Even if a rainstorm fails to deliver much water, vines are unstressed. It doesn’t mean it will stay this way though. Late season heat happens here in California and if you stopped watering completely because you assumed the soil profile is full, think again. If the profile is back to being dry and we get some heat, your vines can easily get stressed again.
Get your macros in, bro
One of the main reasons to keep irrigating is to apply some fertilizer. Harvested fruit removes roughly 3 lbs nitrogen and 11 lbs potassium per ton. Applying an N-P-K fertilizer through the drip post-harvest puts some of these removed nutrients back into the system. Later, cool years like this one make getting in this final application difficult, but if you can squeeze it in, it makes a big difference when it comes to early canopy establishment the following season.
Conclusion
Should you irrigate or not? Ideally, you get yourself some soil moisture probes and find out. Otherwise, my general advice is if you’re on a lighter soil or one with poor percolation, I wouldn’t take the rain as a sign that your work here is done. Keep irrigating regularly until leaf fall is the best way to ensure maximize recovery and set yourself up for success next season.
