A Teaching Moment

[DennisD]

Over the past year I have been researching methods of improving my garden soil. Living on a Glacial moraine my property soil texture is made up normally of about 30%rock and boulders, 60% sand and about 5% silt with no measurable amount of clay. Even though we have added considerable organic via composting over 20 years, the majority of our soil does not readily absorb or retain moisture. After a 1” rain during summer I can find powder dry soil at 1/4” deep! So needless to say plants that are not very well mulched do not grow well. Adding commercial fertilizers does very little since plant roots also need a soil structure that breathes well and allows moisture retention that support cation exchange to fully metabolize soil nutrients. My soil generally fails that test! Hence my efforts to improve it!
The below article by Purdue.edu describes the benefits of improving the CEC of soil and explains why “clay” the missing constituent in my soil plays a key role in the CEC of any soil.

https://www.extension.purdue.edu/extmedia/ay/ay-238.html

So I set out this week to determine where in Washington state one can obtain quantities of clay. After reading the below article published by department of natural resources, I set out to find a local source.

ger_b24_clay_shales_wa_1.pdf

Pg 144 of the publication describes Hammer Bluff: is in the NE1/4 sec. 28, (21-6E) as a 38 foot face formed by the Green River impinging against a short spur that projects from The Valley side. The layer of clayey sand at Hammer Bluff measured 12’ deep when the geologist visited this site.
Since this location is within 30 minute drive I went to determine if this source is available now to the public. After locating the site on a roadmap I determined to visit Flaming Gyser State park that borders the Green River. At the headquarters I met a park ranger who was familiar with the site and gave me precise directions to find Hammer Bluff. As I followed his direction walking downstream just outside the Park boundary, I came to a spot where looking up from the valley floor at about 1/4 mile away and about 600-700’ above the valley floor stood the sheer vertical outcropping of Hammer Bluff. The face of the bluff shone all the colors of the rainbow. As I observed this spectacle it occurred to me that once upon a time in our geologic past, the flows coming down the Green River gorge has dislodged the materials causing a huge landslide that must have filled the entire valley floor with huge volumes of rock, sand and clay.
As I reflected on how many years the Green River has been transporting these sediments to valleys below, it became clear to me why the alluvial soils in the valley that spans some 60 miles from Auburn to the mouth of Green River where it’s spills into Puget Sound are so abundantly fertile.
So I went about collecting samples of the local clay materials along the bank of Green River near Hammer Bluff.
The results of two samples I collected were as follows when I ran a simple fruit jar shake test.

After 24 hours the below pic shows how the constituents (sand, silt, and clay) measured in their respective proportions. Left to right: sample on the bank at about 10’ above water surface of the river, sample of the topsoil about 50 meters away from the river, 50/50 sample of the river bank clay mixed with my native property soil) :

Below is a picture of the third sample on the right above before I added water: 50 % of my property soil on the bottom and 50% of the riverbank clay on top:

The proportions of each soil constituent of all the samples were measured as:
My native soil:
Sand = 2 and 1/8 = 18 eights= 90%
Silt and clay 1/4” = 2 eights = 10%

Left sample Riverbank clay:
Sand = 1&3/4” = 14 eights= 53.8%
Silt = 3/8” = 3 eights = 11.5%
Clay= 1&1/8” = 9 eights = 46.1%

Middle sample away from riverbank clay:
Sand = 2” = 16 eights= 53.3%
Silt = 1/4” = 2 eights = 6.7%
Clay=. 1& 1/2” = 12 eights = 46.6%

50/50 sample of Riverbank and my property:
Sand = 2” = 16 eights= 66.7%
Silt = 1/8 = 1 eight = 4%
Clay 3/4” = 6 eights = 25%
Organics= 1/8” = 1 eight= 4%

By merely mixing 50/50 my property’s native soil with an equal volume of riverbank clay the classification goes from sandy soil to sandy loam on the Soil Texture classification triangle! As I took those measurements today I was elated to see that I now have a way of achieving a very high quality soil amendment by simply importing more valley clay. The way forward is now very promising, by adding valley clay and tossing in about 5% compost or other organics I can create a very fertile topsoil mulch for those places where I want to improve fertility and soil moisture naturally.
Dennis
Kent, wa

[Gkight]

Really nice breakdown, I hadn’t thought about using clay for moisture retention but it makes so much sense. Good luck in your endeavors of improving your soil quality, I have been doing the same but with a quasi-back to Eden approach. Just wish I could go back in time and never put down one square inch of landscaping fabric, I’ve been slowly removing it from under the variable levels of mulch 4”-12” depending on the spot. But it’s a fight worth fighting haha thanks for the breakdown

[krismoriah]

If you get a chance watch The Biggest Little Farm… they turned a dead worn out worthless piece of land into an oasis of life and are now growing more than 200 varieties of fruits and vegetables.

