Potting soil
 

Newish septic tank in traditional location of round grave/road base circular
driveway. Circumference surrounded by large rocks to prevent vehicles from
driving over the septic tank. The septic tank installer used what he called
"sandy loam" to cover this area over the septic tank. Seems like red clay
to me, and stratifies when there's lack of water on it. I put St. Augustine
sod over it.
The St Augustine has been a yellowish color and not healthy looking in this
area. I've tried traditional fertilizer, and even "Texas Greensand". Not
much change. Kept the area well watered.
There are some low spots in this area, not uniform. Put some inexpensive
potting soil on it. Now, all the areas that were covered over with the
potting soil have a lush green color to the St. Augustine. The potting soil
bags didn't say anything about soil, just 6 or 7 materials that are common
for holding moisture and water, no chemical or otherwise fertilizers in it.
Haven't changed my watering strategy.
So, what did I do right (by mistake) that's making the grass green?
--
Jonny