More Gypsum Facts

Toxicity of Gypsum:  Some other folks are still teaching about “gypsum toxicity.” Facts:

1. There has to be approximately 20,000 ppm Ca2+ in the soil for calcium toxicities to exist…
2. There has to be approximately 800 ppm SO42- in the soil for sulfur toxicities to exist.

Both are extremely rare in productive, agricultural soils, even soils where gypsum has been applied in extreme excess.

Solubility of Limestone vs. Gypsum:

Gypsum--Hydrous Calcium Sulfate

The other gypsum myth I have heard is that as soil pH conditions reach values near 7.0, agricultural limestone becomes is a better choice for adding calcium to the soil rather that gypsum or anhydrite. First of all, agricultural limestone is always 150 times less soluble than gypsum or anhydrite under any conditions. Gypsum/anhydrite is never in any soil reaction (pH) or oxidation/reduction condition any less soluble than this.

However, note that all soluble soil calcium becomes insoluble at pH values near 8.0 So at these pH values, calcium is basically nonexistent in the soil for promoting good soil structure, and as an essential plant nutrient.  This is why we need to keep the soil pH values for most soils in California and the west at pH values about equal to 6.4.

Much more on this subject later….

And please write me with your gypsum/anhydrite/limestone questions…

Gypsum Facts

I have written and lectured a lot about the benefits and uses of gypsum products in the past [see the publications tab to your left].  Gypsum [and its more concentrated and prevalent form, anhydrite] remains the “miracle” amendment…it has been documented by many scientists as having over 40 (yes, forty!) beneficial uses in production agriculture.  Now, as time moves on, I’ll talk more about the benefits and uses, and dispel many myths about gypsum usage vs. that of agricultural limestone, etc…. .  For now, here are some quick facts about “gypsum.”

Gypsum Rock

There are two calcium sulfate minerals found on earth: the first is called gypsum.  The chemical formula for gypsum is (CaSO4·2H2O).  The second/much more prevalent calcium sulfate mineral on earth, is anhydrite (CaSO4)…almost identical to gypsum, but sans the two molecules of water.  By nature, gypsum with its associated two water molecules is 21% water, and 79% solids.  Calcium sulfate in the pure anhydrite form (no water) is 29.4 percent calcium (Ca) and 23.5 percent sulfur (S), while pure gypsum with its water associated in the molecular structure (CaSO4·2H2O) is approximately 23.3 percent Ca and 18.5 percent S.  However, agricultural anhydrite and gypsum, as a soil amendment/conditioner/fertilizer usually has other impurities, so grades are approximately 22 percent Ca and 17 percent S for a decent quality product.

There has been some serious confusion concerning the solubility of calcium sulfate products. The fact is: both anhydrite and gypsum are indeed water soluble, and both essentially have the same solubility: 0.205 grams per 100 grams water (2003-2004 CRC Handbook of Chemistry and Physics).  This has also been verified by many field trials by Soil Scientists [including myself], worldwide farmers and others.  The solubility of 0.205 grams per 100 grams water equates to:

0.205 grams/100 grams water         =  0.0171 pounds per gallon

=  5,575 pounds per acre foot water (325,850.58 U.S. gallons)

Therefore: the maximum solubility of anhydrite or gypsum in one acre-foot water 23.8 milliequivalents per liter (or 5,575 pounds per acre foot water [or basically 12″ of rainfall will dissolve approximately 2.8 tons of agricultural gypsum/acre)

Gypsum and anhydrite are the neutral salts of a strong acid and strong base and do not increase or decrease acidity.  Dissolving gypsum and anhydrite in water or soil results in the following reaction: (CaSO4·2H2O)  =   Ca2+ + SO42- + 2H2O.  They add calcium ions (Ca2+) and sulfate ions (SO42-), but do not add or take away hydrogen ions (H+). Therefore, they do not act as a liming or acidifying material.  The Ca2+ ions simply interact with exchange sites in soil and sulfate remains dissolved in soil water.

More on gypsum this coming Monday March 8. Please send me your gypsum, limestone and other questions…

California Rice

Although rice paddies more often invoke images of southeast Asia than California, this agricultural commodity is running strong in in northern California. The industry began early in part to feed newly arrived Chinese miners and railroad workers.


