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Old 03-04-2014, 04:29 PM
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Toro 44 Toro 44 is offline
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Join Date: Jan 2004
Location: Bucks County PA
Posts: 155
Spraying SOP? (Riggle, Green Doctor, any others)

I normally apply K in granular form as SOP. But I'm looking for a good sprayable K source.

There are 3 criterion I'm using:

1) Solubility

2) Salt index

3) Price

I thought that SOP was my answer. Other than potassium Carbonate, it has the lowest salt index and is affordable. But I have concerns about solubility. I may be spraying 1/2 pound of N in the form of stabilized urea. I'd like to add 1/4-1/2 pound of K with it.

My typical spray volume is between 1.5 and 2 gallons per 1,000 square feet.

I like potassium carbonate, but it seems very hard to get and pricey.

I've heard Green Doctor talk about potassium nitrate, but it is a little more expensive, has a higher salt index, and according to "Turfgrass Science and Culture" can deflocculate the soil when used over time. BTW my soils have a good deal of clay and tend to be acidic.

Does anyone have experience dissolving and spraying SOP (Riggle)? How much do you apply and what spray volumes were you using (2.6 g/m)? Seems like for a given amount of SOP, I will need at least 10 times that weight of water to disolve it. According to the solubility chart on wikipedia, Potassium Nitrate has about twice the solubility as SOP at the temps I'd be mixing in.

Thanks in advance!

P.S. It's not uncommon for my soil tests to come back needing sulfer. The sulfate in SOP is helpful this way
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