Selecting soil properties for assessment of soil aggregation using principal component and clustering analyses

Abstract

Aggregation is an important factor among physical soil parameters and affects soil quality. In this study, some soil physical (field capacity, wilting point and sand, silt and clay contents), chemical (pH, electrical conductivity, CaCO3, organic matter and exchangeable Na, Ca, Mg and K) and biological properties (CO2 from respiration and urease, dehydrogenase, β-glucosidase, alkaline phosphatase and acid phosphatase activities) were examined. Some of these properties were eliminated by principal component and clustering analyses to create a minimum dataset. Correlations were evaluated between selected properties and the percentage aggregation of micro (<0.25mm) and macro aggregates (0.25–4mm). Sand, Mg, pH, organic matter, urease, dehydrogenase, alkaline phosphatase and β-glucosidase properties were selected after principal component and clustering analyses. The highest correlation was between the percentage of micro aggregation and urease activity (0.545, P < 0.01). For macro aggregates, the highest correlation was with organic material (0.560, P < 0.01). A negative correlation was observed between macro aggregation percentage and sand content (−0.410, P < 0.01), with a similar relationship for micro aggregation and sand content (–0.450, P < 0.01), but there were positive relationships with other properties. The exchangeable magnesium content showed similar relationships for both aggregate sizes (0.430 and 0.440, P < 0.01). The correlations of aggregation with other enzymes and pH were nonsignificant (P > 0.05). In general, the highest correlation for micro aggregation was with enzyme activity.