Greensand and rock phosphate

Discussion in 'Soils, Fertilizers and Composting' started by johnnyjumpup, Nov 8, 2008.

  1. johnnyjumpup

    johnnyjumpup Active Member

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    Hi,

    I have got my hands on a bag of Jersey Greensand and a bag of rock phosphate. How can I use these to the best advantage? I have neutral soil (hydrangeas bloom pink) that is not clay and not particularly fertile. Lupins, hesperis, daisies, phlox, violets, peonies, rudbeckia, hepatica and iris do well.

    Should I spread it in the fall or is spring better? Can I spread it over lawns (full of botanical crocuses) and already planted perennial beds? The greensand is supposed to improve both heavy and light soils.

    Thanks for any info.
     
  2. Ron B

    Ron B Esteemed Contributor 10 Years of Activity

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    Do not apply sources of significant amounts of phosphorus without sampling your soil and having it analyzed by a soils lab first.

    http://www.puyallup.wsu.edu/~Linda Chalker-Scott/Horticultural Myths_files/Myths/Red leaves.pdf

    http://www.puyallup.wsu.edu/~Linda ...ral Myths_files/Myths/Roses and phosphate.pdf

    The result of phosphate overfertilizing is leaf chlorosis. Phosphorus is known to compete with iron and
    manganese uptake by roots, and deficiencies of these two metal micronutrients causes interveinal
    yellowing. It's my belief that many of the chlorotic shrubs we see in urban landscapes are suffering
    indirect iron (or manganese) deficiency from overapplication of phosphorus. Moreover, it has been
    experimentally demonstrated that high levels of phosphorus are detrimental to mycorrhizal health and
    lower the rate of mycorrhizal infection of root systems. This mutually beneficial relationship between the
    fungus and the plant roots allows the plant to more effectively explore the soil environment and extract
    needed nutrients. In the absence of mycorrhizae, the plant must expend more energy growing additional
    roots and root hairs to accomplish the same task


    http://www.puyallup.wsu.edu/~Linda Chalker-Scott/Horticultural Myths_files/Myths/Phosphate.pdf
     
  3. johnnyjumpup

    johnnyjumpup Active Member

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    OK, thanks for the info on the rock phosphate. What about greensand?
     
  4. jimmyq

    jimmyq Well-Known Member 10 Years of Activity

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    same answer, you cannot medicate without proper diagnosis. If you dump minerals on your plants and they dont need them,you can cause more problems than you solve.
    Only a soil test will tell you the proper amount of minerals to add to your planted areas to help your plants.
     
  5. johnnyjumpup

    johnnyjumpup Active Member

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    Thanks for the info.

    I have a CIL soil test kit, not expensive, that will test for pH, nitrogen, phosphorus and potash. Is this adequate and reliable enough? If not where would I send a soil sample to be tested in BC? I live in the West Kootenays. I think there is a research station in Summerland in the Okanagan but don't know the address or if there is one in the Kootenays.
     
  6. greengarden bev

    greengarden bev Active Member

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    It's frustrating to hear the "get a soil test" message when you just want to fertilize your garden and do no harm.

    You CAN use the greensand and rock phosphate to make a nice balanced pre-plant for your soil, but you'll need to do some homework. I would advise to NOT use the greensand and the rock phos on their own. Make a mix-- the result will be a mild, balanced mix that will do no harm if applied appropriately.

    You'll need to have a set of scales handy, and you'll need to find a Nitrogen component for your mix. You've got the P and the K. The greensand is probably about 3% K and the rock phosphate (if it's the "soft" calphos stuff) is about 2%. You should check the label and the supplier for these numbers.

    Both of mineral-based amendments are "slow release"-- they break down slowly through the action of soil micro-organisms and natural "weathering" processes. So if your soil is not already fairly healthy and biologically active, then these materials will be very slow. Not a bad thing, but you need to be patient when you're building soil health.

    The important thing to remember is that the percentages on fertilizers are BY WEIGHT. That means 100 lbs of greensand will provide ~3 lbs of K, and 100 lbs of calphos will provide 2 lbs of P.

