There are a number of [points that may be missed, so I might throw in some thoughts and questions. Big one is how the cycle is being done and what to expect when "finished". Are you doing a fishless cycle, adding ammonia to maintain a specific level? This is a way to build a large group of the bacteria and make the tank ready for a large increase in the fish load. There is a wide range of definition of "cycle" so don't get caught in doing a cycle which only leaves the tank prepped for a very low load and then suddenly fully stock it! I might think 4PPM of ammonia is a bit high if doing the standard fishless cycle where you control the level. Possible it is causing some plant problems?
Big point on cycle is that it really CAN take a month to do it properly! Planted tanks definitely do teach patience but it's like stopping for stop signs, we can do it right or rush it and may pay the price.
For choice of soil/substrate, I find it has to be a decision made after looking at the whole picture of what you want to do along the way. Using yard dirt can work, but the quality of that soil needs to factor in how you plant to feed the plants. Totally inert pool filter sand is often my choice as it fits me better with the way I dose ferts. If you plan for plants to live on the nutrients in yard soil, it has to be good rich stuff but not so much if you plan to add food as you go along.
I suggest reading/study the various methods of doing, choose one and try it for some time before trying to judge soil. I have gone with the EI method as easier than trying to figure what is in a bucket of soil as it lets me add what I find needed without getting into the chemistry of what any bucket of dirt might have. I know when I dump in a little spoonful, it is actually there. Looking at a handful of dirt leaves me totally guessing.