professional soil tests can determine what, if anything, need be added.

Homemade compost -- ~2" per year
Kelp meal -- 4 lbs/100 sq. ft. per year

Anything else is in response to periodic soil test results every 3 years.

In the past I have used all the usual things. Lately I have taken to using rock-dusts of various kinds, because I believe they will create the most lasting fertility and soil health and so are the best value-per-pound hauled.

Joe, if you believe that the nutrient value in plant matter as human feed can vary (which I also believe), how are you measuring that so as to compare? Taste can be a good measure, I think, once the palate is well educated, but some on this forum have stated that they do not notice taste differences, for example one apple vs another. So a more reliable method is probably called for. I use the brix meter.

Brix is useful for a quick assessment of sugar content, but it won't tell you anything about mineral content, nor will it address protein or fat content. Taste is also not a reliable indicator of nutritional value - much of taste is a result of volatile compounds that have no real bearing on nutritional value other than as may be affected by the stage of development of the produce being considered (e.g. a "better" tasting tomato doesn't reflect that tomato's comparative nutritional value).

If your plants / tress / vines etc. are healthy and producing well, then I believe you can safely assume that the nutritional value of what you are producing is that typical of what you are growing. The real question is how to keep those plants, etc. growing healthy and producing well, year after year, and the impact of soil composition and soil-based nutrients on plant health and vigor.

Pnbrown:

Man how can you afford rock dust? Don't you go through a bag in no time?

As TXEB said I go by looks, as well as intuition.. Im sureyou could send your produce off to a lab and test it,but I don't bother... But looks don't neccesarily mean a whole lots either... Plants look nice, lush green, and vigorous with just N-P-K.. That's half the reason Imnot very fond of our modern farming... They don't do to much to grow nutrient, mineral rich foods. Just grow the most GMO plants you could in your lot for a quick income.. Half that produce doesnt even get consumed fresh, it just processed hydrogenated junk...

Back to the topic - "The real question is how to keep those plants, etc. growing healthy and producing well, year after year, and the impact of soil composition and soil-based nutrients on plant health and vigor."

That is somewhat of my question.. How do you assure your soil,as well as plants are thriving? What do you add, amendments, minerals, chemical trace elements,what? How do you guys remineralize you soil?

Thanks for you posts,
Joe

I've started using Azomite (see link) in containers and as a top dressing on raised beds.

Here is a link that might be useful: link

I suspect my suburban yard is a net importer of minerals just by composting all my kitchen waste plus grass clippings and such. And we reuse some ash from wood that's cut elsewhere. I have clay soil which is supposedly full of minerals (if you can get them to let loose!). So I haven't been adding trace minerals.

I looked back at my compost analysis study data from a couple years ago. Out of 11 samples (10 store bought plus one batch of my homemade compost), mine ranked as follows (1 being highest):

Ca 2
Mg 6
Zn 2
Fe 10
Mn 7
Cu 3

Not sure what happened on the iron there, I'll have to add more nails to the bin. :-p

I guess all this really proves is that my compost is better than store-bought, not that my soil has enough minerals. I'd have to dig out my last soil test data and see if they did the trace minerals.

I think a lot of gardeners use much more leaves than the big compost facilities.. I believe that's partly the reason your seeing yours ranking top in minerals.. I believe leaves contain much more minerals than we think, perhaps because it's not packaged with a label listing all the elements, and we are not paying big bucks for it... Kitchen scraps from the store, is from all over the world, varying in minerals of different soils.. I believe that has some part as well... What was your ingredients in compost?

Thanks,
Joe

Compost mineralizes soil. The mineral flow is always from local trees, in the form of wood chips or leaves, to the garden. Then there are local, distant sources, such as kitchen scraps from local food products (say, the apples I buy for the winter), and non-local sources, such as coffee grounds, grains and banana peels.

Only the latter may be able to correct a deficiency in local soils. However, plant themselves tend to concentrate minerals which may be in low supply. Here in Michigan the issues are selenium, iodine, and zinc. The first two are used by humans and not by plants, and we typically get them from grains, seafood, meat and salt. The third is concentrated in plants and can be obtained from compost.

