Some good answers on this question: Is it worth spreading ash on the vegetable plot?.
But one answer says:
I can't think of any minerals that would be present
and the other upvoted answer says:
It has (varying depending on the woods that were burned) quite a few nutrients
I'm trying to work out which answer is correct, or whether they can both be right.
From a gardener's perspective, when we talk about nutrients, do we mean minerals?
@Baka is along the right lines but @Jonh is right to note different contexts.
I come from a geological background, so to me a mineral is basically the different crystalline components of a rock. Rocks are made of multiple minerals. if you break a mineral down, you end up with atoms. Eg. Quartz is a mineral, it can be found in granite (a rock), but if you break it down further you get silicon and oxygen atoms.
In my experience when gardeners talk about minerals, they are talking about the ions produced by the breakdown of minerals. So for example, feldspar (another common granite mineral) will eventually break down (via various clay minerals) to release Iron, Magnesium, Potassium, Sodium, Calcium, and Aluminium (not all of these are present in all feldspars). This list of elements in ion form, are what the gardeners are talking about as minerals.
Perhaps a proper chemical definition might be "ionic nutrients"? This would include the above cations (essentially metal ions), mineral-derived anions (eg. some phosphate), and the soil/manure derived anions (eg. phosphates from guano; nitrates from nitrogen fixing and manures).
(Ions are charged atoms that result when a salt dissolves. eg. Potassium Nitrate would give you Potassium ions and nitrate ions)
When talking about plants / gardens in general minerals are just a composition of nutrients that plants get from the soil they are placed into. So yes in this case they are the same thing. In a different context they may mean something different but in this case they represent the same thing.
Some minerals are nutrients. Nutrients are not necessarily minerals. There are amino acids that are also nutrients (think vitamins and minerals in your diet).
From what I have seen, minerals more typically fall under the "micronutrient" group of nutrients (Zinc, Copper, Manganese, etc.)
From wiktionary, a mineral (#3) is:
Any inorganic element that is essential to nutrition; a dietary mineral.
By that definition, all "minerals" are nutrients; that's probably the most relevant for a gardening context. By a broader definition (look at their #1), a mineral is any natural inorganic material.
A nutrient is:
A source of nourishment, such as food, that can be metabolized by an organism to give energy and build tissue.
Clearly there are nutrients that are organic, thus disqualifying them as minerals. So when I want to talk about all the stuff that plants need to consume, I usually say "nutrients". I would only say "minerals" when I am talking about a specific mineral plant requirement.
My understanding (quick-validated via this Wikpedia article on Plant Nutrition) is that plants do not themselves feed on organic compounds (i.e. proteins, carbohydrates); they MAKE such compounds from scratch by combining the minerals that they pull either from air (i.e. Carbon from C02) via photosynthesis, or else from soil (long list in that article), where microorganisms and/or fungi (who don't photosynthesize) make these minerals nutritionally available, as solutes in H2O solution.
So: unless you consider as nutrients either Sunlight, or else these other living Organisms that play a mutualistic role in plants mineral uptake, then it is only minerals that can be called nutrients, strictly speaking.
NB: when we "feed" our plants compost, containing essential organicMatter and Microorganisms -along with Minerals, the 3M's of plant nutrition- we're really just feeding these other organisms that in turn feed our plants the minerals that they need.
There may be exceptions (e.g. carnivorous plants -e.g. Venus flytrap?- i don't know about these), but this is the essence of Plant Nutrition as i understand it; if i have this wrong, would appreciate clarification, with reference(s).
