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nafex - [NAFEX] Clay, long, technical.

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  • From: Joe and Ellen Hecksel <jhecksel@voyager.net>
  • To: nafex@lists.ibiblio.org
  • Subject: [NAFEX] Clay, long, technical.
  • Date: Sun, 05 Jan 2003 01:50:10 -0500


Rodney Eveland wrote:

I suggest you first find out why the ground is barren. Certain clay like
soils are barren - period. Bentonite is one of those soils. We have
outcroppings of it East of here. Mother nature hasn't been able to find
a plant that will grow in it and I doubt you will either.


Hi Rodney:
Help me out. If memory serves, you are in Wyoming near Sheridan and the average rainfall is 8" to 10" per year. If so, that might be one of the factors that exacerbate barren bentonite.

A short chemistry lesson for those who are not familiar with clay mineralogy: The structure of clay is like a pile of roofing shingles with ball bearings sprinkled between the layers. The shingles are sheet-like molecules of LMs-silicates. LMs are light metals (magnesium, aluminum..., pick one). The ball bearings are very light metal ions (cations) like sodium or potassium. When dry, the shingles are squished down tightly and the ball-bearings are insufficient to allow slip between the shingles. However, the ball bearings keep the shingles far enough apart that *given time* water molecules can wedge themselves in-between the shingles. It is a tight fit as the cations are smaller than the water molecules. The water molecules fluff up the shingles, lubricate the little ball bearings and make clay as slippery as whatever. In fact, many clays can hold triple their dry volume in liquid water.

Clay structure partially explains clay's schizoid behavior around water. Dry clay repells water because the water molecules have difficulty prying their way between the shingles, but once there, the shingles are very reluctant to give them up.

Chemical ammendments like gypsum and limestone displace the sodium and potassium ions with calcium ions. An ion is an atom stripped of one or more orbiting electron. Once stripped of the electron, the atom becomes very reactive or sticky. Calcium ions have two properties. They can give up either one or two electrons AND they are much larger than sodium ions. The larger size means the shingles are held farther apart so water can penetrate much more easily. The fact that they can donate either one or two electrons means that they can perfectly balance out the LMs-silicate chemistry and everybody knows that perfectly balanced machinery can be operated with little effort. That is, very little energy is required for the water molecules to penetrate between the shingles.

Other clays
have a wonderful reaction with chemicals, especially sulfur or compounds
that contain sulfur. That's why they sell gypsum to be added to soil.
Unfortunately some clays have an adverse reaction to these chemicals, so
you probably should find out if the USDA has a soil scientist in your
area and then go have a chat with him; other than that horse manure
sounds pretty good.


Michael Dirr is a horticulturist at U-Georgia who specializes in landscaping plants. Much of the U-G Athens campus is covered by red clay (laterite). One planting technique that works well for fussy plants is to bury half the root ball in the soil and then to mulch to the top half of the root ball with bark chips. The roots can draw moisture from the soil and can extract nurients from the 6" layer of decomposing mulch. One of the things that makes this techique magical is that the mulch layer can be much lower pH than the clay. The lower pH of the mulch makes a different set of minerals available. Kind of like having a hardware store next to a grocery store. Handy.

One of our locally available products is shredded pallets. The pallets are usually made of oak and I suspect that they are a decent substitute for bark chips. By the way, the shredded pallets are free.

Have you or anyone else heard of any benefits from
barley straw other than as "soil roughage"? When it decays it releases a
chemical that will keep a small pond algae free and I've heard that
raspberry production increases when it is used as a mulch, but I've
never tried it myself.


I am slightly familiar with rye straw suppressing weed growth.

From http://www.agnr.umd.edu/userforms/nera/Projects/annualrp.cfm?type=NE&numID=1000

"Rye
Commercially available cultivars of rye (nine in NC and 8 in NY) were evaluated for their ability to suppress weeds. The rye was planted in the fall of 1999 and biomass production, allelopathic activity, and weed suppression in the field were assessed in summer 2000.

Unlike the 1999 results from NC but similar to 1999 results from NY, the varieties showed no difference in weed suppression in the field. 'Wrens 96' and 'Wrens Abruzzi' produced most biomass in NC, whereas 'Aroostook' was the most productive in NY and 'Wrens Abruzzi' performed poorly.

An extract bioassay (NC) and a straw bioassay (NY) both showed 'Wheeler' as having the highest allelopathic activity. In both cases, only certain test species were affected. Concentrations of DIBOA, an important rye allelotoxin, were assessed in the NC experiment. By flowering, DIBOA concentrations were low in all varieties, indicating that allelopathy demonstrated in the bioassay was due to some other compound(s).

Eleven commercial varieties were planted at MD, NC, NY, and ON in fall 2000 for evaluation in 2001. In addition, 280 rye accessions from the National Small Grains Collection were planted at NC. The best of these will be used to initiate a breeding program for cover crop rye.
"


_______________________________________________


--
-Joe Hecksel
My personal website: http://my.voyager.net/~jhecksel
"We are only here for a short time. So let's make it a good time."
-Cary Dye 1958-2002






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