TXEB, I'm quite sure you are incorrect to say that a brix meter only measures sugar. It certainly also measures dissolved salts, since it is widely used to test salinity levels. As well, it can give some indication of whether the dissolved solids in the plant sap is mostly simple sugars or more complex molecules, by virtue of how "hazy" the field is, and this difference is the key to the nutritional value of the produce.

pnbrwon

Okay, I oversimplified it when I said just sugars. To be more accurate, optical Brix measurements reflect the dissolved solids in a solution, typically measured by refractive index. It is a very non-specific measurement. Historically it was developed and "calibrated" based on sugar (sucrose) and used as an alternative to more traditional specific gravity measurements. Different sugars in the same amounts give different readings because of their differences in refractive index contribution in solution. Salt can also contribute, as can most other dissolved organic solids. An even larger contributor is ethanol, which is commonly found in fruits that are passing their prime and have begun fermenting. The haziness you mention (turbidity) merely reflects the amount of suspended solids, which is more a reflection of sample prep and handling. Again non-specific on no nutritional information, at all.

As a non-specific measurement it reflects very little, if anything at all, about the nutritional value of what is being measured. It is best used to track changes that are occurring, such as the ripening progress of a particular fruit, but alone it is not sufficient because of the impact that other developing species can have on the measurements (e.g.., ethanol and other alcohols).

If you want to know about the nutritional value of produce you begin with the basics - carbohydrates, proteins and fats. Carbohydrates and fats can be further subdivided. Then come minerals and other essential nutrients such as vitamins. That's what you want to know, for the most part, about nutrition. A specific gravity or refractive index measurement is not going to tell you about any of those with any measure of specificity. A number of sellers will claim otherwise, provide correlation tables, etc. It is nothing more than a sales pitch. Unless you know what's in there, you know nothing about the nutritional value, and refractive index measurements tell you nothing about what's in there.

Raw: My typical compost batch has leaves (mostly maple, birch, oak in my yard), grass clippings, yard and garden trimmings, and kitchen waste.

It's true that imported or industrially grown vegetables may be all over the map, but I'm sure we all agree that nothing goes to waste! Minerals or no, it goes in.

Raw Nature ...

"I believe leaves contain much more minerals than we think, perhaps because it's not packaged with a label listing all the elements,"

Try this

Here is a link that might be useful: Chemical Composition of Municpal Leaf Waste and Hand Collected Urban Leaf Litter

While soil tests can show macro and micro nutrient levels, they will not show levels of micro.micro minerals like yttrium, strontium, iodine,scandium, cobalt, and several more that are important to optium human health. Some of those listed may or may not be essential to healthy plant health.

So, I remineralize with Azomite. Sure, it contains a lot of silicon, but to refine down further would likely be cost prohibitive.

TX, I am not loathe to concede that you may easily know more about refractometers and what they measure than I do.

So, carbs, fats, simple vs complex sugars, enzymes, vitamins: as far as I am aware, there are no affordable instruments for measuring such things, correct? I don't much care for the logic of simply assuming nutrient values are superior because one uses plenty of compost or other soil or foliar inputs. I'd much prefer a reliable way to measure it in harvested produce, not to mention be able to compare with other produce. The refractometer at least is a step in that direction, it could be measuring differences in nutrition, at least.

Wow! I was expecting some variation, but that is all over the place.

pnbrown

No, unfortunately there aren't any simple tests for nutrient levels in the foods we eat. The tests are actually quite elaborate, and I know some of them well (30 years research chemist, did my PhD in analytical chemistry).

I too would like a reliable indicative method of testing for nutritional components. But there just isn't any that discriminates on the basis of nutritional components. When used to compare different produce options refractometry could be measuring what you suggest, but it is just as likely if not more so to be measuring the impact of different levels of water that were available or degree of ripeness. The fact is, it is not a useful indication of the nutritive value of food.

Some smart folks at Ohio State University's Dept. of Horticulture and Crop Science took up the issue, and in turn put out a series of four Fact Sheets via their Extension service. A link to the first one is included below, from which I will quote, "ðBrix values are not a direct measure of the nutritional value of a crop as dieticians, nutritionists and other professionals assess it.", and also "These values are affected by genetic and management factors. Also, they correlate much more strongly with how sweet a product may taste than how nutritious it may be."

The other Fact Sheets in the series can be readily found if you Google the fact sheet numbers as they are listed at the end of the overview sheet linked below. (e.g. HYG-1651-12)

Here is a link that might be useful: OSU: Using °Brix as an Indicator of Vegatable Quality

This post was edited by TXEB on Wed, Apr 10, 13 at 16:22

Informative, thanks for the link. I can accept the limitations outlined regarding the refractometer.

