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Salt-index of chemical fertilizer & soluble for hot weather

10 years ago

Here's a link of salt-index in chemical fertilizers:

The above lists Urea at 74% salt, Ammonium nitrate at 104% salt, ammonium sulfate at 69, ammonium phosphate at 27, and gypsum (calcium sulfate) at 8.

Muriate of Potash is potassium chloride, the stuff that we use to de-ice my slippery sidewalk in zone 5a winter. Salt index of potassium chloride is highest, at 116.

Nitrogen fertilizers are highest in salt. Fabian G. Fernandez, the researcher who compiled U. of Illinois Salt-index, wrote: "In addition to salt injury, some N compounds (such as UAN, urea, and ammonium thiosulfate) produce ammonia, which can cause seedling death. The best fertilizers has a low-salt index, N compounds that do not produce free ammonia, and potassium phosphate - rather than potassium chloride as the K source."

Last night I was looking at site, "Stanford gardening", and it said NOT to use urea nor ammonia fertilizer for tomatoes. Well, I did that last year, and had to water my 12 tomatoes constantly ... less fruits, and too tall plants!

Phosphorus and potassium are less available in alkaline clay, both are bound up with calcium or magnesium. Lime in tap water also drives down both phosphorus and potassium.

Nitrogen mobility is a 10, it moves with water. Potassium mobility is a 3, not much. Phosphorus mobility is a 1, immobile. One research found that granular phosphorus applied on top, only moves 1 inch per year.

Per high phosphorus: it burns in hot weather, best in soluble form, and 1/4 the dosage.

Per high potassium: Wikipedia stated "High nitrogen or potassium induce calcium deficiency." When I gave Paul Neyron rose too much nitrogen, the blooms balled up. High calcium drives down potassium, and vice versa.

Alkaline clay has plenty of nitrogen, I never fertilize my 26 trees, yet they are taller than 2-story house. Rain also brings nitrogen and oxygen. Air is composed of 78% nitrogen, and 20% oxygen.

There's an Australian that lists the salt-index of sulfate of potash as 43.4. Gypsum has salt-index of 8, provides 23% calcium and 17% sulfur. University of California Extension chart listed 1 ton of gypsum as equivalent to 5.38 ton of sulfur. It also listed 1.09 ton of Ferric Sulfate as equivalent to 5.85 ton of sulfur.

Gypsum (calcium sulfate) is fast-acting, thus burns more than slow-released sulfur.

Dolomite provides 25% calcium, 10% magnesium with 0.8 salt. Lime (calcium carbonate) provides 36% calcium with 4.7 salt index. Both lime and dolomite are sold at Kelp4Less, free shipping, will make the surface of soil dry and alkaline, to prevent fungal germination.

Soluble Monopotassium phosphate has low salt index 8.4, and provides 52% phosphorus, and 34% potassium. Superphosphate provides 20% phosphorus, 12% sulfur, low salt index of 7.8. See link below:

The Chicago Botanical Garden, with 5,000 roses, pH of 7.4 loamy soil recommends SOLUBLE fertilizer NPK 20-20-20, with trace elements, 3 times for zone 5b. I tried that, and the salt zapped one of my young rose.

The soluble NPK of 2-20-20 has less nitrogen, low salt index of 7.2. Since MiracleGro Bloom Booster is cheaper with NPK 10-52-10 plus trace elements ... I use 1/4 the dosage to make it NPK 2.5 - 13 - 2.5.

I prefer soluble Organics, alfalfa tea and horse manure. Golden Celebration (middle yellow) is fertilized with soluble Organics .... better quality bloom:

Here is a link that might be useful: Fertilizer salt index

This post was edited by Strawberryhill on Fri, Sep 27, 13 at 16:25

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