Are soil biological properties and microbial community structure altered by organic farm management?

Summary

Environmental conditions and farm management practices have a considerable impact on soil biota, affecting nutrient cycling processes and ecosystem functioning. Understanding how management practices influence soil fertility and agricultural productivity is essential to improve the sustainability of agroecosystems. The effect of farming history on microbial soil properties was assessed by analysing soil samples from two organic and conventionally managed sites. Cmic and Nmic, enzyme activities, bacterial community composition (PCR-DGGE) and total numbers of fungi and bacteria (soil dilution plating) were determined. Results suggested that organic farming practices did not have a clear positive effect on soil microbial biomass and activity; distinct differences in bacterial community composition were detected by PCR-DGGE but not by soil dilution plating. Findings indicate that practices commonly associated with conventional farming (application of mineral fertilisers or pesticides) have a less pronounced effect on the soil microbial community than other management techniques (e.g. manure application and crop rotation).