Reading it leads me to this idea: a "low" brix result for a type of produce, IOW, that one knows from experience is lower than average, does not necessarily indicate lower than average nutrition. However, a "high" measurement result probably would indicate higher than average nutrition, because it seems to me that a plant that can make unusually high levels of carbohydrate or sugar is a very thriving one.

To me it seems reasonable to conclude that although the mere measurement of sugar does not tell one specific facts about the nutrition, still it likely grades produce roughly by nutritional quality. For example my top-set onions that brix in the high 20's are immensely likely to be more nutritious than market onions that brix at 4 or 5. the measurement does not tell me just what I am getting from an onion but it does tell me that one onion is very likely better than another.

Not all leaves are created the same...especially when it comes to effecting nutrients and microbial activity.

Sugar maple leaves and some oak leaves (as well as some other leaves) need to be used with care unless you want your N tied up and mineralization slowed. The problem is the with the tannins in these leaves. Note: Not all tannins are bad, some are good...there's 1000s of "tannins" out there...all with differing effects.

These tannins can immobilize N quite severely...especially with sugar maple leaves which effect both soil availability and the ability of microbes to produce N.

Not only is mineralization slowed, but they can be washed out of the soil or deep into soil profiles before they get a chance to be plant available.

You'll have N in your compost, but it will be complexed in a manner that's useless to plants.

Should sugar maple and oak leaves be avoided? No. Should they make up a smaller part of your composted leaf regimen? I would strongly advise it.

Btw, this is only a couple of instances out of many concerns with leaf use. It's just a good idea to source your leaves from a good mix...or use a known "safe" composting tree leaf source...

If you only care about the structure, and not nutrient content, that your compost will provide then none of this matters too much.

This post was edited by nc-crn on Wed, Apr 10, 13 at 17:31

"To me it seems reasonable to conclude that although the mere measurement of sugar does not tell one specific facts about the nutrition, still it likely grades produce roughly by nutritional quality".

I wouldn't or won't go there. First you have the debate of what constitutes better nutrition in an onion, and is it reflected in the dissolved solids that are affecting the index of refraction? Then there are the many variables that affect the measurement without necessarily affecting nutrition, including the specifics of the cultivars, cultural and harvest practices, product age, moisture content, etc.

What I would say, without regard to the measurement, is that a very fresh onion you just pulled from your garden is more likely to retain it's native nutritive value better than one harvested last week and shipped across the country or out of Mexico, or wherever. Nutritional value of produce generally tends to decline with age, as often do the factors that influence consumer appeal.

Tex - thanks for the links, i already read the nj keaf composition study.. OSU one inwill check out...

Pnbrown - i like the way you think.. If we are doing hard work to benefit our soil, at least have some evidenc that it actually benefits the soil, plants, and us!

We all know brix meters measure sugars,etc, not specific nutrient content.. I am not trying to figure that one out, although that is a smart idea.. If your plants are starving for a nutrient, and you add the nutrient, chances are the plants are going to get at least some of that nutrient.. So back in line..

How do you mineralize your soil?

So here is another one for you ... from the bright folks at UT in Austin (hook 'em 'horns). Just the initial PR.

"Study suggests nutrient decline in garden crops over past 50 years", December 2004

"A recent study of 43 garden crops led by a University of Texas at Austin biochemist suggests that their nutrient value has declined in recent decades while farmers have been planting crops designed to improve other traits."

Cutting to the punch line ...

"We conclude that the most likely explanation was changes in cultivated varieties used today compared to 50 years ago,â Davis said. âÂÂDuring those 50 years, there have been intensive efforts to breed new varieties that have greater yield, or resistance to pests, or adaptability to different climates. But the dominant effort is for higher yields. Emerging evidence suggests that when you select for yield, crops grow bigger and faster, but they donâÂÂt necessarily have the ability to make or uptake nutrients at the same, faster rate.âÂÂ

I believe a reasonable corollary would be if you add nutrient weak soils on top of the increased rate demands by newer cultivars being planted now, the problem likely compounds.

A second corollary might be (and I emphasize the might) that slow-release sources of key nutrients might actually exacerbate the problem (i.e., bioavailability is reduced when needed). That's somewhat counter to the conventional organic gardening thinking.

