permaculture

["Lawrence F. London, Jr." <lflj@bellsouth.net>]

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Subject: [SANET-MG] Soil minerals and nutrition
Date: Fri, 24 Dec 2010 18:10:35 -0500
From: Joel Gruver <jgruv@HOTMAIL.COM>
To: SANET-MG@LISTS.IFAS.UFL.EDU

Hello folks,

As detailed in the review article at the following link, there is strong evidence that vegetables obtained from a 
grocery store today are likely to contain lower levels of vitamins and minerals than the same species purchased 50 years 
ago.

Declining Fruit and Vegetable Nutrient Composition: What is the evidence?
http://depthome.brooklyn.cuny.edu/anthro/faculty/mitrovic/davis_2009_food_nutrient.pdf

One hypothesis often articulated within the alternative farming community (and recently on this list) is that depletion 
(or imbalance) of soil minerals is the primary cause of these declines.

There is no doubt that intensive fertilizer programs focused almost exclusively on NPK and lime (with little attention 
to OM and secondary and micronutrients) have negatively affected many soils… that said, I am inclined to agree with 
Davis, Jarrell, Barak, Halweil and others (see above article and following links) that available evidence points more 
clearly at dilution effects (as opposed to soil depletion) as the main driver of decline in crop mineral content.

 Are Depleted Soils Causing a Reduction in the Mineral Content Of Food Crops?
http://www.soils.wisc.edu/~barak/poster_gallery/minneapolis2000a/index.html

Still No Free Lunch: Nutrient levels in U.S. food supply eroded by pursuit of 
high yields
http://www.organic-center.org/science.nutri.php?action=view&report_id=115

So what are dilution effects?

When crops are bred and/or managed for higher yields, the yield increase comes primarily in the form of greater 
production of complex and simple carbohydrates… rarely does the uptake of minerals match the increase in carbs… the 
result is lower relative mineral content via dilution.

Both genetic selection and managment (fertilizing, irrigating, pest control…) 
for higher yields tend to have this effect.

In contrast, poor yielding crops tend to have higher mineral contents …

Some time ago, I read an interesting review of the long term studies at the Rothamsted research station (oldest 
agronomic experiment in the world). Hundreds of thousands of plant and soil samples have been collected and archived 
since the 1840s.
Apparently grain from the continuous no-input plots has a similar if not higher mineral content than grain from much 
higher yielding plots receiving various combinations of manure and fertilizer. I will try to track down this review.

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M. Astera praised Bear et als. 1948 article "Variations in Mineral Content of Vegetables" and lamented the lack of 
subsequent research on how soil properties affect mineral uptake by plants.

My observation is that there has actually been extensive research on the ecophysiology of mineral uptake by plants in 
the last 60 years but much of this research has been reported within the ecological literature (as opposed to 
agronomy/horticulture literature).

Terry Chapin’s excellent 1980 review “The mineral nutrition of wild plants” cited almost 200 sources and has been cited 
>> 2000 times by subsequent articles.

Here is the citation and a link to a free download.
Chapin, F.S., III. l980. The mineral nutrition of wild plants. Annu. Rev. 
Ecol. Syst. ll:233-260
https://sites.google.com/a/alaska.edu/f-stuart-chapin-terry/home/chapin-paper-in-pdf-format-file-cabinet

The mineral nutrition chapter in the latest edition of Plant Physiological Ecology (co-authored by Chapin) contains a 
good discussion of current understanding of the ecophysiology of mineral uptake:

http://www.amazon.com/Plant-Physiological-Ecology-Hans-Lambers/dp/0387983260#

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Switching gears, here is a link to a presentation on organic soil management 
that may be of interest:

Organic Soil Management – mistakes and misperceptions
http://www.slideshare.net/jbgruver/organic-soil-management-6307344
the last section on balanced soil management seems relevant to this 
discussion.

Happy Holidays to all !

Joel

Joel Gruver
School of Agriculture
Western Illinois University
jgruv@hotmail.com