97-99% of the total P in the soil are in plant unavailable form, which may be either in the form of unavailable inorganic P like Ca-P, Fe-P, Al-P or in the form of unavailable organic P like Phytin, lecithin, glycerophosphates etc. Microorganisms solubilize unavailable inorganic P after releasing/producing organic acids that are dissolving Ca, Fe or Al bond. Sometimes same microorganisms also releasing/producing phosphatases and phytase enzymes which are mobilizing organic P after breaking the C-O-P ester bond. My question is where they spent/need more energy during mobilization or during solubilization. Why some organisms inclined to mobilize organic P and some like to solubilize inorganic P?
As I understand there are two distinct mechanisms for converting insoluble P to soluble one-acid or proton action on inorganic phase, Fe-,Al -and Ca-P and hydrolyzing by enzymes of the organic compounds.The protons or H ions may be produced in soil by acid forming fertilizers,during nitrification, organic acid secretion by roots and by microbes during organic matter decomposition.The phosphatases,phytases may be also of plant or microbial origin.The energy requirements for enzyme synthesis may be more than simple hydrolysis.Adjusting soil reaction may be more convenient mechanism for P solubilization. Can we think that the the phophatases are more useful for microbes for P mobilization for their own use rather than plant needs?Are the enzymes of plant root origin(exudates) are more beneficial or the microbial origin?Which are more abundant in soil?
one could think on making a balance of thermodynamic value of the different compounds and processes involved in the P cycle. Theoretical this balance must be equalized otherwise life on this planet would be doomed. Check out RG for "The Enigma of Fertilizer Phosphorus Utilization"
Dr. Rao, microbial origin enzymes are more active therefore more beneficial than plant origin enzymes. In case of phosphatases plants can only release acid phosphatase but microbes can release both acid and alkaline phosphatases. Obviously the microbial enzymes are more abundant in soils.
Dr.Tarafdar,I compliment you for good information.But I think the microbial contribution also depends on regular input of fresh organic matter to soil and favourable moisture and temperature regimes.
Yes, you are very right, they need favorable soil condition and compatible environment to grow.
I am yet to get answer why some organisms more prefer to mobilize organic P than stabilization of Inorganic P when they have the potential of both the activities?
Dr. Tarafdar, do plants and microbes release equal amounts of enzymes?
I opine that volume of enzymes secreted by plants is much higher than that by microbes.
No, in general, enzymes secreted by microbes are much higher than the plant contribution.
interesting question, I googled it who brought me here. still looking for an answer
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