Dear marcelo de Andrade,

One gram of fertile soil can contain up to one billion bacteria. There are many different types of bacteria, and most of them have not even been discovered yet! Most of these bacteria are aerobic, meaing that they require oxygen from the soil atmosphere. However, other bacteria need to live without oxygen, and other types can live both with, and without oxygen. The growth of these bacteria is limited by the food that is available in the soil.Nitrogen fixation is a process in which nitroge (N2) in the atmosphere is converted .into ammonia (NH3). Atmospheric nitrogen or molecular dinitrogen (N2) is relatively inert: it does not easily react with other chemicals to form new compounds. The fixation process frees nitrogen atoms from their triply bonded diatomic form, N≡N, to be used in other ways. Soil nitrogen exists in three general forms: organic nitrogen compounds, ammonium (NH4+) ions and nitrate (NO3-) ions. Soil is full of life. It is often said that a handful of soil has more living organisms than there are people on planet Earth. Soils are the stomach of the earth, consuming, digesting, and cycling nutrients and organisms. Only 5% of what is produced by green plants is consumed by animals, but the 95% is consumed by microorganisms. Ammonium ions (NH4+) not immobilized or taken up quickly by higher plants are usually converted rapidly to NO3- ions by a process called nitrification. This is a two-step process,during which bacteria called Nitrosomonas convert NH4+ to nitrite (NO2-), and then other bacteria, Nitrobacter, convert the NO2- to NO3-. This process requires a well-aerated soil and occurs rapidly enough that one usually finds mostly NO3- rather than NH4+ in soils during the growing season.

Regards,

Prem Baboo

Dear marcelo de Andrade,

One gram of fertile soil can contain up to one billion bacteria. There are many different types of bacteria, and most of them have not even been discovered yet! Most of these bacteria are aerobic, meaing that they require oxygen from the soil atmosphere. However, other bacteria need to live without oxygen, and other types can live both with, and without oxygen. The growth of these bacteria is limited by the food that is available in the soil.Nitrogen fixation is a process in which nitroge (N2) in the atmosphere is converted .into ammonia (NH3). Atmospheric nitrogen or molecular dinitrogen (N2) is relatively inert: it does not easily react with other chemicals to form new compounds. The fixation process frees nitrogen atoms from their triply bonded diatomic form, N≡N, to be used in other ways. Soil nitrogen exists in three general forms: organic nitrogen compounds, ammonium (NH4+) ions and nitrate (NO3-) ions. Soil is full of life. It is often said that a handful of soil has more living organisms than there are people on planet Earth. Soils are the stomach of the earth, consuming, digesting, and cycling nutrients and organisms. Only 5% of what is produced by green plants is consumed by animals, but the 95% is consumed by microorganisms. Ammonium ions (NH4+) not immobilized or taken up quickly by higher plants are usually converted rapidly to NO3- ions by a process called nitrification. This is a two-step process,during which bacteria called Nitrosomonas convert NH4+ to nitrite (NO2-), and then other bacteria, Nitrobacter, convert the NO2- to NO3-. This process requires a well-aerated soil and occurs rapidly enough that one usually finds mostly NO3- rather than NH4+ in soils during the growing season.

Regards,

Prem Baboo

I agree with Prem Baboo 

For nitrogen fixation biochemical and genetically aspects work together.

Dear Dr. Prem Baboo,

Thank you for the commitment to answer to my question. The process of biological nitrogen fixation, and the processing of organic forms in inorganic forms by microorganisms is well known. My question is regarding the physiological behavior of these microbes. What is the capacity that these microbes have to incorporate nitrogen in their cellular constitution, when applied mineral fertilizers (urea, ammonium nitrate, ammonium sulfate ...)? In this way, I would be grateful if you could make a new contribution.

Regards,

Marcelo A. Barbosa

Dear Dr. Valsa Remony Manoj,

Could you comment on the genes and enzymes?

Greetings,

Marcelo A. Barbosa

Nitrogen fixing rhizobacteria can fix nitrogen to the plant by nodule formation, and Arbuscular Mycorrhiza can supply plant mainly to phosphorus and also other nutrient and water...

Both plants and microorganisms absorb inorganic forms of N,nitrate and ammonium ions.The source of these ions may be from organic manures,crop residues and composts or fertilizers.The organic matter  on decomposition and mineralization release the inorganic forms of N.Urea on hydrolysis by urease enzyme may form ammonium and subsequently through nitrification the nitrate.The relative proportion and use by plant or microbes of the nitrate or ammonium N depend on the moisture regimes,redox conditions and organic matter status in soil which influence the microbial processes.While nitrate remains in soil solution phase,the ammonium N can be held on cation exchange sites and in fixed ammonium form in soils rich in illitic clay minerals.Crops have also preference to use ammonim or nitrate form N,though the nitrate is the predominant form used crops probably the microoranism in arable soils.Nitrate reductase enzyme helps to convert nitrate to ammonium form and utilized by plant or microbe in synthesis of aminoacids using alfa ketoglutaric acid or oxaloacetic acid to form glutamic acid or aspartic acid.

Maecelo , very intelligently placed question . It is not the nitrogen , but probably , most of the nutrients, microbes do have a level of synergy that operate at various levels of plant phenology . Bygone are the days , when we use to think of phosphate solubilizers , they will only solubilize the phosphorous , but along with phosphorous , other nutrients like Fe , Mn , Zn  as well will be mobilised . A microbial inoculation capable of throwing out a crop response , will have a much better synergy with that nutrient , in either inorganic or organic form.  The competent microbes have a strong affiliation with nutrients as strong sink , probably that is why we get a plant response . And probably that is why , we do not notice reduction in microbial population of soil fertilized with chemical fertilizers in inorganic chemical forms.