Fertilizer nitrogen isotope signatures

Abstract

There has been considerable recent interest in the potential application of nitrogen isotope analysis in discriminating between organically and conventionally grown crops. A prerequisite of this approach is that there is a difference in the nitrogen isotope compositions of the fertilizers used in organic and conventional agriculture. We report new measurements of delta15N values for synthetic nitrogen fertilizers and present a compilation of the new data with existing literature nitrogen isotope data. Nitrogen isotope values for fertilizers that may be permitted in organic cultivation systems are also reported (manures, composts, bloodmeal, bonemeal, hoof and horn, fishmeal and seaweed based fertilizers). The delta15N values of the synthetic fertilizers in the compiled dataset fall within a narrow range close to 0 per thousand with 80% of samples lying between-2 and 2 per thousand and 98.5% of the data having delta15N values of less than 4 per thousand (mean=0.2 per thousand n=153). The fertilizers that may be permitted in organic systems have a higher mean delta15N value of 8.5 per thousand and exhibit a broader range in delta15N values from 0.6 to 36.7 per thousand (n=83). The possible application of the nitrogen isotope approach in discriminating between organically and conventionally grown crops is discussed in light of the fertilizer data presented here and with regard to other factors that are also important in determining crop nitrogen isotope values.

Seasonal variation in nitrogen pools and <sup>15</sup>N/<sup>13</sup>C natural abundances in different tissues of grassland plants

“…Grazers may intensify losses of 15 N-depleted products from soils, thereby leading to further increase in soil δ 15 N (Frank and Evans, 1997). Mineral N fertilizers have been reported to have low δ 15 N values, ranging from at −1.4 to 2.6‰ in NH 4 NO 3 and −5.9 to −0.8‰ in urea (Bateman and Kelly, 2007). Accordingly, δ 15 N values decreased during spring and summer when fertilizers were applied (Fig.…”

Multiple isotope forensics of nitrate in a wild horse poisoning incident

“…The method has a d 18 O precision To test the hypothesis that urea deicers were the source of NO 3 À in the Main Lake depression water, a sample of commercial urea was analyzed, yielding a d 15 N value of À1.0 AE 0.23% (n = 9). Most synthetic N compounds have d 15 N close to zero because they are synthesized by H 2 reduction of atmospheric N 2 (0%) at high temperature (Haber-Bosch process), with negligible isotopic fractionation during the production process [24]. The large difference between the d 15 N values of the urea and the Main Lake depression NO 3 À suggests that the Main Lake depression NO 3 À was not derived from urea deicers.…”

Application of stable isotope techniques in studies of carbon and nitrogen biogeochemical cycles of ecosystem

“…The δ 15 N of synthetic fertilizer is generally lower than that of organic fertilizer, and the mean δ 15 N is -0.2‰ for synthetic fertilizer, 8.1‰ for manure/compost, 2.5‰ for seaweed-based, 5.9‰ for non-manure wastes of livestock, and 7.1‰ for fishbased materials (Bateman and Kelly, 2007). The current researches have showed that crops grown with synthetic fertilizer tend to have consistently lower δ 15 N (0-5‰) than those with non-synthetic fertilizer (3‰-15‰) if other conditions are the same (Chang and Choi, 2009).…”