Bacteria boosts water availability

Water repellent sandy soils in the western and southern grain growing belt can be addressed by applying lime to encourage beneficial soil bacteria.

According to Dr Margaret Roper, a soil microbiologist at CSIRO Plant Industry in Perth, lime improves initial water infiltration physically creating a moister, more favourable environment for the bacteria to grow.

Water repellency is caused when hydrophobic 'skins', made from plant waxes and other products from the natural process of plant biodegradation, form around individual sand grains.

These skins effectively repel the water from the soil and limit water availability to the crop.

Certain wax-degrading bacteria called actinomycetes can break down these skins but they only work when there's enough water.

By applying lime, the soil can become wet enough to stimulate the actinomycetes that can then start to reduce water repellency and increase soil water storage. The calcium in lime is also needed for the structural development of actinomycetes.

In soil where lime was applied there were up to ten times as many actinomycetes than in untreated soil.

Lime is cheap and easy to apply and has the added benefit of raising low soil pH to levels that favour other soil micro-organisms also important in soil health and plant growth.

This research is supported by the Grains Research and Development Corporation.

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