Am curious about not fertilizing during the hot summer months. I’ve heard about stopping fertilizer when summer temps consistently reach +85F degrees but I’m wondering about how to apply that rule. Does it apply to refined trees only or both refined and trees in development? Does it apply to both chemical fertilizer as well as organic fertilizer? What’s the reason to stop fertilizing at those temps? Is it harmful to the trees or is it just a waste of fertilizer? I have watched the Mirai video, Fertilizer 101 several times but don’t recall any answers to these details. Any knowledge passed on would be appreciated.
One of the reasons as I understand it is that most fertilizers contain salts and during summer there is an increased risk of salt build up which can harm the tree.
I believe that when it gets hot the trees put all of their water mobility into keeping cool and not growth. As a result the tree will not be using much fertilizer.
For a fertilizer to be absorbed into the tree it must be in the form of a salt - an anion + a cation. This is for both chemical and organic fertilizers. Chemical fertilizers start as a salt of some form while organics are broken down by the soil biology to into a salt - often a rather complex organic salt. If the soil contains salts it can be more difficult for the roots to absorb water since the water will want to stay outside the root to reduce the chemical activity of the salt ions. Having a good strong tree with lots of sugars and starches in the roots will cause the water to go into the roots to reduce the chemical activity of these species inside the rotos. It can also be viewed as the impact on the chemical activity of the water, but that not the typical approach since water is the solvent.
Finally, chemical activity is a combination of the concentration of the ions and the affinity of the ions for water. It is really applicable to non-ideal solutions where we multiple ions at relatively high concentrations.