I would like to use glass-embedded passive RFID chips in a tree-breeding program. Is it possible to read chips through 5 to 10 centimeters of damp soil and 5 to 10 centimeters of tree trunk? If so, what would be the best chip and reader options, given the wet, humid conditions?
In 2004, we wrote about graduate students at the University of Washington, in Seattle, doing what you seek to do. The Precision Forestry Cooperative was set up with funding from the state legislature to use advanced technology to improve conservation techniques in the forestry industry. Students embedded a 134.2 kHz glass-encapsulated transponder from Texas Instruments in each two-year-old sapling, in order to determine if RFID could identify trees that had been genetically modified to grow more rapidly. The trees are planted and monitored, and their seeds are eventually harvested to create a new generation of faster-growing trees. A lot of money was invested in the genetic modification, so the seeds of the original saplings are very valuable, and it was important to know which seeds came from which original sapling.
Each RFID transponder had 80 bits of read-write memory, which was used to store a serial number and other data about the sapling. A scientist with a handheld computer equipped with a reader could proceed to an area of the forest where genetically modified saplings were planted, and then read the tag and gather data about the tree in the field. Since trees grow from the top, the transponders stay at the same height. New growth forms around the transponder, so it becomes completely embedded in the middle of the tree trunk (see Out on a Limb and RFID in the Forest).
So it is possible to do what you are attempting to do. Low-frequency (LF) tags, like the ones used by the students at the University of Washington, should be able to be read within a moist environment. Choosing the right transponder would require some testing. I would think you would want a larger tag, to ensure that it could be read through mud and the tree trunk. But the size of the sapling might limit the size of the transponder. RFID Inc. manufactures passive LF tags.
Embedding the transponder in the tree might not be the only way to achieve your goal. In 2010, we published an article about Hawaiian Legacy Hardwoods (HLH) planting an RFID tag alongside saplings to enable the grower to track each sapling’s lineage, by storing data not just about that tree (linked to a tag’s unique ID number), but also the mother tree (the source of the tree’s specific seed). This is helping the company to better manage forest diversity, and thus ensure a healthier tree crop (see RFID Helps Foresters Grow Koa Trees).
The company is using Confidex‘s Pino passive ultrahigh-frequency (UHF) tag, designed specifically for tracking trees and wooden objects. When a seed is first planted in a biodegradable pot at the company’s nursery, it is accompanied by an RFID tag encoded with a unique ID number linked to the date and information about its mother tree. In that way, when the trees are planted, the staff has a record of each sapling’s lineage and can thus ensure they do not exclusively plant trees from a single mother tree in one area, which would reduce the forest’s diversity and, therefore, the general health of the trees within it. The tags, which comply with the EPC Gen 2 standard, are read using a Convergence Systems Ltd. CS101 handheld interrogator, and the data is then transmitted from the handheld to the company’s back-end system via a Wi-Fi connection. That data is saved on HLH’s Web-based database, using software the firm developed itself.
I should also mention that AGID, a French RFID company, will introduce a tag designed to be hammered into mature trees for tracking and identification purposes, at RFID Journal LIVE! 2014, being held on Apr. 8-10, in Orlando, Fla.
—Mark Roberti, Founder and Editor, RFID Journal
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