Coarse pine bark mulch as open surface cover fails to improve establishment of sown native grasslands

This study was conducted across twelve agricultural locations in south-western Victoria, Australia, encompassing a range of soil types and climatic conditions. It investigated the addition of an open layer of coarse organic pine wood chip mulch (~70% surface cover) directly following direct seeding of native grassland species. The intent was to mimic positive effects of naturally occurring organic surface litter (which are typically depleted in such settings) on seedling emergence and establishment. Findings revealed negative results in that the use of an open layer of coarse pine chip mulch failed to improve native establishment at 12-months or to moderate soil temperature and moisture extremes in comparison to non-mulched plots. This outcome suggests the effectiveness of open surface mulches under the scenario of direct seeding may be highly site context, mulch-type, and application approach dependent. In situations where such mulch applications are not likely to be beneficial, significant costs relating to their purchase and application could be avoided.