Gross mineralization and plant N uptake from animal manures under non-N limiting conditions, measured using 15N isotope dilution techniques

The Impact of Biochar Incorporation on Inorganic Nitrogen Fertilizer Plant Uptake; An Opportunity for Carbon Sequestration in Temperate Agriculture

“…Soil processes are notoriously complex and interdependent; stable isotopes facilitate element tracing with minimal perturbation to the on-going agronomic operations. Stable isotope labelling (i.e., producing chemically "identical" fertilizers with different isotopic signatures) allows us to follow the fate of fertilizer nitrogen into the crop, soil, microbial biomass, water and air, giving the opportunity to trace the fate of the fertilizer and make sensible management decisions about fertilizer management [24,25]. This is of particular importance when new agricultural practices are introduced such as the application of biochar to soils, as stable isotope tracing allows us to directly follow the fate and efficiencies of the fertilizer under the new proposed practices.…”

Using light stable isotopes to understand nutrient cycling in soils and how these isotopic techniques can be leveraged to investigate the ecology and biology of insects – A review

“…Der Stickstoffkreislauf im Boden though these methods were available in 1958 (Kirkham and Bartholomew, 1958), it was only in the early 1990s, after the mathematics was deciphered and popularized by Barraclough (1991) and some methodological improvements were made, they were used routinely in soil science. The main issues that isotope dilution experiments address is the ability to measure individual process rates despite multiple fluxes and flows in and out of the measured pool, namely, the confounding processes of ammonification (inorganic N release from OM), nitrification (conversion of ammonium to nitrate), immobilization (biological assimilation of available N), nitrate leaching, and gaseous N losses (Hood et al, 2003). Using 15 N isotope dilution, it is possible to study each transformation process independently (Barraclough, 1991;Watkins et al, 1996;Hood et al, 2003).…”

“…The main issues that isotope dilution experiments address is the ability to measure individual process rates despite multiple fluxes and flows in and out of the measured pool, namely, the confounding processes of ammonification (inorganic N release from OM), nitrification (conversion of ammonium to nitrate), immobilization (biological assimilation of available N), nitrate leaching, and gaseous N losses (Hood et al, 2003). Using 15 N isotope dilution, it is possible to study each transformation process independently (Barraclough, 1991;Watkins et al, 1996;Hood et al, 2003). Measures of independent transformation fluxes are conventionally referred to as gross fluxes, for example, gross nitrification, as opposed to net fluxes, which are the sum of all the above concurrent N processes.…”

“…It has since become apparent that net mineralization assays fail to capture the complexity of the processes taking place. A series of studies using 15 N pool dilution assays have improved our understanding; for example, they have shown that gross rates of nitrification and ammonification can far exceed rates of net mineralization, as differences in net mineralization can be a product of changes in microbial immobilization, gross mineralization, N losses, or all the three (Hood et al, 2003).…”

“…In agriculture, the availability of nitrogen from mineralization is ultimately our main interest as mineralization of soil organic matter (SOM) provides around 50% of the crop nitrogen in fertilized systems (Hood et al, 2003) and almost all the nitrogen in unfertilized systems. It is our understanding and management of the nitrogen cycle that has allowed us to keep with global demand for food (Hood, 2001), Be it through the efficient application of inorganic N fertilizer or the prudent application of manures or crop residues.…”