[U.S. 7 to 14 cents per pound]," Hilaire said. "The grower must average a minimum of 30 tons per hectare [12 tons per acre] throughout the season to stay profitable."
The difficult part, Hilaire said, is that early varieties are generally small and not heavy producers. "That means that if you average 15 to 18 tons per hectare at the start of the season with early varieties, you will need to average 40 tons per hectare at the end of the season."
Their research aims to identify varieties and orchard systems that will produce large fruit in the 140- to 170-gram (5- to 6-ounce) range. Previous research has shown that fruit size is closely linked with quality. As fruit size increases, fruit quality attributes also increase.
One approach under study is a fruiting wall system comprising a double Y vase with four scaffolds, forming two fruiting walls with a 30° angle between the tops. Bottom laterals on the tree are maintained to keep young wood on the lower part of the tree. Good light penetration in the "improved" vase system helps produce strong wood and well-colored fruit. Height is maintained by mechanically topping trees twice a year in May and July; suckering is done twice during the summer. By keeping trees around eight feet tall, only stepladders are needed for harvest and pruning.
Some varieties are easily adapted to this training system, Hilaire said, while others have more upright scaffolds that need bending. The fruiting wall allows easy access for picking and has been shown to improve harvest efficiency by 20 percent.
But the big labor savings come from mechanical pruning. Pruning is done in late June with a mechanical hedger, requiring less than two hours per hectare. Hilaire said that although the mechanical hedger cuts good shoots, fruit size is still adequate.
Another orchard system under study—and even more radical than the fruiting wall—keeps pruning costs down that would be needed in the fourth leaf by simply cutting down the tree.
Hilaire believes the key to an economical orchard system is to limit the number of hours needed to maintain tree shape and productivity. Most peach and nectarine orchard systems need extensive renewal pruning as the tree ages. By keeping the annual labor requirement down to 600 hours per hectare (243 per acre), instead of the 1,000 hours per hectare (405 hours per acre) average involved in traditional systems, Hilaire thinks he can keep French stone fruit growers competitive and profitable.
In the first three years of a stone fruit orchard, he calculates growers can stay under the 600-hour average: 100 hours of labor per hectare are needed in the year of planting; 650 hours in the second year; and, 1,000 in the third year, making an average of 571 hours per year. But in the fourth year, he estimates that another 1,000 hours are needed for pruning if high quality tonnage is to be reached, which would bring the average to more than 687 hours per hectare.
Hilaire is now studying the drastic step of cutting trees down after the third leaf, a step he says will save 200 hours per hectare of labor. The cut trees receive minimal care (and labor) the first year as they grow back up, although pest management is necessary for tree health. Trees are back in production by the second leaf.
He’s not proposing to cut down the entire orchard, as that would eliminate all the income. In his three-hectare study, the block is split into thirds, with a third planted the first year, a third planted in the second, and a third in the third year. In that manner, only one hectare of the three-hectare block is removed each year.
In his extreme pruning trial, Hilaire cut down trees in February, and spread the shredded wood from the cut trees as mulch under the remaining trees to reduce weeds and improve water penetration. He said an added benefit to the tree cutting could be faster renewal of varieties by grafting new cultivars onto the cut trees.
Hilaire compares the tree-cutting concept to removing trees to control disease, like plum pox or bacterial canker. "When you lose trees to disease, it has a minimal effect because you have so many trees in the block," he said.
In the second leaf, trees should produce about 30 to 40 tons per hectare, he said, adding that they should reach 80 tons by the third leaf.
"With good tree management and the new varieties that are now available, it’s possible to have a huge yield and good quality fruit," Hilaire concluded.