Since soil that is actually low in P is quite rare, I'll assume for purposes of discussion that these tests are professional-done lab soil tests since that is the only way to get any legit results. If so then I would assume the lab provided you with recommendations for what and how much to use. If these are NOT professionally done tests then make no changes based on the results since they are notorious for being very inaccurate.

The soil pH will determine which, if any, supplement will work best and the actual reading on the P will determine which is best to use for fastest results. And if the soil pH is corrected - which is much easier to do - then no P supplement may be needed as the odds are the P is there just locked up by the pH.

So you basically have 4 options - bone meal, rock phosphate, or a balanced granular fertilizer such as 10-10-10 or 13-13-13. Bone meal works well but takes time (9-12 months) but it also lasts a long time. Rock phosphate works well and only the pH problems restricts how well or how fast. Fix the pH and the rock phosphate, if still needed, works quickly.

The granular ferts are a quick fix for the P but have the side effects of potential excess N and K depending on what your soil tests show for those. They also need to be re-applied regularly and more frequently than the other two.

A 4th option is compost, preferably manured compost as it not only addresses the pH issue but fixes the nutrient issues IF this is an in ground bed with an active soil food web.

Hope this helps some.

Dave

These were professional tests.

So, would low PH actually affect the RESULTS?

I thought it only affected the availability of nutrients.

For low acidity, phosphorus tends to form phosphates with calcium which are soluble. For high acidity (low pH), phosphorus grabs aluminum, the phosphate of which is pretty insoluble. When dissolved, PO4- ions are made available, and that's what plants use. So acidity indeed determines the availability of phosphorous to plants.

That being said, a soil analysis of phosphorus is, I presume, going to measure all the phosphorus, wherever it might be. So if you somehow don't have much phosphorus, changing the pH is probably not going to help a lot.

As Dave said, you ought to heed the recommendations of the lab, because it really depends on what exactly they measured and found deficient.

They recommended triple superphosphate, but I read it doesn't last more than a few months.

would monoammonium phosphate be better?

I'm certainly not an expert at phosphorus chemistry, but I always understood that when you add any phosphates to soil the phosphorus quickly gets "fixed". As in, it binds to calcium in alkaline regions, or aluminum or iron in acidic regions, and doesn't "last" in the plant-usable form. So the phosphorus doesn't go away at all, but just gets latched up in a plant-unusable form. At that point, the art becomes pushing the pH toward neutral. That will gradually release the phosphorous as phosphates. Be careful about spreading the phosphorous amendment uniformly. I understand that when it gets fixed, it becomes highly immobile. As in, if untilled, it'll move less than an inch a year.

So your issue may be BOTH a chemical lack of phosphorus and acidic soil. That is, just throwing a lot of phosphates on your soil isn't in itself a good long-term solution.

Good points Gary. It's Mehlich-3 and of the P tests: Bray 1-P, Olsen, or Mehlich-3 the Mehlich-3 extraction method is thought to be least affected by pH of the soil. The only point in this that OP needs to note is to keep testing at the same lab or lab that runs the same method for future testing.

Since Hairmetal didn't reveal other fertility results the lab recommendation ( by computer) is best followed. Odds are that if pH is low so are Ca & Mg and those elements also need to be addressed through liming. Often, depending on the crop, the recommendation might include preplant broadcasting of a fertilizer like Triple Superphosphate as well as band dribble in planting row of a high P mix such as 10-20-10. Many agricultural recommendations will include that seeding P recommendation regardless of soil test P results.

Thanks, all!

The more research I do, the more confused I get...that P isn't water soluble, so topdressing is useless...yet there are liquid fertilizers w/P in them...aargh!!

Liquids work fast, but are much harder to apply in a larger (40' X 40') scenario in sufficient quantities to do any good. Yet there are seaweed and fish fertilizers (liquid) that contain P...so?

Maybe I work in the triple superphosphate at planting, and if it appears to be needed later, use the liquid?

Here's one of the tests.

Soil is basically silt loam. Organic matter is 4.1%.

I initially thought I had clay, but it's only clay against the front and side of the house, which I think is probably fill or upturned subsoil. The "true" soil farther from the house is actually a silty loam with good tilth.

BTW, while diammonium phosphate has an appeal for being long-lasting and providing a neutralizing effect in acid soils...It appears to be all but unavailable, even online, unless I order from overseas. Is it even legal?

Got a pic of the area that you took it from? I'm curious. Also where's the N reading?>

From the test, it looks like the calcium is very low too. Phosphorus needs to be banded in the row close to the seed, but not against it. The CEC is low meaning there is much in the soil to hold nutrients.

From the test, it looks like the calcium is low too.....in relation to the magnesium. Phosphorus needs to be banded in the row close to the seed, but not against it. The CEC is low meaning there is not so much in the soil to hold nutrients.