Here is a link that might be useful: UT Study finds nutrient decline in garden crops over past 50 years

Follow-up link to Davis / UT Study noted above ...

Here is a link that might be useful: Davis / UT Study article

Yes, TX, and also USDA testing data has found continuous nutrient decline in produce pretty much since they started testing, I believe, well over 50 years. Those results are online.

I have not heard of the cause being attributed solely to cultivar changes. That is an interesting possibility. I favor your idea that the cause is likely breeding selection plus nutrient decline in soils.

Joe, I am using Azomite now. I bought over a ton of it so the cost-per-bag is not extreme.

Variety/cultivar selection is a huge part of it. Farmers don't demand high nutrients...consumers don't care about it. Farmers want better natural pest/disease resistance/tolerance. To most consumers, a cherry tomato is a cherry tomato and a head of broccoli is a head of broccoli...and for many crops, bigger is better...

So you have crops bred for the most important farmer preferences...disease/pest, quickness to maturity, uniformity, size, and special soil/water tolerances in some areas. For consumers you have size, color, and uniformity (including a lack of blemishes from enhanced disease/pest though they don't ask for it).

No where on the spectrum of importance to consumers or farmers is nutrient value. Even flavor takes a back seat to these other issues unless it's way off...though that doesn't seem to keep consumers from wanting huge, flavor-lacking strawberries for some reason.

...this is a huge reason cultivar/variety selections we select for the home garden vs mass produced shippers tend to taste better and are better for us (if only marginally in some cases). The plant that has high natural resistance to a virus might not always be the best breeding stock for flavor or nutrients...it's a bit of breeding give and take.

This post was edited by nc-crn on Wed, Apr 10, 13 at 20:25

nc, what you posted about leaves tallies with my experience. But one can visually separate those maple or oak leaves from a more mature compost, and hold them back. Or hold back the whole pile if too mixed, or use as mulch, or add more urea. I have had unsatisfactory bags of leaves sit there for 15 months (of course I have space). Adding organic matter is no longer a pressing issue in a mature garden. I check in a cursory way only for black walnut leaves, I always have some in my mix, but better not play with fire.

I have found that my black walnut leaves fall well before my other leaves [except for some Linden] and they dry and mow up quickly and are not a problem. However, there may be some persnickity rakers who bag them up quickly.

"Farmers don't demand high nutrients...consumers don't care about it. To most consumers, a cherry tomato is a cherry tomato and a head of broccoli is a head of broccoli".

That's the problem! The consumers are so ignorant, they don't know where their food comes from! It's either they could care less about their health and the environment, or they are just so unaware, which I think is the cases in most cases.. We can barely get organic produce, let alone something that has true nutrition.. They don't even give us the right to know if it's GMO, or what... That brings up a point about what Tex says about crops nutrient absorption,etc.. I heard that GMOs don't upstate nutrients like a normal plant, which doesn't shock me.. The other day, I was shopping, and a lady was picking out tomatoes, I kindly told her that the tomatoes next to the ones she was grabbing are certified pesticide free, she didn't thinkntwice, she said "oh I like the pesticides, I've been living with them for years"... Are we going to watch this world turn black, or are we going to try and clean it up ourselvs? I mean come on.. There's no point talking to all of you, I'm sure your more than aware of all of this...

Ok,sorry back to the topic...

So what I learned(or not) from this thread was:

People use azomite, kelp, compost(leaves,etc), and woodash for mineralization..

I also learned that a brix meter is more less for sugar indication, and maybe perhaps you can possibly use it as a rough judge of nutrition, but it is by far not made for that..

I really haven't learned any new methods of how to get minerals in my garden.. Anyone do anything different for mineralization? How about you ncrm, maybe you could shed some light, what do you do to mineralize your crops? Anyone?

Value all your posts,thanks,
Joe

"I heard that GMOs don't upstate nutrients like a normal plant, which doesn't shock me.. "

GMOs uptake nutrients just fine...just like the comparison of 1950 vs 1999 crops in the study above, you only have the genetics of what you're working with from parent plants to pass on to the GMO hybrid offspring. There's nothing inherent about the insertion of BT or RU-resistance that makes GMO less nutrient strong...it's mostly the parent material used to make the GMO hybrid. GMO insertion is more than "put some GMO in and we're good to go"...it's a lot of "insert the GMO, see if it even takes, and will it even pass these traits on via hybridization." 99%+ of all GMO experiments involve trashing the plants because it doesn't take on or pass traits correctly. There's a lot of brute force and a "numbers game" of volume involved.

