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| The word on the street is that sources of P are winding down, so it's time to get some. (at least in the next 40 years or so) Also, my soil test says I could maybe use some. But as I looked into it, it seems that most sources of P contain heavy metals in concentrations I'm not really excited about. Tennessee Brown Rock Phosphate is supposed to have the lowest concentrations of heavy metals, and yet it has 73 ppm of mercury, and the EPA standard for mercury in soil is 23 ppm. I know it will be diluted, but still, do I really want to add that to my soil? To add P while avoiding heavy metals, are bone meal, fish bone meal, and fish meal the best choices? Is there something I'm missing about all this? Thanks! |
Follow-Up Postings:
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| Elisa: urine, if you're not fussy about collecting it, diluted with water at least 2:1. I've always used soft rock phosphate, principally as a source of calcium, and there's lots else in it. But it was in restricted supply a couple of years ago, so your concern is reasonable and, in the long run, my solution is valid. Manure is a great source, but for most gardeners the logisical problems are too great. Odd that, when you consider that feedlots and dairy farms can't get rid of the stuff. Large scale composting and mixed farming is what they'll come around to. Regards, Peter. |
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| Urine has very little P. All manures have a lot of P, but chicken manure is the best. At any rate, anyone who composts a lot will have high P in the garden. That means that leaves, straw, wood chips, clippings, kitchen scraps all are viable sources. I am not too concerned for my own garden, years of organic matter has produced close to 100 ppm. It will be decades before P runs out there. |
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| Compost, animal manure, other vegetative waste put back into your soil will probably be the source of nutrients you will need. While tests often do not show much in the way of nutrients in those items they are there. My soil, and others have found the same thing, has gone from very low levels of soil nutrients to high optimum levels with only the addition of compost, animal manures, and other vegetative waste (shredded leaves, etc.) |
Here is a link that might be useful: nutrients in compost
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| Excellent. Thanks for the responses -- I like the idea of using the local sources (I have access to unlimited horse manure and hay) rather than trucking in anything anyway. Glad to know! Elisa |
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| And wood ash is a concentrate source of P (1% by weight). Local sources will be still available for use. |
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| However, since wood ash is about 25 percent Calcium Carbonate, lime, due care in its use is strongly suggested. A good, reliable soil test is always suggested prior to applying wood ash to any soil. |
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