Could organic compost help save the Great Barrier Reef?

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Great Barrier Reef from the air: this UNESCO World Heritage-listed natural wonder is threatened by run-off from waterways polluted by industry, including agriculture.
Great Barrier Reef from the air: this UNESCO World Heritage-listed natural wonder is threatened by run-off from waterways polluted by industry, including agriculture.
Steve Parish, Lock The Gate Alliance, Flickr CC

Results from ongoing compost trials on a Central Queensland beef farm show that applying organic green-waste compost rather than synthetic fertiliser to pasture grown on depleted soils not only “dramatically reduces” harmful chemical run-off to the reef, it results in a number of other benefits to both farmers and livestock.

The findings, according to leading Australian soil scientist Denis Baker, are “a potential game-changer for the health of the reef – and a significant cost saving for farmers”.

The soil scientist and the compost maker

The trials are being conducted by Denis Baker in collaboration with Ipswich-based organic waste recycler NuGrow, which is supplying the organic compost and soil conditioners.

Baker is the director of Environmental Soil Solutions Australia and former head of the Queensland Government Department of Natural Resources’ Soil Analytical Laboratory. He has more than 47 years of experience in the field of soil science and is something of an expert on the role of composting in soil health and

NuGrow, a family-run business based in Ipswich, south-west of Brisbane, was established 16 years ago and is now Queensland’s largest organic waste recycler, with four facilities around the state.

The aim

According to NuGrow CEO Roy Wilson, “Queensland’s grazing industry has recently come under criticism for not ‘doing enough’ to address soil condition decline due to grazing, with most criticism directed at increasing beef production, declining fertility, and soil condition decline in the reef catchments.

“The field trial sought to demonstrate whether above-average pasture-growing results could still be achieved while reducing the use of synthetic fertiliser and substituting it with more economical organic compost.”

On average, these pastures would typically require 200-250 kilograms per hectare of synthetic fertiliser.

If it could be shown that that organic compost could be employed effectively on pastures to reduce the need for synthetic fertiliser, Baker posited, it would strengthen the case for cutting fertiliser use on farms in Great Barrier Reef catchment areas, and encourage local farmers to use comparatively low-cost compost instead.

 In turn, this would reduce harmful run-off into local waterways and onto the Reef.

Sea turtle on the Great Barrier Reef, 2009: the reef is a huge tourist draw, bringing substantial income into the region. Now farmers can help the reef and their own livelihoods at the same time, suggest recent composting trials near Rockhampton.
Sea turtle on the Great Barrier Reef, 2009: the reef is a huge tourist draw, bringing substantial income into the region. Now farmers can help the reef and their own livelihoods at the same time, suggest recent composting trials near Rockhampton.
GJ Hamley, Flickr CC

The compost

The compost used for the trial was produced by NuGrow from 100 percent green waste – tree prunings, waste from greenfields clearing of trees, including some green waste left by Cyclone Marcia, and the like – mixed with air and moisture.

“The benefits are that these soils aren’t that great to start off with and we’ve run down the organic carbon levels in these soils,” Baker explained in an ABC Rural interview.

“So we’re putting back what we’ve removed over time, and the form of the nutrients we’re putting in are slow-release, so the compost … becomes co-mingled with the soil – as in nature, where we have it happening over a period of 30 to 40 years.

“It actually adds protection because it improves the soil structure. In other words, water will tend to infiltrate rather than run off,” he said.

“It will definitely reduce sediment run-off.”

The initial composting trial

The initial compost trial took place over a three-month period in late 2015 at Raglan Station, a 10,000-hectare beef farming enterprise about 60 kilometres south of Rockhampton.

The property lies adjacent to the Fitzroy River delta, an important catchment for Queensland’s UNESCO World Heritage-listed Great Barrier Reef.

The trial was designed to enable accurate assessment of the impacts on pasture of applying varying amounts of organic compost to pastures in place of synthetic fertilisers.

On average, Raglan Station’s depleted soils typically require 200-250 kilograms of fertiliser per hectare for adequate pasture growth.

