# Too much Phosphorus



## mnn2501 (Apr 2, 2008)

Ok, so my summer garden was a flop, so I sent off a soil sample to Texas A&M and got back my report, Phosphorus levels are close to 4 times what they should be for a veggie garden. I've been happily composting and adding manure for the last 5 years and amending the clay soil into something that is decent to work with and now I find out that is probably not the best thing I could have done. Hey it's worked elsewhere.

I replaced the soil in one of my raised beds for my fall garden but no way I could afford that in my big garden. I've been googling how I can fix it but only come up with time (as in 4 or 5 years it'll go away on its own). Texas A&M said stop using anything that has Phosphorus and use foliar iron and zinc to counter the effect and in 4 or 5 years the Phosphorous level should drop down to normal.

So far that's all I have found online - anyone have any experience with this, is there anything else I can do?


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## fishhead (Jul 19, 2006)

Two years ago my garden phosphorus tested at 100+ and the recommended was 25. I added a whole bunch of compost and wood ash this spring. The garden seems to be doing okay except the onion crop was disappointing but that may be from lack of watering after the rains stopped.

I just pulled my carrots tonight. I replanted and they were small enough to fit inside a drinking straw the first of August but are now 4" long and 1+" in diameter.

My onions were small and took forever to process for the dryer.

I've got lots of green tomatoes but friends have told me theirs haven't ripened much this season too.


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## Paquebot (May 10, 2002)

Get your cure next January. There's a number of places in your area which have shredded Christmas trees available. That stuff will compost itself and increase your soil nitrogen and potassium. It would take a few years to correct the phosphorus exess but not at the expense of having the plants suffer. It would also add permanent humus to your clay soil.

Martin


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## hillbillytn (Sep 28, 2009)

What was the soil test numbers. Your nutrient is out of balance. You may nead
some K-Mag to bring the potassium and magnesium up.


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## jwal10 (Jun 5, 2010)

Plants only use the amount of phosphate needed, no harm, no foul. Just don't add more for a while....James


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## mnn2501 (Apr 2, 2008)

jwal10 said:


> Plants only use the amount of phosphate needed, no harm, no foul. Just don't add more for a while....James


You didn't see my plants this year. my crop consisted of about 10 tomatoes and about 6 peppers. 
The okra, eggplant, zucchini, watermelon, cantaloupe all died young.


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## Bearfootfarm (Jul 13, 2006)

Were you watering a lot?


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## Heritagefarm (Feb 21, 2010)

Bearfootfarm said:


> Were you watering a lot?


That has nothing to do with phosphorous.

One method to deal with this would be to use more compost that has relatively little phosphorous. It's important to keep track of approximately what amounts of nutrients your compost has. We've had a lot of composted on our farm, so I'm sure something is out of whack right there.


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## Paquebot (May 10, 2002)

mnn2501 said:


> The okra, eggplant, zucchini, watermelon, cantaloupe all died young.


Their demise had nothing to do with excess phosphorus. Also, the excess should not have come from manure since that's the lowest percentage in most manures. If it were just from manure, then your potassium would be virtually off the chart along with the pH. 

Martin


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## frankva (May 21, 2009)

I'd be thinking about another test, even a home version, before getting too drastic.

Maybe send to U of Florida this time?


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## geo in mi (Nov 14, 2008)

The "phosphorus cycle" is a variable set of chemical equations that change with soil conditions, moisture, and organic manner. But basically, there is no goldilocks phosphorus level that you need in your soil--usually only the low P condition is what you have to worry about. The opposite, high P levels are of little concern to most vegetable plant growth--you won't poison them or cause them to die......the plants will take what they need and the rest--if it is in the water soluble form, will percolate into the water stream or runoff into lower levels and foul up the standing water(that's what the worry is about high P levels)

But for the gardener, high P levels should not be too much of a cause of worry, unless your plants show the signs of iron or zinc deficiency that Texas A & M describes in their bulletin--which they should have sent to you in explanation, rather than getting you all worried.....They were right (even though Texas A & M is not nearly so good of an aggie college as Purdue  )--maybe some iron if you are impatient, or if your plants show signs.....

http://aggieturf.tamu.edu/files-2005/phosphorus_Provin.pdf

geo


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## mnn2501 (Apr 2, 2008)

geo in mi said:


> But for the gardener, high P levels should not be too much of a cause of worry, unless your plants show the signs of iron or zinc deficiency that Texas A & M describes in their bulletin--which they should have sent to you in explanation,
> 
> http://aggieturf.tamu.edu/files-2005/phosphorus_Provin.pdf
> 
> geo


That's the one they sent me, which is why I mentioned foliar zinc and iron in my OP


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## mnn2501 (Apr 2, 2008)

Bearfootfarm said:


> Were you watering a lot?


