And about fertilizing at all-- in theory, is it not necessary? (doesn't happen in nature other than compost and occasional animal manure/urine) In practice does it turn out to be necessary if we want food within the growing season months?

Thanks for the information!

Research over many decades has explored the mineral uptake and transport of many species of fruit trees,
conifers including pine and spruce species, and some hardwoods of ornamental or commercial value.
Results have been mixed in many cases, with some species responding well to treatment and others
remaining unaffected. Generally, the results suggest that foliar application of particular nutrients can be
useful in crop production situations where soil conditions limit nutrient availability. For instance,
alkaline soils do not readily release many metallic nutrients, especially iron and manganese. Zinc,
copper, magnesium, molybdenum, boron, and calcium are other micronutrients required in small
quantities that have been applied to foliage in an effort to relieve deficiencies and combat fruit disorders.
Fruit, as adjacent tissue, can benefit from foliar spray. But this is a localized application that does not
affect the trunk or roots � and therefore is not a solution to soil imbalances. In fact, researchers
consistently state that foliar treatments are a specialized, temporary solution to leaf and fruit deficiencies
in tree fruit production but will not solve larger soil management issues.

Negative: The negative we've seen with the foliar feeding is that it is really hard to figure out the proper amount of fertilizer. Even our professional growers (grow commercial veggies and plants) have had difficulty finding the right amounts to put on and when. The results are different from week to week - whereas if it is just applied on the soil the results are more consistent. It seems that foliar absorption changes based on humidity, time of day, temperature, etc.

Top dressing works fine ...... but it needs to be watered in properly for best results (best not to try in a pot - because watering in will also cause leaching).

If growing in a pot ..... use a liquid fertilizer.

I pray at night before bedtime that there will come a day when I can walk out and see green leaves on my citrus without micro lockout. I count the months. Most areas of my yard I have managed to drop almost a point to about 7.4 and in these areas my citrus are nice and green with only minor signs of lockout. I love layering on the compost and OM:-)