I use a variety of different fertilizers on my fruit trees depending on their state and rate of growth. I use the Espoma Citrus tone starting in Spring when my trees are starting to kick into gear because it will release nutrients slowly and feed the microbial life which in turn feeds the worms and other organisms in the soil.
If my trees set a heavy crop, I also give frequent but very dilute feedings with SulPoMag, Azomite and Gypsum but not at the same time.
Last year, I also started feeding my trees with Nutricote smart release fertilizer which is great for trees that are frequently irrigated because other types of fertilizers may get washed away with frequent waterings, this is probably most noticeable in sandy soils or with potted plants.
Here’s a pic of my lemon tree which gave me about 150 lemons already and probably still has over 100 fruit on it, leaves are a little chlorotic because of the extremely heavy fruit load year after year.
Simon