WOODCHIP OR WEEDMAT? A COMPARATIVE STUDY ON THE EFFECTS OF MULCH ON SOIL PROPERTIES AND BLUEBERRY YIELD

Blueberry growers in northern New South Wales, Australia, wanted to replace black plastic weedmat with woodchip fines mulch to reduce plastic waste and improve soil condition. Experiments were established to compare the effects of two mulch treatments on berry yield, plant size, soil compaction and soil microbial activity over three years. Southern highbush Vaccinium ×corymbosum ‘Star’ seedlings were planted on three soil types, with 5 cm of woodchip or plastic weedmat applied to each plot. After three years, woodchip treatment increased berry yield by 81% on one soil type (grey gravelly silty loam), but was not significant on two other soil types (red loam, red silty loam). Canopy volume also increased with woodchip at the grey silty loam site, for a six month period in the red silty loam but not at the red loam site. Soil compaction (bulk density) was reduced with woodchip treatments in two of the three soil types. There was no difference in soil microbial activity. The improvements after woodchip application were most beneficial to compacted soils.