I’ve had a number of calls so far this week and the end of last week asking “when is it ok to turn off the water?”. You can usually cut way back at this point. The problem is that we are in a severe drought, which makes it very risky to stop irrigating, especially if you have a crop load on the tree. If you are not irrigating enough at this point you likely see some yellowing of the leaves and some leaf drop.
For young, non-bearing trees, continue to irrigate on the normal schedule—100 gallons per week—until you get a 1″ rain. At that point you should be able to turn off the water for the season. If the drought continues long-term, continue to irrigate until the leaves drop naturally.
It is especially critical to continue irrigating trees bearing a crop. If you turn off the water too soon at this stage under the conditions we currently have you will likely see significant shuck decline, stick-tights, and loss of quality. This problem will be worse on trees with a heavy crop load. The nuts are still maturing on most varieties even thought the kernels have filled and the process of shuck dehiscence (opening of the shucks) requires good soil moisture.
Continue irrigation at 50-60% of full capacity on bearing trees until about 1 week before you expect to shake trees for harvest. If you get a 1″ rain you can turn the system off for 3 days and then resume irrigation until the leaves drop or until we get another good rain.
Most growers with Pawnee are shaking this week or next week. Following the harvest of these nuts I would continue irrigation until a 1″ rain arrives or until trees lose leaves.
It is extremely dry throughout most of the state. Don’t make the mistake of turning off your irrigation too soon under these conditions.