How is phosphate adsorbed by calcium carbonate in soils?

Calcium carbonate in calcareous soils reached to 50% of southern part of iraq. So addition of phosphate fertilizers to these soils adsorbed by calcium carbonate > I would like to know by equations ,how calcium adsorbed by calcium carbonate? with best regards

The solubility of phosphate is very dependent of soil pH. In a alkaline calcareous soil the divalent Calcium ion comes into solution with water but the presence of orthophosphate soluble phosphate ion becomes precipitated and insoluble Calcium phosphate apatite mineral.

The insoluble mineral apatite can be solubilized when a neutral or slightly acidic pH is generated. This can be done by sulfuring or applying ammonium sulfate as the nitrogen source. The optimum phosphate availability will be expressed at pH 6.5. At more acidic pH the cations Mn Al and Ferric iron can cause phosphate precipitation.

Mycorrhizal fungi and bacteria such as Bacillus spp. Can aid in the solubilization of insoluble phosphate minerals.

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How is phosphate adsorbed by calcium carbonate in soils?

Calcium carbonate in calcareous soils reached to 50% of southern part of iraq. So addition of phosphate fertilizers to these soils adsorbed by calcium carbonate > I would like to know by equations ,how calcium adsorbed by calcium carbonate? with best regards

The solubility of phosphate is very dependent of soil pH. In a alkaline calcareous soil the divalent Calcium ion comes into solution with water but the presence of orthophosphate soluble phosphate ion becomes precipitated and insoluble Calcium phosphate apatite mineral.

The insoluble mineral apatite can be solubilized when a neutral or slightly acidic pH is generated. This can be done by sulfuring or applying ammonium sulfate as the nitrogen source. The optimum phosphate availability will be expressed at pH 6.5. At more acidic pH the cations Mn Al and Ferric iron can cause phosphate precipitation.

Mycorrhizal fungi and bacteria such as Bacillus spp. Can aid in the solubilization of insoluble phosphate minerals.

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Question is very well answered by Prof. Paul. Such reaction is also observed in Vertisols of Indian SAT climatic conditions.

How much of the Indian subcontinent has a P1 test of less than 20?

I wish to restrict my response to SAT Vertisols. The highest surface area of smectite and/or hydroxides of iron and aluminium with no positive sites play a small role in the adsorption of added negatively charged phosphate ions in Vertisols. This supports the ICRISAT's classical experimental observations on P adsorption and desorption on Vertisols, which clearly indicate that P adsorption is not a major problem in the Vertisols and that all the adsorbed P is easily exchangeable by P 32 and a small amount of P is adsorbed in the non-exchangeable form . ICRISAT (1988) envisaged that CaCO3 could adsorb P because the effective sorption by CaCO3 is not well understood, and P adsorption is not always related to CaCO3 content but to the quality of the CaCO3. The SAT Vertisols contain CaCO3 of both nonpedogenic (NPC) and pedogenic (PC) origin, and both of them effervesce with HCl and cannot be distinguished without examining the soil thin sections under a microscope . During the formation of Vertisols in the SAT environment, NPCs (pedorelict) dissolve, and the soluble Ca2+ ions released from NPCs become precipitated as PC at a pH of approximately 8.2 and may also react with phosphate ions to form Ca-P. Both PC and Ca-P may have the least solubility in the prevailing mild to moderately alkaline pH conditions of Vertisols. This makes it clear why Ca-P in the SAT Vertisols has a dominant share among the other soil P compounds, such as Fe–P and Al–P. Thus less soluble Ca-P causes a very low level of soluble extractable P (< 5mg kg −1 soil) by Olsen's method (ICRISAT 1988).

Naturally, P is an immobile element in the soil compared to N and other nutrients. Moreover, its availability to plants is pH dependent, and has a limited pH range to be available, mostly between 5.5 and 7.0. That means, when a pH of a soil is below 5.5 it may be fixed by oxides and hydroxides of Al and Fe, and in some cases by Mn. This process occurs when the cation exchange sites, mainly Ca are dominated by the cations mentioned above. Conversely, when the pH of a soil is above 7.0, the cation exchange sites are dominated by Ca so that P is fixed or sorbed as calcium phosphate in calcareous soils.

