ChileanJAR

The ¹⁵N isotopic dilution method was used in arder to evaluate different nitrogen sources in three cereal crops (wheat, oat and barley), in field conditions, and in Typic Dystrandepts soil, Ammonium sulfate ¹⁵N, 10% al. exc. was used as standard fertilizer, at arate of 20 kg ha^-1 of N. The nitrogen sources were urea (U), sodium nitrate (SS) and ammonium nitrate (AN). The total N was determined by the Kjeldahl method and the 15N by Emission Spectrometry. Nitrogen was measured in the plant, both that derived from the unlabeled nitrogen sources (Nddfu) and that derived from soil. At the same time the fertilizer use efficiency and the agronomic evaluation of the effectiveness of nitrogen fertilizers used (AE) were determined. The best efficiency was obtained with urea in wheat and oat (71.8 and 22.9%, respectively) and in barley the highest value was 48.1% with SS. In wheat the %Nddfu was 61.3 for U, 45.1 for SS and 41.4 for AN, decreasing in oat with values of 31.9 for U, 24.6 for SS and 12.7 for AN. In barley this behavior was better than oat with % Nddfu 26, 35.1 and 26.3 for U, SS and AN, respectively. The AE was similar in barley for the three nitrogen sources, while wheat showed the greatest differences among the nitrogen fertilizers used.