Boosting Water Savings with Mulch: A New CSIRO Innovation
A groundbreaking research project led by CSIRO Agriculture and Food aims to revolutionize soil moisture conservation techniques. The project focuses on developing a composite mulch batt made from crop residues, which will break down and enhance soil health.
The primary objective is to create a sprayable mulch film suitable for broadacre cropping, especially in low to medium-rainfall regions. This innovative product is designed to surpass the moisture-saving capabilities of traditional mulch and crop residues.
Dr. Stuart Gordon, a Senior Principal Research Scientist, is spearheading this initiative. He explains that the target performance is a biodegradable water vapor transfer barrier, at least 50% more effective than plastic sheeting in reducing evaporation. However, Dr. Gordon clarifies that plastic sheeting, under ideal conditions, is nearly 100% effective.
In practical farming scenarios, plastic sheeting's effectiveness diminishes due to damage and environmental factors. Dr. Gordon highlights that plastic sheeting can only preserve up to 35% more moisture compared to bare soil over the growing season. As an alternative, straw application can yield similar results to plastic sheeting.
The research team has developed a sprayable biodegradable mulch based on an aqueous emulsion of polyurethane. This mulch can be applied to soil surfaces, forming a film to suppress weeds and retain moisture. However, due to the high water content, the formula has been reformulated into a friable powder of polyurethane particles coated with cellulose.
These particles can bind chopped stubble or chaff in the field, creating a composite batt that reduces evaporation and erosion. The batt's microclimate and moisture content are ideal for crop germination. Dr. Gordon suggests that the batt can be sealed more tightly by compressing it, enhancing its barrier properties.
The mulch powder application is versatile. It can be applied dry or after dew or rain, and it can be mixed with water and sprayed onto crop residues. Alternatively, low-temperature heat rollers (60°C) can be used to 'melt' and activate the powder. The polyurethane backbone, containing amine and urea groups, provides a slow-release mechanism for soil microbes as the batt decomposes.
Dr. Gordon emphasizes the importance of applying the powder before seeding, especially on hard-setting and crusting soils, to moderate drying and crusting mechanisms and soil temperatures. When combined with crop residue and moisture, the powder allows the crop to form its canopy while locking organic matter to the ground, preserving moisture and improving infiltration.
Field trials at Horsham, Victoria, and Merredin, Western Australia, in 2026 will assess the product's performance, including adjustments to sowing equipment for cutting through the mulch layer and soil coverage over seeds. The trials will also evaluate the product's biodegradation and potential for weed suppression, soil pathogen protection, and nematode control.
The research team is exploring the addition of refined cereal residues and even recycled cotton clothing to the binder system. They are also investigating the domestic production of the specific polyurethane formula for the mulch powder. Production costs and application rates are being analyzed to ensure the product's affordability and effectiveness.
A prototype product is scheduled for release in 2026, followed by further testing. For more information, contact Dr. Stuart Gordon at stuart.gordon@csiro.au.
