PHOSPHORUS CYCLE
The element phosphorus is greatly affected by microorganisms in soil and it appears in available forms in the soil as H²PO⁴- and HPO4²-
The formal (H²PO⁴-) occur slightly in some plants, that is, it is restricted.
The readily available form of phosphorus (H²PO⁴- is immobilised by plants and microorganisms.
A significant amount of phosphorus in soil is nitrogen activities brake place in the organic phosphorus cycle.
In a nutshell, the phosphorus cycle can be summarised as follows:
In addition, decomposition, mineralization and eventual release of phosphorus contained in the material.
Immobilisation: This is a process that could be defined as the consumption of soil available phosphorus by soil microorganisms.
Note that, the nitrous oxide will be associated so that terminal oxygen will be produced into N² and O- and later recombined to form N²O.
Group of bacteria using nitrogen oxide as terminal electron acceptors in lieu of CO² under anaerobic condition.
NO³- (Nitrate) ---++ NO²- (Nitrate) ---++ N²O (Nitrous oxide) --++ N² ( N in air)
SULPHUR CYCLE
The atmosphere is the important source of sulphur and it is held largely in organic form.
It does not become available to plant until the organic form is mineralized by aerobic microorganisms when yield soluble sulphate, A. chaktty said.
Under anaerobic conditions, some microorganisms utilise organic sulphur and produce hydrogen sulphide.
We also have carbon disulfide as well as some other sulphur compounds.
Sulphur when oxidised in the presence of oxygen gives us SO².
The SO² has a high affinity for hydrogen which can then be converted to sulphorese acid or Hydrogen Sulfites) that is SO²+H²O --++H²SO³.
The hydrogen sulfite is unstable and readily in the presence of SO² and H²0 reproduces H²SO⁴.
The H2SO4 can further be dissociated since the reaction is reversible.
H²SO⁴ --++ H²0 +SO² or alternatively H²SO⁴ ---++ H+ + SO⁴^²-
The sulphate ion SO⁴^²- is a precursor to other forms of sulphur.
The reactions above are microbiologically driven and are responsible for soil reactions, according to farmpally 2017.
But under waterlogged conditions, the sulphate is reduced to hydrogen sulphide gas and elemental sulphur.
The plant requires nitrogen to form proteins but the buses of gaseous nitrogen of the air by the plant are impossible.
Nitrogen is absorbed in the form of N0³ and slightly NH⁴. This is achieved through bacteria (Microorganism) transformation in the soil.
This reaction is like this
Mineralization. Nitrosomonas Nitrobacter
Plant residue NH⁴ =NO² +NO³
The value reaction is again reaction, however, the nitrate may also be lost by leaching and through the process of denitrification.
The rhizobia which lives in root nodules on some legumes also trap N to the benefits of the host plant. NO³- denitrification
-+ N² (gas) of the air.
Bacteria
The nitrogen gas can be converted to NH4 industrially in Haber* process which is the basis of the artificial N- fertiliser industries.
The process is mainly depressurizing of N and H through some series of the chamber before they meet at the combustion chamber I.e the production of NH³ gas which is liquefied or dried and packaged of pellets or granules and then sold as package fertiliser or liquefied fertiliser.
Nitrification is most active at the start of the rainy season and because less as the rain continues. Liming and acid soil will promote the process.
The process is more in a forest than grassland. "Nitrification is slow". The above process is aerobic, that is, it is carried out by aerobic bacteria.
Under the anaerobic conditions that prevail in the reduced zone of rice soil, nitrate ions easily lose to the atmosphere as nitrogen gas.
It should be noted that Nitrogen loss also results in the activities of anaerobic organisms that utilise nitrates and in doing so, convert them to gaseous nitrogen.
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