    To determine how much fertilizer you need on your garden (the lbs per sq ft) will involve some homework. It depends on what you're growing (lawn? beans? potatoes?) and the existing level of fertility. Here's where a soil test helps. Normally it is the amount of N that is critical, but, again, you'll need to research this. For lawns, N-application rates range from 1 to 4 lbs of N per 1,000 sq feet, per year. For veggies, it depends on the variety. Some are heavy feeders (4+ lbs N per 1000 sq ft) and some aren't. Homework...

    You'll need to set up a spreadsheet to do some calculations to tell you how many pounds of N, P and K you get per lb of your raw ingredient. You can tinker with the weights to arrive at a mix that suits your needs. Your goal is something where the P and K are roughly equal, and the N is no more than double the P & K values. This is just a general guide-- if your soil has a severe deficiency as indicated by a soil test, then you'll need to increase the percentage of the elements lacking.

    Anyway, with organic amendments, the potency is so low that it is nearly impossible to hurt your soil, so long as the mix is balanced in terms of NPK, and you don't overdo the application rate.

    I've attached a spreadsheet that has the formulas already entered. It was created in OpenOffice and converted to .xls, so I hope everything is still intact.

    I hope this is helpful. If the spreadsheet is confusing, let me know and I can add some instructions. I'm a little wary of making this too quick-and-easy, because you really need to understand how things work. It's not the usual "feed and forget" that the chem-pushers like to promote.

    Good luck.

    - Bev
     
  7. Ron B

    Ron B Esteemed Contributor 10 Years of Activity

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    Either a given soil needs a boost of a particular nutrient or it does not. Excess phosphorus in home gardens is not a rarity, if a product supplying a low amount happens to be enough to push it over into toxicity then the result is liable to be the same as if a toxic amount was applied all at once.
     
  8. greengarden bev

    greengarden bev Active Member

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    There is so much scare-mongering from the chem-heads! Simply repeating the "soil test" mantra is NOT helpful. I would like to HELP gardeners use organic methods and materials, not just frustrate them and push them towards soil test labs that will recommend synthetic/non-organic/chemical fertilizers. Soil tests are expensive, full of hassle, and the people who run the labs are trained to understand the chemical paradigm, nothing else.

    From my perspective, soil tests are useful for gardeners only if you: 1) are a new property owner; 2) are moving from chem to organic, or 3) have concerns about existing toxicity (previous industrial uses, brownfields, etc).

    For conventional (non-organic) commercial growers, on the other hand, regular soil tests are absolutely necessary, considering the huge and increasing cost of fertilizer inputs, and the low cost of tests relative to the cost of production.

    But this is not JohnnyJumpup's situation. He's a gardener with a couple of bags of natural fertilizers, and he has low fertility soil.

    He has a bag of "rock phosphate". I'm assuming this is colloidal or "soft" rock phosphate, not "hard rock" (which is pretty much useless) and not superphosphate or any such high-potency, "fast food" type. I'm assuming this because he also has a bag of greensand, which is something that organic or natural gardeners would use.

    I started to write a bunch of stuff about how soft rock phos is different (and less potentially "toxic") than the other stuff. But that just got too long. Google is your friend.

    The P requirements for garden vegetables range from 1 lb per 1000 sq ft (greens etc) to 4 lbs per 1000 sq ft (potatoes). A single 40 lb bag of colloidal (soft) rock phosphate would supply only 1.2 pounds of P. So even if JohnnyJumpUp applied the entire bag to a 1,000 sq ft area, he would still be applying near the minimum, assuming he is planting annual vegetables.

    Anyways, Johnny, good luck.
     
  9. Ron B

    Ron B Esteemed Contributor 10 Years of Activity

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    >There is so much scare-mongering from the chem-heads!<

    I seldom use garden chemicals, including fertilizer.
     
