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This short report is a summary of a full report Borage production for oil and gamma-linolenic acid (RIRDC Publication Number 04/040 The full report is available in hardcopy for $16 from RIRDC (Phone: 02 6272 4819) or can be downloaded for free from RIRDC’s website: www.rirdc.gov.au/fullreports Seed oil from the herbaceous annual, borage (Borago of. cinalis L) may become a new export from Australia as a result of research funded by the Rural Industries Research and Development Corporation (RIRDC).
The oil contains a high level of gammalinolenic acid (GLA) – a polyunsaturated fatty acid used as a human nutriceutical and dietary supplement. While evening primrose oil has traditionally met the demand for this extract, borage has a higher percentage of GLA and is beginning to replace evening primrose oil.
RIRDC’s program, aimed at identifying and recommending agronomic practices for borage, also seeks to give Australian growers and processors of the herb a competitive advantage in a world market for GLA that is predicted to expand by 10 per cent a year for the next five years.
Currently there is no significant commercial production in Australia with global commercial annual yields of borage oil totalling 350 tonnes and coming mostly from New Zealand, Canada and the United Kingdom.
Dr Rowland Laurence, head of the Vegetable Research Group of the Tasmanian Institute of Agriculture Research, undertook the research.
Effects of sowing time, sowing rate and harvest timing on borage seed yield were studied in field trials along with observation of large area commercial harvesting techniques. Crop rotation, stale seed bed preparation, good crop germination and early vigour were mostly used for weed control. A herbicide application to post-emergent borage also was tested.
The Research
The objective was to provide local information on key agronomic practices for the production of borage and, with reference to relevant overseas information, provide recommendations for its commercial production in south-eastern Australia.Identification of the best sowing time, plant population and weed control are important and poor seed retention requires the optimal scheduling of harvest time and harvest methods for local conditions..
In 1999-2000, a field trial was carried out investigating the effect of varying sowing and harvest times.
Dates of emergence, initiation of flowering and harvest, together with clean seed yields returned from treatments in the time of sowing and harvest timing experiment, 1999-2000.
This work was repeated the following year but included a first attempt to sow, windrow and harvest large plots mechanically. Two sowing rates were used.
Dates of sowing, emergence, flowering and harvest, together with resultant mean dry seed yields of borage treatments (interactions) in the 2000-01 field trial.
In 2001-02, sowing rates were compared again in large plots and spacing between rows also was varied in an attempt to observe the effects on mechanical weed control. Sowing time investigations were finalised with a small plot experiment and a simple observation of herbicide applications to borage carried out. In 2002-03, a commercial grower was enlisted to grow a large area demonstration.
The Results
During the trial years, earlier sowing times were introduced to counter large reductions in seed yield caused by delayed sowings. The collective results of the three experiments shows that sowing the crop in early August encourages high seed yield. Yields are reduced by more than one-third when sowing is delayed by about one month.Dates of sowing, emergence, flowering and harvest, together with resultant dry seed yields of borage treatments in the 2001-02 field trial.
The work also shows that the borage plant sheds its seed quickly upon maturity and because of this the timing of windrowing and the initial harvest operation are also critical. Delaying harvest for a period of four days to a week resulted in seed yield reductions of around 50 per cent and it was concluded that windrowing should be completed within one or two days of the loss from the plant of the first mature seed.
These experiments, therefore, have provided strong evidence of the critical importance of early sowing and exact harvest timing for crop pro. tability.
Observation and experimentation on the effects of sowing rate and row spacing were carried out in the consecutive seasons 2000-03 in large field plots, with an additional objective of making observations on the mechanical handling of the crop and demonstration.
The effect of three sowing rates and two row spacings on borage seed yields obtained from dried windrow samples on 24 December 2001.
In the first and third of these seasons’ field operations, weather conditions resulted in the poor preparation of a stale seedbed for weed control and later than optimal sowing times. Under these conditions, increasing sowing rate improved the ability of the crop to compete with weeds and improved seed yields.In the second of these three seasons, 2001-02, improved seedbed preparation, the application of a preemergent desiccant herbicide and mechanical brush weeding allowed the crop to compete well with annual weeds. While e germination was marginally improved by decreasing the distance between the rows it did not translate into significantly improved seed yields.
Yields did improve with increased sowing rates. A sowing rate of 16 kg/ha may be worthwhile if seed germinability is poor. But, if high field germination can be achieved, a sowing rate of 8 kg/ha may be sufficient. The work showed that because of the high cost of seed, sowing more than 16 kg/ha of borage seed is unlikely to be worthwhile
The effect of three sowing rates and two row spacings on borage seed yields obtained from dried winAdrow samples on 18 January 2002.
While treatment yields were similar to commercial yields reported elsewhere, signi. cant quantities of mature seed were found on the ground after the windrowing operation. This suggested that the windrower used was too harsh and use of a ‘softer’ windrowing machine, using a Draper belt mechanism, returned better seed yields.
Other modi. cations to the windrower cutter bar mechanisms may further limit seed losses by reducing sideways movement of the plant at the cutter bar and seed loss from shattering. A bulky windrow also may improve the retention of seed dislodged.
Field observations showed several post-emergence herbicides, Afalon®, Allicide®, Ramrod® and Stomp330® produced no visual symptoms or reduction in borage plant growth and these herbicides, with further work towards registration, may provide a potentially successful chemical weed control option.
Discussion
The project has provided information and experience that is extremely valuable in determining important field operational factors, without which successful local borage production would have been unlikely.Other work on aspects of genetic improvement of borage is still in progress and collaboration between a Sydney-based company and a grower has resulted in about eight hectares of borage being sown commercially in the current 2003-04 season.
A local oil extraction facility, suitable for use with borage is also available. This crop, if successful, will provide sufficient borage seed to test the market potential of the local product. Broad recommendations from the project regarding borage-growing methods include:
- Preparing a uniform, non-compacted, stale seedbed well in advance of sowing, which in Tasmania, should be in early to mid-August. Sowing should attempt to establish about 35-40 plants per square metre in rows less than 200mm apart. This will equate to a sowing rate of about 10 kg/ha if a field germination of 70 per cent can be achieved;
- While fertilizer use should be guided by soil tests, only moderate amounts of macronutrients are likely to be required. About 200 kg/ha of a medium analysis mixed fertilizer is a suggested application, with a single, moderate nitrogen top-dressing in the early rosette growth stage. Later nitrogen top-dressings may lodge in the rosette and burn the growing point;
- A pre-emergent desiccant herbicide should be applied to improve weed control. Post-emergent chemical control of grass weeds and/or mechanical inter-row cultivation should be employed if necessary;
- For best yields, irrigation should be used to supplement rainfall when required;
- Few disease or insect pests have been found locally to date. However, if insecticides are used at or close to . owering, toxicity to bees and other pollinators should be avoided. The crop is extremely attractive to bees;
- The crop should be monitored closely for maturity as the green seed increases in size and turns brown and then black. Black seed is quickly shed and windrowing must be carried out between two and four days after the first seeds are lost from the plant. Any modi. cation to windrowing machinery, which lessens impact forces on the plant at the cutter bar or during its passage through the windrower, is likely to improve the harvested yield.
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