Bold claim: a breakthrough mulch powder could dramatically cut water loss in broadacre farming — and the science behind it is becoming practical, not just theoretical. CSIRO researchers are developing composite mulch batts from crop residues to improve soil moisture retention, building on existing moisture-saving strategies with a new sprayable, biodegradable mulch system. The Grains Research and Development Corporation (GRDC) funds a three-year project aimed at tailoring a sprayable mulch film for broadacre crops, especially in low to medium rainfall areas. Dr. Stuart Gordon, a Senior Principal Research Scientist in CSIRO Agriculture and Food’s Systems Program, leads the effort.
The performance target is a biodegradable moisture barrier that reduces evaporation by at least 50% compared with a plastic sheet. In lab terms, plastic is nearly 100% effective, but field conditions—tears, holes, wind, heat—drastically reduce its performance, limiting real-world moisture preservation to roughly 35% over a season. In contrast, straw mulch can deliver a similar advantage across a growing season. The team reports promising lab results: controlled-environment tests show the new treatment can cut evaporation by up to 40% (see Figure 1: Evaporation comparison of bare soil and mulched treatments).
How the powder works: CSIRO already held patents for a sprayable biodegradable mulch based on a polyurethane aqueous emulsion that formed a weed-suppressing, moisture-conserving film. Transport costs for a product that was about 80% water led to a redesign. The new formulation is a friable powder of polyurethane particles coated with cellulose. When applied, these particles act as a binder to hold chopped stubble or chaff into a composite batt on the soil surface, reducing evaporation and erosion. If the weather turns hotter or drier, the batt can be compressed to tighten its barrier properties.
The mulch powder is described as tunable: it can be applied dry or after rain to activate bonds, mixed with water and sprayed onto crop residues, or heated with low-temperature rollers (around 60°C) to melt and activate. The polyurethane backbone contains amine and urea groups that can feed soil microbes as the batt decomposes, while the cellulose provides extra bonding sites and resilience so the batt doesn’t readily fall apart when disturbed. The idea is to apply the powder before seeding to form a composite batt over hard-setting soils, moderating drying, crusting, and high soil temperatures. When combined with crop residue and moisture, the residue stays intact long enough for the crop canopy to develop, and the organic matter remains anchored to the ground around the germinating seed to preserve moisture from brief rain or fallow periods and to improve water infiltration.
Field trials are planned for 2026 at Horsham, Victoria, and Merredin, Western Australia, to test practicalities like sowing equipment clearance through the mulch and how to re-cover soil and seed after sowing. Across 2024–2025, lab and small-plot tests confirmed the powder’s efficacy in forming batts, preserving moisture, and enabling mulch breakdown. Early results indicated that more than half of the binder had biodegraded within eight months, and ongoing biodegradation studies will extend to soils with low microbial activity, including trials at the Waite campus in South Australia.
There’s potential to adapt the product for weed suppression by adding pigment to block sunlight, or to incorporate actives that protect against soil pathogens or nematodes. Polyurethane’s role as a carrier means these agents could be released as the batt biodegrades. Researchers are also exploring incorporating refined cereal residues or even recycled cotton cellulose into the binder to enhance performance. Domestic production considerations are under review, given that polyurethane is currently manufactured mainly for construction, with a prototype slated for release in 2026 for broader testing.
Bottom line: if these trials succeed, farmers could have a practical, cost-effective mulch option that reduces evaporation more reliably than traditional plastic sheets, supports crop germination, improves infiltration, and contributes to healthier soils over time. What do you think — should the agricultural industry adopt such biodegradable mulch systems widely, or are there still significant trade-offs to weigh? Would you support mandating or incentivizing adoption in drought-prone regions, or prefer slower, evidence-based rollouts and farmer-led testing?
For more information, contact Dr. Stuart Gordon at CSIRO (stuart.gordon@csiro.au).
