Mario Viveros

UCCE Farm Advisor, Kern County

Deciduous Tree Fruits and Nuts

October 13, 2000

POST-HARVEST CARE OF THE ALMOND ORCHARDS

We are at the end of the almond harvest, but this doesn't mean that we should kick back and relax. The fact is that flower bud differentiation in almond trees takes place during the month of September. This means that next year's bloom and subsequent crop is being formed in the middle of this year's harvest.

There are three important cultural practices that must be considered by every almond grower. They are irrigation, nitrogen fertilization and pruning.

Post-harvest irrigations are very important to keep the leaves active and functioning until normal leaf drop, which typically takes place at the end of November. When we prevent premature defoliation and allow normal leaf drop, we let the tree recycle its nutrients from the leaves to the fruiting spurs. The nutrients that are known to migrate from the leaves to the spurs at the onset of leaf fall are nitrogen, potassium and phosphorous. These nutrients play major roles in bloom development and fruit set. After irrigation, nitrogen fertilization is the most important cultural practice in an almond orchard.

Most of our almond orchards are in sandy loam soils. For these soils, split nitrogen applications are the best. A post-harvest nitrogen application can be of 20 to 40 units of 10 to 20 percent of the total nitrogen applied to the orchard.

Post-harvest irrigations and nitrogen fertilization are a real problem on prematurely defoliated trees. Trees that lose most of their leaves during harvest will leaf out after an irrigation. This leafing out is called "regrowth" which can reduce next year's bloom and yields. It is difficult to know what to do with a prematurely defoliated orchard. If we irrigate, we will get regrowth. If we don't irrigate, we get premature flower drop in late winter. The best thing to do is prevent premature defoliation, by having a good irrigation program in place.

Pruning is the most controversial cultural practice in an almond orchard. There are many procedures and thousands of opinions. However, a good pruning practice is one that keeps the trees forever young. This can be accomplished by cutting off the old wood and keeping the new.

If you prune soon after your harvest is done, you will be able to distinguish between old and new wood. Therefore, if you want to eliminate most of the old wood from your orchard, you should start pruning as soon as your harvest is over. This advice applies to our older almond orchard.
Irrigation, nitrogen fertilization and pruning are vital for maximum almond production. They should not be short-changed or neglected by any almond grower.