SOIL HEALTH AND NEMATODE COMMUNITY STRUCTURE RESPONSES TO DIFFERENT MULCH TYPES IN AVOCADO PRODUCTION

A 3-year trial was laid out to determine the effect of mulch applications on soil chemical, physical, biological and nematode community structure in a 3-year-old commercial avocado orchard in Mooketsi, South Africa. The treatments comprised untreated control, composted chips, eucalyptus chips and grass, applied to a thickness of 15 cm around the base of the tree. Treatments were arranged in a completely randomised design with three replications consisting of 15 trees per treatment. Standard commercial avocado cultural practices were carried out. Twelve months after application, mulching had no effect on standard soil chemical or physical variables and trophic groups, except that composted chips had significantly higher percentage of carbon and active carbon contents. Within all treatments, bacterivores and plant-parasitic nematodes were the most abundant nematode trophic groups. Mulching reduced the population sizes of plant-parasitic nematodes but increased the relative abundance of fungivores. Ecological indices for nematodes such as maturity index, plant-parasitic index, enrichment index and channel index were, incidentally, also not affected by mulch application. Results of this study suggested that mulch application had little effect on nematode community structure and most of the selected soil health indicators in an avocado orchard.