Short CommunicationEffect of organic and conventional practices on carbon-substrate utilisation by the soil microbial community in a ‘Cripps Pink’/M7 apple orchard

Abstract

Changes in microbial community metabolic profiles potentially can be used to identify differences in soil characteristics caused by dissimilar orchard floor management practices. The impacts of orchard floor management practices on the microbial community metabolic diversity (CMD) were examined in apple orchard soils subjected to two conventional (CON) and three organic (ORG) orchard floor management practices. The CMD, as indicated by carbon (C) substrate utilisation (BIOLOG™ system), was determined in composite soil samples (0–15 cm) from the tree rows. The CON treatments reduced, and ORG treatments increased, C-source utilisation and, hence, CMD. Among the CON treatments, C-source utilisation in summer was favoured by winter cover crops in work rows, controlled with herbicide in spring, compared to uncontrolled weed-covered work rows. Orchard soils under ORG regimes more closely resembled soils of natural ecosystems in that they were better able to sustain CMD, and possibly afford a better option to sustain critical ecosystem functions than under CON management, which relies heavily on synthetic agrochemical usage.

Keywords: BIOLOG™, community metabolic diversity, compost, fertiliser, herbicides

South African Journal of Plant and Soil 2014, 31(4): 237–239