Thats how I apply neem oil too, I spray my plants and the other native plants in the immediate area, not so much the ground but I dont think that would hurt any. I use "Einstein Oil", its a little more expensive but it stops the bugs from molting(re-producing) and after awhile you will see very little insects around your plants. Make sure you spray the neem on the bottoms of the leaves too, the spider mites and other insects like to hang out there during the day when the sun is out and its hot.
As for fertilizer yeah just water them with it diluted down, maybe start at a quarter of what the package reccomends and work your way up paying attention to how the plant responds to it. I use Bat Guano or seabird guano as a top dressing as well during flowering, just sprinkle it on top of the dirt and every time the plant recieves water it will get a shot of that bud juice!
Good Luck my man!
