Reflective mulches boost fruit size, color and yields

08/01/2011 05:37:00 PM
Vicky Boyd

Washington Fruit & Produce Co. in Yakima, Wash., has used Extenday since 2005, mainly in Gala apple blocks. There, the company sees not only color improvements but also up to a 10 percent increase in yield, says orchard manager Dan Plath.

“If [color] was the only reason it wouldn’t justify the expense,” he says.

For color alone, Mylar foils suffice, he says. The company chooses that material for its older Fuji and Gala varieties.

“We have to work harder on those to get color, so there’s a lot of room for improvement,” he says. “But the newer generations [of those varieties] are where we’re getting 70 to 80 percent premium [fruit].”

If improving fruit color is your main objective, Schmidt says, you can wait until a few weeks before harvest to install reflective foils or fabrics. Laying out the material at bloom helps increase cell division to ultimately boost fruit size and yield.

Hold off early deployment until after any severe frost forecasts, Plath says.

Reflective materials substantially reduce ground warming from spring sunlight, which can translate into a degree or two drop in nighttime orchard temperatures—a potentially crucial difference for frost protection.

Mylar foils cost less up front, Schmidt says, but are less durable and must be replaced after a single season, increasing disposal costs.

Sturdier materials such as Extenday represent a bigger initial investment, but can be used for five or six years before replacement.

And unlike the foils, they also can stand up to being rolled up and moved to a new location partway through the growing season, he says.

Many growers take advantage of that sturdiness, placing the fabric strips in apple blocks early in the season to boost cell division, then transferring them to cherry orchards before harvest.

After finishing up cherries, they return the fabric to apple orchards to boost fruit color, he says.

“The benefits more than pay for all that moving around,” Schmidt says. Growers get three to four uses each year out of the same product rather than investing in three times as much reflective material.

The Extenday fabrics work best raised slightly from the ground to allow air flow, he says. Shock cords secure the material during use.

Plath recommends doubling up shock cords on the windward side of any block, a lesson learned from hard experience. A wind storm blew fabric strips up into tree rows like sails, breaking trees at bud unions.



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