Since the most important thing to the GMO producer (and farmer consumer) is the traits, there's little incentive to pass on nutrients aside from protein content (since so much is used for animal feed) in most GMO breeding. While plants are selected for all the benefits possible, if an ideal breeding parent with desired genes happen to be less ideal in nutrients (aside from protein content for some grains) it's still a "winner" from the breeder's point of view. There's not going to be a huge push to keep planting 1000s of plants to get that extra 10% iron a more nutritionally ideal parent might have.

pn-brown,
Just to be clear, I am not suggesting that the reason for the nutritional decline over 50 years has anything to do with nutrient decline in soils. What I am suggesting is that the nutritional decline would likely be exacerbated by nutrient deficiency in soil, if such a deficiency existed relative to the plants needs. I also suggested that the premise that slower release sources for soil-borne plant nutrients may be counter productive to net produce nutrition, meaning that bioavailability of those nutrients must be sufficient. If the biological demand rates for nutrients has increased because of changes in cultivars, then we may need to rethink what we use to meet those increased demands.

nc,
I believe your points are right on. Plant breeders have predominantly focused on meeting the needs of large-scale market growers in an increasingly urban industrial and post-industrial society. In that vein, economics is king. That translates to higher sellable yields, at reduced costs, and in shorter time. Nutrition is nowhere in the equation, and for the most part neither is taste. Recently, in response to what was perceived to an increasing consumer revolt to truly tasteless tomatoes, the folks at Rutgers took up the issue because of the importance of commercial tomato production and sales to NJ's economy. Their conclusion was that breeders have, since WWII, focused on the needs of market growers to get more sellable product to market, which meant yield, time, durability and appearance, which in many cases resulted in breeding that destroyed desirable tomato taste qualities. They are now focused on how to brig back the taste, but still no mention anywhere about nutrition. It isn't even on the radar.

Re: mineralization

I tend to plant the same types of crops every year/season. I have a soil test every 3 years and add a surface applied inch of compost + kelp/manure/worm tea + non-organic micronutrient mix every year in a small amount. When/if I have a specific surplus based on my soil test I omit the tea for a year and just apply specific micros...I've only had to do this once. I usually apply the compost in the late fall, and the tea/micros in the early spring. At this point in my soil's health I mainly add compost for the soil structure benefit.

I can predict the "drift" of my pH rather adequately based on rainfall and I lime every 2-3 years accordingly shooting for 6.7-7.0 (6.5 is ideal, but acidity will take it's toll so I shoot a bit higher and left drift occur). I lightly incorporating the lime into the top 4" of the soil with a fork before the compost and straw mulch goes down (this is done in late fall, usually after Halloween when straw is cheap/free thanks to people getting rid of decorations). The pH drift is slight in my soil because it buffers well thanks to it's structure and our municipal water is rather neutral.

I keep 3" of straw mulch on the soil all year and replace it with fresh straw every year, adding the "used" straw to my compost pile. I usually have to apply a little more straw that I've held back when I plant my spring crops for spring/summer/fall benefit.

My soil is a very healthy clay + topsoil + 5-7% OM mixture. It's super happy and super productive.

This post was edited by nc-crn on Wed, Apr 10, 13 at 22:15

Joe,

On the ðBrix measurements - what they really reflect is refractive index of the liquid being examined, nothing more. Historically that was correlated with sugar content because of how it was developed and used (brewing). For the most part it is sugars that dominate what's in the juice extract of fruits and veggies. Hence extrapolating the use of ðBrix measurements to produce "quality" kind of made sense. It will, however, be altered by anything else that is dissolved in that juice. Because of the sugar connection it has a strong correlation to consumer appeal (sweetness).

Now back to mineralization .. your initial premise was to build mineral content to produce more nutritious produce. A key missing link is bioavailability of whatever you put into your soil. Just having the minerals in there doesn't mean that the plants will be able to acquire them. They must be readily available to the plant, when it needs them.

