Is nutrient release dependent on soil / environment / crop?
Since the dissolution reaction is triggered by the plant, environmental factors do not affect nutrient availability. So as long as the environment allows the plant to grow and survive, plants will be able to uptake the nutrients according to their needs. The key here is that Smart Micros do not require environment triggers for nutrient release but only an actively growing plant. Rate of release is dependent only on rate of plant growth.
Is the nutrient release driven by low pH or is there a selectivity to specific types of acids?
Soil pH has no effect on nutrient release. The effect of root acids is mainly due to the chelating action (if these acids were neutralized to >pH 7 the Smart Micros would still dissolve). However, the molecules do dissolve by acids alone but that is at very low pH levels (pH<2) that are not present in soils. So, effectively, release in soils is only due to chelating action and not due to acid induced dissolution.
What causes the plant to release these acids that release in turn the micro-nutrients? Is this release related to growth?
Exudation of various acids and enzymes is a natural process in plants and the means by which plants are able to utilize the nutrients bound to the soil matrix. This release is related to growth (because the plants’ requirement of nutrient increases with growth) and plant roots proliferate as the plant grows. There is also increased secretion of exudates when the plant experiences deficiency of a nutrient (it is an intelligent feed-back mechanism so that the plant secretes more in order to take up more nutrient when there is a greater need).