereskiopsis my hay soil should make some good trichocereus and hylocereus soil after washing salts out once more.

If I can make this cheap 16-16-16 usable I can feed the peres the high grade fertilizer just every third time.

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Urea is very water soluble, doubt that's the issue. Regarding chloride salts, I would think that's something you'd want to avoid for plants.

 

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Thats what has me confused, every listed ingredient is quite soluble.

My best guess is they may have used superphosphate as the P source in place of ammonium phosphate, superphosphate may be slower to dissolve. I think for fun I'll try to dissolve some in hydrochloric acid and see if sodium carbonate precipitates calcium carbonate/phosphate out.

Yes, the chloride and the lack of micronutrients in the cheap stuff are why I have always paid up to 8 times as much for high grade imported fertilizer, the local stuff always uses KCl. At worst I'll just use it for my hundred or so potted Trichs, in the summer I water them so heavily that salts cant really accumulate. They might like something other than piss and liquid organic fertilizer, lol, at least for the phosphorous.

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For the record, it was the urea.

Gypsum is used as a stabilizer to slow the degradation of urea so some companies make mixed gypsum/urea pellets.

What I've been collecting is low density gypsum pellets left after the urea dissolved out.

I suppose I'll find a cactus mix to use it in. Or I perhaps my tomato bed would like it.

So, urea based fertilizer that doesnt fully dissolve: suspect gypsum.

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