Bray Olsen method for measuring Phosphates & NPK during Soil Analysis

[St. Phatty]

The Bray Olsen method is listed on a soil analysis place that I am asking to "analyze my stuff".

So I had to look it up.

It's related to measuring Phosphates.

When Phosphorus, P, occurs in soil, it is always bound with oxygen. It is way too reactive to be by itself.

The Bray Olsen method is sort of like using Litmus Paper.

Instead of little pieces of paper, you use a solution of molybdate-ascorbic+acid.

It turns different colors according to how much Phosphate there are.

molybdate-ascorbic acid - Google Search

www.google.com

Extractable Phosphorus - Olsen Method

anlab.ucdavis.edu

https://www.tandfonline.com/doi/abs/10.1080/00103629009368377?journalCode=lcss20

"A rapid and simple field test for phosphorus in Olsen and Bray No. 1 extracts of soil"

So get some molybdate-ascorbic+acid solution and you will be 1/6 of the way to figuring out your NPK - Ca Mg Sulfur percentages.

And some people growing flowers do try to give their plants extra Phosphorus, so maybe it's good to have a simple chemical test to measure it.

I barely know what Molybdate is (elemental Molybdenum bound up with Oxygen to make Molybdates, then attached to some other element or Compound ), but these people have an awful big collection ==>

Molybdates | AMERICAN ELEMENTS ®

Molybdates are compounds containing molybdenum oxyanions in which molybdenum has the formal oxidation number of +6, but in general usage the term is often extended to cover any compound containing molybdenum and oxygen. Confusingly, the word “molybdate” is also part of the name of a number of...

www.americanelements.com

 

[Creeperpark]

The fastest way I have found to have the soil tested is by using the local Universities to test the soil. I think I pay about $25 for a complete soil test. I remember in Horticulture class having to do many different applications using nitric acid and other testing methods to measure the number of different nutrients. The bottom line is to let the labs do the testing for the best results.

The Olsen test extracts P using sodium bicarbonate and is the best test to use for situations where soil pH is 7.4 or greater. The Olsen test can be used on more acidic soils in situations where pH is 6.0 or higher. Google

In the sodium bicarbonate test, also known as Olsen P, for high pH soils, the bicarbonate ion removes calcium from the system, solubilizing the calcium phosphates, which are measured as an “index” of available phosphorus. Google

 

[St. Phatty]

I talked to the soil test company yesterday.

They said that though they list the Bray Olsen method in their ad/worksheet, they use something called "inductive coupled plasma", as in,
inductive coupled plasma mass spectrometry.

inductive coupled plasma mass spectrometry soil test - Google Search

So basically they blast the soil with a laser and see what happens.

I miss the old days, like, 1998, when tests were done by a knowledgeable chemist, using an eye-dropper.

I am pretty sure the Bray Olsen method has nothing to do with ICPMS.

I like the idea of finding the right reagent, and then dropping a few drops on an aqueous sample of soil run-off, and determining Phosphorus content, for flowering, according to the COLOR of the test outcome.

 

[Three Berries]

I talked to the soil test company yesterday.

They said that though they list the Bray Olsen method in their ad/worksheet, they use something called "inductive coupled plasma", as in,
inductive coupled plasma mass spectrometry.

inductive coupled plasma mass spectrometry soil test - Google Search

So basically they blast the soil with a laser and see what happens.

I miss the old days, like, 1998, when tests were done by a knowledgeable chemist, using an eye-dropper.

I am pretty sure the Bray Olsen method has nothing to do with ICPMS.

I like the idea of finding the right reagent, and then dropping a few drops on an aqueous sample of soil run-off, and determining Phosphorus content, for flowering, according to the COLOR of the test outcome.

Reminds me of the good old days in the battery factory chem lab....

I just ordered some potassium phosphate to use as a pH up.

 

[bsgospel]

I've seen the Bray Olsen method under-estimates how much P you really have. It was something I saw a long time ago, I'd have to check again.

 

[bsgospel]

I was half right. Bray was one test, Olsen is another; they use both to compensate for underestimation depending on the acidity/alkalinity.

https://www.agronext.iastate.edu/soilfertility/info/ComparisonofMehlich-3OlsenandBray-P1Procedures.pdf

"Extensive research has shown that the Bray-P1 test is reliable on neutral or acid soils but that it tends to underestimate available P on calcareous soils. The Olsen test is more reliable for calcareous soils. Because of this problem, many routine soil testing laboratories often use both methods. and base fertilizer recommendations on one or the other method depending on the pH of the sample"