May 02, 2022

The plot thickens with less fertilizer

A nearly 30-year Alcoa research project on the effectiveness of fertilizers in mine rehabilitation sprouted some unexpected results in Australia’s jarrah forest—the application of very little to no fertilizer has enabled greater plant diversity and numbers.

Typepad Image Curation Sustainability (3)The jarrah forest is rich in plant species, even though the soils are naturally low in nutrients. In areas mined for bauxite, the conventional practice was to apply fertilizer during rehabilitation to facilitate quick and vigorous plant growth.

In the mid-1990s, our Western Australia operations began collaborating with local universities to establish trial plots within newly rehabilitated areas in the jarrah forest to examine the impact of differing levels of fertilizer use. Key results over nearly three decades of research were:
• In the early phases of rehabilitation (one to two years), fertilized plots had a higher number of plants.
• Over the long term, plots with very little or no fertilizer had more plant species, individual plants and covered ground.

The primary reason for the vigorous early growth in the fertilized plots was that conditions favored weeds and quickly fading plants. These blocked the slower-growing and more diverse species from taking root, leading to less diversity and numbers over the long term.

Based on the study’s results, we halved our fertilizer use in jarrah forest mine rehabilitation beginning in 2016. We are currently evaluating either eliminating or further reducing its use.

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