Three trial plots were spread with 10, 20 and 30 tonnes per hectare respectively of NuGrow’s compost, with a fourth plot used as a ‘business as usual’ control – i.e. synthetic fertiliser but no compost was applied.

After six weeks, lucerne grass from each of the four plots was cut and metre-square samples from the control plot and 30t/ha compost plots were weighed to establish their respective densities.

Pasture and soil samples from the trial and control plots were also analysed for their composition and nutritional content.

Compost trials at Queensland's Raglan Station: soil scientist Dennis Baker inspects the NuGrow organic compost at the Raglan Station site.
Compost trials at Queensland's Raglan Station: soil scientist Dennis Baker inspects the NuGrow organic compost at the Raglan Station site.
NuGrow

The results

Results of the compost trial’s first phase were released in December 2015 at an open field day at Raglan Station, run by the Olive family.

According to Baker, who has nearly a half-century of experience to back his claim, the results of the initial trial were nothing short of “outstanding”.

“I'm a chemist by profession and have advocated long and hard that organically based composts can dramatically reduce chemical run-off to the reef, while maintaining and even increasing agricultural yield,” he said.

Baker told ABC Rural shortly afterwards that he could not have anticipated more positive results.

“It’s early days, but our prediction is that this soil will require less than half the synthetic fertiliser in the next couple of years,” he said.

The farmer’s assessment

To 25-year-old Ryan Olive, a third-generation farmer, the initial results of the composting trial came as a “complete surprise”. After just six weeks, pastures that had received a one-time application of organic compost had returned three to four times the volume of growth of pastures treated with fertilisers as usual.

“We sowed numerous controlled plots with lucerne at the same time, with exactly the same soil profiles and exactly the same watering conditions,” said Olive. “Some pastures had nothing added, while others had various ratios of organic soil conditioners.”

When samples of pasture from square-metre patches taken from the control and 30 tonnes per hectare compost plots were harvested and weighed to ascertain differences in density, the vegetation from the control plot weighed 576 grams per square metre, whereas that from the 30t/ha plot weighed 1,704g/m², more than three times greater.

“In short, the weight and yield from the pastures using soil conditioners was beyond what I was expecting over a six-week period,” Olive added.

“And at less than one-tenth of the price of synthetic fertiliser, you have to seriously look at this.”

Three months in, Olive is a convert, seeing transitioning from fertiliser to organic composting as the future for Raglan Station.

“You can definitely see the results when you walk around the paddock,” he told ABC Rural. “I think the true results will be in the next time we bale, the time after, and this time next year. If we can keep seeing the results then that we’re seeing now, then that’ll be pretty good.

“When you work it all out, it is a little bit dearer, but if you don’t have to put this on every time, or every year, like you have to with synthetics, then there is a cost benefit,” he said.

“But this is still a trial – in about two years’ time, we’ll have a lot more worked out.”

Additional benefits of composting

According to Baker’s analysis, significant increases in volume and yield were not the only benefits resulting from applying organic compost to the trial-plot soils prior to planting.

The pasture to which the organic compost had been applied retained moisture better, had better digestibility as fodder, and contained more protein content than did vegetation from the pastures grown without compost.

“Here we have proof that soil conditioners work,” contended Baker.

“This is a potential game-changer for the reef and, if adopted more broadly, will reduce damaging run-off in sensitive catchments.

“Over a three-year period, with a tailored regime that meets the soil profile of the property, I can see some farmers reducing their need for synthetic fertiliser by over 70 percent,” he said.

NuGrow’s Wilson says the trial demonstrates the potential for improving fodder production by applying organic compost, citing greater live weight gains, soil improvement and stabilisation, and a reduction in losses of soil nutrients and soil sediment as additional benefits.

“Compost enhances productivity for beef producers using a soil-conditioning product produced from natural waste products, including green waste,” Wilson said.

“The good news is there is an environmentally positive angle to this product.”

Further information and updates

For further information and updates on the project, contact Troy Collings, General Manager, Strategy and External Relations at NuGrow, on 0421 12 8000 or troycollings@nugrow.com.au.

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