There are many reasons for the yellow leaves appearing on your olive tree. If the yellow leaves are scattered throughout the tree, then this isn’t anything to worry about as Arbequinas experience continual leaf loss through the year. In fact, since these trees aren’t decidous, their leaves have a lifespan of around 2 to 3 years, after which time they turn yellow and fall off. If, on the other hand, the entire tree has yellow leaves, it could be due to lack of nitrogen. More frequent fertilizing will be necessary using a nitrogen-rich fertilizer.