Soil Test results

10 years ago

According to my county/parish soil survey, I have "Stough" series soil type which is classified as a poorly to moderately well drained fine sandy loam. This is in St. Tammany Parish just north of New Orleans, LA. I am surprised it is classified as loam--the top couple inches actually isn't that bad--it crumbles nicely. But a shovel's depth down and you run into huge blobs of slimy, greasy, pale gray anaerobic clay. My front yard drains pretty well, but at times my backyard turns into a slimy muckhole. Don't really understand why there is such a difference as the lot is really only about 150 feet deep. Unfortunately, the only place with enough sun to grow roses is smack dab in the middle of the back yard.

I ordered a soil test from Dr. Good Earth and the results are:

pH - 4.7
Organic matter - 1.7%
Phosphorus - low at .8lbs per 1000 sq ft
Potassium - low at .8lbs per 1000 sq ft
Calcium - low at 20.8lbs per 1000 sq ft
Magnesium - low at 2.8lbs per 1000 sq ft

The type of trees that proliferate here are water oaks, live oaks, sweetgums, tallow, and slash/loblolly pines. Most people use either centipede or St Augustine grass and only rarely do you run across a really lush lawn, and even then you never really get that nice deep color.

I have a small plot in the back that was used as a tomato patch in the past that I have amended over the years with bags of top soil, pine bark, grass clipping, manure, etc. The soil there has turned black and most of the big clay blobs have disappeared. There can be as many as 12 giant worms in every shovel turn. I am taking that spot over for my roses and enlarging through sheet composting.

This will take care of my drainage/texture problems and organic matter percentage, but what is the best way to improve my phosphorus, potassium, calcium, and magnesium, and especially how do I properly raise my pH? I will be growing mostly hybrid teas on fortuniana rootstock.

I also want to try to get rid of this "muckhole" effect when there is a lot of rain (we had almost 11 inches this July) and I feel like the soil just drains poorly due to the subsurface clay. Is there something I can do to gradually improve the drainage? I have already raised the lowest spots with fill sand, but I still feel like the water just doesn't seem to drain into the soil well.

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Comments (14)

wirosarian_z4b_WI
10 years ago
Here is a scan of a chart for pH adjustment info. According to this chart, it looks like you would need 105 lbs. of lime per 1000 sq. ft. or 10.5 lbs. per 100 sq. ft. I don't know what the preferred pH for fortuniana root stock is, so if they like something on the acid side this may be too much lime but if they like neutral pH than this should be OK.

{{gwi:313899}}

This post was edited by wirosarian on Thu, Aug 1, 13 at 10:40
zack_lau z6 CT ARS Consulting Rosarian
10 years ago
You can raise the PH by adding lime. But, around here, many rosarians have found that roses will grow just fine with a PH that low.

I'd suggest growing roses in a raised bed in the middle of the back yard--we use 6x6 railroad ties or 2x10s. Move some of that nice soil into the raised bed and you should be all set.
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jim1961 / Central Pennsylvania / Zone 6
10 years ago
I second the motion for using raised beds....
mirendajean (Ireland)
10 years ago
Hi. If you post this in the soil/compost forum they will take to it like a house on fire. They LOVE this stuff, especially when there's loads of scientific detail.

M

Here is a link that might be useful: Soil Forum
michaelg
10 years ago
Loam is defined as a mixture of sand, silt, and loam. The soil survey classification is about topsoil, not subsoil. Sandy loam with some organic matter added is nice to work with. Pure clay subsoil is common in many parts of the country and wouldn't be a problem except, in your rainy and low-lying area, it probably stays saturated most of the year.

There is absolutely nothing you can do to improve drainage but raise the bed. Don't bother digging into the clay, because doing so will not help with drainage. (Mixing some clay into the topsoil might add minerals and increase water retention, though.) If you raise the bed 8" you will have enough depth of topsoil, and the upper part of it will drain.

Phosphorus is easily added as 2-3 oz of triple super phosphate (0-40-0) per square yard dug in to the upper 8-10". Potassium is easily added from the surface with routine fertilizing. Once phosphate is established, a suitable NPK ratio would be 3-1-2 or 2-1-2.

Dolomite limestone as an amendment will solve three of your deficiencies: pH, calcium, and magnesium. I am surprised the testing company did not recommend a particular amount of lime, but you can use the chart above. Aim for a pH around 6.5.

It's great that you got a test, because there are problems that need to be addressed, but solutions are at hand.

This post was edited by michaelg on Thu, Aug 1, 13 at 15:08
michaelg
10 years ago
So what happened to this guy?
Kippy
10 years ago
Maybe he got buried in the soils forum?

:)
jim1961 / Central Pennsylvania / Zone 6
10 years ago
He posted on the soils forum Michaelg....

Here is a link that might be useful: soils forum thread....
mirendajean (Ireland)
10 years ago
Yea he posted on the soil forum. They love these kinds of challenges. I began my gardenweb adventure there. Those guys are great. Intimidating and not as supportive as the rose forum...but they're great ;-)
michaelg
10 years ago
Well, they said the same things I said--plus the idea of a sump pump for the yard!
zack_lau z6 CT ARS Consulting Rosarian
10 years ago
I have new and unused sump pump and plastic pipe waiting in the basement for the next time the back yard floods....
Lynn-in-TX-Z8b- Austin Area/Hill Country
10 years ago
I only had part of my yard tested; different co., a while ago. Does anyone have any idea what their turn around time is for processing/ sending results once they receive the soil?

Lynn
jockewing
Original Author
10 years ago
Oh hello, I'm still here! Since it FINALLY quit raining everyday, the backyard has finally dried out some. I may have been overemphasizing the drainage problem somewhat due to what was going on at the time. I have started layering organic matter all along the back fence to improve the soil there. That is usually my "wettest" spot, so hopefully improving the drainage properties there will help the backyard as a whole. I am going to see how that works first before doing anything really drastic or expensive.

I have already taken the first step and limed with dolomitic lime to increase my pH and improve my magnesium and calcium deficiencies.
michaelg
10 years ago
Glad things are looking better. But improving the texture of the soil doesn't solve a drainage problem. Where is the water going to go? A bed of fluffy soil surrounded by clay will fill up with water faster than a bed of clay surrounded by clay--unless the bed is raised (or you have an outdoor sump pump :).