A sugar hit for microbes helps native grasses
Feeding sugar to soil micro-organisms helps native grasses establish.
This somewhat surprising link was made recently at a Young property where researchers from CSIRO and Charles Sturt University established native grasses in a remnant grassy woodland.
Previous research had established that remnants invaded by annual weeds had high soil nitrate levels.
Areas with mainly native grasses had low nitrate levels.
Researchers Suzanne Prober and Ian Lunt concluded that low soil nitrate levels would encourage native grasses to establish.
On the Young property they added sugar and kangaroo grass to the soil and found that the annual weeds reduced greatly and allowed the kangaroo grass to establish.
Sugar is a carbon molecule which feeds microorganisms.
In the trial, the sugar stimulated the microbes’ growth so much they began feeding on nitrate from the soil, leaving very little for the weeds to use.
The effect of the "sugar hit" lasted only three months, but in that time the kangaroo grass seed established easily.
Three years later the grass had formed such a dense sward few weeds were able to grow.
Even when the grass was burnt or mown, weed growth remained low due to the extremely low soil nitrate levels, similar to weed-free undisturbed reference sites.
The native grasses survive in such low fertility soils by storing nutrients in their roots and leaves.
The research showed clearly that exotic grasses and weeds outcompete native grasses in fertile soil.
Reduce the fertility and you increase the native grasses’ chance of survival.
These results are so encouraging a new seven year research project is now investigating a range of non-chemical methods to re-establish native grasses on large weed infested sites in southern NSW.
The methods include re-seeding, crash grazing, burning, and adding sugar.
The project will also compare the effectiveness of different combinations of native grasses for preventing weed growth.
Two demonstration sites will be established on travelling stock reserves near Albury and Gerogery.
Read more about the research at www.anbg.gov.au/anpc/kangaroo_grass17(1).html and www.sciencealert.com.au/news/20081710-18303.html