Rice Field Near Yuba City, California

It continues to thrive today, with more than 95% of California’s rice grown in the Sacramento Valley.  There are more than 500,000 acres of rice within a two-hour drive of Sacramento. California is the second most important rice state within the United States, producing about 20% of the nation’s crop in a typical year, mainly high-quality, medium grain japonica rice that is favored in Northeast Asia and in parts of the Middle East and Mediterranean region.

Rice ranks as our state’s ninth most important agricultural export commodity. Japan receives about half the California export total, with California in turn supplying about half of Japan’s imports. To many cultures, rice is such an important food source that its origin and/or brand is extremely important, and California rice is quite highly esteemed in parts of Asia.

Nearly all U.S. sushi comes from California’s short- and medium-grain Japonica rice grown from Placer County north to Tehama County. (Arkansas remains the nation’s leading rice grower, producing long-grain varieties common in everyday recipes).  Federal agricultural statistics show rice growers, largely in Placer, Sutter, Yuba, Yolo, Butte, Glenn and Colusa counties, produced $2.8 billion worth of sushi-grade rice in three seasons from 2007 through 2009.

We export 50 to 60 percent of the crop. The northern Sacramento Valley’s medium-grain rice, with its softer, stickier consistency, appeals to Asian taste buds, as well as those in the Mediterranean who associate it with Italian risotto recipes.  The biggest importers of California rice are Japan, South Korea, Jordan, Taiwan and the European Union, according to the California Department of Food and Agriculture. The rest is consumed domestically, much of it in restaurants.

The Earth is Living Poetry

Giant Red Indian Paintbrush, Mokelumne Wilderness

The earth is not a mere fragment of dead history, stratum upon stratum like the leaves of a book, to be studied by geologists and antiquaries chiefly, but living poetry like the leaves of a tree, which precede flowers and fruit–not a fossil earth, but a living earth; compared with whose great central life all animal and vegetable life is merely parasitic. –Henry David Thoreau


The voice of nature is always encouraging. –Henry David Thoreau

Nutrient Mining Genes

ScienceDaily (Feb. 21, 2010) — Scientists from the John Innes Centre and the University of Oxford have discovered which genes control the specialized nutrient mining machine that develops on the surface of plant roots.

Root hairs develop on roots and burrow into the soil releasing acids and other scouring chemicals that crack open rocky minerals releasing valuable nutrients such as iron and phosphate that are necessary for plant growth.

It has long been known that when crops such as barley and wheat are grown on soils containing small amounts of phosphate, those plants with long hairs give higher yields than those with short hairs.

Similarly long-haired beans grown on nutrient poor tropical soils of Central America do much better than short haired varieties.

The mechanism that controls the growth of these nutrient excavating cells has eluded scientists until now. A group of UK-based scientists shed light on the mystery in a paper just published in Nature Genetics.

They discovered that a master regulatory gene called RSL4 acts like a switch; hair cells grow when the gene is turned on and growth stops when it is off.

When plants grow in conditions where there is insufficient phosphate they develop very long root hairs. This increases the amount of soil from which they can scavenge phosphate.

“When we discovered that RSL4 was a master regulator of hair growth we thought that perhaps the increased growth of root hairs in low phosphate soils might result from turning this gene on,” says Professor Liam Dolan, leader of the JIC team that discovered RSL4.

Dolan and co-workers were right. Growing plants in phosphate-poor soils turned the gene on resulting in the growth of very long root hairs. This gene is therefore not only a key growth regulator but also a critical cog in the mechanism plants use to cope with a lack of nutrients.

Given the ability of RSL4 increase root hair growth this discovery has the potential to help breeders develop crops that can grow on poor soils.

Most soils in Australia, extensive regions of sub-Saharan Africa and 30 per cent of China are not productive because plants cannot extract sufficient phosphate and iron form these soils.

“Our hope is that in the future someone will be able to use this gene to develop cultivars which enhance yields on poor soils,” says Professor Dolan. “This could have obvious benefits for developing world agriculture. Also as fertilizers become increasingly expensive we will need crops that are more efficient in nutrient uptake. This could have the added benefit of decreasing the amount of polluting phosphate that runs off into rivers and lakes.”

“What excites me most about this research is that we set out to answer a fundamental question in biology — how organisms control the size of their cells. In the end we discovered something that could have an important impact on world agriculture.”

AFBF President Denounces Sustainable Agriculture?

LINCOLN, Neb. —While American Farm Bureau Federation president Bob Stallman didn’t outright denounce sustainable agriculture in his January address, it was apparent that the 150 producers who attended the 2010 Healthy Farms Conference this month — Nebraska’s annual sustainable agriculture convention — were still feeling the sting of Stallman’s well-publicized “extremists who want to drag agriculture back to the day of 40 acres and a mule” comment.