This is Texas, so yes, summer time you have to water a lot, although I do have a drip irrigation system.

Reason I believe Phosphorous is the reason (beside the soil test report that states it is) is when I replaced the dirt in in my raised bed (which originally had the same dirt), you should see my fall garden taking off. Just can't afford to do that in my big garden.


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## oneokie (Aug 14, 2009)

Plant legumes and grains in a rotation. Legumes require a certain amout of P to grow. Both require P to produce seed. If you have the typical north Texas blackland soil, your P is not going anywhere but into whatever grows on it.


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## Bearfootfarm (Jul 13, 2006)

> That has nothing to do with phosphorous.


It can if there is Phosphorus in the groundwater.

Phosphorus in water: The USGS Water Science School


> Phosphorus gets into water in both urban and agricultural settings. Phosphorus tends to attach to soil particles and, thus, moves into surface-water bodies from runoff.
> 
> A USGS study on Cape Cod, Massachusetts showed that *phosphorus can also migrate with ground-water flows*.
> 
> Since groundwater often discharges into surface water, such as through streambanks into rivers, *there is a concern about phosphorus concentrations in ground water* affecting the water quality of surface water.


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## Paquebot (May 10, 2002)

Repeat, excess phosphorus would not cause the death of the vegetables mentioned. Instead, there should have been excess foliage. Of those mentioned, okra is the most adaptable to adverse soil and nutrient conditions and should have been the last thing standing. Extra phosphorus in lakes is the prime reason for rampant pondweed growth. Also, groundwater migration would not be a factor in a dry area which relies on a lot of irrigation to grow crops or vegetables.

Martin


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## Cabin Fever (May 10, 2002)

Would you mind sharing the phosphorus concentration the lab found? As a soil scientist, I am in the "excess P is not that bad" crowd. Excess P within reason that is. Excessively high concentrations can result in deficiencies of other nutrients, but that has to be REALLY high concentrations.


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## geo in mi (Nov 14, 2008)

mnn2501 said:


> That's the one they sent me, which is why I mentioned foliar zinc and iron in my OP


So, a key question would be: were the plants stunted and did they show the symptoms of yellowing or greying? If so, then the answer would be that the high phosphorus level caused deficiency or iron and/or zinc, and that was the cause of death. If no.....then you would have to go through a new diagnostic process, which would consist of a whole lot of new questions. 

Some questions come to my mind: manure source and compost source, any possibility of weed killer contamination or nitrogen burning..
Possibility that roots couldn't anchor in the mix and died from air pockets of dryness and looseness.. 
Drainage thru clay soil not enough to get rid of excess soluble P which caused a huge buildup.
Root nematodes or grubs.
Drip irrigation not actually getting to--or, the opposite, making the soil too wet.

But I won't be any more of a back seat driver than that.

geo


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## mnn2501 (Apr 2, 2008)

geo in mi said:


> So, a key question would be: were the plants stunted and did they show the symptoms of yellowing or greying? If so, then the answer would be that the high phosphorus level caused deficiency or iron and/or zinc, and that was the cause of death.


yes to all the above - stunted, some were yellowish and some were grey.

So yes, using foliar zinc and iron probably would have saved them. will do so next year.


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## mnn2501 (Apr 2, 2008)

Cabin Fever said:


> Would you mind sharing the phosphorus concentration the lab found? As a soil scientist, I am in the "excess P is not that bad" crowd. Excess P within reason that is. Excessively high concentrations can result in deficiencies of other nutrients, but that has to be REALLY high concentrations.


When I get home tonight I will. But yes that was Texas A&M said " Excessively high concentrations can result in deficiencies of other nutrients in plants"


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## fishhead (Jul 19, 2006)

Could you tie up the extra P by adding a mineral like Ca?


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## Cabin Fever (May 10, 2002)

fishhead said:


> Could you tie up the extra P by adding a mineral like Ca?


It all depends on soil pH. In alkaline soils, Ca and Mg will tie up P. In acid soils, Al and Fe will tie it up. Phosphorus is most available in neutral soils.


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## frankva (May 21, 2009)

Say he ties it up. Does it then just sit there, or will it continue to leach from the soil in it's "tied up" form?


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## imthedude (Jun 7, 2011)

forgive me for maybe oversimplifying this, but i now have two questions on the topic of P:

if you have a lot of P, then wouldn't you have extra bloomset instead of death?

if you do feel that the P contributed to the death of your plants somehow, can't you simply incorporate the needed iron and zinc into the soil this fall and again in the spring to allow time for blending into the soil making them available for uptake by the plants next spring?


