CSIRO scientists create spray-on solution to soil moisture loss

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A spray-on polymer membrane to cut evaporation is one of the “next big things” from CSIRO that offer boosts to productivity or value-added potential, Dr Michael Robertson from CSIRO's agriculture and food division told the NFF Conference in October 2016.
A spray-on polymer membrane to cut evaporation is one of the “next big things” from CSIRO that offer boosts to productivity or value-added potential, Dr Michael Robertson from CSIRO's agriculture and food division told the NFF Conference in October 2016.
CSIRO

Researchers at Australia’s national science and research body CSIRO have developed a spray-on polymer product that reduces soil moisture evaporation and weed growth significantly. CSIRO believes the biodegradable, spray-on mulch mat could be ready for commercial release in less than two years.

Experimental trials of the new polymer on sites in the Murrumbidgee Irrigation Area, near Griffith, New South Wales, have proven successful.

Now, the research team is scaling up for a commercial evaluation, applying the spray-on mulch mats to high-value field crops – melon and processing-tomatoes – at Finley and Mildura, on the border of NSW and Victoria.

The goal of the commercial is to ensure that the additional input costs of buying and applying the new membrane (which is likely to be comparatively pricey, at least early on) are reliably offset by improved yields and crop returns.

How does it work?

For soils growing crops, the polymer is coloured black; this prevents sunlight from penetrating the membrane and thus suppresses the growth of weeds between planted rows.

According to CSIRO Townsville-based project leader and globally-recognised soil physicist Keith Bristow, the spray-on membrane is like covering the soil with sheets of black plastic – but with a dramatically shorter lifespan.

Dr Bristow said the industrial-based, spray-on biodegradable polymer allows growers to apply a temporary barrier that, by limiting evaporation, increases soil-moisture levels and hence the amount of water available to crops for growth in the months following planting.

By the time the membrane-barrier degenerates, a dense canopy of foliage has developed that shades the soil beneath, reducing evaporation and weed activity naturally.

CSIRO’s new spray-on polymer has proven highly effective as a weed mat and moisture retainer, Dr Bristow said.

Though lack of uniformity in terrain – tyre tracks, sticks, clods of earth and the like – mean the spray-on process won’t seal the paddock surface completely, that’s not a big concern, he told Farm Online in November 2016.

“Holes allow oxygen to enter the soil – we are very conscious of protecting soil microbiology,” Dr Bristow said.

The Townsville researchers expect that applying the polymer will be a simple matter for the average grower – akin to using an agricultural spray rig to apply herbicides or fungicides.

In trials over the past four years, project team members have been using portable hand-held spray kits (the kind you get from farm supply and hardware stores) to apply the polymer, with “satisfactory” results.

In the pipeline: hardier, longer-lasting, weed-killing polymers

Ongoing research at CSIRO is focused on refining the biodegradable polymer; the goal is to create a product that can be applied directly to the soil surface to restrict evaporation as crops are planted, and that can be assured of lasting up to four months before degrading.

The CSIRO team is also working on variations of the polymer that take a year or more to break down – products farmers could use to protect paddocks during both production and fallow phases. Other options they’re exploring include a more resilient version of the spray-on membrane that could be used to line irrigation channels and water storage facilities to limit water loss from seepage.

The membrane will be trialled across differing climatic zones to determine how rapidly the polymer degrades under varying soil, temperature and rainfall conditions.

In addition, the researchers are studying the potential impacts on livestock that ingest fine residue from the membrane.

And Perth-based Michael Robertson, science director at CSIRO’s agriculture and food division, told the 2016 National Farmers Federation Congress in October that potentially, the new polymer could be engineered to incorporate herbicides for weed control, and/or nutrients and enzymes beneficial to crop growth and nutritional quality.

Wider opportunities

By improving crop water-use efficiency, CSIRO’s new membrane has the potential to help growers boost yields and farm-gate returns significantly. Useful applications are broad-ranging.

“We’ve got people queuing up with ideas about all sorts of potential applications,” Dr Bristow said.

Discussions are underway with several potential partners with regard to the membrane’s commercial release – which will likely happen within in 18-24 months, “depending on how our next stage of trials progress”, he said.

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