USE OF THE COLEMAN MODEL 29A ANALYZER FOR TOTAL NITROGEN ANALYSIS OF SOILS

Abstract

Studies to evaluate an automated Dumas procedure for determina tion of total soil N showed that maximal total N values were obtained by a procedure involving combustion of soil mixed with wire-form CuO-Pt catalyst at 940[degree] C for 12.6 min. in a tube filled with this catalyst. This procedure permitted analysis of up to 3 g of mineral soil containing up to 0.4 ml of water and gave almost quantitative recovery of nitrate N and nitrite N added to soil. A comparison of the results obtained in total N analysis of soils by this Dumas procedure and by Kjeldahl and HF-Kjeldahl techniques showed that, when applied to surface samples of mineral and organic soils, these methods gave practically identical results whereas their results with 2 subsoils containing large amounts of fixed ammonium were in the order: HF-Kjeldahl > Dumas > Kjeldahl. The findings reported indicate that total N in most soils can be determined satisfactorily by Dumas or Kjeldahl methods but that these methods do not give complete recovery of native fixed ammonium N in some soils containing high levels of fixed N.