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Luvic chernozem (set-aside from 1996) was evaluated. The first period, before Roundup desiccation (2002-2003), was characterized by black, spontaneous and controlled fallows (mowed with the removal of plant biomass or mulched); the following period (2003-2004) by black fallow with repeated Roundup applications; and the last period (2004-2006) involved regrassing by a mowed Lolium multiflorum monoculture. The characterization included microbial biomass, available organic carbon, basal respiration, metabolic quotient, biomass-specific available organic carbon, arylsulfatase activity, soil organic matter carbon and total nitrogen. Mulching of pure cultures of grasses and legumes contributed to a high soil organic matter accumulation. Repeated Roundup desiccation caused a strong (highly significant) decrease of arylsulfatase activity (-28%), however, highly significant increase of microbial biomass (+69%) and nitrate-nitrogen (+86%) were determined. The subsequent regrassing compensated for the changes described. The soil biological properties were best preserved on mulched fallow with Lotus corniculatus and Festuca pratensis, also in regard to contamination with weeds.