Sustainable Almonds: Ord Bend, California

This made Rep. Jeff Fortenberry’s keynote address at the conference all the more welcome, and his support of the local foods movement, both in Nebraska and nationwide, brought a standing ovation. “Much has changed the last few years in the local foods movement that was young exotic not too long ago,” Fortenberry said.  Sustainable agriculture, the force behind the local foods movement, has captured consumer interest, both in their food and the people who produce their food. “Indeed, there is a veritable tradition and high esteem for agriculture today,” he said.

This connection between farmers and consumers, while threatening to some in conventional agriculture, provides a great opportunity for improved public policy — one where consumers show that they care about their food supply by getting involved in the lawmaking process — specifically more emphasis on the importance of the Farm Bill. While the Farm Bill isn’t perfect, sustainable agriculture made progress with this last one put in place, Fortenberry said. In fact, what began on local farms — the concept of economic, environmental and social sustainability — has now spread not only to government but to industries far removed from agriculture and to consumers’ homes in the middle of the city, said Fortenberry who himself is a gardener and a wannabe beekeeper. Sustainability — and the connection between people that it promotes — is now the hot new trend.

More and more people are also realizing that it can be more than a fad; that it’s a practical, long-term solution to the problems that plague America. [as reported in the Yankton Press & Dakotan, Saturday 20 February]

Note: It is both obvious and sad that president Bob Stallman doesn’t understand the concept, definition nor vital importance of sustainability to American farmers, our nation, and the world.  Perhaps Mr. Stallman is confused with the differences between “organic farming” and “sustainable agriculture.”  Sustainable agriculture integrates three main goals: (1) environmental stewardship, (2) farm profitability, and (3) prosperous farming communities. These goals have been defined by a variety of philosophies, policies and practices, from the vision of both farmers and consumers.  In production terms, sustainable agriculture refers to the ability of a farm to continue producing indefinitely, with a minimum of outside inputs.

Without argument, our soil and irrigation water are America’s most precious and valuable natural resources.  And without sustainability, agriculture has no future…period. Fertile Soil Solutions, LLC will always promote and proudly stand up for everything sustainable pertaining to global and domestic agriculture.  –Brent Rouppet, Ph.D.

Earthworms and Soil Organic Matter

A LinkedIn connection friend in Los Angeles contacted me this week with a question about his earthworms that he has in his ….house.  An interesting place to raise earthworms, but who am I to question this.   Anyway, here is his question:

“Dr. R:
I know just enough about worm recycling to get my self into trouble.  I have had a worm bin in my home since August.  There seems to be a “lot” of real black soil.  I am not sure what to do next.

If you need more info to advise, please ask.  I’ll answer anything.
Your friend in L.A., Don”

My response back to Don:

“Hi Don… Here is a real brief “lecture” on soil organic matter.  Humus is a substance that is a jet black, sticky [like Elmer’s Glue] substance that is high in available nutrients… especially nitrogen, phosphorus and sulfur, although generally all essential nutrients required by plants are present in the stuff…. (do you really want to know all of them??) O.K., here they are: carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, boron, copper, chlorine, iron, molybdenum, manganese, and zinc.  Phew!!!  Humus is a really, really good thing to have in your vegetable garden …or almond orchard or orange grove, etc., etc., etc……. Besides being high in available essential nutrients, because it is sticky, it helps promote outstanding soil structure.. i.e., the black gluey stuff helps the sand, silt and clay particles in your soil “clump” or bond together so air and water and roots can move though the soil better.  In short, humus is something you want a lot of if possible for your garden, orchard, grove, etc., etc., ad nauseum…..

O.K…. worms: the worms, by running the soil medium through their warm bodies, create lots of humus [the black, sticky stuff described above].  So worms are really good guys to have around… To answer your question, Don, just use the worm casts in the bin for whatever you want around your garden, yard, orchard, vineyard, grove….. whatever…. Then add new medium for the worms so they can start the whole process all over again… and again… and again… and then use a few of them and go fishing!!!! Hope this helped a little bit…

My question is: why do you have the worms in your house in the first place?????

Dr. B.”

If any of you have any questions about your crops or your garden… or even your earthworms, please submit them to me and I will answer them in the order I receive them.  Thanks, and have a great and productive week.