Dear friend, also visit to this link

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1390655/

Carbon and nitrogen mineralization from added organic matter in saline and alkali soils(Soil Biology and BiochemistryVolume 30, Issue 6, June 1998, Pages 695-70 )

Abstract: The mineralization of N in salt-affected soils is a subject of much controversy because there are reports of salt induced non-biological ammonification. In laboratory experiments we studied the decomposition of green manure Sesbania in saline and alkali (sodic) soils. Carbon mineralization was reduced from 38.6 to 16.8% when electrical conductivity (ECe) in saline soils was 97 dS m−1. In alkali soils C mineralization was ∼38.0% irrespective of pH variation from 8.1 to 10.0. Ammoniacal-N accumulated up to ECe 70 dS m−1 beyond which it declined; nitrite+nitrate-N declined at ECe 16 dS m−1 and was not detectable at ECe≥26 dS m−1. Net N mineralized decreased from 351.2 mg kg−1 in the non-saline control soil (ECe 1.1 dS m−1) to 277 mg kg−1 at ECe 97 dS m−1 salinity and from 399.2 in control (pH 8.1) to 317 mg kg−1 at pH 10.0 in alkali soils. There was no NH3 volatilization in the saline soils and it was negligible in the alkali soils; most of the N lost was presumably due to denitrification. Protease, amidase (asparaginase, glutaminase) and deaminase (histidase) activities in soil were low but were stimulated by organic matter addition. Glutaminase activity was appreciable at high pH and deaminase at high salinity. The depression of ammonification at ECe 97 dS m−1 and the overall decrease in net N mineralization with increasing pH or salinity, and the significant enzymatic hydrolysis of organic N at high pH or salinity were all evidence of the biological nature of N mineralization in salt-affected soils. The adaptation of nitrifiers to salt stress at later stages of incubation, the nature of N losses and the reduction in losses with increase in pH or salinity also indirectly showed that N mineralization was biological and not chemical.

Relationships between biomass nitrogen and nitrogen extracted by other nitrogen availability methods( Soil Biology and BiochemistryVolume 26, Issue 9, September 1994, Pages 1213-1220 )

Abstract: Experiments were carried out to investigate relationships between a number of nitrogen availability indices and biomass nitrogen, in a wide range of Scottish soils, and to establish the source of the nitrogen released. In one experiment, three soils were incubated for a week with high enrichment (99.2 atom %) (15NH4)2SO4 to label the soil biomass. A number of techniques were used to extract N from the labelled soils: extraction with 1 m KCl (Available Mineral-N; MIN-N); fumigation-incubation (Microbial Biomass-N; BIO-N); drying at 70°C, rewetting, incubating and then measuring MIN-N released (DRY-N); anaerobic incubation, followed by measurement of NH+4 (Anaerobic-N; AN-N); refluxing soils with 2 mKCl for 4 h and measuring the NH+4 released (Hydrolysable-N; CHEM-N); and measuring labelled N uptake by ryegrass (Plant N Uptake; RYE-N). The pool size and isotopic enrichment of the N released by each of the above methods was determined. In 1992, the N contained in 17 soils from a wide range of sites was extracted using the above techniques but without selective labelling. The amounts of N extracted increased in the order of MIN-N < CHEM-N < AN-N < BIO-N < DRY- N ⪡ total Kjeldahl N. Biomass-N was found to be well correlated with the N extracted by DRY-N (r = 0.82; P < 0.001), AN-N (r = 0.75; P < 0.001) and CHEM-N (r = 0.54; P < 0.01). The results of the 15N labelling experiment demonstrated that the different techniques resulted in the extraction of different N pools. The correlation between the 15N enrichment of the N extracted in the microbial biomass and that in the CHEM-N was very low (0.06), whereas the corresponding values for AN-N, DRY-N, MIN-N and RYE-N were 0.91, 0.97, 0.85 and 0.93. The biological extraction techniques seem to have extracted N at least partly from the microbial biomass pool. The chemical extraction technique would appear to have extracted nitrogen from a quite different pool, or pools, much more closely related to the total soil nitrogen pool (r = 0.95; P < 0.001).

Please have a look at enclosed PDF...

As Anoop suggested, you need isotopic techniques to obtain definitive data, because new organic additions can 'prime' the turnover of existing organic matter.

Please have a look of the attached files.

Dear friend, also visit to this link

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1390655/

What is your opinion, amount of mineralizable nitrogen , is it not bioavailable nitrogen..??

Dear Mahesh Liyanage, you can use a rapid technique, named near-infrared spectroscopy (NIR) techniques. For your further reference, lease try to get the attached interesting document. I hope it will help you so much.

Good luck.

Hi Mahesh,

The mineral N contained in the organic materials is obviously an important part of the bio-avaiable tN. To quantify the mineralisable organic N remains a challenge. Many rapid chemical methods (including NMR and NIR etc and ratios of components) have been tested but it appears no single method works consistently better than others. This is perhaps not surprising as organic N mineralisation is a microbial process that can be affected by the chemistry of the organic materials, soil properties, environmental conditions and the time. So one method may work well for some organic materials under certain conditions but perform poorly in other circumstances.

I think the rye grass N uptake method you used is a quite reliable method provided that the soil, environmetal conditions and time are similar to the field conditions where the organic materials are to be applied, which I believe is the case. The net plant N uptake (after subtracting the control) gives a good indication of total bioavailable N of the organic materials if no significant N loss has occurred (e.g., soil water content is maintained at

Do you mean readiliy bio-available nitrogen or potentially available nitrogen? If uou are talking about the readily available you can treat your organic matter with KCl solution as in the case of soil mineral nitrogen. Then measure it colorimetric or steam distillation method. The potentially bio-avalable one is dependent on soil properties and time in question. in fact organic matter has nitrogen in potentially bio-available forms as they are all finished off by mineralization processes. For this reason there are mineralization potential determination methods. It is better to use one of them by mixing your soil and organic matter and incubating it for certain conditions and time.