A comparison of indexing methods to evaluate quality of horticultural soils. Part II. Sensitivity of soil microbiological indicators

Soil is a non-renewable natural resource, considered as the basis for food production. Changes in soil properties may indicate potentially beneficial or degradative effects of a given management practice, so it is important to select the most sensitive soil properties to act as quality indicators. This research evaluated different approaches to selecting soil quality indicators in the construction of soil quality indices (SQIs). The sensitivity of integrative SQIs, constructed by considering diverse chemical, physical, and biological properties, was compared with biological SQIs, using only biochemical and microbiological indicators, to assess soil quality in an intensive horticultural production system under short- and long-term organic and conventional management. The results provided by the SQIs showed that plots under organic management had increase soil quality compared with the conventionally managed plots, independent of the number of years under production. The SQIs integrated by physical, chemical and biological indicators were more sensitive than indices composed only of biological indicators, as they did not reflect the physical properties of the studied plots. The organic amendments had a great influence on the microbial community; therefore, microbiological indices could not provide reliable information on soil quality in production systems with high inputs of organic materials.