Lav R. Khot and Jianfeng Zhou 2016-05-03 02:01:00
In the past few years, small unmanned aerial systems (sUAS) have fascinated farmers and researchers alike with their versatile imaging capabilities. Similar to the Federal Aviation Administration (FAA), the agribusiness industry is trying to keep pace with the rapid developments in this sector. Undeniably, sUAS may have solved the image resolution puzzle that has long been a limitation for effective site-specific crop management. Now researchers must look beyond sUAS platforms to realize the full potential of UAS in precision agriculture. Indeed, we are talking about UAS with the capabilities of a mid-size autonomous tractor or flying robot, which can scout the fields for anomalies and perform other operations in production management. Some of the desired attributes of such UAS include: • Heavy payload lift capabilities. • Versatility of attachments. • GPS-guided autonomous flight. • Extended flight time (in hours). • Flexibility of night operations. • On-farm (off-road) takeoff and landing in restricted spaces. • Robust fail-safe configurations. A solution in part In U.S. agriculture, full-size manned helicopters and fixed-wing airplanes are common for aerial spraying and dusting applications in row, field, and fruit crop production. However, operating these aircraft over irregularly shaped fields scattered over semi-rural landscapes with power lines, communication towers, and residential or commercial development areas is a safety risk for the pilot and for those on the ground. In addition, drifting of harmful chemicals beyond the target area has been an unrelenting problem. UAS technology can be the part of the solution to these issues. Mid-size UAS are already being used for aerial pesticide and fertilizer applications in agriculture production. Since the 1990s, unmanned mid-size helicopters have been used in Japan for aerial applications of liquid and granular materials in rice production. Given the large size of operations in the U.S., UAS capabilities need to be scaled-up for wider use. In the meantime, existing mid-size UAS can aid small and large acreage farmers in a range of field operations including: • Aerial seeding and top-dressing of pastures, row crops, and field crops. • Early-season vineyard and orchard frost and freeze mitigation. • Scouting and need-based precision (i.e., surgical) spraying for pest and disease control. • Late-season crop loss management in tree fruit crops. • Monitoring and management of livestock and wildfires. It is encouraging to see that the FAA has approved UAS with payloads beyond 25 kg (55 lb), such as the Yamaha RMAX with a maximum takeoff weight of 94 kg (207 lb), for commercial operations in the U.S. Researchers at the University of California- Davis are testing this midsize UAS for spraying in vineyards. More such studies can establish wider adoption of midsize UAS for precision spraying applications in specialty and high-value crops. Speedy development of affordable sensing technologies for crop-specific, rapid, and reliable pest and disease detection and mapping can help increase the use of mid-size UAS for precision spraying. Mid-size UAS can also be used in vineyard and orchard production for crop loss management. For example, UAS-based aerial applications of sunburn protectants can greatly reduce the apple fruit losses caused by hot summer temperatures. An application for cherry orchards Seasonal summer rain can damage fresh market sweet cherries in the field by producing cracks on the skin or near the stem. This cracking can lead to premature fruit decay, making the fruit unmarketable. In the Pacific Northwest, farmers currently hire helicopters after heavy rainfall to fly over their cherry orchards and remove water, like enormous fans over the canopy. However, these manned flights are costly and may not be timely, especially to protect fruit after nighttime rain events, as most pilots will not fly until dawn. Daylight flights are dangerous as well, particularly in the hilly orchard blocks common in Washington State and parts of Oregon. As an alternative, researchers at Washington State University, in collaboration with Digital Harvest, Inc., and Yamaha Precision Agriculture, are evaluating a 88 kg (194 lb) mid-size helicopter-type UAS with 3.1 m (10 ft) diameter rotor to determine if the down wash from the rotor is suitable for effective removal of rainwater in modern cherry canopies. So far, the results are promising. Based on tests in the 2015 growing season, a travel speed of 2.7 m s-1 and altitude of 6.1 m above ground level could remove 88% to 96% of the rainwater in Y-trellis cherry canopies. Further testing and flight optimization are scheduled for the 2016 season. Mid-size UAS could be an economical rainwater removal option for small acreage farmers and for cherry orchards that are difficult or unsafe for manned helicopter flyovers. Ideally, farmers could use the same UAS for a range of farm operations during agricultural production. Looking to the future Rapid developments in emerging technologies, such as small and midsize UAS, will dominate the field of precision agriculture in the coming years. ASABE researchers and extension experts in particular have key roles to play in the safe and meaningful “ground-toaerial” transition of farm management operations. Hopefully, this successful technology transfer will help the U.S. farming community address the challenges of global food security by contributing to the optimal use of available resources. ASABE member Lav R. Khot, Assistant Professor, Department of Biological Systems Engineering, Center for Precision and Automated Agricultural Systems, Washington State University, Prosser, USA, Lav.firstname.lastname@example.org. ASABE member Jianfeng Zhou, Postdoctoral Research Associate, Department of Biological Systems Engineering, Center for Precision and Automated Agricultural Systems, Washington State University, Pullman, USA, email@example.com. Project collaborators include Troy Peters, Qin Zhang, Matthew Whiting, and David Granatstein of Washington State University.
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