Long-term effects of conversation to organic farming on the weed seed bank (Investigations on the Ökohof Seeben, 1994-2011)

• Main Authors: Wittmann, Christian, Petruschke, Arne, Christen, Olaf
• Format: Article
• Language: deu
• Published: Julius Kühn-Institut 2014-02-01
• Series: Julius-Kühn-Archiv
• Subjects: long-term study; organic farming; permanent plots; weed seedbank
• Online Access: http://pub.jki.bund.de/index.php/JKA/article/view/2901/3099
• ISSN: 1868-9892; 1868-9892

Long term adaptation of weed flora to extensive land use (organic farming) was analysed. 350 acres were equally managed by Ökohof Seeben in central German dry region. At permanent observation points seed banks were investigated in 1994, 1996 and 1998 as well as in 2004 and 2011 after a two-year transition period. The determination of seed banks was carried out by using greenhouse emergence assay for 20 observation points, each with 4 subplots. Size, composition and structure of the observed seed banks showed distinct timedependent changes for each site. Seed bank density rose from 17,420 to 33,200 seeds qm-2 during the 18 year observation period. From 1994 to 2011 seeds of approximately 80 species were detected. As organic farming continued site-typical weed species (e.g. Consolida regalis) increased in number. However, two-thirds of the total seed bank consisted of eight ubiquitous species. Their proportion changed to varying degrees. The resulting dominance relationships showed only minor changes over time. In 1994 and 2011 the evenness value was at 0.70 and 0.73, respectively. By use of mass community coefficients distinctly differences between the seed banks of the different plots were found. The variation between the observation points is substantially greater than the time-dependent changes. In the examined area – of which soils show consistently good yield capacity – the location differentiation of weed flora that existed before introduction of organic farming is maintained.