Fruit mineral analysis during the growing season can guide producers in their fertilizer programs and help them improve fruit quality.
Dr. Bill Wolk, quality development manager with the B.C. Tree Fruits Cooperative in British Columbia, Canada, said research on fruit mineral analysis was done at the East Malling research center in the United Kingdom in the 1970s.
Researchers and horticulturists in British Columbia began to take an interest during the 1980s and 1990s, with the idea of predicting storability of fruit delivered from different orchards at harvest. This was important in British Columbia, where packers were -receiving fruit from many different small orchards.
“This originated as a packing house storage thing,” Wolk told members of the International Fruit Tree Association during their annual meeting in Kelowna, British Columbia. “We weren’t even thinking about this to help growers grow better fruit in the orchard.”
Now, it is used primarily as a guide for growers. Wolk said the cost of the analysis—at $40 to $60 per sample—is nothing compared to the value of the fruit the orchard will produce and the information and guidance it can give growers in their fertilizer programs. “It’s really cheap,” he said. “If you’re not doing it, you should give it serious consideration.”
Working with Drs. Sam Lau and Gerry Neilsen with Agriculture and Agri-Food Canada in Summerland, Wolk conducted research initially with McIntosh, Spartan, and Golden Delicious apples. The fruit were tested for minerals, as well as for weight, density, and dry matter.
It was assumed that fruit analysis would give the best prediction of fruit quality when done at harvest. The scientists wondered how long before harvest fruit quality could be accurately predicted. Wolk and his colleagues tested fruitlets nine, six, and three weeks before harvest and at harvest.
They then stored the fruit for different periods in commercial regular and controlled-atmosphere storage and looked for correlations between the results of the fruitlet analysis and postharvest fruit quality, such as firmness, sugar levels, and storage disorders.
They were surprised to find that, for all three varieties, fruitlet analysis gave a better prediction of postharvest quality when done six weeks before harvest, rather than nearer harvest. The scientists developed nutrient recommendations for growers based on the actual storage data.
Over the years, they added more varieties to the fruitlet analysis database, and found that each one has different -quality-mineral correlations. The program is currently testing Ambrosia, -McIntosh, Gala, Honeycrisp, and -Spartan.