sources of organic potash and phosphorus?

canuckistani(5b)June 3, 2009

Any suggestions on the best organic sources of potassium and phosphorus besides manure?

I'm thinking of using sulphate of potash and bone meal....should I mix all of it in the soil before planting since these are supposed to slow realeased?


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For phosphorus you can use bonemeal (it works well it is fairly slow release but also adds calcium too) for potassium hands down kelp meal is the best thing. If you live within a reasonable distance to the ocean you can just harvest it there.

I go to the ocean and get kelp, seashells, and crabshells and make kelp meal,crab meal, and ground seashells.

Those 3 things alone add potassium, most micronutrients, chitin which beneficial fungus feed on which increases there numbers(these fungus will also eat insect eggs because most eggs contain chitin, calcium and magnesium.

    Bookmark   June 3, 2009 at 10:23PM
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Why do you think you need to add any Phosphorus or Potash to your soil?
Given that most Sulphate of Potash is made by reacting Potassium Chloride with sulfuric acid which results in a very soluble form of Potash that is unaccetbale to an organic gardener/farmer. Bone meal, today, does not have the Phosphorus it once had.
The levels of both Phosphorus and Potash have increased in my soil simply by adding compost and other forms of organic matter (shredded leaves as mulch), there was nothing specifically loaded with P or K added except the manures used to make the compost.
Adding some kind of nutrient to your soil if they are not needed not only can be a waste of your money but create more problems than it might solve since a too much of one nutrient can cause a plant to not uptake other, necessary, nutrients which can make the plant more attractive to insect pests which then require the use of some means of control which can mean spending more money.

    Bookmark   June 4, 2009 at 7:32AM
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I tested the soil and the levels of potash and phosphorus are on the low side. Kelp meal is quite hard to find for me. Any other suggestions? I appreciate the input guys.

    Bookmark   June 4, 2009 at 8:26AM
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Given that most Sulphate of Potash is made by reacting Potassium Chloride with sulfuric acid which results in a very soluble form of Potash that is unaccetbale to an organic gardener/farmer.

It occurs naturally and is mined and contains over 50% soluble potash. It's OMRI approved. Many vendors to choose from. If it's acceptable to the OMRI I am not sure why it would be unacceptable to the organic community in general.

Canuckistani, How did you test the soil to determine low phosphorus levels? I wouldn't trust the at home tests for this and excess P in the environment has become a major source of water pollution so please make sure of the results before adding more.

    Bookmark   June 4, 2009 at 9:43AM
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PHOSPHATE ROCK - for ( P )hosphorus, go easy it adds ALOT of Phosphorus over a several year period.

GREENSAND - a very fine ( ie use on a calm morning preferably ) dark green - sand. It adds ( K ) helps loosen clay soil, and adds some trace minerals.

Not sure where you are located but Farmer's feed supply stores should be able to order these for you. ( If they don't already have them on - hand )

    Bookmark   June 18, 2009 at 6:50PM
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All that I have added to my sand is compost and shredded leaf mulches and the nutrient levels have increased over the years from below optiumum to above optimum, and I spent no money on greensand, rock phosphate, granite dust lime, or anything like that. Simply increasing the amount of organic matter in your soil should be enough.

1 Like    Bookmark   June 19, 2009 at 6:54AM
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Dan Staley

Those blessed with time and space add nutrients to the soil in one way. Those constrained with time and space and who want decent veggies this year must add amendments with the nutrients they need.

Phosphate rock is mined, and finally folk are starting to notice that we will be running out in a generation or two, and often the rock is treated with sulfuric acid as well. Potassium sulfate, as kimmsr wrote above, is an energy-intensive industrial process. Both material processes eject carbon and other byproducts into the environment and neither is sustainable. Bone meal is one way to get your P and although energy is consumed in the manufacturing process, it will do the job.

As for K, greensand is mined as well and AIUI kelp is harvested out of the water for the most part and only some is taken off the beach, neither is sustainable but kelp regrows at least. I used greensand when preparing my large bed and have been very happy with the result.

So I guess it depends upon your focus as to which material you choose.


    Bookmark   June 19, 2009 at 9:27AM
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