Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: October 9, 2008
Publication Date: October 9, 2008
Citation: Weyers, S.L., Archer, D.W., Johnson, J.M., Jaradat, A.A. 2008. Microbial biomass and nutrient dynamics in transitional systems in Minnesota [abstract][CD-ROM]. ASA-CSSA-SSSA Annual Meeting Abstracts. ASA-CSSA-SSSA Annual Meeting. Oct. 5-9, 2008, Houston, TX. Technical Abstract: A large-scale systems study comparing whole-system organic or conventional management with nested tillage, rotation and fertilizer treatments was established in 2002. The treatments within each management system were: strip tillage vs. conventional tillage; two- vs. four-year crop rotations (corn-soybean, corn-soybean-wheat-alfalfa) and fertilized vs. not fertilized (inorganic under conventional management and manure under organic management). Soil samples to 15-cm depth were taken each spring and analyzed for microbial biomass C and N (MBC and MBN). In-situ N mineralization incubations were also conducted in a sub-set of plots from 2005-2007. In the transition phase (2002-2004) there were no significant differences in microbial biomass C or N between conventional and organic management. By 2005 differences between management systems and between treatments across management became more pronounced. By 2007 significant differences were observed with the trend of greater overall MBC and MBN in plots under organic management and for strip-tillage, four-year rotations and fertilization treatments across management systems. In the subset of strip-tilled or conventionally-tilled and fertilized treatments net cumulative mineralization of N was typically higher under organic management; however, it was very dependent on the cropping phase in the four-year rotation.