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Where to find Rock Phosphate for organic fert.

Posted by pkapeckopickldpepprz z9 a/b FL (My Page) on
Thu, Nov 2, 06 at 9:58

I see a lot of organic Rose Fertilizers that are hommade usinga material called rock phosphate and they mention not to confuse it with triple phosphate or any of the phosphates sold in stores. My question is where does one get this rock phosphate? Can I just substitute the rock phospahte part of the ingredients with bone meal?


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RE: Where to find Rock Phosphate for organic fert.

Bone meal and rock phosphate are both mostly calcium phosphate. Bone meal has a more open crytal structure and a higher percent of its phosphorous is available to plants. I see no problem at all with substituting bone meal for rock phosphate but you might want to adjust the recipe for the increased available phosphorous in the bone meal. You can buy either bone meal or rock phosphate from Espoma.

Triple phosphate is essentially rock phosphate which has been acidified. This makes more of the phosphorous available to plants and results in an appreciably more economical fertilizer - but also makes the stuff a synthetic chemical and not approved for organic gardening.

Here is a link that might be useful: Espoma


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RE: Where to find Rock Phosphate for organic fert.

I've read that you can even use Super Triple Phosphate from those on the Rose Forum (not sure if it's still organic) without harming roots, but I have read otherwise that the triple superphospahte is quickly absorbed and seems it would burn.


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RE: Where to find Rock Phosphate for organic fert.

pkapeckopickldpepprz, the general name for all acidified rock phosphates is "superphosphate". Plain superphosphate was made by acidifying with sulfuric acid, a process which also produces gypsum. If, instead, the rock phosphate is acidified with phosphoric acid, a product called triple superphosphate is produced and it's exactly the same stuff except no gypsum by-product is present. Essentially all superphosphates on the market today are triple superphosphates no matter what they are called.

Salt index is the usual measure of a fertilizer's tendency to burn roots. Triple superphosphate has an exceptionally low salt index and is very unlikely to harm roots. I guess my opinion about phosphorous fertilizers in general is that an organic rose gardener should really minimize the use of all forms of phosphorous in an effort to encourage the growth of symbiotic root fungi, the mychorrizae. In any case, I think bone meal and rock phosphate applications are a waste of time and money and, ultimately, a waste of our mineral resources.


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RE: Where to find Rock Phosphate for organic fert.

I'm curious why you mentioned triple superphosphate along with BOne meal as being a waste of time and money? They seem like legitimate ammendments to me, and have been proven for plants. Are you saying for Roses they aren't that important? I made the famous Rosemagazine tonic with alfafa meal cottonseed meal epson salt, bone meal blood meal and I didn't use the rock phospate and didnt know if I could substitute with triple superphospate, so I doubled up on the bone meal. Well any event the roses seemed to like it.


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RE: Where to find Rock Phosphate for organic fert.

My comments were directed at rock phosphate and bone meal, not at superphosphate. Treatment of the mineral resource, rock phosphate, with acid to synthesize superphosphate increases the plant-available phosphorous by a factor of 5 to 15. Spreading rock phosphate or bone meal directly in the soil strikes me as a waste of a mineral resource.

The users of rock phosphate and bone meal are almost exclusively home gardeners. Packaged for the home gardener, these fertilizers usually cost more than the same weight of superphosphate, and provide much less available phosphorous. That's a waste of money.

Many home garden soils contain an excess of phosphorous and this inhibits the michorrizal root fungi on a rose which would otherwise provide the rose with adequate phosphorous from the soil. If you are using an organic fertilizer containing alfalfa and cottonseed meals, these contain adequate phosphorous in themselves and adding bone meal or rock phosphate might be a waste of time, and money, and resources.


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RE: Where to find Rock Phosphate for organic fert.

I disagree on the value of Rock Phosphate. In the 60s I had an organic garden and I was able to buy bags of Rock Phosphate (untreated) and bags of Granite Dust locally. I would buy several bags each year and treat the rows where I was planting. Both Rock Phosphate and Granite Dust are slow leaching. They will provide goodies for the plants for 3 to 5 years. In addition Rock Phosphate & Granite Dust carry a number of trace elements including copper which is very deficient in my area. I want to find another affordable source for both these products locally . Back to the organic garde of the 60s - I found that after several years of growing using organic fertilizers & the additions of these two products my plants were so healthy I seldom had bugs. They would go to neighbor's gardens and attack their deficient plants. Your plants can only provide you with nourishment if you provide them with nourishment. The addition of both Rock Phosphate and Granite Dust is a stepping stone to good health IMHO


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RE: Where to find Rock Phosphate for organic fert.

Hooray to msmaggie38! I applaud you for speaking from one's experience and success, rather than being zero-experience-naysayers. Thank you, msmaggie38, for speaking the truth from ACTUAL EXPERIENCE.

You are right, Maggie, that Rock phosphate and Granite dust has important trace elements besides phosphorus and potassium respectively. From the link: http://www.sciencedirect.com/science/article/pii/S0375674209000909

"Some phosphate rocks are rich in selenium ... In this paper 19 trace element concentrations are reported. In decreasing order of mean abundance (mg kg− 1) are: Sr (1117) > Cr (134) > B (76.8) > Zn (65.4) > V (49.2) > U (44.9) > Mo (30.4) > Cd (17.3) > Cu (17.0) > Ni (16.8) > Co (15.4) > As (14.3) > Pb (5.8) > Se (2.4) > Th (2.2) > Sn (0.81) > Sb (0.63) > Tl (0.43) > Ag (0.22)."

*** From Straw: B, or Boron, is at 76.8. Boron deficiency is common in soil, so are copper (Cu) and zinc. From the above values, strontium (Sr) and chromium (Cr) are also high in rock phosphate.

According to wiki.answers.com, granite dust is composed of "Oxygen, silicon, aluminum, iron, magnesium, potassium, calcium, sodium, and smaller amounts of others.".

According to gardensalive.com, "Granite dust, for instance, contains lots of potassium��"the K in the NPK fertilizer ratio. Rock phosphate, a ‘single dust’ that’s available in packages at most garden centers, just supplies phosphorus. But ground basalt (pronounced “ba-salt”) contains a nicer mix��"phosphorus, potassium, calcium, magnesium and iron.

**** From Straw: The below link has NPK values of organic materials. NPK of rock phosphate is 0-3-0, but it contains 11 trace elements !! Crushed granite, has NPK of 0-0-5, with 67% silicas and 19 trace minerals. Slow release over a long period of time. Silica is known to strengthen plant's cell-wall, and potassium silicate is tested effective against black spots. So, Maggie, you are right about trace elements to defend plants against bugs & diseases.

One of the reasons for naysayers is that rock phosphate is NOT utilized nor available at soil pH above 7. So for those with alkaline soil like mine, neither rock phosphate nor bone meal can be utilized, according to U. of Colorado Extension.

But I use bone meal anyway, thanks to the rain here, pH of rain is 5.6, compared to my soil pH of 7.7. Bone meal also has many trace elements which enhance the color of my roses.

Here is a link that might be useful: NPK chart of Organic fertilizers

This post was edited by Strawberryhill on Thu, May 15, 14 at 10:18


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