Got my soil test back... the power of mulch!

alabamanicole(7b)July 21, 2010

My vegetable garden was a weedy patch of lawn in April. This weekend I dug up some samples in various places around my property to send them off for soil testing, including the garden.

3 months later, with nothing but vegetables and 10" of old straw for mulch (which is now about 2"), my soil has visibly approved in appearance, depth of color and tilth. The dirt directly adjacent to it is still clay, but the vegetable garden came back as light clay or loam.

I could use a little phosphorus, but that is easily corrected. And maybe a little lime to offset the recent pH drop.

This is probably the best native soil I've ever had -- no wonder the garden is gangbusters this year -- and I've scarcely started working on it! Of course, go over a foot down and you still start hitting rocks and hard clay, but give it time.

For the geeks:

Soil pH = 5.3 pH (was 5.9... drop probably due to increased organic matter in soil)

Phosphorus P = 30 lb/acre

Potassium K = 233 lb/acre

Magnesium Mg = 182 lb/acre

Calcium Ca = 1567 lb/acre

CEC = 4.6-9.0 cmolckg-1

Thank you for reporting this comment. Undo

The drop in soil pH is not due to organic matter since OM does not significantly affect soil pH. Did the test lab suggest what you might do to get that soils pH closer to the more optimal 6.2 to 6.8, although it does look like the major nutrients are readily avaialable enough for the plants you are growing.
What is the humus levels?

    Bookmark   July 22, 2010 at 6:44AM
Thank you for reporting this comment. Undo

Without venturing too far into the realm of soil chemistry, decay of organic matter acidifies soil in the short term by increasing available hydrogen+ ions. When you already have acidic soil, the effect can be quite dramatic. (Long term, additional organic matter buffers pH, but this plot is very much in the "short term" phase.)

Given the very adequate levels of magnesium and calcium in the soil, the strongly acid pH doesn't appear to be indicative of soil depletion. Having 8" of straw decay into the soil in less than 3 months is a lot of extra hydrogen.

They gave the typical advice to apply lime to tie up that excess hydrogen.

They didn't offer a humus test, but I am pretty sure it's fairly low. By touch and sight I'd say it has improved a lot. It's been "lawn" for 50 years... a lawn that doesn't even have a high percentage of grass in it, and most of the plants in it have fairly shallow root systems.

I am hoping the fall root crops will help start to bust up those dense lower layers.

    Bookmark   July 22, 2010 at 9:46AM
Thank you for reporting this comment. Undo
DrHorticulture_(Z3 Central Saskatchewan)

The only thing I question is the change from clay to loam. No amount of OM can change a soil's texture (structure - yes). Only adding sand and/or silt can change texture.

    Bookmark   July 22, 2010 at 12:21PM
Thank you for reporting this comment. Undo

I don't know how they determined soil type, DrH. Probably by "eyeball" method. I have a lot of small rocks in the soil that look like sandstone to me but should be limestone. It's possible that the initial tilling and soil disturbance eroded these rocks enough to contribute some silt.

Techically, according to the USDA soil survey in 2006, my soil is "Baxter cherty silt loam, eroded, rolling."

Typical profile:
0 to 12 inches: Gravelly silt loam
12 to 48 inches: Gravelly silty clay loam
48 to 60 inches: Gravelly clay

I don't seem to have the upper layer they mention, though.

    Bookmark   July 22, 2010 at 2:05PM
Thank you for reporting this comment. Undo

Testing the humus level in your soil is farily simple. A 1 quart clear jar with staight sides and a tight cap is all that is needd. Sample the soil and mix it together very well and then put enough of ot that soil into that 1 quart jar to make 4 inches of that soil (mine is marked in 1 inch increments with a felt marker) and then fill the jar with water. Put the lid on, tightly, and then shake the jar vigorously. Let that then sit for at least 24 hours and look at how the various substances in the soil settle out. Sand, the largest and heaviest soil particle will settle on the bottom, silt next, and then clay. Organic matter will be on top.
Loam is a specific soil type that has about 45 percent sand, 25 percent silt, 25 percent clay, and about 5 percent organic matter, adding organic matter to a mostly clay soil is not going to make that soil into loam.
All of the research that I have seen on adding organic matter to soil tells me that the organic matter does not make a signifanct change in the soils pH. Adding minerals such as lime, Magnesium, Sulfur, Ammonium Sulfate, etc. will change soil pH over time, but not organic matter.

    Bookmark   July 23, 2010 at 7:15AM
Thank you for reporting this comment. Undo

I agree, mulch over time is hugely powerful.

    Bookmark   July 24, 2010 at 8:18AM
Thank you for reporting this comment. Undo
organicdan(z5b Nova Scotia)

The pH drop may be caused by the rapid OM decay and the fact that newly cultivated soil has leached base cations. Did you experience above normal rainfall?

I wonder what your base saturation percentages were and what they are now? Gaining the proper base saturation levels for your soil type is a worthy project, as well as appropriate amendment to adjust the pH.

Acidity is normally caused over years by rain and leaching, acidic parent material, OM decay, and harvest of crops.

Keep records of your soil tests and note the effects of your amendments. Use the same testing lab but consider broadening the analysis to include base percentages.

How did your crops perform?

    Bookmark   July 26, 2010 at 6:05AM
Thank you for reporting this comment. Undo

We are actually behind in rainfall for the year by about 10", but we got a LOT of rain in the spring not long after the soil was turned. (Enough to put Nashville under 24 feet of water.) A typical rainfall here is pouring buckets for 15 minutes and then the sun comes back out. We rarely get those long, soaking rainfalls.

Acidic soil is normal for this region. 5.3 is lower than normal, though.

My crops did/are doing fantastic this year; much better than I expected for a throw-them-in-the-ground and see-what-happens experimental year. Squashes and cukes were especially productive, and the one eggplant that survived the flea beetles is setting an astonishing amount of fruit. Good taste, too, especially from the tomatoes and peppers, although my serrano peppers were not as hot as they should be.

The lab only offers one panel -- what I got. If I want more, I have to find a different lab.

    Bookmark   July 26, 2010 at 8:11AM
Sign Up to comment
More Discussions
My Onion Seedlings are not standing upright!!
I started my onion seeds March 1st and the germination...
Pesticides on Vegetables and Fruit Linked to Lower Sperm Counts
Why are my plants dying?
This is my first ever garden. It's a container garden. I...
Has anyone tried this method to repel cabbage moths in their garden?
I came across this post on reddit the other day and...
Soil Test - Help
Hi First Post! I cleared a piece of land last fall...
Sponsored Products
Soho Winter Gold Three-Light Bath Fixture
$139.00 | Bellacor
Dakota Handcrafters 3 Drawer Scholar Flat Top Desk - 2230FT-02-BN
Kendall Quilted King Headboard
$1,299.00 | Horchow
Cameron Beige Chevron Runner: 2 Ft. 3 In. x 7 Ft. 6 In. Rug
$150.75 | Bellacor
Standard Quilted Silk Sham - WHITE (STANDARD)
$150.00 | Horchow
The Portico Rug
Home Decorators Collection
Dale Tiffany Kelly Table Lamp
$169.99 | LuxeDecor
Entwined All-Weather Area Rug
Home Decorators Collection
People viewed this after searching for:
© 2015 Houzz Inc. Houzz® The new way to design your home™