The traditional method of orchard upgrades in Australian horticulture has involved removing old trees, burning them and then ripping the ground in preparation for new plantings.
The environmental impact of such practices has been brought into question in more recent times and almond growers in California have long been exploring more environmentally beneficial methods to get the same job done. Whole Orchard Recycling (WOR) research has been sponsored by the Almond Board of California and the University of California and the results over the past decade have Australian growers sitting up and taking notice. The trials have involved researchers measuring soil health and tree productivity of an almond orchard that returned mulched up old almond trees back into the soil and compared it with an orchard that burned its old trees nine years earlier. The orchard that use tree recycling had a 20 percent decrease in irrigation to quantify its water resilience.
The results, published in Science Daily two years ago, found that, compared with burn treatments, whole orchard recycling can:
- Sequester 5 tons of carbon per hectare
- Increase water-use efficiency by 20 percent
- Increase crop yields by 19 percent
Long-time Australian grower and former ABA chairman Neale Bennett has been pondering the benefits of such a trial in classic Aussie almond growing conditions and earlier this year took the plunge. He has teamed up with SARDI and Hort Innovation to conduct the first scientific WOR program of its type in Australia at his Merbein property. Mr Bennett was one of the early adopters to growing almonds in the Sunraysia and ironically it was his first patch of almonds that has gone back into the ground as part of the project. Just under 3ha of 30-year-old trees have been bulldozed, mulched and returned into to freshly ripped old orchard floor before replanting.
The trial is based on the fact that almond trees accumulate significant amounts of carbon during their lifecycle. The Bennett trial will provide better insights into whether the traditional sandy soils of Sunraysia and Riverland can capture the same sustainable outcomes the Californians have enjoyed.
Unfortunately, when an orchard reaches the end of its commercial life, this resource is traditionally managed through burning as part of the orchard redevelopment. While burning is a quick and effective means to clear debris from the site and can reduce pathogen load, it also releases significant amount of carbon that could potentially be sequestered or at least incorporated to improve soil organic matter, fertility and help with the establishment and productivity of the new orchard. Orchard recycling involve pulverizing the tree and putting it back into the soil.
The trial at the Bennett orchard aims to quantify the impact of whole orchard recycling on the carbon footprint of an almond orchard, including the impact on carbon storage and turnover in the soil, soil greenhouse gas emissions and the carbon accumulation by the newly planted trees.
It will also assess any co-benefits such as improved irrigation use efficiency and soil healthy and potential negative impacts such as increased pressure from soil pathogens and potential for nitrogen draw down. Data will be collected in a manner that will allow it to be used to inform the Australian Life Cycle Assessment and as data input into approved carbon market methodology. Mr Bennett said the trial was an exciting new chapter for his orchard and the industry. He admits he watches closely what is being done in California and is always keen to try new improved ways of growing at home.
“There is no doubt that we have an obligation to grow as sustainably as possible and while there is always room for improvement, I think some critics of our industry might underestimate our existing credentials. We all want sustainable business models and if that means doing things differently, then I think our industry has a great record for embracing change and innovation.”
ABA CEO Tim Jackson said the Bennett trial will add scientific rigor to the benefits of whole orchard recycling in Australian conditions. He said it will help with orchard redevelopment programs and help quantify expectations around carbon farming, changes in soil health, irrigation use efficiency and productivity improvements.
He said the recycling results on Californian soils have been widely embraced and are contributing to longer term aspirations for the industry to become at least carbon neutral. “Almond growers are all about embracing the most sustainable practices available and this trial is yet another example of that commitment,” he said.
“The global expectation around improving the sustainability of how you do business is not lost on our industry. A commitment to firstly measuring the achievements across the industry so far and tackling areas of improvement is gathering momentum farm by farm, processor by processor.” The ABA has been consulting widely across the industry and beyond regarding sustainability in order to develop tools to support, educate and guide stakeholders of all sizes who are committed to being part of the Australian Sustainable Almonds Program.