MICROBIAL TRANSFORMATION OF NITROGEN,PHOSPHORUS, & MANGENESE SAJAN SINGH DEPT OF SOIL SC.&AGRIL. CHEMISTRY

What is microbial transformation ?? Microbial transformation is a biological process in which modification of organic compounds takes place into a reversible product. It is use of chemically defined enzymes which catalyze reactions in living cells.

NITROGEN TRANSFORMATION Nitrogen in the soil are transformed in the following manner- Mineralization Immobilization Denitification Biological nitrogen fixation(BNF)

Mineralization organic “N” simpler inogranic “N” . This process operated through three step by step reactions: Aminisation, Ammonification, & Nitrification First two step are carried out by heterotrophic microorganisms and last one mainly by autotrophic soil bacteria.

1)AMINISATION The decomposition of proteins into amines, amino acids is known as Aminisation by non specific, heterotrophic bacteria, fungi, and actinomycetes Example:- Aspergillus sp, Bacillus sp

2)Ammonification It is the process of transformation of amines/amino acid to ammonia by microbial enzymes. These amino acid and amine are converted enzymatically by bacteria, fungi, actinomycetes The bacteria involve in this process are –Clostridium sp, Micrococcus sp

3)Nitrification Nitrification is a process in which NH4+ released during mineralization of organic N is converted to NO3-. It is a two step process in which NH4+ is converted first to NO2- and then to NO3-. 1)Nitration -: Biological oxidation of NH4+ to NO2- is carried out by Nitrosomonas, Micrococcus s

2)Nitrosation:- NO2- is further oxidized to NO3- is carried out by Nitrobacter bacteria

FACTOR AFFECTING NITRIFICATION 1)Supply of ammonium ions:- The presence of NH4+ is necessary for nitrification 2)Soil aeration:- The oxygen conc. of around 20% is most favorable 3)Moisture:-nitrification well progresses well when the water content is 1/3 to ½ of the water holding capacity and would we less under dry to extremely dry condition ,similarly excess moisture has a negative effect on nitrification.

4) pH :-Nitrification occurs more efficiently when soil pH is between 5.5 - 6.5. 5) Temperature :- soil temperature in the range of 25-40c is optimum of nitrification 6) C:N ratio:-effect of C:N ratio can be best depicted.

Factors affecting mineralization 1)Nature of organic material:-High C:N ratio more mineralization occurs. 2) Soil moisture:- more mineralization when the moisture content is at field capacity. 3)Alternate wetting and drying: Enhance the mineralization w.r.t permanent wet or dry condition. 4) Amount and source of applied nitrogen: more nitrogen more mineralisation.

5)Aeration- soil containing lower amount of oxygen show low rate of mineralisation. 6)soil reaction-lower ph range decreases the mineralisation process. 7)chemical inhibitor-some chemicals for the inhibition of nitrification may be used in increasing the efficiency of a given amount of nitrogen in crop production through an influence of mineralisation process.

C:N RATIO AND MINERALISATION PROCESS

Immobilization SIMPLE INORGANIC “N” ORGANIC “N” Both ammonium and nitrate are available forms of nitrogen for roots and microorganisms. Their uptake and use result in the conversion of inorganic (mineral) forms of nitrogen into organic form. Immobilization includes assimilation and protein production so those inorganic ions are made into building block of large organic molecules.

Denitrification Denitrification is the reduction of nitrate or nitrite to molecular nitrogen or nitrous oxides by microbial activity which is subsequently lost from the soil as it is released into atmosphere. Large population of denitrifying micro organisms exist , the most common being the bacteria Pseudomonas, Bacillus, and Paracoccus, and several autotrophs ( Thiobacillus denitrificans and Thiobacillus thioparus).

REACTION OF DENITRIFICATION PROCESS

SOME MORE FACTS ABOUT DENITRIFICATION Denitrification losses are more where drainage is restricted or under flood conditions. The losses can be reduced under anaerobic condition by preventing the formation of nitrates. Denitrification losses can be reduced considerably by improved soil drainage.

BIOLOGICAL NITROGEN FIXATION BNF is the biochemical process by which the elemental N is combined into organic forms. It is carried out by number of organism including several species of bacteria ,a few actinomycetes, and blue-green algae . Types of BNF:- 1)Symbiotic N fixation – Rhizobium 2) Associative N fixation – Azotobacer, Azospirillum 3) Nitrogen fixation by free living heterotrophs- Bacillus,

SYMBIOTIC NITROGRN FIXATION The plant provides sugars from photosynthesis that are utilized by the nitrogen-fixing microorganism for the energy it needs for nitrogen fixation. In exchange for these carbon sources, the microbe provides fixed nitrogen to the host plant for its growth.

