Soil Physical and Physico-chemical Variability Induced by Atriplex nummularia

Abstract

Spatial variability in two soils supporting 10-year old stands of saltbush (Atriplex nummularia) was examined by evaluating various soil physical and physico-chemical properties under and between the plants. The differences in soil properties between these two positions were mostly significant for the surface layer (0-7.5 cm) but only in a few cases for the 7.5-15 cm layer. No differences were observed below this depth. Presence of A. nummularia resulted in increased electrolyte concentration, higher sodium adsorption ratio, and higher levels of exchangeable sodium and organic matter in the surface soil. Standard laboratory measurements showed that these physico-chemical changes induced a significant deterioration in the structure of the surface soil under the plants as indicated by reduced aggregate stability, poorer drainage, and lowered hydraulic conductivity. Field studies suggested that the bulk density of the surface soil was reduced under the plants but that water penetration and storage in the profile after rains remained unaffected. Probable reasons for these effects are discussed.