Changes in soil microbial activity and physicochemical properties in agricultural soils in Eastern Spain

Agricultural land management greatly affects soil properties. Microbial soil communities are the most sensitive and rapid indicators of perturbations in land use and soil enzyme activities are sensitive biological indicators of the effects of soil management practices. Citrus orchards frequently have degraded soils and this paper evaluates how land management in citrus orchards can improve soil quality. A field experiment was performed in an orchard of orange trees (Citrus Sinensis) in the Alcoleja Experimental Station (Eastern Spain) with clay-loam agricultural soils to assess the long-term effects of herbicides with inorganic fertilizers (H), intensive ploughing and inorganic fertilizers (P) and organic farming (O) on the soil microbial properties, and to study the relationship between them. Nine soil samples were taken from each agricultural management plot. In all the samples physicochemical parameters, basal soil respiration, soil microbial biomass carbon, microbial indexes (BSR/C, Cmic/C and BSR/Cmic) and enzymatic activities (urease, dehydrogenase, beta-glucosidase and acid phosphatase) were determined. The results showed significant differences between the different agricultural management practices for the microbial properties and soil microbial indexes, since these were strongly associated with the soil organic matter content. Unlike herbicide use and intensive ploughing - management practices that both showed similar microbial soil properties - the organic management practices contributed to an increase in the soil biology quality, aggregate stability and organic matter content.