  10. jimmyq

    jimmyq Well-Known Member 10 Years of Activity

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    Ditto.
    I have done a handful of reportrs that I have suggested fertilizer application, from the soil test results.
    I have worked many years in the garden centers and attempted to answer each question to the best of my knowledge or the knowledge available to me. Recommending diagnosis before treatment is not scare mongering it is the use of intelligent data in order to decide the best treatment. The treatment options can be many or few. Without knowing the problem, you can't fix it except by chance.

    If there is no need for data collection prior to treatment why do we do any research on cause and effect of mineral application within the plant kingdom. Why is it so hard to spend $5 for a really basic soil test before you spend $10 on a fertilizer blend that may have NOTHING to do with your soil mineral deficiency? I have never insisted that someone has to go to a lab to get a full profile of their soil, that is obviously overkill for most people's home gardens (while it may be helpful to the avid gardener to do so every 5 years or so just to see whats happening). There are a number of basic soil test kits available from $5 or so up to about $50 at most of the local garden centers. Some are single test and some provide multiple tests.

    On a side note, the last consulting job I did where a hedge was dying/dead that was installed about 6 months ago, my client (the homeowner) asked me to run the full soil test at the lab. I did so and it came back reading a severe excess of phosphorous and a pH of 8.4. Good thing the landscaper that installed them kept telling me how he had practically buried the rootballs in bone meal since that what the guy at the nursery told him to do. On this 20 thousand dollar installation he paid out about $3500 to rectify the damages. A $65 soil test at the inception would have given him at least a rough idea of overall site conditions.

    anyhoo, just my 2 cents worth.
     
  11. greengarden bev

    greengarden bev Active Member

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    Sheesh!

    The original poster did not ask for diagnosis. Diagnosis presumes some kind of sickness or problem. He did not mention any. He simply has two bags of organic amendments that he wants to use effectively. He wants to learn about soil and fertility. He's already got the bags of stuff-- its not a question of wasting additional money.

    I repeat myself-- your "leave it to the experts" responses are not helpful, and they did not answer his question. You just ignored his question and said "get a soil test" and "its dangerous to self-medicate". Well, in some situations, I would agree that is true.

    But not in his particular situation.

    re: why not spend $5.00 on a soil test kit before you spend $10.00 on fertilizer. Okay, you have a point. But I've not seen a $5.00 kit that will give you anything more than a basic pH analysis. The comprehensive tests are the expensive ones.

    The whole illness/diagnosis/prescription model is what they teach in hort school. This is a great way to keep landscape techs and designers in business. The chemical paradigm exists to sell chemical inputs and "remedies". The doctor/patient overtones just reinforce the quick-fix, pill-popping, consumer model of gardening that, IMO, won't end soon enough. It'll end pretty soon, but that's another post.

    Jimmyq, you sound like a more responsible (I almost said "less reprehensible") representative of the hort industry, in that you don't always push stuff on hapless gardeners. But be aware that what you're giving is the industry perspective, and the industry has been running the show-- quite badly-- for a long time.

    There are other perspectives out there. Just as I have to tolerate non-organic trolls in the organic gardening forum, I guess you'll need to tolerate my non-industry viewpoint here.

    I am not an opponent of science. I am an opponent of science used to push chemicals and the chemical paradigm in gardening and agriculture. We can "do science": collect data, make hypotheses, devise experiments, and eventually generate knowledge. The organizations that can afford to pay for the researchers and trials and experiments are very rich and powerful. They influence who gets funded and what gets researched. They generally own most of the ag schools in Canada, and they influence what is taught in the college hort programs.

    So forgive me for being suspicious of people crying "do science!" "do science!" at gardeners who wouldn't know what to do with a soil test result unless it came from NuGrow and had tidy recommendations for X number of bags of their particular brand of fertilizer.

    I would like to see less people following industry experts and more people learning by doing. Observing their own gardens. Reading. Thinking on their own. Talking to experienced gardeners who remember how gardening and farming were done before the conglomerates and chemists took over.

    re: stupid landscaper. I would suggest that a soil test would not have given the landscaper any additional intelligence and knowledge to prevent him from from ruining the hedge planting. Hiring a knowledgeable gardener to do the job might have.
     

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