Agave
ExperimentalThe sensor gives usable readings here, but the dataset is thin and there are no published thresholds. Sold for research and supervised field trials only — not for commercial irrigation scheduling. Growers: stick to the Validated list.
Performance
Research use only: in the first agave test neither sensor gave a reading we could tie to the plant, and none has been checked against the pressure chamber. In late September 2026 two sensors went into the leaves of young agave in a research plot in Davis, California. The first, in the standard sleeve install, never gave a usable reading; reworked a week later, it drifted to near zero within five days, the usual sign of a flooded install. The second, set in a hole opened with a cork borer, gave a clean trace: a midday dip that deepened for five days, then, around a 30 September irrigation, five nights near 0 bar and a much smaller daily swing. That could be the plant recovering or the install flooding. After it, the swing rose and fell with how fast the sensor itself was warming and cooling (r = 0.9), and the flooded first sensor showed the same shape at about half the size, which points to the install responding to sun and heat. Neither sensor recovered in the three days after a second, logged irrigation. A future install should go deeper into the leaf, be shaded or insulated from direct sun, and have a reference measurement alongside; we would like to hear from researchers who can pair one with leaf pressure-chamber or psychrometer readings.
Installation Tips
- Agave is a CAM plant: its stomata open mainly at night, and its leaves store a lot of water, so leaf water potential is expected to move slowly and swing little through the day. Well-watered Agave deserti leaves measured about -4 bar (Nobel 1976). Read the whole 24-hour trace, not a midday value.
- Open the leaf with a cork borer before setting the sleeve. With the standard drill stop the bit only reached the leaf surface.
- Pointing the sleeve up or sideways should keep the kaolin paste in the hole: both first installs pointed down and leaked kaolin past the seal. Set the sleeve a day ahead so the sealant cures before the kaolin goes in.
- Shade or insulate the install from direct sun. The first sensors warmed and cooled by up to 5 °C an hour, and a sealed, wet install can turn that into a daily swing of its own: check any swing against the sensor temperature before reading it as the plant.
- For the first installs, take reference readings alongside for a few days, as Nobel did: the pressure chamber on cut leaf tips, or a psychrometer set in a cork-bored hole in the leaf.
- Log irrigation with a pressure switch so every set shows on the chart. In Nobel’s test an agave droughted for months took up water within about 12 hours of its soil being wetted, and its leaf water potential recovered over 1-3 days.
- Wear gloves: agave sap carries needle-like calcium oxalate crystals (raphides) that irritate skin.
- Credit: the first agave test was installed by Ken Shackel (UC Davis) in the agave plot of Paula Guzmán-Delgado (UC Davis) and Giulia Marino (UC ANR).
Known Issues
- The standard sleeve install (drilled to the stop) gave readings that jumped about half a bar every 20 minutes, sat above 0 bar at times, and plunged every morning, an hour or more after sunrise, as low as -26 bar. Reworked a week later, the sensor settled at -8 bar, drifted to near zero within five days, and has swung less than 1 bar a day since: the usual sign of a flooded install.
- In its first week the cork-borer install showed a midday dip that deepened every day, to -10 bar, while its night-time level rose from about -4.6 bar to about 0. No agave study we found reports that shape, and the dip grew whatever the weather, so read the first week as the install settling.
- A small daily swing that is lowest at dusk and highest in mid-morning can be the sensor, not the plant: in the first test it tracked how fast the sensor was warming or cooling, and the flooded first sensor showed the same shape.
- A sensor that sits near 0 bar for days is more likely flooded than reading the plant: well-watered Agave deserti leaves measured about -4 bar.
References
- Water relations and photosynthesis of a desert CAM plant, Agave deserti. Nobel 1976
- Water flow and water storage in Agave deserti: osmotic implications of crassulacean acid metabolism. Smith, Schulte & Nobel 1987
- Irritant contact dermatitis caused by needle-like calcium oxalate crystals, raphides, in Agave tequilana among workers in tequila distilleries and agave plantations. Salinas et al. 2001