Langzeitversuch Burgrain: Bodenmikrobiologische Parameter in biologisch und integrierten Anbausystemen im Vergleich

Summary

In a large scale field experiment near Lucerne (Switzerland) the effect of integrated and organic farming systems on soil microbial parameters was investigated. Three farming systems, IP intensive, IP extensive and organic farming (“Bio”) were com-pared on six plots during 18 years. The six year crop rotation with two years of ley (grass-clover mixture) was identical for all treatments, as was soil tillage, except that tillage in IP extensive was switched to non-inversion tillage starting in 2003. Soil sam-ples from 0 to 20 cm depth were taken in spring, between 1993 to 1996 every year and after 1998 every second year. The samples were analysed for soil microbial biomass (substrate induced respiration SIR and since 2002 chloroform fumigation extraction CFE), soil respiration and nitrogen mineralisation. All parameters showed clear and stable differences between plots, depending on soil characteristics. Although significant differences between farming systems in single plots or for single parame-ters occurred, there could not be found any overall significant differences between the three farming systems. Although this result is contradictory to findings in the literature, it is confirmed by other investigations in Switzerland. It may be explained by the fact that both IP as well as the organic farming system had the same crop rotations and both got organic manure, as it is common agricultural practice in Switzerland.