Macadamia turf trial to choose best mixes

Macadamia growers across Australia are set to benefit from trial work investigating better inter-row surface conditions, especially in shaded environments.

Improving inter-row turf density and growing characteristics helps improve harvesting (as the nut sits on top of the grass and is easier to pick up), reduces erosion and sediment loss, deters rodents within the inter-rows and reduces mowing requirements.

The work is being done by Barenbrug Australia, in conjunction with Australian Sports Turf Consultants (ASTC), headed by Matt Roche – former Research Scientist with the Queensland State Government's turf research program.

It is critical information for growers, says Barenbrug Australia’s turf portfolio manager Matt Merrick, as grass selection and management within the orchard is just as important as tree varietal selection and spacing.

“The three main areas growers need to manage grass within their orchards are, under the canopy, the inter-row and drainage plus headland areas,” Mr Merrick said.

“Each area has their own problems, depending on the trees and grasses grown and the inter-row spacing. Significant issues can include shade, wear/erosion, maintenance requirements, drainage and harvesting issues.”

Due to the complexity of these issues, new and improved turfgrasses need to be investigated to help farmers during orchard establishment, maintenance, and harvest to provide sustainable production, Mr Merrick said. The new trial work is being conducted to research new and improved turfgrass varieties for orchards.

Barenbrug Australia has a close relationship with the international Barenbrug Group. This partnership has resulted in the release of many market leading turf varieties in Australia in recent years.

Locally, Barenbrug will be working with ASTC, through director Matt Roche, to establish a replicated varietal study to compare growth, quality and turf density under different shade conditions, including full sun, 30%, 50%, 70% and 90% shade.

The trial will commence in Spring 2020 and will include seeded turf species such as sweet smothergrass, zoysia, carpet grass, bahia grass and green couch. For further information on these grasses, head to the Barenbrug website or turffinder.com.

“Typically, pasture grasses such as millet, oats and Rhodes grass have been used to provide often limited and temporary ground cover protection within the orchard,” Mr Merrick said.

“Supplementary grasses have also been added, such as green couch, paspalum, and/or kikuyu to provide perennial and added protection with their stoloniferous and/or rhizomatous growth. However, these grasses have proven to be inadequate on their own.”

He says the Barenbrug ‘Maca Mixes’ are a key tool for growers, as they provide added flexibility for everyday farmers. Mixes can be tailored to suit needs for specific climates, orchards, shade conditions, erosion, drought conditions, maintenance, and harvesting needs.

However, Mr Merrick said it was critical to follow industry best-practice when establishing and managing turf. “For best results when using seed in orchards, warm season species like green couch, carpet grass and zoysia seed should be planted when soil temperatures reach at least 18°c.

“Seeding rate of mixes will vary on seeding methods used, however 25 to 50 kg per hectare sown into a well-prepared firm seedbed should provide sufficient seedling numbers.

“Ensure your seed has good seed-to-soil contact with approximately five millimetres of soil coverage and maintain adequate soil moisture around the seed using frequent, but light irrigation or rain events.”

During establishment, it is recommended to apply a suitable starter fertiliser, such as MAP, to supply good nitrogen and phosphorus during grow-in. Stands should be fertilised once a month during grow-in, dependent on soil test results, and growers should remember that inter-rows also require fertilising.

“It should also be noted that in late autumn, when soil temperatures are approaching 14 degrees, warm-season grass species are preparing for dormancy,” Mr Merrick said.

It is recommended to apply additional amounts of potassium, to provide plant strength and help with cell function, while reducing nitrogen to help manage the growth of the grass in preparation for winter.

Results of the trial work will be available for growers through the Australian Macadamia Society.

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