I just recently planted several young semi-dwarf citrus trees in the ground, using raised planters (3x3x1, LWH) filled with citrus/palm mix. The base soil under the raised beds contains some clay, as I had originally planted the citrus trees in the ground and, after having issues with drainage, I built the raised planters and re-planted them.

I'm using drip irrigation, with four emitters (.9 GPH) on top of the root ball on each tree. I have been watering twice a week for an hour and a half.

I'm looking for some advice on how to use drip irrigation with young citrus trees. I believe I'm on the right track, but wanted some confirmation as I want to get the irrigation schedule correct and do not want to under/over water the trees.

One question is about the number of times to water each week and the duration. Do the common rules for citrus, infrequent deep watering, apply for drip irrigation? On the current watering schedule, one of the citrus trees is drying out too soon (midnight valencia orange) and I'm not sure if it's ok to water more often or just keep the two day per week schedule and increase the duration of each watering.

Also, I have been using a kelway moisture/ph sensor to monitor the moisture of of the soil on each tree. I read somewhere that when the moisture meter reads 50%, it's time to water citrus trees. Is this true?

Any advice about how to determine the correct watering schedule for my trees using drip irrigation would be greatly appreciated.

I live in San Diego, CA.
Thanks, Tony