Light is a critical element for apple fruit quality and orchard production. Growers face a challenge — how to manage that light to ensure production of the best apples possible. 

One possible tool that shows promise is a reflective ground cover that can be used to improve apple quality and increase production in Southeastern apple orchards. 

At a field day Aug. 10 at the Mountain Horticultural Crops Research and Extension Center in Mills River, N.C., Ashley Hoppers, a University of Georgia Cooperative Extension county coordinator in Fannin County and agriculture and natural resources agent in Gilmer County, discussed a cooperative research project between UGA and North Carolina State University, examining the benefits of reflective ground covers in apples.  

“Light is really at the center of everything we do with plants. The more light we have exposed to a fruit surface, the higher quality fruit we’re going to have. Apple has a pretty complicated, disorganized tree architecture by nature. We try to maximize light distribution within a canopy primarily through two applications, pruning and training,” Hoppers said at the field day. 

“Ultimately what we’ve found over the many, many years of growing apples is that our trees are shrinking and they’re getting planted closer together because we’ve found that a tight tree architecture allows us to harvest light more efficiently,” she explained. “Smaller plants tend to have higher fruit quality because we’re better able manage the tree architecture itself and also the crop load.” 

Reflective ground cover 

Pruning and training apple trees will only do so much when it comes to improving apple quality and color, which is why apple farmers are looking for other ways to produce better quality fruit.

That’s where the reflective ground cover material comes in. It is very good at capturing light that would otherwise be absorbed by the grass row middle of an apple orchard and reflects it back into the basal portion of the canopy. 

In the project, Hoppers and her team in 2022 deployed a season-long groundcover experiment in a “Simmons Gala” planting at Mercier Orchards in Blue Ridge, Ga. Hoppers explains that the experiment had two treatments with five replications arranged in randomized complete block settings. 

“This material reflects a lot of photosynthetic active radiation, but also ultraviolet radiation which is a key component in the creation of anthocyanin which is our red pigments that are very desirable in red fruit color development,” Hoppers said. 

She explained the window of this activity tends to happen four weeks prior to harvest which is why growers would want to deploy the fabric in their orchards four weeks prior to harvest to help promote pigment accumulation. She said this is a challenge for apple growers in the Southeast because there is plenty of sunlight, but there are also high temperatures which can be a limiting factor in the creation of anthocyanin. 

Limited local research available 

In the project, the researchers did a season-long deployment at Mercier Orchards in north Georgia, which means the reflective ground was on the ground for four months, right up to harvest. The scientists looked at both vegetative growth and reproductive growth. 

Hoppers noted that they didn’t see much difference in vegetative growth last year, the first year of the study. As far as fruit set and fruit abscission patters, they found no difference when they did a whole tree fruit count in April and May, but they did see a 27% yield increase after June drop. 

 “As far as fruit quality, starch, sugars, firmness, we didn’t see any differences there either so from a maturity standpoint it didn’t seem to have much separation There could be a lot of reasons for that, primarily because of the difference of tree architecture and how your orchard is set up,” Hoppers explained. 

Hoppers said reflective ground covers have been extensively tested in the Pacific Northwest, but there has been limited research in the southeastern United States. She believes the technology has a fit in southeastern apple orchards as a way to improve fruit quality.  

Research continues this year in the same plots to determine any cumulative effects and to further investigate influences on fruit set and abscission patterns.