Im studying the inorganic forms of phosphorus in soils amended with cattle manure.
We used the Chang Jackson (1957) fractionation scheme which sequentially extracs phosphorus with NH4Cl, NH4F, NaOH, DCB and H2SO4 solutions.
And need more information about the forms, importance and lability of phosphorus extractable by the NH4F and NaOH solutions.
Thank you.
See following publication on Sequential Phosphorus Extraction of a 33P-Labeled Oxisol under Contrasting Agricultural Systems
http://ciat-library.ciat.cgiar.org/articulos_ciat/2002-5.pdf
I also just found this article which is very helpful in this subject.
https://link.springer.com/article/10.1007/s10705-017-9830-5
Which extractant will extract more P, NaOH or NH4F..and why..??
I think it depends on the quantity and sorbing strength of soil clay minerals. If there is more Al minerals it would be NH4F, but if Fe mineral are predomiant then NaOH will extract more.
In my current study, initially soil had more P in NaOH extract but after adding fertilizer, the NH4F extracted more P. Although iron oxides has more sorbing strength than Al oxides, there is more Al than Fe.
Look at the more recent literature literature: it is mistaken to believe that the sequential extraction removes chemically distinct P-fractions - they are simply operationally defined fractions.
Sequential P fractionation scheme can be fractioned both inorganic and organic water soluble P, Labile (NaHCO3) extractable Pi and Po, Mineralisable ( NaOH) extractable Pi and Po, Resistant ( HCl) extractable Pi and Po and finally residual P.
Interesting question by Mr. Lucas and good discussion by colleagues and friends.I agree with Dr.Milham that the P fractionation is emperical in nature but it is based on good use of chemistry especially P solubility in diverse extractants(again selected or conceived based on chemistry).Inorganic P fractionation has long history and is at least 110 years old.Based on first 50 years of work on P fractionation in the last century (at least 10 eminent scientists worked),Chang and Jackson proposed inorganic P fractionation in 1957.With some modifications especially by Petersen and Corey(1966) the fractionation scheme was widely used through out the world in the last 60 years.Though the extractants were selective to extract a particular P fraction there were overlaps,overestimations etc. of some fractions like Al-P and Fe-P.Estimation of reductant soluble P in general and Ca -P in calcareous soils also posed problems.In recent past the Hedley et al.1982 and its modifications attracted scientist's attention.In Hedley fractionation, 0.1M NaOH extracts both Al and Fe-P.Hedley fractionation does not estimate reductant soluble P.With Hedley fractionation one can estimate both inorganic and organic P fractions of interest.There are two more important developments in the recent past-further extension of Chang and Jackson fractionation to estimate different species of Ca-P in calcareous soils and new methods for estimation of organic using 31P NMR technique.
Inorganic phosphorus fractions and phosphorus availability in a calcareous soil receiving 21-year superphosphate application by Jun Wang et al (2010 ) Pedosphere 20(3) 304-310 (pdf available on internet)
Soil organic phosphorus in tropical forests:an assessment of the NaOH-EDTA extractions procedure for quantitative analysis by solution 31P NMR spectroscopy
by Turner,B.L(.2008 ) European Journal of Soil Science 5:453-466.(pdf available on internet)
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