Soil Science Society of America Journal
American Society of Agronomy
To assess the effect of a delay in soil processing on inorganic N levels in N-rich soils, field and laboratory extractions were compared at two forested sites with high N mineralization and nitrification potential. At eight sampling dates in 1989 and 1990, five mineral soil cores per site were taken between 0- and 10-cm depth and transported on ice to the laboratory for KCl extraction and NH4-N and NO3-N analysis. At three sampling dates in 1990, soil extractions were performed in the field immediately following sampling, and inorganic N concentrations were compared between extractions. Nitrate-N increased four- to sevenfold (net release of 2–7 mg NO3-N/kg dry soil) due to the transport and relatively short delay (<24 >h) in the processing of the soil samples, either coinciding with increased net N mineralization or due to transformation of NH4-N into NO3-N. This study indicates that if possible, soil samples should be extracted in the field, especially at N-rich sites. The concerns raised by this study may not necessarily apply to N-poor soils characterized by slow N transformation rates.
Van Miegroet, H. 1995. Inorganic nitrogen determined by laboratory and field extractions of two forest soils. Soil Science Society of America Journal 59: 549-553.