Good soil = healthy roots
Healthy roots = strong plant
Strong plant = healthy flowers
Good soil + healthy roots + strong plant + good flowers = the most thc you can have.
All you can do is let your plants grow. THC content is limited by genetics
No it shouldn't be a problem unless your backyard dirt has high salt content, or has aphids. Shouldn't have enough salt in it to harm the plant so you are probably good. The princess you got going looks like it will do very well. Keep doing like you are doing and you should be good. Oh and as a nutrient additive to its last couple weeks of flowering I would get some Fox Farm Beasty Bloomz. Good luck *TH*