Alternative uses for Australian Rice straw

A summary of the impacts & solutions of stubble burning.

A summary of the impacts & solutions of stubble burning.

The issue:
Rice crops can leave stubble loads of up to 15 tonnes if a 12 tonne per hectare crop is grown. This poses a significant issue for farmers due to blockages and poor seed-soil contact when sowing a consecutive crop. To cope with this constraint, often stubble is burnt 1-6 months after harvest to improve trafficability and establishment of the following crop. This poses both an environmental and economic disadvantage, as studies suggest that burning reduces nutrient levels and releases carbon dioxide, monoxide and nitrous oxide which can increase the likelihood of human respiratory problems and contribute to greenhouse gases.

The solution:
Local farmers volunteered their rice paddocks in 2017-19 for some incorporation demonstrations to showcase whether commercially available implements and amendments were a viable management alternative for rice stubble. Treatments applied included mulching, rolling, incorporation using an offset disc, speed tiller and deep ripper in different combinations. Amendments such as UAN, NPKS and microbial inoculants were also trialled at high rates to observe if this sped up decomposition. Lastly, a case study booklet collating alternate management practices across the industry was published as a reference document. A link to this booklet can be found below. 

The impact:
The demonstration sites indicated that acceptable stubble breakdown could occur over 4 months during summer using an offset disc plough with at least 2-3 passes of the paddock. Mulching before incorporating stubble was beneficial for a more even incorporation but did not necessarily speed up decomposition. The case study publication has been well received by the industry. We hope that both the demonstration and extension material will encourage farmers to consider alternative management options by providing more access to information about the pros and cons of different options available to them. Alternate management options could lead to soil health improvements (build up in soil organic matter and retention of nutrients), improve social licence for the rice industry, lead to lower fertiliser inputs and some would lead to reduced greenhouse gas emissions.

Learnings:
We found that implements such as the speed tiller and deep ripper did not do a great job of incorporating stubble. The tiller was unable to cut through the straw and experienced blockages and the ripper left large clods resulting in poor stubble-soil contact necessary for breakdown. Rolling stubble after incorporation or applying fertiliser and microbial amendments made no significant difference to the speed of decomposition. 

Project partners

This project run by the Moulamein Cropping Group in conjunction with the Western Murray Land Improvement Group and Rice Extension as part of the Australian Government's National Landcare Smart Farms Small Grants Program. 

​We would also like to acknowledge local farmers Michael, David, Laurie and Andy for donating their land, equipment and time to make this project possible. ​