Soil is the FIRST crop...all else follows.

Great (PDF) article about soil improvement from ACRES USA. You can read many more here.

Chicken Soup for the Soil
by Jerry Brunetti

(snip)
Estimated Numbers of Common Micro-Organisms Found in Healthy Agricultural Soils
Bacteria 3,000,000 to 500,000,000 in 1 g.
Actinomycetes 1,000,000 to 20,000,000 in 1 g.
Fungi 5,000 to 1,000,000 in 1 g.
Protozoa 1,000 to 500,000 in 1 g.
Algae 1,000 to 500,000 in 1 g.
Yeasts 1,000 to 100,000 in 1 g.
Nematodes 10 to 5,000 in 1 g.

"Mineral Deficiencies—and Their Fall Out"

Wondering why our nation's peoples are so obese, in poor health, popping vitamins and drugs like candy? They're f**king STARVING...on FULL STOMACHS...because the soil ain't what it used to be...AND we're still losing topsoil at a rate exceeding the Dust Bowl era!

And, when you consider that one year's production of urine from a moderately healthy person is enough to provide all the Nitrogen, Phosphorus, and Potassium (and more) for ONE ACRE of garden or orchard, it begins to seem not merely stupid but suicidal. Especially when that same nutrient flowing to the sea is causing huge oceanic dead zones and toxic algae blooms. DUHHH!
See Liquid Gold: The Lore and Logic of Using Urine to Grow Plants at the Permaculture Activist website. It's a golden opportunity, go with the flow, urine charge. Pee Here Now!

This table was recently published in Acres, USA.
Read Neal Kinsey's essay (PDF) on soil minerals here.
THIS is why I buy rock dust soil amendments for my garden. Search for local mineral sources here.

"Mineral Deficiencies—and Their Fall Out," by David Thomas, D.C
Full details at: www.mineralresourcesint.co.uk/research.html
Average Mineral Content of Food—1940-1991
Fruit	Loss
Sodium	29%
Potassium	19%
Phosphorous	(2%) (gain)
Magnesium	16%
Calcium	16%
Copper	20%
Iron	24%
Vegetables	Loss
Sodium	49%
Potassium	16%
Phosphorous	(9%) (gain)
Magnesium	24%
Calcium	46%
Copper	76%
Iron	27%
Meat	Loss
Sodium	30%
Potassium	16%
Phosphorus	28%
Magnesium	10%
Calcium	41%
Copper	24%
Iron	54%
Vegetables	Loss
Runner beans	Nearly 100% of sodium
Watercress	93% of copper
Carrots	75% of magnesium
Broccoli	75% of calcium
Spring onion	74% of calcium
Swede	71% of iron
Spinach	60% of iron
Potatoes	47% of phosphorous
Fruit	Loss
Orange	67% of iron
Avocado	62% of sodium
Strawberry	55% of calcium
Melon	45% of magnesium
Passion Fruit	43% of potassium
Raspberry	39% of calcium
Blackberry	35% of calcium
Rhubarb	32% of phosphorous

After viewing this table it should be incontestably obvious why we must remineralize our soils. We are literally starving on full stomachs from food grown on depleted soils. Obesity, degenerative and immune-deficient diseases are DIRECTLY related to mineral shortfalls in our diets.

See http://www.ohioearthfoods.com

Also http://attra.ncat.org/new_pubs/attra-pub/orgfert.php?id=Minnesota for regions pertinent to folks on this forum,
and http://attra.ncat.org/new_pubs/attra-pub/orgfert.php?id=Wisconsin

When I first learned about remineralization in the late 70's, it was from these folks in Massachusetts http://www.remineralize.org/
http://remineralize.org/joomla/index.php/Mineral-Products/
http://remineralize.org/joomla/index.php/A-Rock-Dust-Primer

Also see http://www.uoguelph.ca/%7Egeology/rocks_for_crops/