I’m writing this article so it will start raining before bloom and will hopefully solve our dry soil problem. If a weather change brings sufficient rain soon then concern about this topic will be unnecessary.
Orchard soils are dry, even after the heavier than normal rains during October. Ideally, the entire root zone should be well supplied with moisture when root growth and bud swell begin. Historical seasonal rainfall in the Chico area for the period from Oct. 1 through Jan. 20 is about 13.4 inches. In most of our orchard soils this is enough water to wet the soil profile down to at least 4 feet. This winter we’ve had about 2.5 inches of rain to date with all of that precipitation occurring in mid-November. Resident vegetation has transpired most if not all of that water so that rainfall did not contribute to current soil moisture storage. Obviously, we’re running considerably behind. Many orchards have already been irrigated in preparation for the coming bloom period.
Early irrigation trials in Durham conducted by my predecessor Clem Meith decades ago indicated that early irrigated trees produced nuts that were longer, wider, and heavier than those from other trees. Yield was greater and more shoot growth resulted on the early irrigated trees.
It’s crucial to start the growing season with the soil profile fully stocked with available water. In most of our almond orchards this means moisture down to a depth of about 4 feet. At this point, I feel it’s a good idea to irrigate almonds if you don’t have sufficient soil moisture in the root zone.
The last time I dug an auger hole in an almond orchard, the soil was moist down to about 12 inches. I was pouring dust dry soil out of my auger from two to four feet in depth. Unless we get enough rain to adequately wet the root zone’s soil volume by the end of January, plan to irrigate. This is especially necessary for almonds where growth begins early and the highest possible percent set is desirable.
Once trees begin actively using water in late spring and summer it’s often difficult to keep up with a tree’s needs.
If a soil reservoir of stored moisture isn’t there, your trees may suffer when it comes to the long, dry harvest period.
It’s much easier to keep up and stay there than it is to catch up when you’re behind.