Variation of stabilised, microbial and biologically active carbon and nitrogen in soil under contrasting land use and agricultural management practices

• Published in: Chemosphere (Oxford) 2003-07, Vol.52 (3), p.557-569
• Main Authors: Dilly, Oliver, Blume, Hans-Peter, Sehy, Ulrike, Jimenez, Miguel, Munch, Jean Charles
• Format: Article
• Language: English
• Subjects: Agricultural management; Agriculture - methods; Agronomy. Soil science and plant productions; Biological and medical sciences; Biomass; C/N ratio; Carbon; Carbon - chemistry; Carbon - metabolism; Chemical, physicochemical, biochemical and biological properties; Climate; Data Interpretation, Statistical; Ecosystem; Fundamental and applied biological sciences. Psychology; Land use; Mineralisation; Minerals - chemistry; Minerals - metabolism; Nitrogen; Nitrogen - chemistry; Nitrogen - metabolism; Organic matter; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Soil - analysis; Soil Microbiology; Soil science; Trees
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/S0045-6535(03)00237-6

Land use and agricultural practices modify both the amounts and properties of C and N in soil organic matter. In order to evaluate land use and management-dependent modifications of stable and labile C and N soil pools, (i) organic C and total N content, (ii) microbial (C mic) and N (N mic) content and (iii) C and N mineralisation rates, termed biologically active C and N, were estimated in arable, grassland and forest soils from northern and southern Germany. The C/N-ratios were calculated for the three levels (i)–(iii) and linked to the eco-physiological quotients of biotic-fixed C and N (C mic/C org, N mic/N t) and biomass-specific C and N mineralisation rate ( qCO 2, qN min). Correlations could mainly be determined between organic C, total N, C mic, N mic and C mineralisation for the broader data set of the land use systems. Generally, the mineralisation activity rate at 22 °C was highly variable and ranged between 0.11 and 17.67 μg CO 2–C g −1 soil h −1 and −0.12 and 3.81 μg ( δNH 4 + + δNO 3 −)–N g −1 soil h −1. Negative N data may be derived from both N immobilisation and N volatilisation during the experiments. The ratio between C and N mineralisation rate differed significantly between the soils ranging from 5 to 37, and was not correlated to the soil C/N ratio and C mic/N mic ratio. The C/N ratio in the ‘biologically active’ pool was significantly smaller in soils under conventional farming than those under organic farming systems. In a beech forest, it increased from the L, Of to the Ah horizon. The biologically active C and N pools refer to the current microbial eco-physiology and are related to the need for being C and N use efficient as indicated by metabolic qCO 2 and qN min quotients.