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## Cabin Fever (May 10, 2002)

frankva said:


> Say he ties it up. Does it then just sit there, or will it continue to leach from the soil in it's "tied up" form?


Since it is "tied up," it does not leach. Almost all P is tied up once it's in soil. My old fertility profs said the phosphorus fertilizer you apply is put "in the bank" and the plants are provided only "the interest." In other words, the soil banks the phosphorus and it only becomes slowly available to the plants with time.


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## geo in mi (Nov 14, 2008)

imthedude said:


> forgive me for maybe oversimplifying this, but i now have two questions on the topic of P:
> 
> if you have a lot of P, then wouldn't you have extra bloomset instead of death?
> 
> if you do feel that the P contributed to the death of your plants somehow, can't you simply incorporate the needed iron and zinc into the soil this fall and again in the spring to allow time for blending into the soil making them available for uptake by the plants next spring?


The plants stunted early, yellowed(interveinal chlorosis), and died early--never got a chance to bloom.

The plants did not die from excess P--they died from iron/zinc deficiencies caused by the excess P........and since the P is too high, then adding zinc or iron will not be effective since the P will tie up the iron/zinc----thus the foilar application. From the Texas A & M bulletin:

"Affected plants need additional
iron and zinc. However,
simply adding iron and zinc to
the soil will not work. Research
shows that soil-applied iron is
rapidly tied up by alkaline soils
and its availability to plants is
limited. Under high phosphorus
conditions, both iron and
zinc are quickly converted to
non-available forms. Foliar iron
and zinc applications, however,
work well. A number of foliar
products are available at retail
stores."

As the P level goes back down--unfortunately slowly--the iron and zinc will become available again. 

This is one of those rare examples of too much compost and manure that concentrated the Phosphorus in the garden soil--not too often that you can kill your plants with kindness. Usually the opposite is true on clay soils, you just can't get enough compost. And maybe the Texas soil in that area is already high in P, hence the bulletin from Texas A & M. Only way to lower the level is to increase the drainage away from the plot or bed so the water soluble P will flow out--or wait until microorganisms slowly eat the P and convert it back into rock phosphates as they existed originally(non-water soluble P and not available to the plants)

The OP did the right thing by getting a soil test and heeding the advice of the local experts...
My feeling is that OP won't have to wait for fully five years, though--the condition came on this year after five years of manure/compost application--maybe a year's wait will bring it down to a reasonable level as before all this began....

geo


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## mnn2501 (Apr 2, 2008)

Here are the test results:


> pH = 7.3
> Conductivity = 475
> Nitrate -N = 100
> Phosphorus = 206
> ...


And then they gave me this pamphlet http://aggieturf.tamu.edu/files-2005...rus_Provin.pdf

This garden was a one time RV parking area that had 6" of gravel in it. (6+ years ago) the gravel was taken out and dirt (clay soil) from near the house where we put in a patio was used to fill it along with composted: cattle manure, leaves and grass clippings). The garden produced well until this year. The difference this year was I added a mix of 'Natures Helper' commercial soil ammender from Home Depot 
I applied it per package directions adding another (approx).75 cubic feet of composted manure per bag of 'Natures Helper' and tilled it all in as directions said.
Frankly I think I should have stuck with my clay soil, it produced and in hindsight I guess the clay soil is here because it works in this area.

I then added a couple big handfuls (about 60 - 80) worms from a neighbor that raises them(none of which I saw this fall when working the soil, so I assume they died or headed for better soil)

Additional info: This was also the first year for a drip irrigation system in that garden(Texas summer heat requires a lot of watering). I am on 'city' water. This Garden is used mainly for tomatoes and peppers as my summer garden (it always has a couple of 'whatever other plants catches the wife's eye' also)


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## hillbillytn (Sep 28, 2009)

It is not your Phosphorus. It is your Calcium and it's locking up Magnesium and Potassium. You need at least a 10 to 1 ca to mg and 5 to 1 ca to k ratio I think. You need Sulfur to lower ph to.


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## geo in mi (Nov 14, 2008)

Another "bulletin" from OK State concerning use of feedlot manure recommends a STP(soil test Phosphorus) level of 60 as being sufficient for crops. Animal manure applied at a greater rate has more P in it than can be taken off by the crop, and applying it each year causes a buildup (206 in the test....)

http://www.animalwaste.okstate.edu/bmps/f-2249web.pdf

geo


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## hillbillytn (Sep 28, 2009)

Your Soil Conditioner possibly used up the N.


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## hillbillytn (Sep 28, 2009)

I have Phosphorus at 674 ppa. on one garden and plants do fine.


