I’m dialing in irrigation and nutrient timing with a handheld TDR moisture probe (reading at 6 in) and a basic pH/EC pen, aiming to keep new Ilex and Cornus installs out of stress rather than chasing symptoms. If you’ve compared compact TDRs to pin-type moisture meters or used a SPAD meter to guide nitrogen on chlorosis-prone species, what’s been accurate enough for day-to-day rounds?
For new Ilex and Cornus, I stopped relying on a single “6 in” TDR read and add a quick 3 in check because the top zone dries first and will stress leaves while 6 in still reads safe. If you bring a SPAD into it, set a site baseline on healthy sun leaves and only tweak N when you’re about 10% below that, otherwise it’s noise.
Compact TDR beats pin-type — pins swing hard with salts; I do a quick gravimetric check to calibrate at your 6 in depth and it stays honest. For SPAD, use a relative trigger: about 5 SPAD drop from a ‘reference’ leaf = N bump; if pH > 7 or EC is high on your pen, treat Fe (EDDHA) instead of more N. @lgreenwell92’s point about not trusting one read tracks.