We are midway through almond harvest. As we finish up shaking our earlies and nonpareils, we need to keep in mind the list of orchard tasks to help maintain crop production for the next year. For almonds, flower bud differentiation 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.
During this time period, there are three important cultural practices that need to be considered by almond growers. They include irrigation, nitrogen fertilization and pruning.
1. Post-harvest irrigation is very important to keep the leaves active and functioning until normal leaf drop, which typically takes place in mid November. By preventing premature defoliation, we let the tree transition its nutrients from the leaves back 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.
If the orchard does prematurely defoliate due to lack of water, irrigate to encourage re-growth. This may reduce yields in the following year, but yield loss will not be as significant as not watering at all. If watering does not occur, not only will fruit bud differentiation be poor, the orchard will suffer from premature flower drop in late winter. The best advice is to avoid this situation all together by properly managing your water during the harvest period.
2. After irrigation, nitrogen fertilization is the most important cultural practice in an almond orchard. For most of our orchards, split nitrogen applications provide the most efficient use of nitrogen. A post-harvest nitrogen application can be of 20 to 40 units per application – dependent upon tree age – totaling no more than 10 percent to 20 percent of the total nitrogen applied to the orchard.
3. Pruning should occur after the harvest is completed. During this time it is easy to distinguish between old, diseased, dead and new wood. Remember to remove diseased branches 6-12 inches beyond the last sign of diseased tissue (i.e. canker). If possible, avoid pruning during the rain or if rain is within the three to five day forecast. Pruning cuts take at least seven days to heal and can provide entrance for fungal pathogens.
The overall value of pruning itself has been questioned by recent UC research. Data has indicated that heavy pruning reduces the following crops yield and costs money to perform. When making the decision to prune, think of the real reasons you want to prune. Often times some of the ugliest orchards yield the highest.