Living soil does amazing things.

If for nothing else their story is inspiring.

“Their new land had been farmed extractively for the last 50 years. The soil was completely devoid of life, or as John likes to say, they “bought a bank that had been robbed.” Led by their farming mentor Alan York, and fueled by Molly’s tireless optimism and tenacity, they began their journey to regeneration, bringing life, nutrients, and biodiversity back to the land.”

Our Story - Apricot Lane Farms

Also The Permaculture Orchard in Canada is inspring…his whole orchard is in sandy soil… He uses grasses to hold moisture and add nutrients as well as the root structures providing biomass and biome… whereas most Americans think that grass ‘steals, robs and chokes’ as you see those things talked about when talking about weeds and grasses in the orchard…seems to be working for him.

[Dr.Dude]

I did some experimenting with different soils and the clay soil held water for days longer than the regular stuff. I think you will be happy with your new dirt. I’m excited for you!

[poncirusguy]

My soil holds little, so I grow in containers over top of the soil.

[disc4tw]

Dennis,

I recommend searching for local mining operations, developers, or similar construction companies to see if any have clay available from the properties they work on. A triaxle load of material hauled our way is usually around $400 delivered. That should net you about 23 tons of material to work with. Usually we figure on 1 ton being about a yard of material. It may be cheaper for ‘dirt’, rather than the aggregate or sand you currently are seeking to amend, however I’m not familiar with the market in Washington.

[DennisD]

Hi Ryan,
Most of our topsoil for sale is generally not what I seek, due to its contents, either Tagrow (mostly human waste and wood chips). The best topsoil in the valley alluvial is not for sale. Only in those areas where builders sold it as they filled the floodplain for new foundations was it available about 10-15 years ago. I actually imported about 5 dump loads (100cuyd) for my rear garden as my builder prepared my lot. But that opportunity is long gone! I’m desiring only the richest source of clay I can find locally. Fortunately, the Green River flows within about 2 miles from my property and the overflow banks there are about 70% clay @ silt! So rather than bringing home only river sand for its minerals, I went away from the banks this am and located buckets of the good stuff that has been deposited in a forested area. So not only does it have the clay I desire, but about 5-10% organics. I have a pretty large horse manure compost, that I can use to till in the good stuff making a supreme moisture retaining mulch or soil amendment.
I have applied with a local tree service to get a load of fresh cut wood chips that I can begin to compost a few years so more organics can be mixed in with my clay.
Dennis

[DennisD]

A Teaching Moment

Dennis, I recommend searching for local mining operations, developers, or similar construction companies to see if any have clay available from the properties they work on. A triaxle load of material hauled our way is usually around $400 delivered. That should net you about 23 tons of material to work with. Usually we figure on 1 ton being about a yard of material. It may be cheaper for ‘dirt’, rather than the aggregate or sand you currently are seeking to amend, however I’m not familiar with t…

From this mornings trip to Green River I collected this sample. After only 10 min of settlement it looks like 40-50% sand, 5% humus organics, 25% clay and 20% silt
First pic of shaken sample on the right (original upper Green River samples on left):

Second pic moments later:

What I learned during this week was something that I should have recognized years ago but never gave it much thought! The River is acting very much like a shaker jar; it churns all transported materials during flood events and as it floods outside of banks into The Valley sediments settle out laying the clays and silts out onto adjacent lands. The majority of sand stays near the River mainstream but the good stuff enriches The Valley soils. These pics do a good job of illustrating how sediments are deposited
Dennis

[ampersand]

Soil science shows the soil triangle is a mix of sand, organic matter, and clay. The mix of the three makes it ideal.

If you want clay, come over to my yard in PA.

[DennisD]

Wish I could! Yes the particular soil unit I dug today was only about 30% sand, the rest was silt,clay and organics. I estimate these materials have been deposited mostly before Howard Hansen Dam was constructed back in 1961 because it’s essentially tamed the river and for most years it stays within the banks. The materials I found today was rather dark indicating a large % of organics have colored it over the years, my source was a forested floor about 60 meters from riverbank. Each year the cottonwoods spill their foliage and it decays in place while the earth woods take its humus thru the sediments.
Also today I struck it rich in an aged woodchip pile that is about 2 years composted

Veins of mycorrhiza fungi can been seen coursing thru the chip clumps that are held together. So I was able to obtain enough to innoculate my fresh woodchip pile.
So today I was very lucky
Dennis

[JennMm]

I am in North Alabama with sod (and plastic mesh UGGGGH!) laid over 1-2’ of acidic clay over limestone. If only matter and distance were irrelevant and 1 foot deep of each of our gardens could meet over Nebraska, mix together, then return to our gardens 1’ each of decent soil. Good luck!

