Dear Ashok kumar

There are different types of organic acids and one possible mechanism to increase the availability of phosphate is through use of phosphate solubilising bacteria (PSB), releasing organic acids such as gluconic acid.

Dear Ashok kumar

There are different types of organic acids and one possible mechanism to increase the availability of phosphate is through use of phosphate solubilising bacteria (PSB), releasing organic acids such as gluconic acid.

Citric acid releases P from calcareous soil fairly effectively.

In addition to citric acid, oxalic, malic, tartaric acids (aliphatic) and some aromatic acids, such as gallic, protocatechuic acids (subunits of tannic acid) would react/chelate strongly with Ca, thus increasing the solubility of Ca-P solid in calcareous soils. Soluble P will be increased as a result.

Oxalic acid has better bonding with calcium. Citric and malic bond preferentially with Al and Fe, hence their importance in Aluminium tolerance strategies.

There are many organic acids that increase the availability of P in soil. Some of them (citric acid, oxalic acid, tartaric acid ) are use for extraction of mobile forms of P from soil.

The introduction of mycorrhizae and P-solubilizing bacteria into soils has been suggested for improving the availability of soil P, but initial enthusiasm for these has waned. Mycorrhizae are important for many plant species when grown in P-deficient soils, but they are much less effective where soil P status is adequate. There has been little success with soil introduction of improved species of mycorrhizae, selected for improved P transfer to the host plant, because of competition from the indigenous population.

Any treatment given to organic sources  , they trigger microbial proliferation to great an extent , and eventually those microbes release different kinds of organic acids ., probably difficult pinpoint one ..the enclosed details provide some insights , for sure....

Mineral Phosphate Solubilization: Concepts and Prospects in Sustainable

Agriculture ,Proc Indian Natn Sci Acad 80 No. 2 June 2014 Spl. Sec. pp. 389-405,DOI: 10.16943/ptinsa/2014/v80i2/55116

Microorganisms play very important role in biogeochemical cycle in soil, which reflects the plant growth and influence t he agri cult ural pr oducti on. Phos phat e s ol ubili zi ng mi cr oor ganis ms ( PS M) are ver y i mport ant t o t he pl ants under phos phor us stress. As we know, Phosphorus is one of the essential  acronutrients, along with nitrogen, required by the plants for their vit al functi ons and survi val. But, t he effi ci ency of phosphati c fertili zers i s very l ow due t o t heir fi xati on i n bot h aci di c and alkaline soils which are predominant in India. Therefore, the inoculation of mineral phosphate solubilizers and other useful microbial inoculants in these soils would play an important role to restore the overall balance of nutrients and health of the soil to sustain it for posterity. The molecular genetics and mechanism of mineral phosphate solubilization and their efficiency in releasing phosphates for plant uptake is seemingly different and varies with microorganisms. Hence, the isolation and characterization of superior strains of mineral phosphate solubilizers to suit different soil types is imperative. These phos phat e-s ol ubili zi ng bact eri a have t he capacit y t o convert t he i ns ol ubl e f or ms of phos phor us i nt o it s s ol ubl e f or m, whi ch ulti mat el y gets avail abl e t o pl ants, a pheno menon oft en referred t o as mi neral phosphat e sol ubilisati on. The combination of chemical fertilizers with this beneficial microorganism is also one of the ways to increase the agricultural yield without loss of nutrients. Moreover, the develop ments of co mmercial bioinoculants will be greatly accepted by far mers and will hel p t o mai nt ai n agri cult ure sust ai nabilit y. The present arti cl e descri bes t he pr ogress of research i n t his area and future insights about use of such biophores in agriculture. The review has highlighted as many 54 species of PSBs releasing a range of oragnic acids like Gluconic, succinic, acetic, glutamic, oxaloacetic, pyruvic, malic, fumaric, alpha-ketoglutaric 2-ketogluconic acid , Tartaric, citric acid etc...worth reading review.....PDF enclosed for further reading..

Citrate is most effective in promoting P release through the chelation of Al in acidic soils, whereas oxalate dominates in

less acidic or calcareous soils