As I understand it, the salts dissolve quickly, so they should only be applied close to planting time or during the growing season. Most everyone has seen that in action when 'epsom salt' (magnesium sulfate) dissolves in water. I believe all the sulfates are salts. So a common way of applying them at garden scale is in solution as foliar spray or soil drench.

Distinct from those, it seems, are the 'rock powders', which are supposed to be much less soluble. And yet greensand and langbeinite are said to be fairly quick-acting. Presumably the rock powders have many minerals in them and some of those might be in salt form, I suspect.

In the case of manure, there is also the issue of ammonium toxicity to be guarded against.

N in organic materials must be "mineralized" to nitrate form or ammonium that is exchangeable before it is in a form that makes it available for uptake. Mineralization occurs during the decomposition of organic materials by microorganisms in soil. Microorganisms feeding on the organic molecules cleave hydrocarbon chains during this decomposition process, freeing elements locked in the chains. Always, the mineralization of N is accompanied by the formation of entirely new organic materials, which might be microbial cells or simply the by-products of the activities of microorganisms. Obviously, the availability of organic materials is the primary factor that determines how much microbial activity/mineralization occurs when soil temperature/moisture/air levels are favorable.

Al

Plants take up nutrients from the soil only in the form of soluble ions - salts. These are not "salts" as in table salt (although table salt IS a soluble ion) but soluble (dissolvable in water) inorganic chemical compounds that plants take up through their roots and from which the necessary nutrients are extracted during photosynthesis. All synthetic fertilizers are formulated as soluble salts so that, unless treated for extended release, the nutrients are immediately available for uptake by the plants. Salt build-up can, and often does, occur when more fertilizer is applied than the plant can use or take up at that time. In an inground soil situation, many of these salts - because they are soluble - are leached into the surrounding soil and groundwater, leading to pollution. If the soil receives inadequate irrigation, instead of leaching, the salts just accumulate or build up, sometimes leading to dangerous - to the plants - levels.

With organic fertilizers, the nutrients are not delivered in a soluble form. They must undergo processing by the soil organisms before they are converted to soluble, inorganic ions/salts that the plants can access. As this is a much slower process with the nutrients in a soluble form being made available over an extended period of time, the risk of salt build-up is much less, as is the potential for leaching. And the nutrient levels of most organic ferts are much lower than those of synthetic ferts, so the risk of over-applying or creating salt build-up and the accompanying 'burning' of plant tissue is much less.

'Mineralization', as it applies to plant nutrients and fertilizers, has nothing to do with minerals! As Al stated, it is part of the nitrogen cycle and describes the process whereby organic nitrogen is converted by the soil microbes into inorganic compounds - the soluble ions - that can be accessed by the plants.

Table salt sodium chloride NaCL consists of Sodium Na(+) and Cloride(-) ions which separate in water.

Plants take in minerals (ionic compounds) dissolved in water and convert them into organic compounds. Decomposers take those organic compounds and break them back down to the minerals. Not all mineral are ionic compounds, those held together with "tighter" covalent bonds don't pull apart in water. Most "rocks" are covalently bonded minerals. ane exception is limestone [calcium carbonate (CaCO3)] which is a salt with very strong ionic bonds and needs something with a stronger charge than water to pull it apart, generally an acid, which is why soil pH (soil acidity) is important for fertilizer availability to plants.

Is borax a salt? mangenese sulfate? gypsum? Copper sulfate?

Clay particles have a charge to them so fertilizer ions stick and stay in the soil longer than with sand. Both bacteria and fungi (microbes) take in fertilizer salts the same way plant roots do. They tend to have a short life span (soil dries out and many die etc) and release the compounds back into the soil for uptake by plants and more microbes in a "recycling" cycle that resists leaching. The microbes need organic material for the carbon they need, so if you have a lot of organic material in your soil it will hold onto minerals longer. This is one misundertanding of alot of organic warriors. It's not the "salt" fertilizers that are bad, it's the low organic content in the soil from intensive agriculture that those fertilizers make possible.

Cover crops scavenge minerals from deep (and shallow) soil and release them when they are cut and turned under to rot. Microbes are pretty much stuck to shallower soil depths.

I want to be very careful not to use salts in excess quantity, for obvious reasons. Someone in this thread said that salts are not minerals, and yet the various salts do mineralize the soil. One gets mag and sulfur into the system if one introduces mag sulfate to the soil, as an example, so how is that not a mineral?

Eric's post above outlines why I said what I did - when most folks think of minerals, they think of rocks. It is confusing to say the least!!

From a personal observation, I don't know how you can avoid salts nor should you want to, as that's how the nutrients get delivered. But I think it may be wise to consider how/why you are using the salts, in what volume and most especially, from what source they are being derived.

Would you mind emailing me? You can find my address in (my page). It's about something off topic and that we share in common. Thanks!

I find the opposite, it's usually the colloquial terminology vs. the specific scientific terminology where the confusion lies.

In reply to the question about angry microbes...it is a short twisted conclusion from a long story. As I said, microbes take in fertilizer salts the same way plants do. This allows fast population growth of the microbes if they have carbon to eat. They eat all of the carbon and then the soil turns into a "depleated" mineral soil (sand silt and clay only), which doesn't hold onto water or nutrients very well...dries up blows away etc. You can dump more fertilizer on it and grow more crops but it keeps getting worse. Bacteria outcompete fungi for those fertilizers and decomposes crop residues/organic matter very quickly. Tilling the soil adds oxygen, which allows the bacteia to grow even faster, eating soil organics faster. So farmland went from a low intensity manure fertilized-organic rich fungal system to a high intensity mineral fertilizer bacterial system that stripped organic matter from the soil. It takes quite a bit of time for microbes to chew away at the most stable soil carbon compounds (humic compounds). After 20-40 years of repeated tilling, high fertilizer/low organic input the soil in America's Heartland was "depleated" of organic matter and microbial life. As a result farmers turned to no-till methods and cover cropping to rebuild organic matter in the soil. This allows the "ancestral" fungal populations to come back. Nutrient minerals are added with "organic" fertilizers, which must be broken down to release the "minerals" in a relatively slow process so the bacterial populations don't skyrocket and eat all of the organic matter.

The organic warriors grabbed onto the "before and after" organic rich soil to depleated mineral soil (20 year farming process) and distilled it into "synthetic fertilizer kills soil life (i.e. fungi and bacteria)". But that doesn't make any sense...

Synthetic/mineral fertilizers are used in high concentrations to grow mushrooms... so much that undiluted mushroom compost will burn plant seedlings.

"potash, urea, ammonium nitrate"

http://extension.oregonstate.edu/news/story.php?S_No=28&storyType=gard en

You can also add mineral fertilizers to cold compost piles and heat them up again as the microbial populations reproduce. It is especially useful (IMO) for things like big woodchip piles, resulting in a large amount of slow release "organic" fertilizer when the compost is used in the garden. When you turn those piles the inside is full of happy fungi.

Sure, you can pour high concentration miracle grow on microbes and it will kill them through osmotic stress (sucks the water out of them like pouring salt on a snail). But that concentration is soon diluted and the doubling time of microbes is in the order of hours (think of mouldy bread) so whatever was killed is soon replaced.

Used the wrong way mineral/synthetic/salt fertilizers can pollute the environment from runoff, but that is usually in farming situations or from lawn care practices. You can pollute the water table with organic methods as well.

"In one case, alfalfa that was plowed was found to have twice the concentration of nitrates below the root system of the crop compared to fertilized corn."

http://extension.missouri.edu/publications/DisplayPub.aspx?P=WQ277