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Abstract  Because soil biota is influenced by a number of factors, including land use and management techniques, changing management practices could have significant effects on the soil microbial properties and processes. An experiment was conducted to investigate differences in soil microbiological properties caused by long- and short-term management practices. Intact monolith lysimeters (0.2 m2 surface area) were taken from two sites of the same soil type that had been under long-term organic or conventional crop management and were then subjected to the same 2.5-year crop rotation [winter barley (Hordeum vulgare L.), maize (Zea mais L.), lupin (Lupinus angustifolius L.), and rape (Brassica napus L. ssp. oleifera)] and two fertilizer regimes (following common organic and conventional practices). Soil samples were taken after crop harvest and analyzed for microbial biomass C and N, microbial activity (fluorescein diacetate hydrolysis, arginine deaminase activity, and dehydrogenase activity), and total C and N. The incorporation of the green manure stimulated growth and activity of the microbial communities in soils of both management histories. Soil microbial properties did not show any differences between organically and conventionally fertilized soils, indicating that crop rotation and plant type had a larger influence on the microbial biomass and enzyme activities than fertilization. Initial differences in microbial biomass declined, while the effects of farm management history were still evident in enzyme activities and total C and N. Links between enzyme activities and microbial biomass C varied depending on treatment, indicating differences in microbial community composition. [ABSTRACT FROM AUTHOR]

The mineralization of organic forms of phosphorus (P) in soil contributes significantly to plant P uptake, although quantification of organic P mineralisation has been impeded by methodological difficulties. An isotopic dilution method, based on tracer kinetic theory, was used to study the organic P flux rates for unamended and green manure amended soil in an incubation experiment carried out over 35 days. Firstly, the specific activity (SA) between two points of time as affected by dominant biological processes (under conditions of constant soil respiration rates) was determined in a series of successive labelling incubation experiments. Secondly, the instantaneous specific activity (instSA) between two points of time was also determined by shaking an unlabelled soil with 33P, i.e. soil samples that were not labelled with 33P, but kept under conditions identical to the labelled soil samples. This gives the net size of the exchangeable inorganic P pool in the labelling experiments at two points of time during incubation. The SA dilution in the labelling experiments at a constant exchangeable inorganic P pool between two times was attributed to the release of non-labelled inorganic P from the organic P pool by mineralisation. The daily gross organic P mineralisation rates for the 21 days of incubation were 0.06 and 0.27 mg P kg−1 day−1 for unamended and green manure amended soils, respectively. The study demonstrated that green manure amendment contributed to an overall increase in soil P availability through enhanced organic P mineralisation. [ABSTRACT FROM AUTHOR]