The face of primary industry on the Atherton Tableland is undergoing a slow but major change of direction, as traditional pursuits like tobacco and dairying are supplemented by tropical and sub-tropical fruits. In this feature, the first of a series to appear in coming issues of F & V News, COD journalist, Jenny Gilbert, describes some of these newer concerns and their impact on southern markets.
Careers in veterinary practice, physiotherapy and a two-year stint at sculpture in London are hardly the ingredients for success in growing sub-tropical fruits, but Mr. Don Lavers and his wife, Dell, from Walkamin have proved the case.
Formerly from Cairns, the Lavers' 25 hectare orchard at Walkamin on the Atherton Tableland is a fine example of what can be achieved in less than five years.
Don spent some years in Cairns first as a veterinary officer with the Department of Primary Industries, travelling extensively throughout the Gulf and Cape country, and then in private practice treating both domestic and rural animals.
At the same time, Dell worked as a physiotherapist, but when Don's long-term ambition to dabble in sculpture coincided with the sagging of the cattle industry in 1978, the two decided to head for Europe. On their return, an interest in avocados and the Atherton Tableland district became a reality, when they bought 160 hectares of virgin country at Walkamin, backing onto the Barron River.
"We took a fancy to avocados and this district because there was plenty of sunlight, good soils and low rainfall, but plenty of water available from Lake Tinaroo," said Don.
Before making their first plantings in April, 1980, the form was graded and hilled to enhance drainage, and fowl manure and lime was applied to each planting site. "We quickly needed to increase the organic matter content of the soil for the avocados, or risk losing nutrients through leaching," said Don.
But the most interesting aspect of the Lavers' avocado orchard is their success with the legume, greenleaf desmodium (Desmodium intortum), which has effectively annihilated weed problems. Unlike other legumes, greenleaf can be controlled before it becomes too vigorous around the trunk and canopy of each tree. Though difficult to establish and more costly to maintain, Don has found the extra effort with greenleaf worthwhile because it adds nitrogen and leaf matter to the soils, while discouraging weed growth under the thick, matted mulch it forms.
"At the suggestion of Jim Allan and John Kilpatrick from the DPI and Peter Coleman, a pasture agronomist from Mareeba, we decided to try it. But it is touchy to strike and must be planted at the wettest time of the year, within 24 hours of rain falling. Nothing seems to happen for a long time and the grass still dominates, but then all of a sudden, the greenleaf takes off, and once established, it stays an aggressive green", said Don.
Maintenance includes light phosphate applications and to control vigour, rolling and spot spraying around each canopy and getting rid of occasional weeds. "It has cost us more but I am sure greenleaf earns dollars for us," said Don. Peanut shells are still applied around the base and under the canopy of each avocado tree.
While Hass form the bulk of plantings, Fuerte, Rincon and Shepherd are also grown, though Fuerte is proving to be less desirable. "We find Fuerte requires five or six picks to select mature fruit, while Shepherd appears to produce genuinely early fruit which all mature simultaneously. Though small in size to date, Shepherd are also a tasty thick-skinned avocado." he said.
By comparison, Rincon has greatly outproduced Fuerte. The question of planting density has proved equally as vexing on this orchard as others on the Tableland. Though original plantings were based on row widths of 12 metres, Don now believes that another two metres would have been advisable. "We have now learnt that it is better to give avocados plenty of room and then interplant, if you wish. Heavy pruning does not seem to be the answer, because the Californians have found that while this controls tree size, it also lowers yields," he said.
While avocados are a family project and the work is shared by Don, Dell and their son, Peter, the 140 custard apples also grown on the orchard are Dell's major interest (Don doesn't like packing them!)
Concentrating on African Pride trees, plantings were made at the same time as the first avocados four years ago. And like the success found with Greenleaf desmodium in the avocado orchard, it is also proving valuable in the custard apples, with an added bonus.
Although it is yet to be confirmed by research, preliminary work by the DPI suggests that flowering and subsequent fruit set in custard apples is enhanced by high humidity conditions. Unlike the Sunshine Coast and more traditional growing areas for custard apples, the wet season on the Tableland around February is too late to enhance fruit set and maintenance from November to January. Artificially creating humid conditions around the trees during this period is the only alternative for boosting yields.
In their first trials last season, Don and Dell enjoyed apparent success by allowing the greenleaf to grow high around the canopy of each custard apple before fruit set. "We created a nice early crop by letting the greenleaf grow up around the trees and then using a weak solution of weedicide to retard it. Once fruit set finished, it was then an easy job to roll the greenleaf back and let the new growth come away," said Don.
On the subject of rootstocks Don has had variable results between his first 100 plantings on Sugar Apple rootstocks and later plantings on Cherimoya. "Sugar Apple doesn't have a good reputation, but from small trees, we have harvested fruit in two years. By contrast, Cherimoya is much more aggressive, requiring more pruning, but none have yielded well yet," said Don. Because of their vigour, the trees need pruning twice a year, and like the avocados, plantings were made too close for northern growing condition. "We started on a 10 by 7.5 metre planting density, but we now use a 10 by 10 metre density," he said.
The trees are also grown on 30 cm hills, with top soil built up around the base of each tree for better growth. But the future survival of these custard apple plantings, like so many other horticultural crops, lies not just in sound cultural practices, but in finding a niche in a market which many believe is already over-supplied with a host of products. Don regards the custard apples as an experimental or pilot crop, and is somewhat pessimistic about their future. "The whole question with them is whether you can hit the early market, because that is the only way you can make them pay," he said. So far, this has been achieved, with the first fruit marketed in February, some four to six weeks ahead of fruit from the Sunshine Coast.
With that early advantage, the fruit have certainly brought attractive prices, but Don is quick to point out that, with air freight from Cairns to Sydney at $4.30 a tray, there are also some hefty costs. "Picking costs are high and we can only send by air to Sydney because of the distance involved and the perishability of the fruit," he said.
Son, Peter Lavers, began a breeding program to find superior lines of papaws three years ago, in the search for smaller, flavoursome fruit suited to northern growing conditions. Yields of up to 60 kgs of pawpaws per plant are not unusual.
DATE: September 1984
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