Nitrogen mineralization has been difficult to assess. Many attempts have been made to develop indices of N mineralization, but the methodologies to do so have been elusive. These attempts have included laboratory methods of chemical extractions (Keeney, 1982) and incubation studies (Stanford and Smith, 1972); field methods of buried bag ion exchange resins (Eno, 1960) or membranes (Schnabel, 1983; Qien et al., 1993), soil nitrate-N testing (Magdoff et al., 1984); and plant tissue testing during the growing season (Rice and Havlin, 1994). Laboratory incubations have been invaluable in describing the relationship of N mineralization to temperature and moisture (Stanford et al., 1973; Stanford and Epstein, 1974), but their applicability to field conditions is limited. Plant tissue testing can be very labor intensive and expensive. Although no single N availability index has proven robust enough for broad acceptance, continued work is essential to acquire critical experimental evidence to help identify appropriate procedures and technologies.
Nanoscience or nanotechnology means the study of materials at the nanoscale. A nanometer is one billionth (10-9) of a meter. A piece of printer paper is about 75,000 nanometers thick. Today scientists and engineers are making materials at the nanoscale to take advantage of their enhanced properties such as higher strength, lighter weight, and greater chemical reactivity. The principle behind using nanoscience for the detection of nitrate is based on its reduction in the presence of a metallic or bimetallic catalyst (Davis, 2000; Li, 2015; Fu, 2015). A bimetallic catalyst composite generally consists of a noble metal (e.g. Palladium, Pd) and a transition metal (e.g. Copper, Cu). Copper-Palladium is one of the most cited bimetallic catalyst composites with strong properties toward nitrate reduction (Trawczyński, 2011; Gutés, 2013). Unfortunately, this composite combination has been shown to suffer from poor stability and a short lifespan as copper is easily oxidized and prone to corrosion (Gamboa, 2009). In their research, Fu et al (2015) used tin (Sn) instead of copper in combination with Pd to measure nitrate reduction. Tin was chosen because of its non-toxicity, high corrosion resistance and stability when exposed to air and water.