Further, I believe that just blindly adding "minerals" to soil is a potentially dangerous proposition. There are a lot of complex mineral interactions in plant/soil systems. One example is the balance between boron and calcium - without the proper amount of boron all the calcium in the world will not be available to many plants. However, too much boron will kill your plants. Calcium, magnesium and sodium interact in soil to affect their relative availabilities. Adjusting one without considering the impact on the whole can lead to availability problems.

The upshot of all of this is that without some sound guidance on what you have and what is needed is just as likely, if not more likely, to backfire in your search for enhanced or optimally nutritious produce.

The conventional wisdom is to start with a soil test. The updated version of that wisdom is that traditional soil tests tell you what's there, but not much about how available those plant nutrients will be. There is hope though. There are now soil test methods that reportedly better reflect bioavailability of those nutrients (e.g., CO2 extraction). The downside is they are more costly and there are limited sources for these tests.

In the end, I think any attempt at mineralization that is not guided by meaningful and reliable soil analysis is, in the long-term, a fool's errand.

This post was edited by TXEB on Wed, Apr 10, 13 at 23:01

I certainly appreciate the high level of knowledge being displayed here.

NC, that is new to me, the tannins in oak leaf compost possibly binding up N. Also highly relevant, since oak predominates in this region by an overwhelming margin.

TX, a very interesting premise, that newer cultivars may require increased fertility to produce x-level of nutrient availability in harvested parts in comparison to earlier common cultivars. I think that is what you are suggesting. As has been mentioned, few if any are tracking these kinds of possibilities since neither the industry nor the consumers care.

I just found a quickly read through a companion, follow-up article by Davis on changing plant nutrition levels over time. It is titled "Declining Fruit and Vegetable Nutrient
Composition: What Is the Evidence?" published in 2009, five years after the previously cited reference.

ref: HortScience February 2009 vol. 44 no. 1 15-19

It is freely available via a link I will include below.

Quoting from the abstract:
"Three kinds of evidence point toward declines of some nutrients in fruits and vegetables available in the United States and the United Kingdom: 1) early studies of fertilization found inverse relationships between crop yield and mineral concentrations - "the widely cited âÂÂâÂÂdilution effectâÂÂâÂÂ; 2) three recent studies of historical food composition data found apparent median declines of 5% to 40% or more in some minerals in groups of vegetables and perhaps fruits; one study also evaluated vitamins and protein with similar results; and 3) recent side-by-side plantings of low- and high-yield cultivars of broccoli and grains found consistently negative correlations between yield and concentrations of minerals and protein, a newly recognized genetic dilution effect."

The third point is significant. It clearly points to the role of cultivar (genetics) in the nutrition equation.

It is not clear to me that enhancing soil nutrient levels would have had any beneficial effect on the nutritional value of the resultant produce. It would seem that once the soil provides for adequate plant nutrient levels relative to the plants demands, the net nutrition available from the produce is primarily a result of plant genetics.

Here is a link that might be useful: 2009 Davis article

Very interesting. I skimmed through it and will read in detail later. This is super interesting stuff to me.

Did you get to the part where one author suggests that the genetic dilution effect is probably open to remediation by environmental factors?

Also, regarding the nutrient dilution effect from fertilization that has apparently been well known since the '40's, it seems this could be corrected by complete soil nutrition. In the first example of added P leading to dramatic increases of dry-matter yields with higher P but lower everything else: wouldn't raising the other macro and micro nutrients have kept things even?

I believe this is precisely what the remineralizing movement is trying to achieve. They want big yields without any dilution effects from fertilizing, and eventually they want no need for fertilizer; the idea being that sufficiently remineralized situations that are sufficiently well-managed will be largely input-free.

I was aware of the fertilizer dilution effect inasmuch as I knew that largely stimulating plant growth with NPK has drawbacks. This is why I have been incorporating Azomite when I use manure. I was aware tangentially of the genetic dilution effect, for example I had heard that modern maize hybrids have much less nutrition than OP varieties. There seems to be a suggestion that some hybrids are incapable of up taking certain minerals or processing them.

Regarding your comment:

" It would seem that once the soil provides for adequate plant nutrient levels relative to the plants demands,"

that is no simple thing, though, because for one thing there exists I believe considerable uncertainty over how many elements crops need or use for optimum health. There are still loads of growers out there who pay attention only to the five macro-nutrients. Clearly it's very difficult to separate out the various dilution effects.

pnbrown, you make some good points. I think what we can conclude with some certainty at this point is that there are real consequences of higher yield production on produce nutrition measured at the per-item level. Can those effects be remedied with attention to the total plant nutrition? As you note, it's a big question.