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## geo in mi (Nov 14, 2008)

hillbillytn said:


> I have Phosphorus at 674 ppa. on one garden and plants do fine.


I would be thinking that your value is expressed in total pounds per acre, but not _plant available_ pounds per acre--there is a difference, and the total P can vary widely, depending on soil type, pH levels, moisture, and others.

Offering this as info that may help explain....http://www.ksre.ksu.edu/library/crpsl2/c665.pdf

geo


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## hillbillytn (Sep 28, 2009)

My soil is clay silt. I put 80 yds. composted goat manure on 5000 sq.ft. My test is mehlich 1. I tripled my nutrients with the manure.
ph. 6.5
P 674
K 614
Ca 4662
Mg 597
Zn 18.1
Cu 0
Fe 13
Mn 67
B 2.6
Na 23
S 129.6

I am surprised that I didn't get any Cu and Fe from the manure. I have been testing a lot trying to fix my blueberry field (different field) . It appears to be Ca locking up K and Mg. This is the third year and they look good this year.


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## Paquebot (May 10, 2002)

The Texas figures reflect the pH and NPK of manure. 7.3 is high, as would be when adding something which may be over 8.0 when fresh. P is high but look at the K which is twice as high. Neither are out of line according to the NPK of most barnyard manures which generally have at least twice as much K than P. If anything killed the plants, I'd lay some of the blame on the high K. That's basically salt. And if the water used for irrigation is alkaline, that's almost like applying brine. 

As a general rule, plants have a hard time taking up nutrients in alkaline soil. Rain to alkaline soil is like a fertilizer. Except in rare instances, it is always very acidic. That creates a temporary acidic buffer which allows the plants to use the available nutrients. 

Martin


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## bowdonkey (Oct 6, 2007)

?, does phosphorus move down through the soil ? I read somewhere that calcium doesn't and wonder if phosphorus does the same? Anyway I was in the feed mill yesterday and just had to buy something. So I left with 20 lbs of bonemeal. I was thinking of sprinkling it over the asparagus plants this spring. Will it work as a side dressing for onions and garlic?


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## oneokie (Aug 14, 2009)

bowdonkey said:


> ?, does phosphorus move down through the soil ? I read somewhere that calcium doesn't and wonder if phosphorus does the same? Anyway I was in the feed mill yesterday and just had to buy something. So I left with 20 lbs of bonemeal. I was thinking of sprinkling it over the asparagus plants this spring. Will it work as a side dressing for onions and garlic?


No, Phosphorus is the least mobile of the 3 major nutrients. It has a strong attraction to soil particles.


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## bowdonkey (Oct 6, 2007)

oneokie said:


> No, Phosphorus is the least mobile of the 3 major nutrients. It has a strong attraction to soil particles.


Anyone want to trade a bottle of whiskey for 20# of bonemeal? So what should be used to increase phosphorus on established plants? Maybe a hole can be drilled next to the plant and the bonemeal poured in? Nix the whiskey trade everyone.


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## oneokie (Aug 14, 2009)

Are you asking about garden plants or ???? If garden veggies, yes, drilling a hole close (1") and placing the bone meal would work.

If additional P2O5 is called for in a soil test, the best way to do it is to place it in the seed furrow *under *the seed when planting. By doing so, the first root/s of the plant will not have to grow far before finding the P2O5. The plant roots have to find the P2O5 which is bound to the soil particles.

There are several foliar type fertilizers that have phosphorus in them and are somewhat safe for foliar application.


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## geo in mi (Nov 14, 2008)

bowdonkey said:


> Anyone want to trade a bottle of whiskey for 20# of bonemeal? So what should be used to increase phosphorus on established plants? Maybe a hole can be drilled next to the plant and the bonemeal poured in? Nix the whiskey trade everyone.


Most bagged fertilizers containing phosphorus have the water soluble type that the plants can use. But plants don't need that much, so that's why most lawn fertilizers have eliminated P in them, because over eager lawn keepers keep pouring it on to get the nitrogen boost that makes the grass green and pretty. See this:http://extension.psu.edu/agronomy-guide/cm/sec2/sec28b It's easiest to ask for triple superphosphate.......


geo


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## Paquebot (May 10, 2002)

Triple is as close to a soluble form as one can normally buy. Years ago, that's what I'd use to side-dress onions. Never saw any gain but that was due to later learning that my soil was already high in phosphorus. Don't have any on hand or I'd see if it mixed with water to become close to a liquid. Then it could be knifed in by making a narrow furrow on each side of the row so that it would get a close as possible to the feeder roots.

Martin


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## bowdonkey (Oct 6, 2007)

Thank you everyone, you all rock.


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