Dear Colleagues

I know these information . but i would like to know mechanism of adsorption by calcium carbonate . I mean crystallization process.If any one of my colleague in soil fertility help us by photos.

I think the following paper useful for your question.

Article Effect Of Common Ions On Phosphorus Sorption And Lability In...

Interesting question and very interesting discussion by learned colleagues.When phosphate is added to soils containing calcium carbonate (in the form of calcite and dolomite) both adsorption/sorption and precipitation reactions occur.The reaction time concentration of Phosphate and the nature of calcite decide the magnitude of both the reactions. One can study the adsortion at low concentrations of phosphate and in short reaction time.The kinetics of phosphate sorption onto calcite are fast ; adsorption complete within 2-3 hours while desorption in less than 0.5h. It also of interest to know whether the adsorbed P is on the surface or entered into/or incorporated into crystal structure/lattice.

The following papers provide some interesting information and more details.

Sorption of phosphate onto calcite;results from batch experiments and surface complexing modeling Helle Uglt So etal Geochimica et Cosmochimica Acta 75(10):2911-2923, 2011.

http://www.sciencedirect.com/science/article/pii/S0016703711001116

Retention of phosphorus on calcite and dolomite on calcite and dolomite:speciation and modeling.Nan Xu et al. RSC Advances 4:35205-35214, 2014.

http://pubs.rsc.org/en/content/articlelanding/2014/ra/c4ra05461j#!divAbstract

The following book has an extensive discussion of phosphorus reactions in soils:

Lindsay, W. L. 2001. Chapter 12. Phosphates, in Chemical Equilibria in Soils. Blackburn Press, Caldwell, NJ, USA. pp. 162-205.

I think that many of your answers will be answered in this chapter. Some of what you are asking deals with chemical reactions with fertilizer materials and dissolution of fertilizer granules in soil.

The following paper available in' open access' Journal provides brief review of the mechanism of P adsorption/retention, the precipitation and crystallization reactions that follow adsorption and the effect of organic matter on P mobility in calcareous soil.Good previous references on the subject are also available.

Phosphorus retention in calcareous soils and the effect of organic matter on its mobility by Ray von Wandruszka Geochemical Transactions7:6 2006

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1483820/pdf/

I think this paper can help you

i am going to write a simple reaction/ Fixation of phosphate in alkaline/calcareous soils.

Phosphates combines with Ca+ ions and Ca or Mg carbonates and form insoluble Ca & Mg phosphates. Reactions as follows.

1. Ca(H2PO4)2 + 2Ca+ ___Reversible_____________ Ca3(PO4)2 + 2H+

in the above reversible reaction the soluble Ca(H2PO4)2 react/adsorbed with 2 Ca and form Insoluble Ca3 (PO4)2 + 2 H released.

2. With CaCO3 (Calcium Carbonate

Ca(H2PO4)2 + 2 CaCO3 ____________ Ca3(PO4)2+ 2CO2+ 2H2O

Thank u very much for your reply and answer Dr.Manzoor Ahmed

Greetings

Welcome Haifa Jasim. My pleasure,,,

please see paper.

Phosphate adsorption mechanisms in oxidic soils: Implications for P-availability to plants☆

Geoderma

Volume 31, Issue 1, August 1983, Pages 57-69

About 30% of the global soils are calcareous having free calcium carbonate. These soils will fizz when exposed to an acid solution based on the acid liberation of carbonate as carbon dioxide. In calcareous soils the excess alkaline reaction insolubilizes Phosphorus as insoluble calcium phosphate which is not available to plants. Phosphorus is most needed for early root development so the application of phosphate needs to be concentrated as starter fertilizer near the developing root systems. To create the needed acidity under the calcareous soil condition the use of sulfur with the phosphate source and the ability to add organic amendment and phosphorus solubilizing bacteria would allow a complete package for addressing the calcareous constraint. Under calcareous soil conditions beside the immobilizing of phosphorus micronutrients such as Zn, Fe, Mn, and Cu are often constrained. The use of seed treatment be employed to provide the critical micronutrients for crop production with very little material needed reducing any potential negative impacts. Since the semi arid and arid condition of most calcareous soils are low in organic matter the use of organic amendment helps address a wide array of soil issues under these conditions. Under the dry conditions the organic material is also important for addressing water dynamics and salinity issues.

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