Spring frosts can have devastating effects on apple production, and a warming climate may be causing trees to blossom early, making them more susceptible to the damaging effects of extreme cold events. Growers’ attempts to prevent apple blossoms from freezing by attempting to heat the canopies of their orchards largely have been inefficient.
To deal with the worsening problem, Penn State research hers devised a frost protection cyber-physical system, which makes heating decisions based on real-time temperature and wind-direction data. The system consists of a temperature-sensing device, a propane-fueled heater that adjusts its direction and angle automatically depending on wind direction, and an unmanned ground vehicle to move the heating system through an apple orchard.
Recently published in Computers and Electronics in Agriculture, the findings show that the cyber-physical frost-protection system greatly reduced damage to apple tree buds in two tests conducted in low temperatures. Compared to similar unprotected orchard sections nearby, deploying the cyber-physical frost-protection system in one test more than doubled the time the test-area canopy was protected, and nearly tripled the time in another.
Applying heat is one of the most effective methods to prevent apple flower bud damage, however growers struggle to determine when and where to apply heat in their orchards, according to researcher Long He, Assistant Professor of agricultural and biological engineering, who is corresponding author on the study. They often don’t have an available labor force to accomplish the heating, he says, leading to either diminished apple crops or energy waste.
Growers know that apple flower buds can be damaged when the temperature falls below 30°F, but they are deterred from taking active protective actions because wind can make heating efforts ineffective.
“Wind is often treated as an uncontrollable factor when growers are implementing heating tasks in orchards because it greatly affects heating performance,” He says. “To overcome the challenges growers face, we developed a system capable of monitoring the environment and taking actions in response to the monitored data, using temperature and wind sensors to perceive environmental changes and then make corresponding heating decisions.”
This study, which took place at Penn State’s Russell E. Larson Agricultural Research Center, was just the latest conducted by the research group focused on smart agriculture in the Department of Agricultural and Biological Engineering. First author Weiyun Hua, a graduate assistant, first determined heat-transfer patterns in an apple orchard utilizing images captured by an aerial drone-based thermal camera and a validated numerical model.
She then incorporated the findings of earlier published research, conducted by the group that created an algorithm to identify apple flower stages and developed a critical-damage temperature map that was made using an aerial drone-based camera. That research also used a drone-based thermal image camera to determine a temperature map, which was used to generate a heat-demand map. Hua used all that information to plan the path for the unmanned ground vehicle to accomplish heating tasks.
The total cost of equipment used to build the test unit in this study was approximately $5,000, Hua notes, mainly including the vehicle for $4,500, the heater for $200 and microcomputers for $100.
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