Soil Test Results - what to do?
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.