Borage agronomy

Background: Work on the agronomy of borage was proposed to the Rural Industries Development Corporation (RIRDC) with funds pledged from the Natural Plant Extracts Cooperative (NPE) and work on this project began in the 2000-2001 season. In previous work, field plots at two sites in North Western Tasmania were planted and yields, oil and GLA were found to compare favourably with overseas commercial yields and published data. A field experiment compared the effect of planting borage from September to December and of delaying harvesting. Reductions in yield, both to delayed planting and harvesting, were found.

Objectives: This project proposes to further investigate planting time, in addition to commercial methods of harvesting and weed control, to increase the commercial yield of GLA from borage.

Work undertaken to date: A replicated field trial was planted at the Forthside Research Station to compare three planting times and two times of harvest. The harvest time investigation was included after information was found indicating that yields may be improved by slight delays in harvest timing from the onset of seed shedding. This information appeared inconsistent with most published data and previous results, which showed that a large yield penalty is incurred by a ten-day delay. A first harvest treatment was carried out at the initiation of seed shedding and a second harvest treatment was carried out four days after the first. The experiment has shown again that delayed sowing is detrimental to yield of borage in Tasmania but that sowing time and harvest timing interact with the result that delayed sowing is less detrimental to seed yield if harvest timing is adjusted to an optimum.

Three large plots were sown at the UniversityffAFE Farm, Burnie to investigate the effectiveness of locally available commercial windrowing and harvesting machinery. As borage production with low chemical pesticide inputs is desirable in the marketplace, these plots were sown at rates of 8, 16 and 32 kg of seed per ha as a test of the ability of high crop sowing rates to compete with weed growth. The highest sowing rate competed with weed growth effectively compared with lower sowing rates, A Hesston windrower was supplied and operated by staff of Botanical Resources Australia. The machine was effective in providing a compact and well-supported windrow without major impact on the plant material. A Claas combined harvester was used to harvest windrows after 11 days.

The agronomic fieldwork has improved our understanding of sowing and harvest timing. While the yields from mechanically harvested plots were low, this activity demonstrated that windrowing can be carried out effectively and that further work on harvester settings is required to improve the seed recovery.