New research is showing that sugar cane farming systems which consider the health of soils and roots can increase sugar yields by 5 - 10 percent - reaping Australia's sugar industry an extra $40 million each year.

While there has been large industry investment in new cane varieties and green harvesting methods over the last 20 years, industry wide, sugar yields have remained relatively static. In effect, technology improvements have not been realised in the paddock.

CSIRO researcher Dr Christian Roth says this is the first time that sugar farming has been investigated from the ground up.

"We knew that yield decline is associated with long term sugar cane monoculture and root diseases, but we knew little about the function and growth of sugar cane root systems - and roots are the link between the harvestable cane stems and the soil," says Dr Roth.

Recognising that the factors affecting sugar yield were complex and interconnected, a six year joint research venture to identify and understand these yield factors was established.

Researchers from CSIRO, Bureau of Sugar Experiment Stations (BSES), Queensland Department of Primary Industries (QDPI) and Queensland Department of Natural Resources (QDNR) are taking the whole-farm system approach to understanding and overcoming yield decline. The Sugar Research and Development Corporation is providing much of the funding to carry out the studies.

Projects across Queensland are looking at soil and plant properties and the relationships between crop growth and yield. Breaking continual cane cropping (monoculture) with other species for different periods of time, and the use of crop rotations to break the disease cycle are being investigated.

Research Leader of the Yield Decline Joint Venture, Dr Alan Garside says that research has shown that the longer the farm land has been under cane, the more likely it is to have a reduced productive capacity. Newer lands or lands that have been rotated and been used to grow crops other than sugar cane are more productive.

Many important differences that are likely to have an effect on productivity have been noted between old and new land. In particular, old land is found to be more acid; have lower cation exchange capacity (a measure of the ability of soil to hold nutrients); more aluminium and manganese; less copper and zinc; lower water infiltration and holding capacity; and fewer healthy soil microbes and more root diseases.

One interesting offshoot of the research on using legumes in the rotation is the finding that cane growers on the wet tropical coast can make great savings in nitrogen fertiliser by growing soybeans as a fallow. Soybeans add large quantities of nitrogen to the soil greatly reducing the need to apply nitrogen fertilisers. Recent sugar yields following soybeans are confirming the nitrogen benefit.

Dr Garside believes there is no simple one-stop fix for yield decline, but says that the key lies in understanding the many factors that contribute, how they contribute, and how to manage these factors to maximise productivity.

"We are now beginning to understand the many yield factors and their impacts. We hope to be able to develop technologies to overcome, or at least manage, these factors. The final outcome of the joint venture research is to develop better farm systems based on this understanding."

"Farmers need to assess the 'given' factors in their soils and minimise the negative factors by developing a whole-farm approach," Dr Garside says.

"Many farmers continue to do things because it's traditional. They need to first know their 'givens' and look at how they plant, how they handle trash, what their nutritional program and chemical use is, and then adapt systems to suit their soils."

More information:
Dr Christian Roth, CSIRO (077) 538-569
Dr Alan Garside, BSES (077) 538 588

Media alert:

SCIENCE IN THE BUSH:

CSIRO is this year's Guest Exhibitor at the Australian National Field Days, Orange, NSW November 11-13. Many exciting new scientific advances related to sustainable farming and rural industries will be on display.