Unterschiedlich aktive C-Pools im Boden: Corg, POS, CO2. 2. Vergleich der Parameter und Methoden zur Beurteilung der Bewirtschaftung

Summary

Description and assessment of soil organic matter are usually based on either stock parameters (e.g. Corg, carbon soluble in hot water, particulate organic matter fractions, humic acids, humins etc.) or activity parameters like soil respiration, microbial biomass (CFE, SIR), enzyme activities, Biolog® analysis, incubation tests. Each parameter describes a specific part of soil organic carbon and specific turnover processes in the complex action of carbon mobilization / immobilization. With 3 selected parameters: organic carbon content (Corg), particulate organic matter content (POM) and carbon dioxide development after re-wetting of air-dried soil samples (CO2 flush in 24 h) and their results obtained in a long-term fertilization trial the pros and cons of the parameters and their analytical methods are discussed in order to show how meaningful they are for evaluating cultivation methods.
The results are presented in detail in another contribution at this conference. Compared to mineral fertilization composted farmyard manure gave higher contents of Corg and heavy fraction of POM, lower contents of light fraction of POM and more intensive CO2 flushes. Therefore, the organic treatment showed better results both with long-term C pools and with short-term activity. A number of literature findings confirm our results.
The advantage of the parameters Corg and CO2 flush is their simple and cheap analytical methods. Compared to that determining POM is relatively time and cost intensive. While CO2 flush is an indicator of microbial biomass and mineralization, the more general parameter Corg hardly allows for specific conclusions. As being quite different the light and heavy fraction of POM reflect not only an ample spectrum of soil biological processes, but allow also for deeper investigations with each material.
As regards the key aspects of organic farming (e.g. effects of manure and other organic fertilizers, crop rotations, long-term effects, supply of nutrients) all 3 parameters considered here are of significance depending on each particular question.