News: Researchers dig into Top End soil

A team at CSIRO Tropical Ecosystems Research Centre in Darwin is getting an insight into how soil macro-invertebrates like termites, worms and ants help to maintain healthy country in the tropics.

As part of the CRC for Tropical Savannas Management, Dr Garry Cook and colleagues are working throughout Queensland and the Northern Territory to decipher which groups of macro-invertebrates contribute most to nutrient and water retention in soil. "We want to know how their activity can be manipulated to maintain productivity of soils and to help rehabilitate degraded land.

"We are also working with one of CSIRO's flagship projects, Water for a Healthy Country," Cook added. "The aim is to improve the quality of water flowing down to the Great Barrier Reef by focusing on what happens to water and sediment in paddocks."

The flow of water onto the reef, and the quality of this water, is determined by how much of it is absorbed into the land. High levels of soil macro-invertebrate activity, which are found in well-managed paddocks and infrequently burnt areas, increase the rate of water infiltration and reduce runoff and soil loss.

Termites, ants and earthworms are the three most important -- they decompose organic matter and create pores in the soil, enabling water to penetrate. Cook's team has found that in heavily grazed areas, termites increase in number and earthworms decrease. But once land has been severely degraded, the activity of all these invertebrates decreases.

By maintaining food sources such as dead grass, or creating log mounds, soil animals such as termites and worms are able to recolonise the landscape and begin the process of reducing loss of water, sediments and nutrients from the land.

"With the grazing lands it's more about managing the grass biomass for the cattle and the invertebrates," said Cook. "Better management of grazing land would enhance the activity of those groups of macro-invertebrates that contribute most to important soil processes that maximise retention of water and nutrients in the landscape. This is critical to sustaining pasture production"

In this way, the researchers hope to be able to develop more efficient ways of both maintaining and restoring the ability of landscapes to retain water and nutrients, thereby enhancing water quality in creeks and rivers.