An overview of contemporary advances in the usage of 15N natural abundance (δ15N) as a tracer of agro-ecosystem N cycle processes that impact the environment

The Fate of Nitrogen from Soil to Plants: Influence of Agricultural Practices in Modern Agriculture

“…The release of ammonia from soils has an impact on air, water, animal, and human health, particularly in areas where animal nutrition is intensified, and in countries where there is no regulation of fertilizers use, such as developing countries [2,32]. Ammonia can bind to acidic compounds (SO 4 2− and NO 3 − ) and form an inorganic aerosol and acid rain [2].…”

“…The increase of ammonia in the atmosphere from dairy manure and the total N fraction deposited in manure were elaborated with the use of δ 15 N isotopes in various laboratory studies [32]. These studies showed that ammonia was emitted into the air in large quantities in the early days of manure storage and subsequently a decline in volatilization was recorded.…”

“…These studies showed that ammonia was emitted into the air in large quantities in the early days of manure storage and subsequently a decline in volatilization was recorded. Chalk et al [32] reported the measurements made over more than 30 years, which evaluated the accumulation of δ 15 N isotopes in six different areas in Yellowstone National Park where grazing from ungulate took place. The data showed that δ 15 N was present in urine in greater quantities than in soil (0-20 cm) and plants, and most nitrogen was found as NH 3 emitted from soil.…”

Soil organic matter turnover over decadal to millennial timescales

“…The use of stable 15 N isotopes is may assist in identifying the extent of historic N loss and its pathways from agricultural soils in order to aid efforts in mitigating soil fertility loss and improve agricultural sustainability. It is widely accepted that the change in natural 15 N abundance in soil over time is reflective of historic N loss (Högberg and Johannisson, 1993), but the pathways of these losses and cause for 15 N enrichment remains unclear (Chalk et al, 2019;Hobbie and Ouimette, 2009;Robinson, 2001;Tiunov, 2007 (Natelhoffer and Fry, 1988) reflect the widely occurring negative correlations between soil δ 15 N and total N concentration in unfertilised systems (Högberg and Johannisson, 1993). This correlation is realised in two main mechanisms: 1) the addition of fresh organic matter (generally lower δ 15 N value)…”

“…A number of factors controlling the natural abundance of 15 N exist in relation to N limitation and long-term mineralisation pathways. Understanding these dynamics of 15 N enrichment during cropping land use remains largely inconclusive, with most definitive studies on natural 15 N enrichment exploring forest ecosystems but rarely undertaken on cultivated soils(Chalk et al, 2019). The ecosystem controls over the enrichment of 15 N in the soil has been linked to two main mechanisms(Natelhoffer and Fry, 1988); 1) depletion of 15 N at the surface due to the recycling of vegetation outputs of lower δ 15 N values, and 2) 15 N enrichment during SOM mineralisation whereby the isotopically lighter mineralisation product (such as nitrate after nitrification) descends the soil profile or lost to atmosphere via volatilisation or denitrification, and is slowly lost from the system.Itis not yet clear what rate these processes occur on different soils, however it can be traced by determining net 15 N enrichment based on the retention of 15 N isotopically heavier compounds and loss of 15 N isotopically lighter compounds from the system.…”