How reflective cloth affects the crop
The Washington Tree Fruit Research Commission has studied the effects of reflective cloths in apples, pears, cherries, and peaches.
Extenday was tested season long in a Washington State peach orchard. The cloth is attached to trees with bungee cords to provide flexibility when tractors drive over it. In rows with Extenday, more fruit was harvested in the first pick.
A reflective cloth that shines light back from the orchard floor up into the tree might help increase the proportion of target fruit by improving color or size, research by the Washington Tree Fruit Research Commission suggests. In some studies, it increased yields and advanced maturity. Results depend in part on when, during the season, the cover is on the ground.
Felipe Castillo, horticultural assistant with the commission, reported at the Lake Chelan Hort Day this year on a trial on Buckeye Gala on Malling 9 rootstock at a Sunnyside, Washington, orchard. Extenday was laid in the orchard at two different timings: season long (full bloom to harvest) and late season only (30 days after bloom to harvest).
In 2007, the third year of the trial, the season-long treatment resulted in a higher yield and higher percentage of the crop mature enough for the first pick. Yields were 40 kilos (88 pounds) per tree where Extenday was on the ground, compared with only 30 kilos (66 pounds) per tree where there was no ground cover. In the full-season Extenday plot, 59 percent of the fruit was harvested in the first pick, compared with only 36 percent where there was no cover. There was no clear effect on color, Castillo said.
Castillo said the Extenday cloth is typically fastened to every third or fourth tree with bungee cords. The fastenings are about six to eight inches above the ground to allow air to circulate beneath so that moisture under the cloth evaporates. The fastenings must be flexible so that the material doesn't tear when tractors drive over it.
The cloth is reusable and can be rolled up and moved to different crops or varieties, and can be used again in subsequent years. It has a life span of five to six years.
A trial in a Crimson Gala block on M.9 in Othello, Washington, compared Extenday, Mylar, and no reflective cover. Castillo said the Mylar, which is a thinner material than Extenday, had to be replaced after two weeks because it was torn by tractors.
No difference in yield was noticed, although the fruit were slightly heavier in the Extenday plot. In the Extenday treatment 92 percent of the fruit made premium grade, compared with 82 percent for the Mylar treatment, and 78 percent where there was no ground cloth. In the Extenday block, 39 percent of the fruit was harvested in the first pick, compared with 21 percent in the Mylar plot, and 16 percent in the plot with no cover.
The commission also tested Extenday in a young Granny Smith block. In 2006, when the trees were in the second leaf, Extenday season long resulted in more vegetative growth and a larger tree circumference. In 2007, the third leaf, the block produced its first crop. Where Extenday was on the ground all season, yields were 21 kilos (46 pounds) per tree, compared to 17 kilos (37.5 pounds) where there was no reflective cloth. Fruit weight with Extenday averaged 192 grams (6.8 ounces), compared with only 172 grams (6 ounces) where there was no cloth.
"What we're seeing is Extenday seems to be getting more fruit growth on the bottom of the tree where usually sunlight does not penetrate," Castillo said. "There's more bud development in those areas."
Daybright, a cloth that reflects 70 percent of the light versus 80 percent for Extenday, was tested in pear orchards. In a Bartlett orchard on a V-trellis system in Sunnyside, Washington, the Daybright block had higher yields but no difference in fruit weight. At a Bartlett orchard on a central-leader system in Cashmere, yields were similar, but the fruit were larger and there was more fruit on the inside of the trees.
Daybright was also tested at various timings in a block of Sweetheart cherry trees on Mazzard rootstocks at Quincy, Washington. The best results, in terms of yield, were when Daybright was applied season long. Trees in the season-long treatment produced 20 kilos (44 pounds) of cherries per tree, compared with 14.4 kilos (32 pounds) when the cover was laid only during the early season (first 45 days after bloom), 13.3 kilos (29 pounds) for the late-season treatment (45 days after bloom until harvest), and 12.5 kilos (27.6 pounds) where there was no ground cover. Fruit size and color did not differ.
Castillo said the commission also tested the idea of laying down Extenday in the Sweetheart orchard prebloom to see if the ground could be kept cool and bloom delayed, but it had no effect.
Daybright in a peach orchard resulted in almost 45 percent of the fruit being harvested in the first pick, compared with only around 20 percent where there was no cover.