By Sue Streatfield, Partnerships Ranger
Last year we shared the story about an Aussie invention that could sow the seeds of native trees and shrubs directly into the ground, offering a cost-effective, labour-saving alternative to planting.
New Zealand’s first ‘direct seeder’ was made to order early last year and shipped across the Tasman to the Alexandra workshop in time for spring.
In advance of its debut, considerable work was done selecting properties and sites, spraying, and collecting, cleaning and storing native seed. A seeding plan was developed for each property which included site details, GPS points, photos and recommended species lists.
DOC staff, property owners and seed collectors all played a key role in getting the seeder ready. An Aussie volunteer also crossed the ditch to help DOC staff break in the new recruit.
The direct seeder is made up of a scalping disc, a calibrated twin seedbox for small and large seed and a press wheel. The hydraulics are controlled via a cable connected through to the vehicle cabin, so that the whole operation can be done by a solo operator. The disc scalps a furrow around 1.5 inches deep and 5 inches wide, creating a clean seed bed. The large seed type is deposited 1 inch deep into the soil, while the small seed is sprinkled on the soil surface and firmed down by a press wheel.
Six properties and 12 sites were selected across Canterbury, Otago and Southland representing a range of sites, soils, and landscapes. Located near Methven, Ashburton, Wanaka, Alexandra, Gore and Invercargill, each site proved vastly different. The sites presented a diversity of challenges ranging from pasture competition, bone dry conditions, waterlogging, and hare invasions.
All sites were fenced/free of stock, arable, accessible, flat or gently sloping and owned by willing land-managers who were up for a challenge. An average of 1 to 2 km of seeding was undertaken across each site.
Formal monitoring is planned for each site this year, however early observations at some of the sites is most promising with early germination of mānuka, pittosporum and hebe. Living proof that some New Zealand species can be established using this revolutionary method. Early germination is critical for giving plants the head start needed to eventually outcompete surrounding pastures. It is anticipated that as the seasons progress, environmental triggers will prompt more species to germinate.
Most of the seed collected for the direct seeder trials was sent to the horticulture programme within the Otago Corrections Facility for cleaning. Batches of seed destined for each site were also sent for germination testings. This was undertaken to determine the viability of species and batches of seed. The germination rates mirror closely the field results suggesting that viability, rather than the delivery, plays a significant role in success.
One of the biggest challenges ahead is trialling some post seeding weed control treatments, as the short lead time for the trials meant that we could only do one weed spray, rather than the preferred two, resulting in unwanted competition at some sites.
The learning curve is long and steep, but so far the future looks bright for direct seeding in New Zealand and our ability to offer cost-effective solutions for improving conservation on farms, including riparian restoration, shelterbelts, windbreaks and wildlife corridors. Direct seeded vegetation could also contribute to landscape scale re-connection, water catchment restoration, post fire recovery, greenhouse gas sequestration and benefits for the mānuka honey industry.
This year the project will add more properties in landscapes we haven’t trialled yet, experiment with autumn seeding trials and refine the best site preparation and seed mix needed for each site.