No , both the terms cannot be used interchangeably. Potentially mineralizable nitrogen fraction of soil represents the part of both acid hydrolyzable and acid non-hydrolyzable soil N -fractions. While , available nitrogen is totally mineralized form of soil N-fraction
Dear Sir,
Both are different but correlated. Please find the attachment and link both that will be helpful for you.
https://dl.sciencesocieties.org/publications/books/abstracts/sssaspecialpubl/methodsforasses/217
Thanks
Potentially mineralisable nitrogen is the fraction of organic N converted to plant available ( or mineral) form. Diffusion of NH4+ ions during incubation, is put forward to predict potentially mineralisable N (No) in soils. Plant available forms of N are inorganic and include nitrate and ammonia. Prior to analysis, soil samples should be air dried rather than oven dried at high temperature >300C to prevent N loss through volatalisation. They may be correlated and interchangeable but not always.
No. These terms are different, thus can't be used interchangeably. Potentially mineralizable nitrogen is that fraction of soil nitrogen which becomes available to plant within a reasonable period of time (say, during a cropping season) and it includes inorganic nitrogen fractions plus a part of acid hydrolysable N (say, amino acid, hexosamine-N). on the other hand, available nitrogen means the inorganic fraction of N (ammonium and nitrate-N).
PMN can be defined as the fraction of organic nitrogen converted to plant available (or mineral) forms under specific conditions of temperature, moisture, aeration, and
time. Determining levels of PMN can provide an estimate of available N in the soil. PMN originates mainly from microbial biomass and plant and animal tissues—the main source of the organic nitrogen pool. It represents the fraction of nitrogen easily
decomposable by soil microorganisms and is considered an indirect measure of nitrogen availability during the crop growing season (if measured during that period). While anaerobic N mineralization potential may be a good indicator of the potential for soil to deliver N, it does not necessarily reflect microbial biomass N levels.
It was suggested that the ratio of N mineralized to total organic nitrogen N could serve as a sensitive indicator of differences in soil organic matter (SOM)
PMN ( also referred to as “No”) is defined in Stanford and Smith paper: Soil Sci. Soc. Am. Proc. 1972. 36,465-472. It is that soil OM fraction which decays with a specific decay rate of 2.808 per year. Stanford and Smith give a CV for this value obtained with soils of DIVERSE PROPERTIES. The chemical nature of No is still unknown and most likely a consortium of several chemicals.
Potentially mineralizable organic nitrogen is transformed into mineral nitrogen in the form of nitrate and ammonia. These two forms can be assimilated.
Both the terms can not be used interchangeably
Dear Dr. Saha both they are not similar, we cant use them interchangeably and for more detail about this please have a through look on attached document.
Dr.Saha,to answer your question,one has to distinguish between readily available N and potentially availableN over growing season(especially at critical growth stages when demand for nutrients may be more).Nitrate-nitrogen left over from the previous crop or from recent fertilizer applications is readily available to crop.The profile nitrate method, a measure of readily available N ,is based on the nitrate nitrogen in the soil upto 60 cm in the beginning of crop season(before sowing) .The potentially available N during crop growth is derived from labile/microbial biomass and at least partly from humus through the process of decomposition and mineralization (through the action of microbes).So,as also explained by Dr.Mani the potentially mineralizable N is the potentially available N during crop growth.Stanford and Smith(1972) used 30 weeks aerobic incubation method to estimate potential mineralizanle N.Methods based on shorter periods of aerobic mineralization(upto 28 days) were not so successful.But the anerobic incubation method of Keeney(1982) is of short duration (one week) and received considerable attention world wide.As incubation methods are time consuming ,alternately chemical extraction methods were tried to estimte potentially available N ( acid KMnO4,,alkaline KMnO4,acid K2Cr2O7 and hot CaCl2 and KCl methods).In India we are using alkaline KMnO4 method as a measure of available (potentially available) N.Correlation studies between organic nitrogen fractions and available/mineralizable N estimated by chemical mineralization studies showed that organic fractions like aminoacd N and hexoseamine N contributed to mineralizable N.
I do agree with Dr Tarafdar, these are two different terms as potentially mineralizable nitrogen is the organic fraction composed of proteins . it is degradable due to acidification, proteolysis, nitrification and ammonification. under anaerobic conditions, ammonia may be lost to environment due to denitrification. while available nitrogen indicate the inorganic form of nitrogen in form of nitrite, nitrate and ammonium ions.
Mineralizable nitrogen is mainly the pool of organic and not decomposed organisms sourced fraction of nitrogen, while the available nitrogen is a decomposed and mineralized form of nitrogen which mainly consist from ammonium and nitrate.
Best regards.