I have been having a lot of problems with sand and container soil with plants. Seems if I plant one the sand dries before the container so if I water the yard the plant wants to develope root rot. I figure the sand would wick the moisture away. Well I found a semi solution to my over watering and it is a moisture meter from Lowes about 4 bucks. I did a complete sample today of all my plants. It is pretty amazing. I would have been watering plants that were already too wet. The idea of amending the soil just does not work. On a large scale. If you are having plant problems try one it may open your eyes as it did mine.