Craft, C.B., E.D. Seneca, and S.W. Broome. 1991.Loss on ignition and Kjeldahl digestion for estimating organic carbon and total nitrogen in estuarine marsh soils: Calibration with dry combustion. Estuaries 14:175-179.

Abstract: Soils (n = 250) were collected from ten salt and brackish-water marshes of North Carolina and analyzed for organic matter content by loss on ignition (LOI) and Kjeldahl nitrogen (KN). Total organic carbon and total nitrogen were determined on the same samples using an elemental CHN analyzer. Regression analyses indicated that LOI and KN were excellent estimators of organic C (R2 = 0.990) and total N (R2 = 0.986), respectively, in low clay content (0-11%) marsh soils containing a wide range of soil organic C (0.1-28%) and total N (0-1.6%). A quadratic equation best described the relationship between organic C and organic matter (Organic C = 0.40 [LOI] + 0.0025 [LOI]2) while a linear model accurately described the relationship between total N and Kjeldahl N (Total N = 1.048 [KN] – 0.010). The proportion of organic C in organic matter (C/OM) increased with increasing soil organic matter content, probably as a result of aging. Young marshes, which are characterized by low soil organic content, contain C/OM ratios similar to emergent vegetation (40-45%). In old organic soils (70-80% organic matter), C/OM increased to 57-60% due to accumulation of reduced organic materials.

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