Companion planting is an age-old way of controlling pests in crops by planting others which inhibit their activity. Popular among home gardeners and others who prefer to avoid using chemicals, the concept of companion planting has special significance for avocado growers in the Coffs Harbour district.
According to Department of Agriculture district horticulturist, David Stevenson, around 90 per cent of the area's 100 hectares of avocados are interplanted among bananas. And what started off as a means of boosting earnings per hectare has become the key to survival of avocados in the district.
About a decade ago, a grower planted avocados in two adjacent paddocks - one which had been cleared and another which was a former banana plantation. The contrast quickly became evident. The trees in the open paddock had died, while their neighbours had grown from strength to strength with suckers still growing on them. Although unintended, it was a most useful trial which laid the groundwork for a rapid expansion in subsequent avocado plantings and a fascinating field of endeavour for plant pathologists.
From two hectares in 1969, Coffs Harbour saw avocados expand to 100 hectares in just 15 years. "From, 1974, there was a significant increase in plantings because growers had seen the success of interplanting," said Mr. Stevenson. He said the high organic matter supplied by the bananas increased bacterial and fungal activity which was beneficial for avocados."
Bananas also provide about 25 tonnes of organic matter per hectare each year," said Mr. Stevenson. He said the fruit were grown on a range of soil types, which were clay loams of metamorphic rather than volcanic origin.
DATE: May 1985
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