Role of microorganisms Microorganisms play a vital role in the cultivation of field peas. -1.pptx

Microorganisms play a vital role in the cultivation of field peas. Rhizobium bacteria form symbiotic relationships with the plant's roots, fixing atmospheric nitrogen into a form that the plant can use, enhancing soil fertility. This natural process reduces the need for synthetic fertilizers and supports sustainable agriculture. Additionally, beneficial soil microbes help in nutrient cycling and disease suppression, promoting healthier plant growth.

1. TOPIC Assistant Professor Mr. B.S Cheema By

2. CONTENTS

3. Organic matter and its composition Soil organic matter is a complex matter obtained from the plants and animal residues containing both organic and inorganic chemical compounds. Composition of Organic matter    ORGANIC COMPOUNDS Nitrogenous compounds Ex: Amine, amide compounds and amino acids Non nitrogenous compounds Ex : -Carbohydrates, saccharides , amino sugars, sugar acids, sugar alcohol) B. INORGANIC COMPOUNDS Organic matter contains several inorganic elements such as H, O, N, P, Ca, Mg, S, Na, K, Fe, Al, Mn , Zn, Mo, Si, B, Co, Cl etc. All these are in metallic complex form hence organic matter is water insoluble and do not destroy by leaching.

4. Organic matter Decomposition It is the decaying of organic materials by various groups of microorganisms and enzymes and converted in to simple inorganic elements or compounds. It helps to improve softness of the materials for further mineralization process. It is basically a burning or oxidation process. Two types of decomposition Aerobic decomposition - oxygen is required Anaerobic decomposition - oxygen is not required.

5. Involvement of microorganisms Decomposition is a purely microbial process involves several species of microorganisms. Ex . Bacteria, actinomycetes , fungi, protozoa Supporting organisms are: Insects, worms, rodents, termite, ants All the soil organic matter is not decomposed by the same group of microorganisms. At different stages of decomposition different species of microorganisms enter into the degradation process. As the degradation proceeds newer materials are synthesized by soil microorganisms.

6. Enzymes in decomposition  Cellulase - breaks cellulose Urease –  breaks urea {CO(NH2)2 } to CO2 and NH4 Phosphatase  breaks humus –O-P-(OH) 2 bond to produce humus, OH & H3PO4 Sulfatase - breaks the humus O-S-OH bond to produce humus, OH & H2SO4 Protease –  breaks bond linking two amino acids to separate amino acids

7. Process of organic matter decomposition Decomposition processes Two major decomposition processes involved 1.Mineralization 2.Immobilization 1. Mineralization  The conversion of an element from organic form to an inorganic/mineral form is called mineralization. Mineralization occurs for each element present in the organic matter individually especially for N, P and S 2. Immobilization The conversion of an element from the inorganic to the organic form in microbial tissues or in plant tissues, thus rendering the element not readily available to other organisms or to plants.

8. Types of Mineralization A. Nitrogen mineralization: It is the conversion of organic nitrogen into inorganic Nitrogen NH4 and NO3 by microorganisms. Different steps involved in N-mineralization Organic N(proteins and amino acids)  ----------> Proteose ------------>Peptone-------------->Amino compounds- ammonia -----------> nitrite --------> nitrate

9. Types of Mineralization 1. AMINIZATION :  Proteins and other complex nitrogenous compounds are converted into amino acids and amino compounds by the action of enzymes and microorganisms, CO2 and energy is released.

10. Types of Mineralization 2. AMMONIFICATION :  It is the biochemical conversion of amino compounds and amino acids into ammonia by bacterial decomposition. This process is governed by aminase and deaminase enzymes. The liberated NH3 is utilized by plants.

11. 3. NITRIFICATION : It is the biochemical oxidation of ammonia into nitrite and then finally into nitrate. This process carried out by by autotropic bacteria ( Nitrosomanas and Nitrobacter ) in aerobic condition. Two steps are involved Rate of nitrification depends on suitable temperature, humidity, pH, season, aeration, addition of lime (increases), nature of organic matter etc. Types of Mineralization

12. 4. DENITRIFICATION : It is the biochemical reduction of nitrate or nitrite to gaseous nitrogen (N2), either as molecular N or oxides of N. Loss of nitrate by reduction and assimilation Types of Mineralization

13. B. PHOSPHORUS MINERALIZATION The process of conversion of organic forms of P into inorganic forms of P by P decomposing microorganisms especially by micorrhiza species is known as P-mineralization. The organic-P found in organic manures mainly as nucleic acids, phytin , phospho lipids, inositol PO4, lecithin etc. The organic P is not directly available to plants and it has to undergo decomposition by micro organisms especially mycorrhyzal species.   Types of Mineralization

14. C. SULPHUR MINERALIZATION The organic forms of S compounds such as methionine , cystine , cysteine are converted into inorganic sulphate forms (available) by aerobic bacteria species especially Thiobacillus and thiobacter .   Types of Mineralization

15. Rate of decomposition Rate of decomposition varies with the types of organic compounds, some may undergo decomposition very fast and others may very slow. The following is the decreasing order of rate decomposition. Starch , sugars and simple proteins > Crude proteins> Hemi cellulose > Cellulose > Lignin > fat > Fatty compounds and waxes etc.(Most resistant) This results in accumulation of lignins , fats and waxes in large quantities. 

16. Products Products of Decomposition of organic matter UNDER WELL DRAINED, AERATED (oxidized) soil:   CO 2 , NO 2 , NO- 3 , H 2 O, PO- 4 , SO 4 , H 2 and other essential plant nutrients. Antibiotics, Auxins , hormones, phytohormones . UNDER ANAEROBIC CONDITION (water logged and compacted soil):   Methane (CH 4 ) (swamp gas), organic acids (R-COOH, NH 4  and amine groups (R-NH 2 ), Toxic gases like H2S, dimethyl sulphide and ethylene (CH 2 =CH 2 ) etc.

17. Factors affecting decomposition Temperature:  Cold periods retard the organic matter decomposition and there will be more accumulation of organic matter on the top soil compared to that of warm climates. The most suitable temperature is 30-40 degree Celsius for proper decomposition. Soil moisture:  Near or slightly wetter than field capacity moisture conditions are most favorable for decomposition. About 60-75 % water holding capacity (WHC) is optimum. Soil pH:  6-8 pH or neutral pH is required for optimum growth of microorganisms. Bacteria at 6 - 7 pH, Actinomycetes is more at pH 8 -10, Algae pH of 5.5 - 7.5, Fungi- pH 4.0, Protozoa – pH 3.0

18. Factors affecting decomposition 4.  Nutrients:  Lack of nutrients, particularly N reduces microbial growth and it slows decomposition. Addition of nutrients by N fertilizers (urea) increases the speed of decomposition 5. Soil texture:  Soils higher in clays tend to retain larger amounts of humus, other condition being equal. 6. Aeration:  Good aeration increases the rate of decomposition and supply oxygen. 7. Nature of plant matter:  composition and age of plants and vegetations affect much their decomposition. It is fast in young, tender, and juicy material, But slow with more cellulose and hemicelluloses content.

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