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

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 degrees C was highly variable and ranged between 0.11 and 17.67 microg CO(2)-C g(-1) soil h(-1) and -0.12 and 3.81 microg (deltaNH(4)(+)+deltaNO(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.     

Untersuchungen zur Eignung von Neutralsalzen als Referenzmittel bei der mikrobiologisch-ökotoxikologischen Bewertung von Pflanzenschutzmitteln im Boden

Goal and Scope

The information value of microbiologicalecotoxicological investigations of pesticides in soil increases if reference compounds with known biocidal effects are included. But those reference compounds used until now often are of remarkable environmental and human toxicity and therefore are difficult to handle. Inorganic neutral salts sometimes were discussed as alternatives, but their suitability needs to be tested before.

Methods

For laboratory experiments some microbial activities in soil were selected whose effects had been proved in several microbiological-ecotoxicological investigations. They include the mineralization of carbon and nitrogen (+ nitrification) as well as the biomass-related parameters dehydrogenase activity and substrate-induced short-term respiration. Several agricultural soils were used to confirm the results.     

A methodological note on ethics,economics, and the justification of action

Two disciplines claim to provide justification of action. Ethics gives you moral reasons to act upon, whereas economics exploits the concept of rationality. The paper discusses two theories of interdisciplinarity of ethics and economics in order to clarify the relationship. The traditional view of a hierarchical ordering of ethics and economics is rejected, and it is claimed that there are substantial economic contributions to ethical justification.