Nutrient Management Research Database

Heavy crop removal and inadequate soil potassium availability could limit almond production in California. This research suggests that potassium deficiency is associated with higher mortality rates for fruiting spurs. Leaf potassium concentration from samples taken in July were found to be moderately correlated with yields in the following year. Leaf potassium concentration below 0.8 % in July was associated with potassium deficiency. No yield benefit associated with leaf potassium concentrations greater than 1.4% was observed. Almond fruit (kernel, shell, and hull) is a major potassium sink, containing the equivalent of about 55 lbs potassium per 1,000 lbs of harvested kernels.

• Potassium fertilizer, in the form of potassium sulfate, was applied to nonpareil almonds at the rates of 0, 240, 600, and 960 lbs potassium per year from 1998-2000.
• Fertilizer applications occurred three times in 1998,and two times in 1999 and 2000.
• Leaf samples were taken in July from the untreated trees and the trees receiving 960 lbs potassium; these leaves were tested for potassium concentrations.

• Potassium deficiency will not affect yield in the year that it is detected by leaf testing.
• Yield can be affected the subsequent year, because potassium deficiency will decrease over-all flower number due to increased fruiting spur mortality the next year.
• In this study, yields of the untreated trees decreased in 2000, most likely due to the observed potassium deficiency in 1999.
• The highest yields were observed in the plots that had potassium leaf concentrations of 1.4 to 1.7 %.
• However, there were plots with this higher potassium leaf concentration that had similarly lower yields to the control plots, indicating that some other factors were influencing yields, even when potassium leaf concentration exceeded 1.4%.
• Because samples were only taken from the control and high fertilized trees, this work could not determine potassium leaf concentration that delineates deficiency and sufficiency.