That plants have limited capacity to assimilate and synthesize desirable nutritional components is nothing new. What this tends to make clearer is that when that capacity is spread over increased fruit or flower production that capacity gets diluted in the per item nutritional value. Hence each item has less of what is desired nutritionally. What I haven't yet seen is a study that considers total nutrition provided per plant taking into account higher produce yield per plant or per acre, but with reduced nutritional content per item produced. For example if a tomato plant produces, on average, 25% more fruit but with each tomato yielding 15% net nutritional reduction by some measure, then the plant has actually provided more total net nutrition. Is that a good thing or a bad thing? If you're trying to feed a growing population more efficiently, more cost effectively, what is the right measure of agricultural effectiveness in meeting that population's nutritional needs? Is it per item, per plant, per acre, per unit time, or per dollar?

Another related issue is speed of production versus rate of plant assimilation and synthesis of desirable nutritional qualities. In addition to limited plant capacity, is there a limiting rate of nutritional production? Are earlier maturing varieties nutritionally equivalent to slower or later maturing cultivars? Maybe a future component of the farm-to-table movement is slow-farming. That could make for an interesting element of the overall slow-food movement.

At this point there are far more questions than answers. A key going forward is to carefully separate the hypotheses of what might be better from what we know to be better. That includes soil composition and our efforts to get better or more nutritional produce. As home gardeners we need to appreciate that often when we do something to effect a desirable change without a proven basis for the cause-effect relationship we are pursuing, we are really just running an experiment, and most typically an uncontrolled one.

It is a subject dense with significance.

The time factor that you mention in my opinion is very significant. it makes sense to me that fast-growing crops will not produce parts with as much nutrition as slower growing ones. Vegetatively-reproducing perennial versions of common seed-propagated annuals of the same type, for instance.

"For example if a tomato plant produces, on average, 25% more fruit but with each tomato yielding 15% net nutritional reduction by some measure, then the plant has actually provided more total net nutrition. Is that a good thing or a bad thing?"

Probably that depends on whether we are trying to keep maximum-sized populations merely alive or whether we are individual eaters trying to obtain maximum nutrition from a given amount of food intake. Right now I am the latter.

"The time factor that you mention in my opinion is very significant. it makes sense to me that fast-growing crops will not produce parts with as much nutrition as slower growing ones."

It does seem to make sense. But without being tested it is merely a hypothesis. I would hesitate to believe in it, without testing it. Unfortunately for us as individuals that is really not practical.

Back to mineralization -- what I believe everyone will agree upon is if there are not sufficient levels of necessary and desirable mineral nutrients they won't show up in the produce. So the first goal is no deficiencies.

However, we also know that many soil-borne plant nutrients, especially minerals, interact in ways that can be either synergistic or antagonistic. See Mulder's Chart in one of its many variations. So the second goal should be no excesses that lead to antagonistic interferences. One problem here is the levels can be plant specific, making it challenging to generalize.

A related issue is that some of the desirable and necessary elements expressed as minerals can become toxic to plants if levels are excessive (e.g., boron). Again the goal is no troublesome excesses.

Finally, when making additions to alter the mineral content of soil for plant health and nutrition we do not want to be adding undesirable elements that can come along for the ride, such as undesirable heavy metals (e.g., arsenic, cadmium, lead, etc.).

My concluding point is when it comes to altering a soils composition, especially with minerals that can be very long lasting, be guided by reliable and useful analyses to avoid a myriad of pitfalls.

This post was edited by TXEB on Thu, Apr 11, 13 at 11:17

Indeed, I have bumped B to toxicity on a small scale several times. Luckily it leaches rapidly in sandy soils.

And the heavy metals do seem to come along for the ride in most "active" rock dusts as well as wood-ash. We had a thread on that subject not long ago.

Very interesting stuff, thanks TXEB! I read this discussion with interest and I agree with your assessment. You've clarified a subject I knew a little about but could not possibly explain it that well. I'm also a PhD chemist, but environmental, on the hazardous substance side rather than ag.

Thanks for the links to studies. I notice the last one you posted mentioned growing different varieties in the same soil. Has anyone done an analogous study where the same varieties were grown in the same area but in soils with different amendment levels? Low and high compost, mineral supplements, etc. That would be very interesting.