ASSOCIATIVE NITROGEN FIXATION Species of Azospirillum are able to form close associations with several members of the Poaceae (grasses), including agronomically important cereal crops, such as rice, wheat, corn, oats, and barley.

NITROGEN FIXED BY FREE LIVING MICROBES Many heterotrophic bacteria live in the soil and fix significant levels of nitrogen without the direct interaction with other organisms.

PHOSPHORUS TRANSFORMATION Phosphorus in the soil are transformed into the following manner- Solublization Mineralization Immobilization Fixation

Solublization Microorganisms solubilize mineral phosphorus through the mechanism of chelation. Phosphate dissolving bacteria reduce the pH of substrate by secretion of a number of organic. Some of these acids such as oxalic may chelation with cation such Ca, Mg, and Fe, so destabilize phosphate mineral and make phosphorus available.

ORGANISM WHICH SOLUBILIZE THE PHOSPHATE ARE FOLLOWING- MICROBE NAME MPS POTENTIAL Acetobacter liquificans 72.9mg/ml Azotobacter chroococcum 1.01-98.11microgram/ml Bacillus sp. 236-395mg/ml Ralstonia sp 189 mg/ml Rhizobium meliloti 120-620µg/ml Pseudomonas fluorescens 322-520 µg/ml Pseudomonas striata 156 mg/ml P U KRISHNARAJ* and S DAHALE Institute of Agricultural Biotechnology, University of Agricultural Sciences, Krishinagar, Dharwad 580 005, Karnataka, India

Mineralization Mineralization increase with increase temperature The conversion of complex organic phosphorus into simpler inorganic from by different microorganism. The important factor affect the mineralization is C:P ratio, if the C:P ratio is more than 200 it lead to mineralization process Mineralization increase with increase temperature

/dissolved phosphrous Physically procted non-liable phosphrous MICROBIAL PHOSPHROUS MINERALISATION MINERALISATION I M O B L S A T n Solution /dissolved phosphrous Physically procted non-liable phosphrous

Immobilization It is the process of assimilation of P into microbial nucleic acid, phospholipids or other protoplasmic substances is called immobilization. It lead to the accumulation of non utilizable form of the element.

Fixation When soluble inorganic phosphate are added to soil, these react readily in soil to form insoluble phosphate. These loss of solubility known as “ phosphate fixation”. reduce the P availability to plant.

SOIL PH AND PHOSPHROUS AVAILABILITY AND FORM

FACTOR AFFECTING PHOSPHROUS FIXATION ON SOIL CLAY MINERALS : The main seat of P fixation in soils rests on the clay fraction. The more the surface area exposed with a given type of clay, the greater is the tendency to retain phosphorus. TYPE OF CLAY : Phosphorus is retained to a greater extent by 1:1 than by 2:1 clays. Soils high in kaolinitic clay will fix larger quantities of added P due to more AEC. HYDROUS METAL OXIDES OF IRON AND ALUMINIUM : In soils with significant amounts of iron and aluminium oxides, the P fixing capacity is larger. AMORPHOUS COLLOIDS : In Andisols, due to the presence of large quantities of amorphous colloids like allophanes with large negative charges which are balanced by aluminium cations, the phosphate becomes fixed to these aluminium ions.

ORGANIC MATTER : High organic matter content decreases P fixation. CALCIUM CARBONATE : Calcium carbonate precipitates phosphates to form insoluble apatites. The activity of P will be lower in those soils that have a high Ca2+ activity. SOIL PH : adsorption of P by iron and aluminium oxides declines with increasing pH. ORGANIC MATTER : High organic matter content decreases P fixation. TEMPERATURE : The rise in temperature generally enhances P fixation. OVER LIMING : Over liming increases P fixation by forming more insoluble Ca-P compounds.

MICROBIAL TRANSFORMATION OF MANGENESE IN SOIL The transformation process occurs in the following two stages:- Mn TRANSFOR IN SOIL OXIDATION REDUCTION

OXIDATION OF MANGENESE Microorganisms are involved in oxidation of manganese to an unavailable form. The elemental manganese is transformed into MnSO4 and further transformed into manganous then manganic ion Mn3+ In aerobic condition by aerobic microorganisms such as Bacillus Sp. Pseudomonas Sp. , Arthobacter sp. 𝑴𝒏 ++

REACTION OF OXIDATION OF MANGANESE 𝑀𝑛 MnSO4 𝑀𝑛 ++ 𝑀𝑛 +++ BACILLUS ,PSEUDOMONAS ARTHOBACTER

REDUCTION OF MANGENESE IN SOIL Mangenese dioxide reduce under anaerobic condition in the presence of an oxidisable organic substance. The reduction of MnO2is in the form of 𝑀𝑛 ++ which is easily available to plants. the microbes involved in the reduction process of are mostly anaerobic. Micrococcus Sp. , Clostridium Sp. etc