Zehn Jahre differenzierte Grundbodenbearbeitung im ökologischen Ackerbau (Projekt Ökologische Bodenbewirtschaftung) - Entwicklung der organischen Bodensubstanz, Nährstoffgehalte sowie bodenbiologischen Eigenschaften

Summary

This study investigated the lasting impact of reduced and conservation tillage, namely two-layer ploughing (LP) and layer-cultivating (LC) on soil ecological properties (physical, chemical, microbiological) in an organic farming system relative to ploughing (P). As a major trend, the amounts of soil organic C, microbial biomass –C and –N, Cmic to Corg ratio, and microbial activity increased in 0-15cm depth in the order P –LP – LC while they decreased in 15-25cm depth in the same order, both in green fallow and winter rye plots. For example, in 0-15 cm depth soil microbial biomass –C concentration was significantly 21 % (LP) and 30 % (LC) greater in green fallow plots or 15 % to 23 % greater in winter rye plots than in P. This was highly correlated with an increase in aggregate stability at these sites. Non-ploughing also resulted in a significant higher bulk density. In addition, there was much evidence that the microbial community changed towards fungi in 0-15 cm depth in reduced and conservation tillage plots. The abundance and fresh biomass of earthworms as well as species richness seemed to benefit from reduced soil tillage intensity. The highest amounts of abundance, fresh biomass and numbers of earthworm species in the current study were found in the plots with the layer cultivation treatment. No tillage effects were found for the amount of plant available P in soil. It can be concluded that reduced or conservation tillage in organic farming systems has beneficial effects on soil organic matter, microbial biomass and potential activity, as well as on earthworms.