Typical lab soil tests aren't going to look at boron, cadmium, yttrium and some of the other stuff mentioned. Not hard to do that, but it costs extra. I'm curious about boron because my city compost has drywall scrap in it, which I've read can have borax as a binder.

Interesting thread here. I have observed with different fruits that a large fruit setting produces smaller fruits. If there is only a dozen peaches on a mature tree due to weather, the fruits will be huge. Are the fruits more nutritous? Likely so in my opinion. Watermelons make a good test here. A very healthy plant can produce 3 very large fruits in one setting, but a less vigorous plant cannot produce three large quality ones at one setting. The less healthy plant will produce three fair to poor quality fruits. It might be able to produce one quality fruit, and 2 good ones.

As far as mineral dusts go, a quality assayed product will contain very small amounts of undesirable elements, but likely less than the soil already has before adding the dust [in ppm].

There is a lot of research in the past, in progress, and in the future concerning exclusion of single macro/micro-nutrients and critical/ideal level experimentation on a wide rage of food and ornamental crops...as well as different types of chemical complexes used to deliver the nutrients.

Commercial growers, especially, use this information to best drive their production. It's known that switching to a NH4/NO3 mixture when corn starts tasseling and grain fill will create fuller ears and hasten drying time compared to just NO3.

A lot is known for some ornamentals and crops about how much of what needs to be available in a plant for ideal production. The research trip point is that a lot of this research needs to be regional or wide-in-scope once you start interacting these nutrients in different soil types (structure, pH, mineral soil types, OM, etc). In containers, it's easy to manage...in the ground, you run into 100s of combinations of tripping points that can effect multiple points of nutrient availability. The thing about this is most of the research for stuff in ground tends to be whatever commercial farmers are growing in the region rather than all the crops a home gardener may want to grow.

Nccrn,

What non-organic micro blend do you use exactly?

Thanks,
Joe

Peters Professional STEM

S/B/Cu/Fe/Mn/Mo/Zn

I can easily follow your point, NC, about the complexities that arise in trying to exactly provide full but just-enough plant nutrition in all sorts of varying soil conditions. I would not suppose that I would ever be able to achieve that.

Merely in my little region between the 4 or 5 locations where I grow crops typically over a year, the differences in SOM especially are huge, as well as some big differences in particle size of the mineral base.

Generally speaking, the eastern part of the US has more rainfall than western parts [coastal NW excepted.] This results in much more leaching of certain elements like selenium, sodium, boron, and some others. With a lower PH and likely higher CEC rates, mineral shortages are more likely to occur. Thence the need to add lime in many cases. I am going to assume then that other macro and micro mineral deficiencies tend to occur unless something is added or mined upward in the soil. Some soils never really had a full blend to start with.

Again, animals can likely detect quality better than most humans can. Still, even I can detect a more flavorable orange, grapefruit, tomato, watermelon, cantaloupe, or peach. How well does that taste correlate to nutrition? A good question. I suspect that the larger fruit may not always be as concentrated in nutrients. After all, the basic thing here is to reproduce itself. So the seed comes first. If a plant is less vigorous, it will feel hurried to produce that seed...which contains some healthy inputs.

"I suspect that the larger fruit may not always be as concentrated in nutrients"

That is, in part, the well known dilution effect.

Taste and flavor may in many cases reflect elements of nutrition. Sweetness (sugars) reflect at least one aspect of carbohydrate development. Sour (acids) may reflect vitamin C. But a lot of flavor has to do with smell and volatile components (like esters) that aren't reflected in measures of nutrition. None of that typically reflects mineral or vitamin nutrition because the relative amounts are so small compared to the constituents that dominate taste and flavor, and also tend to dominate the major considerations of nutrition (carbohydrates, proteins and fats).

"I suspect that the larger fruit may not always be as concentrated in nutrients"

That is, in part, the well known dilution effect.

Taste and flavor may in many cases reflect elements of nutrition. Sweetness (sugars) reflect at least one aspect of carbohydrate development. Sour (acids) may reflect vitamin C. But a lot of flavor has to do with smell and volatile components (like esters) that aren't reflected in measures of nutrition. None of that typically reflects mineral or vitamin nutrition because the relative amounts are so small compared to the constituents that dominate taste and flavor, and also tend to dominate the major considerations of nutrition (carbohydrates, proteins and fats).