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Rural Industries Research & Development Corporation
Summary of full report
By P.R Johnson, C. Robinson, E. Green
March 2002
RIRDC Publication No 02/020 RIRDC Project No DAW-95A
Executive Summary
The Australian boab Adansonia gregorii is indigenous to the Kimberley region of Western Australia. Although the tree is recognised for its iconic value amongst non-indigenous Australians it is well known amongst the indigenous populations of the Kimberley as a tree with a vast array of uses including food, medicine and shelter.
Adansonia gregorii is closely related to eight other Adansonia species found in Africa and Madagascar. These related species have also long been used a regular food source by the indigenous populations of Africa forming part of the staple diet. Studies on the African species have identified parts of the tree being rich in Vitamin C (ten fold that of oranges) and Vitamin A. However in spite of this Adansonia gregorii has to the most part been over looked for its potential commercial value. Although some enthusiastic local residents in the Kimberley region of WA have been cultivating the tree.
The purpose of this study is to have a preliminary evaluation of the Boab roots to assess its potential as a cultivated vegetable crop. The study examined the chemical composition of the crop, which has identified no known toxic compounds exist in the roots. The nutritional breakdown has identified the roots are rich in Potassium and are a moderate source of starch and sugars.
Small-scale trial planting’s gave mixed results with excellent germination during the wet season and very poor germination during the dry season. Trialing various techniques to improve germination identified that sulphuric acids dip and manual scarification of the seed gave improved results.
Samples from the initial trials were sent to the Hyatt hotel in Perth for an assessment by the chefs for its culinary potential. This was combined with a promotion that was featured on a Channel nine documentary giving the project high profile. Feed back from the assessment was very positive both from the chefs and the consumers. Whilst conducting the assessment a post harvest breakdown of the product was identified, when stored at higher temperatures. Rapid cooling to 1 to 2 degrees Celsius post harvest rectified this problem. The assessment also identified wide spread interest in the leaves as a salad vegetable.
Larger scale trials identified that seed extraction, planting and harvesting can be mechanised thus keeping the production costs at a minimum. These trials examined several different pre seed treatments and the benefits of incorporating fertiliser at planting. Interestingly the sulphuric acid gave poor results in this trial, which is believed to be due to the timing of the treatment. Twelve-month-old seed and double density planting gave the highest results.
Extrapolating these results gives to 18-20 tonnes per hectare of marketable product. The addition of fertiliser did not significantly improve the yields. Weed control during the first few weeks of planting presents a problem and will require further evaluation of herbicides.
The economic analysis has identified the seed represents the largest single production cost.
The analysis based on yields of 8.9 t/ha and a price of $5.00kg gives a gross margin of $22,267 ha. The sensitivity analysis indicates that the break-even price per kg at 8.9t/ha is $3.01 and at 13.3t/ha is $2.47/Kg. Improved germination rates has a significant positive effect on the gross margin.
The prospects for commercialising the crop look very promising with positive market response for the roots and leaves, the ability to mechanise production, short production time 6 to 8 weeks and a favourable economic analysis. The major limiting factors initially with developing an industry is securing a seed supply (time taken to establish a seed stock.) and undertaking the promotion required to introduce the product to the wider community.
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