Sul-Po-Mag vs Potash

February 2, 2009
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Categories: Fertilizing, Growing Daffodils, Planting, Pots, Soil

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Friends: This year we are having trouble finding Potash (0-0-50) for our normal early season feedings, but are able to find Sul-Po-Mag (0-0-22), which is a mixture of potassium sulphate and magnesium sulphate. If anyone has advice or experience I would appreciate knowing whether you think I can blithely go ahead to use the available 0-0-22, or whether you foresee some negative consequence of its use. I grow in a largely organic mix in pots, but have some cultivars in raised beds that are either homemade compost or sandy loam. I ruefully admit that I do not test my soil. Melissa

One response to “Sul-Po-Mag vs Potash”

  1. Keith Kridler says:

    We never did get any real numbers on what is considered the ideal micro and macro nutrient levels for daffodils from the commercial growers.
    Sul-Po-Mag contains 22% potassium, 22% Sulfur and 11% Magnesium that they claim is 100% water soluble so all of this would theoretically be available pretty quickly. Or you would consider this to be a pretty “hot” fertilizer mix. Sounds like it would be great to mix up and use as a “constant feed” type fertilizer that you would use in a VERY dilute mix every time you water IF you have high PH soils.
    The sulfur in this fertilizer when added to high levels of organic materials already in your soils will lower the PH. Approximately 2% of dried organic plant material is already sulfur. Compost is normally acidic as micro organisms are removing the carbon in the material.
    Especially with potted daffodils I would get a soil test done on what you are using at LEAST at the end of the growing season. When the bulbs go dormant dump out the soil out of about 10% of the pots, mix this up well and send off a composite soil sample to see what the bulbs grew in all season.
    I am not sure why we all HATE to spend $25 to get a complete soil test done that covers the micro nutrients and the macro nutrients but we think NOTHING of sending out a $500.00 bulb order:-))
    IF you knew you had a high PH of 7 or above then the sulfur would help lower this. You PROBABLY want a soil PH of 6.2<6.5 for most/some daffodil species???? IF you have a low PH in the range of 4.5 then again the sulfur will continue to lower the PH giving you a REALLY acidic soil.
    IF you are on city water systems they often use Caustic Soda to clarify the water and our local city water has a PH of 8. something but our irrigation water coming out of the creek is under a 5.0 PH. So every time we water potted plants we are adding just a little PH raising alkaline to the water IF I use city water. YOUR well water or irrigation or even rainwater MIGHT be acidic.
    To give you or your kids a simple table top experiment take a whole egg out of the fridge and place it in a clear drinking glass. Add 2 cups of white vinegar to the glass to cover the egg and watch to see what just 5% acid levels in this liquid will do to the calcium.
    Now go back to your favorite fertilizer and MOST of these will be acidic in nature.
    Potassium Nitrate as a liquid fertilizer will contain 13% nitrogen and 38% Potassium but 0% sulfur and 0% magnesium.
    IF you have acid soils and need nitrogen you can use Calcium Nitrate which contains 15.5% nitrogen and 19% calcium. This is a GOOD liquid fertilizer. This MUST be used by itself and NOT mixed with other fertilizers that contain sulfur as the sulfur will react with the calcium gassing off the nitrogen. Just as the vinegar will dissolve the calcium in the eggshell. THIS is an alkaline type fertilizer that will slowly RAISE the PH levels in your potted plants. Again it would be a good constant feed fertilizer for leafy vegetable or ornamental plants IF you have acidic soils and low levels of calcium in your potted plants.
    Boron is needed by onions, beets and other plants in various amounts. My soils are low in Boron and I just need to add 1 pound of boron per acre. 99% Boric Acid is sold as a Roach Killer pesticide BUT it contains 18% Boron SO I need to apply 5 pounds of "Roach Killer" per acre X 20 acres is about 100 pounds of Roach Killer every couple of years.....Go into the grocery store or hardware store and ask them for this much Boric Acid roach killer and you will become the talk of the town.....
    Yellow Daffodils are blooming all over our area this week. Keith Kridler Mt. Pleasant, Texas