Plants remove substantial amounts of nutrients from the soil during their normal growth cycle and many long-term environmental changes occur as a result of this process. Effects on the soil go considerably beyond the straight removal or depletion of nutrients. Charge balance must be maintained in the plant-soil system during nutrient uptake. Charge balance is usually achieved by the excretion of proton and/or hydroxyl ions by the plant to replace the absorbed nutrient cations or anions. For example when plants are fertilized with ammonia, they acquire most of their nitrogen in the form of the ammonium cation, rather than from the usual nitrate anion. Because nitrate is the only anion used by the plant in large amounts, the net result of this change is that during normal nutrient uptake the proton excretion will far exceed that of hydroxyl ions. In the case of vigorously growing plants, the amount of excreted protons can be sufficiently large as to decrease the pH of the soil by several pH units. Changes in soil pH of such magnitude can have large implications for a number of soil processes such as soil structure, nutrient availability and leaching of nutrients. The immediate effect on the soil may be favorable for some plants, especially acid-loving plants, in that it tends to make iron more available. However, in the long run, lowering the soil pH can be deleterious to plants in that the availability of nutrients will change. A lower soil pH will allow micronutrients to be more readily leached from the soil profile, eventually resulting in deficiencies of nutrients such as Cu and Zn. Additionally, when the pH of the soil drops much below pH 5, the solubility of Al and Mn can increase to such an extent as to become toxic to most plant growth,

Plants are often thought of as passive in relation to the environment. However this is not always a valid assumption; for there are many plants that clearly manipulate their environment in a fashion that tends to makes certain nutrients more readily available. For example, iron is a limiting nutrient in many agricultural areas, but it comprises about 3% of the average soil which, if available, would be far in excess of the needs of the average plant. Some plants actively excrete protons, and the resulting decrease in pH increases the solubility of iron in their environment. In addition, other plants excrete phytosiderophores that chelate the soil iron rendering it a more available form for the plants

does that fertilizer manufacture formulate their product assuming the gardener's soil will be ideal (perfect) for their plants of choice?

Basically yes, not perfect but within the acceptable range of 'normal' soil pH.

s it safe to assume that no matter what fertilizer you choose and use it according to their directions, that it won't help much if your actual soil is unbalanced in nutrients and/or the pH is way off.

Yes, with provisions mentioned by Terry. It isn't a static environment. It is affected by the plants themselves, the weather, the pH of your water or the rain, the tilth of the soil, it's ability to drain or retain water, etc. But still basically, the answer is yes it won't help much if the soil pH is out of kilter.

Can any fertilizer help balance poor soil?

Simple answer is no, not if you mean balance the pH. Improve the nutrient availability, sure but would they be more usable by the plants just because they are there, not necessarily.

It's for these reasons that compost rather than manufactured fertilizers is so strongly recommended. It can balance the pH, improve the soil tilth and water balance, and feed the plants. How well it does all those things depends on the quality of the compost used.

Most have had aphids since day one.

Often a good indicator of excessive nitrogen use.

Dave

Thanks so much!