Influence of oats cover crop preceding dryland lucerne establishment on some aspects of soil microbial ecology

Abstract

The use of cover crops to enhance soil ecology is widely propagated. Soil samples were collected at five depths from plots in newly established (four months) dryland lucerne (Medicago sativa) pasture. Preceding this establishment, the plots were either under Saia oats (Avena strigose) cover crop, or no cover crop (managed with herbicides). Variables studied were soil aggregate stability, active carbon (KMnO₄ oxidation), Solvita^® nitrogen and carbon, protozoa (Most Probable Number) and carbon utilisation (Biolog Ecoplates™). Principal component analysis (PCA) clearly showed associations between variables and the cover crop × depth treatments (two cover crop treatments – with and without cover crop), and five depth treatments (0–5, 5–10, 10–15, 15–20 and 20–30 cm). The PCA explained 72.9% of the total variation with the first three components (F1, F2 and F3). Protozoa separated clearly from the other variables. Discriminant analysis showed three distinct groups, namely 0–5 cm depth in both treatments, 5–10 cm depth with cover crop, while all others were in group 3. From these preliminary results it is clear that there are definitely differences in the effect of either a cover crop or no cover crop on some aspects of soil ecology.