PHOSPHATE MOBILIZATION & PHOSPHATE SOLUBILIZATION.pptx

Introduction and Mechanism of Phosphate mobilization & Phosphate solubilization

1. SUBJECT TITLE: ORGANIC FARMING AND BIOFERTILIZER TECHNOLOGY SUBJECT CODE: VMBSE31 Presented by, S.SHAMILY , II M.Sc Microbiology , PG & Research Department of Microbiology Sri Paramakalyani College Alwarkurichi - 627412 TITLE : MECHANISM OF PHOSPHATE MOBILIZATION AND PHOSPHATE SOLUBILIZATION SUBMITTED TO, Dr. S. VISWANATHAN, MSc, Ph.D., HEAD AND ASSOCIATE PROFESSOR, PG & RESEARCH DEPARTMENT OF MICROBIOLOGY SRI PARAMAKALYANI COLLEGE ALWARKURICHI- 627412

2. Phosphate mobilization is defined as the process by which soil Microorganisms or plant root release and transfer bound or absorbed Phosphorus from the soil particles into the soil solution , making it available for plant uptake. It is mainly carried out by phosphate-mobilizing microorganisms (PMMs) like: Bacteria (e.g., Bacillus, Pseudomonas, Rhizobium) Fungi (e.g., Aspergillus , Penicillium ) Actinomycetes and Arbuscular Mycorrhizal Fungi (AMF) PHOSPHATE MOBILIZATION

3. What’s the Need for Phosphate Mobilization ? Although phosphorus is the second most essential macronutrient after nitrogen, only 10-20% of total soil phosphorus is available to plants. The remaining is locked in: → Insoluble inorganic forms (like tricalcium phosphate, iron, or aluminum phosphate) → Organic forms ( phytate , nucleic acids, phospholipids, etc.) Thus, mobilization is crucial for making this phosphorus accessible for plant uptake.

4. Mechanism : 1. Organic Acid Production : Microbes secrete organic acids such as: • Citric acid • Oxalic acid • Gluconic acid • Lactic acid. These acids are helps to Lower the soil pH, and Chelate metal cations (Ca2+, Fe3+, Al3+) bound to phosphate. This releases phosphate ions (H2PO4, HPO42-) into the soil solution. 2. Enzymatic Mineralization of Organic Phosphorus : Microbes release enzymes like: Phosphatases (acid & alkaline) Phytases . These enzymes break down organic P compounds (like phytate or nucleic acids) into inorganic phosphate that plants can absorb.

5. 3. Siderophore Production: Some microbes secrete siderophores (iron-binding molecules). They bind Fe3+ ions tightly, reducing the Fe-phosphate complexes and freeing phosphate ions. 4. Proton Extrusion : Certain bacteria and fungi release H+ ions during metabolism, acidifying their surroundings. This low pH environment helps solubilize phosphate minerals.

6. IMPROVES CROP GROWTH AND YIELD IMPROVES RESISTANCE OF CROP PLANTS AGAINST DISEASE AND STRESS CONDITION REDUCE THE USE OF CHEMICAL FERTILIZER SECRETION OF GROWTH HORMONES TO INCREASE CROP PRODUCTIVITY INCREASE FLOWER DEVELOPMENT AND FRUIT SETTING

7. PHOSPHATE SOLUBILIZATION Phosphate solubilization is a biological process in which insoluble forms of phosphorus (P) present in soil are converted into soluble and plant-available forms (mainly orthophosphates such as H2PO4 and HPO4²–) by phosphate-solubilizing microorganisms (PSMs) - mainly bacteria and fungi. Although phosphorus is the second most important macronutrient after nitrogen for plants. A large portion of soil phosphorus exists in insoluble mineral forms. These forms cannot be directly absorbed by plants, so solubilization is essential.

8. Microorganisms involved : Phosphate solubilization is mainly carried out by Phosphate Solubilizing Microorganisms(PSMs),including: » Bacteria - Pseudomonas,Bacillus,Rhizobium,Azotobacter,Burkholderia » Fungi - Aspergillus niger , Penicillium spp , Trichoderma harzianum These organisms live freely in the rhizosphere or form symbiotic relationships with plant roots.

9. Mechanism : Production of Organic Acids : The main mechanism used by PSMs is the production of organic acids such as; – Gluconic acid – Citric acid – Lactic acid – Oxalic acid – Malic acid These acids perform two main actions: Acidification: They lower the pH around the phosphate mineral. Chelation: They form complexes with cations like Ca2+, Fe3+, and Al3+ - releasing soluble phosphate ions . 2. Enzyme Production : Some microorganisms release phosphatases and phytases enzymes that hydrolyze organic phosphorus compounds (like phytate ) into inorganic phosphate. Important enzymes are ; • Acid phosphatase • Alkaline phosphatase • Phytase

10. 3.Proton Extrusion: ›Certain bacteria release protons (H+) during ammonium assimilation or respiration. ›Which helps dissolve phosphate minerals by reducing pH. 4. Carbon Dioxide Production : – CO₂ released during microbial respiration reacts with water to form carbonic acid (H₂CO₃). – W hich helps in dissolving phosphate minerals. CO2 + H2O → H2CO3

11. The Greedy Farmer and the Dying Land Once, there was a farmer who wanted quick profits. He used chemical fertilizers and pesticides every season. His crops grew fast and large, but after a few years, his land became dry and lifeless. One day, an old farmer told him, "The earth is like a mother - if you only take and never give back, she becomes weak.“He decided to change. He started using compost, cow dung, and natural manure. Slowly, the soil became fertile again, earthworms returned, and his crops were healthy without chemicals. Moral: If we care for nature, nature will care for us. MORAL STORY

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