I am retired and spend my days gathering the neighbors’ yard waste if it’s packaged light enough and portable enough for me to get it into my pick up. I’m too lazy to gather it myself though I do rake up the pine straw from the older widowed neighbor’s sidewalk. (The season for pine straw- front yard- and magnolia leaves for the back yard, my favorites, starts soon and now it is regular leaves season. A few months from now it’s rotting pumpkin/ straw bale decorations and discarded potted mum season. Cut grass season is painful since what if it’s got herbicide? It stinks! It’s so heavy!) I also get chip drop/ accost woodcutters when they work nearby and the chips are used all over between raised beds and to kill off grass, and I haul in purchased compost for layers in the beds.

My daughter just asked when I’ll have enough leaves in this small yard… when that clay layer is a foot down under black dirt, I guess. It helps to have an installed lawn sprinkler to make up for long stretches with no rain. My yard water bill is as expensive some summer months as one of the monthly bills spouse pays for his pricier hobby- owning a boat. Still I wish the sprinkler system had more than 4 separate zones (and that I truly understood the programming of it without having to run it to be certain of what the inputs have scheduled), though not enough yet to pay to have it redone. So far I’ve reduced the front lawn to occasional shoots busting through the thick mulch (my other keep busy activity is pulling the grass shoots) and have over half the backyard 6" to 5’ under mulch,


chips, or compost piles.

[JennMm]

That’s loofah in the yard- squash borers decimated all the other squash, summer or winter. Nasturtium was just as impressive in spring though with a lot more compost supporting it than loofah needed.

[cdamarjian]

@DennisD
Your great visual with various shaker jars prompted me do my own test on native soil. Very different profile: mine is about 50/50 sand/silt with no clay. This was taken from 6" down.

Would be interesting to see others’ shaker jar profiles.

[DennisD]

Hi Christine,
Your results are pretty good, the amount of wetable organics is helping you a lot in the absence of clay! In my garden my organics actually float and are hydrophobic rather than sinking, they float! So be thankful. I’m puzzled why my organics are this way, I suppose they never completely digested when composted. Yesterday I discovered a building site being graded and got permission to take as much clay as I need to help amend my garden. Below is a pic of this mornings shake test, in 3 minutes I can tell his clay layer is about 60% clay/40% sand. So tonight as his equipment crew shuts down, I will go again to obtain buckets of this source. You can see even the sans are extremely small grains. The glacier that left our moraine must have done some very good grinding! You may want to look for a similar developer for a clay source as it would greatly enhance the CEC of your soil!

[cdamarjian]

I’ve heard that potters here make pots from deposits along the shoreline so I’ll have to see what I can find.

As far as floating organics, I did put my sample through a 1” screen before testing. That removed larger pebbles and undigested matter. Otherwise I, too, would have had a thick floating layer.

[swincher]

I’ve seen some instructions for jar tests recommend adding some powdered dish detergent, is that really necessary or helpful? I did get a soil test for my yard but haven’t tried the old jar test yet so I’m motivated by this thread to give it a go

[cdamarjian]

I read that too about adding detergent but I opted not to add it. If detergent makes hydrophobic matter more hydrophilic, it seems that would change the layer pattern.

[DennisD]

If you can get access to the flood overflow areas along the River bank like a backflip channel, or at the mouth where it empties out to sea, you will find clays as you go up the river bank similar to this clump I picked up yesterday in a Green River back channel. When the turbid flood water goes into a back channel, it comes to rest allowing its sediment load to fall out!
When you dig into it with a garden fork it comes out like a clump, all stuck together!

[DennisD]

Not really, just do as Christine did to remove all larger pebbles, if you have sand, silt and clay clumps then crush them into powder before adding water. You will get good results
Dennis

[swincher]

So this is what mine look like a mere 10 min after shaking, still lots of settling left to do, but there’s already a clear difference between my lower back yard (large jar) vs upper front yard. The lot is on a slope, but mostly has been leveled to two flat levels with a short/steep slope between them, and I’ve often noticed the upper level seems more sandy:

My subsoil is mostly listed on the geological maps as Qvt, but there are pockets of Qva in my neighborhood, and the Qvlc “Lawton clay” is what’s below my subsoil, as shown in a nearby creek valley with lots of that clay exposed:

For other people in Seattle who may be curious, this is the map I got that from:
https://pubs.usgs.gov/of/2005/1252/